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Best DC-DC Chargers and Battery Isolators for Vanlife (How to Charge Your Van…

Best DC-DC Chargers and Battery Isolators for Vanlife (How to Charge Your Van…

    QA: DC to DC Battery Chargers FAQ (Frequently Asked Questions)

    Here are the answers to all of the questions that we’ve heard regarding the DC to DC Battery Charger Line (this blog will be updated as additional questions are asked). This has been broken down categorically and covers both of the DC to DC Battery Charger models:


    What battery types do they work with? SLA (Sealed Lead Acid), Flooded Lead-acid, Gel, AGM (Absorbed Glass Mat), Calcium, LiFePO4 (Lithium Iron Phosphate_ batteries

    What is the max size battery or battery bank I can use?The 25A model can accept battery sizes from 50Ah. 500Ah and the 40A model can accept 80Ah. 800Ah battery banks.

    How do you adjust the charger for different battery types? If yes, how it it done?Long Press the Mode button to select the battery type. There are 5 battery chemistries available: Standard Lead Acid, Gel, AGM, Calcium and LiFePO4. Keep pressing the button momentarily until the Battery Chemistry LED you want is flashing. After you release the button, your selection is entered and saved. Your selection will be restored automatically even after the Battery Charger is fully disconnected and reconnected. The default Battery Chemistry is STD ( Standard Lead Acid).

    Can you mix/match battery types (like 2 different chemistries)?Yes you can in certain scenarios.If your starter battery is a standard battery type: SLA (Sealed Lead Acid), Flooded Lead-acid, Gel, AGM (Absorbed Glass Mat), then it can be used with any above listed aux battery including LiFePo4.

    Can batteries be different sizes (different Ah ratings)? I have a starter battery that is 50 amp-hours and an aux battery that is 100 amp-hours.The batteries can have different Ah ratings; they do not have to match.

    Do I need a BMS (Battery Management System) for lithium batteries?Yes, you must use a BMS to safely charge LiFePo4 batteries.

    Can I charge other lithium batteries (not LiFePo4)?No, this charger is not compatible with other lithium-ion or metal battery types.

    What is the input voltage range?The charger can accept between 9V to 32V.


    Do I have to use a solar panel?No, this system can be used with or without a solar panel

    What type of solar charge controller is inside?Our charger utilizes sophisticated MPPT (Maximum Power Point Tracking) solar regulator technology.

    When the ignition switch is off does the MPPT solar controller still work? Where is that getting power from?The Solar charge controller will still work. Power is provided from the solar power once the unit switches from alternator power.

    What is the efficiency of the charge controller?The static efficiency of the MPPT algorithm is 97%, and the dynamic efficiency is 95%.

    How do you select the input voltage?The system has voltage auto-detection built in, you don’t have to do anything; it will automatically sense the voltage and make the change automatically.

    What is the max solar panel size I can use?The 25A charger can accept 375W at 12V and 750W at 24V. The 40A charger can accept 600W at 12V, and up to 1200W at 24V input.

    Does the solar panel type matter (monocrystalline, polycrystalline, thin-film)?No, our system can use them all.

    Can I use this to charge a second battery in the back of my cargo van and without a solar panel? Yes, you can use this for your application and without a solar panel.

    How do you engage solar priority mode?Press the Solar Priority button to prioritize input from the solar panel over charging from the alternator. The solar priority LED will light up when selected.

    Can it charge from solar and car alternator at the same time?No, it will only pull from one or the other.

    How many inputs are there on the DC charger?Aside from the battery input, our DC to DC Chargers feature an additional input for Solar/Wind/other input.


    What is intelligent battery charging?It’s a high-speed microcontroller and a proprietary charging algorithm that delivers a sophisticated 3 stage charging process.In other words, it senses the battery’s needs and adjusts the charging profile to match; ensuring the battery is optimized for safe and complete charging.

    How many stages of charging are there?Our chargers feature 3 stages.

    What do the battery charging stages do (what is their purpose)?The first stage, bulk charge (constant current), charges the battery fast while the second stage, absorption (constant voltage), ensures the battery is thoroughly charged. The third stage, float, monitors and keeps the battery at a safe voltage allowing it to be maintained and ready for use.

    What voltage does the charger operate at while charging?It depends on the battery type, p lease see the chart below.


    What protections do the chargers have?Spark-Free Protection, Reverse Connection Protection, Over and Under Voltage Protection, and Over Temperature Protection.

    What do the protections do? Spark-Free Protection: The DC to DC Charger will not start charging the battery (no output) unless the load is securely connected (except the LiFePO4 mode which allows 0 volt start); this prevents the leads from sparking due to accidental short circuit making the charger safer to use around batteries. Reverse Connection Protection: Reverse Connection or reverse polarity on input and output terminals will not damage the internal circuitry. Our Charger detects reverse connection conditions and indicates to the user whether input or output connection is reversed. Over and Under Voltage Protection: The charger will automatically shut down if there is an over voltage or under voltage condition detected to protect the user and the charger. Over Temperature Protection: The charger will lower its output current if the temperature of the unit begins to exceed its pre-set threshold.

    What size alternator do you need for this to workThese will work with all standard vehicle alternators.

    Do I need to do anything (once installed) for this to work? No, they are fully-automatic and will start to charge once they sense the battery is low and the alternator/solar panel is outputting power.

    Can this controller be mounted on a vertical surface but rotated 90 degrees. So the cables enter on the right side? Yes, installation orientation does not matter.

    Are the chargers vibration resistant? Yes, the units have been designed to work in vibrating, wet, dusty and muddy environments.


    Is there an installation video of how to install the charger in the vehicle?Yes, take a look at our YouTube Channel.

    Can they get wet?Yes, they are internally protected from water/dust and are IP66 rated.

    Where can they be mounted?They’re designed for a variety of installation environments, including chassis rail, engine bay, interior cabin, etc.

    How do I mount the unit?Depending on the mounting location, you can bolt the DC to DC Charger down or use and adhesive like industrial Velcro or VHB double sided tape. Ensure the charger is in a location that is free from heat, water, and vibration for best performance.

    When do I use the blue wire?If your vehicle has a fixed voltage or temperature compensating alternator (standard alternators) installed, leave the Ignition Override cable (BLUE color) open. If your vehicle has a Smart (variable voltage) alternator installed, the Ignition Override cable must be connected to the vehicle’s ignition. The Batt

    Is wiring the charger hard?Wiring the units is not hard as we provide detailed wiring instructions (in the manual) as well as color-coded wires with clearly marked labels.

    How do you wire them?We include butt connectors to be used for wiring; they can also be soldered. Utilize a connection method that is solid and creates the least electrical resistance. Wire nuts, twisting, splicing, and other less-secure connections are not recommended.

    What type of wire do I need?Please see the chart below.

    How do I know if my car has a Smart alternator?Most modern cars from 2015-year model and up do have Smart alternators. If unsure, contact the car dealership.

    Do I have to use the remote control?No, the remote control is an optional item for remote viewing and control.

    What else do I need for installation?You’ll need connection tools: wire cutters, crimpers, or a soldering iron and solder. In addition, you’ll need: wire to extend the connections, 2-3 fuses, heat-shrink tubing or electrical tape.

    What type of fuses do I need?

    • The 25A DC-DC Charger model requires two 40A fuses.
    • The 40A DC-DC Charger model requires two 60A fuses.

    Note: If utilizing the blue wire from the Smart alternator, an additional 3A fuse is required for both models.Bolt down fuses are preferred because they ensure a low resistance connection. Blade-type fuses are not recommended as they can result in a high resistance connection which causes excess heat and may damage the fuse holder and/or the wiring. Self-resetting circuit breakers are not recommended as they may trip prematurely due to the heat generated by the current flowing through the wires.

    Do I need a dual battery isolator so it won’t drain both batteries? No, this replaces the inefficient isolator with something that charges, monitors, and enhances the battery’s life/performance.

    Can I get the step-by-step wiring guide?Of course! Here it is:

    Note: It is very important that the connection wires are firmly connected. It is recommended to use the included Butt Splice Connectors or properly solder the joint. After completion, heat shrinkable tubing must be used for insulation to prevent short circuits and water intrusion.

    Disconnect the negative battery cable (Earth) from the vehicle’s starting battery or disconnect power to the trailer. Note: To prevent the loss of vehicle electronic memories, radio presets security codes, it is recommended that an “Electrical System Memory Protector” be used.

    Connect the Auxiliary Battery positive terminal to the Output Cable (RED color) from DC-DC Charger. Fit the appropriate size (see chart above) fuse to the cable as close as possible to the Auxiliary Battery positive terminal.

    Connect the Auxiliary Battery negative (-) terminal to the DC-DC Charger Common Ground cable (BLACK color). Alternatively connect both Auxiliary Battery negative (-) terminals and DC-DC Charger Common Ground cable to vehicle chassis ground.

    Connect the Starter Battery positive terminal to the DC-DC Charger Alternator Input cable (YELLOW color). Fit the appropriate size fuse to the cable as close as possible to the Starter Battery positive terminal.

    If your vehicle has fixed voltage or temperature compensating alternator (standard alternators) installed, leave the Ignition Override cable (BLUE color) open. If your vehicle has Smart (variable voltage) alternator installed, the Ignition Override cable must be connected to the vehicle’s ignition. The DC-DC Charger will only operate when the vehicle’s ignition is turned on.

    When 12V solar panels are present, connect the solar panel positive terminal to the DC-DC Charger Solar Input cable (GREEN color). Fit the appropriate size fuse to the cable as close as possible to the Solar Panel positive terminal. Then, connect the Solar Panel negative (-) terminal to the DC-DC Charger Common Ground cable (BLACK color). Alternatively connect both Solar Panel negative (-) terminals and IDC45 Common Ground cable to vehicle chassis ground.

    Restore the negative connection of the battery. Now test the system to ensure it is working properly.

    What do the flashing-colored lights mean? Please reference the chart below.

    What size is the mounting plate?Measuring from center of hole to center of hole, the 25A mounting plate is 120mm across and 70mm down while the 40A is 120mm across and 80mm down.

    What are the overall dimensions?The 25A model is 5.7L x 5.1W x 1.7H while the 40A is 7.3L x 5.1W x 1.7H.

    Are the actual internal wires CCA (copper clad aluminum), pure copper, or?We utilize tinned copper wires for the best transfer of electricity while protecting the copper wire inside.

    Why do you say they’re waterproof, vibration resistant, etc. but say to mount it away from heat and water?Like any electronic device, to get the best performance you should keep it in a cool dry place that is free of dirt, heat, vibration, etc. Our chargers are made to easily withstand less-than-ideal mounting locations; we’ve had our test unit mounted on the battery tray in the engine compartment of our V8 LX470 overland vehicle since early-2022.

    Will the DC to DC charger do well in the engine compartment, or better to install inside the vehicle?Our DC-DC Charger can handle normal engine operating temperature ranges, but (like any electronic) would perform best inside of the vehicle. Our unit operating temperature range is.4°F to 176°F (-20°C to 80°C).


    Are they potted or do they have a conformal coating? Yes, the DC to DC Chargers both feature a clear thick layer of resin (known as potting) that seals the components from water and dust, dampens vibration and physical shock, keeps heat out, and helps with electrical performance.

    What is switchmode technology?The Battery Charger converts your vehicle’s 12V DC/24V DC alternator power to a 12V system; allowing your batteries to be fully charged, prolonging battery life and reliability. With the latest synchronous switching technology, the efficiency of the Battery Charger is up to 95% at a typical full load condition. This is what we call, switchmode technology.

    Are these units dual-input?Yes, they are dual-input. The Battery Charger allows two energy sources to power your auxiliary battery. Solar input takes precedence if solar input power is strong enough. When solar input cannot provide enough energy to charge the battery, the Battery Charger will draw power from the alternator.


    What is the power ecosystem?The power ecosystem is the sum of all your electrical devices combined. Your car’s electronics all of the stuff you add (lights, refrigerator, power inverter, solar panel, extra batteries, etc.Our DC to DC Charger completes the power eco-system by providing a way to connect, power, and recharge everything.

    What are the DC Chargers made of?The cases are aluminum with impact-resistant plastic faceplates.

    Is the body a heat-sink?Yes, it is finned and acts as a heat-sink for fast cooling.

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    Why a DC to DC charger over an isolator?The Battery Charger is specifically designed for charging auxiliary batteries. It includes all the features needed to maintain an auxiliary battery at its optimum condition and to prolong battery life. Isolators do not have sophisticated charging profiles, they are not multi-chemistry capable, and they aren’t solar compatible.

    What is the coldest operating range?The Operating Temperature Range:.4°F to 176°F (-20°C to 80°C).

    Is the remote control included?The remote control is an optional accessory and is not included. (Click Here)

    What does the remote control do?An external remote monitor (Part. No. 5605) is available to show the status of the charger. It shows how the auxiliary battery is charged by the alternator or the solar panel, and other useful information. Click here to learn more

    Can I jump-start my car from this?No, you cannot. However, all it takes is a pair of jumper cables from your auxiliary battery to your starter battery to jump it! Or, you can use one of our jump-starters that we sell.

    Are these certified?Both models carry CE and BC certifications.

    Did this blog answer your Qs? Leave a comment below!

    Need more help?Shoot us an email or call us! Email: customerservice(at) or 1.800.231.5806

    Best DC-DC Chargers and Battery Isolators for Vanlife (How to Charge Your Van While Driving)

    Having electricity in your van is just plain awesome. It means you can live completely off the grid with lights, a fridge, phones and computers – all while not worrying about electric bills or power outages.

    Many vandwellers install solar power in their rigs. But sometimes solar just isn’t enough – especially if your budget doesn’t allow you to throw down for a huge multi-panel system.

    Cloudy weather, wildfire smoke, and camping in shady forests can limit the amount of sunlight getting to your panels, leaving you scrambling for adequate sun to recharge your depleting batteries. Even with our larger 400W system we’ve run into problems with battery drain after about 4-5 days in poor sunlight conditions.

    That’s why we highly recommend setting up your campervan electrical system to charge your batteries from your van’s alternator while you’re driving.

    Charging from your alternator is a great way to supplement your van solar panels and make sure your batteries stay topped off no matter the weather. And if you’re on a tight budget, you can even skip the solar and still have basic electricity in your DIY van build.

    Life on the road means a fair amount of driving, and having the ability to charge your batteries while driving is essential for vanlife.

    How To Charge Your Van’s Batteries While Driving

    Every vehicle has an alternator. An alternator is a device that converts the mechanical energy from your van’s engine into electricity, and uses that electricity to power electronics in your van and charge your starting battery.

    You can easily use your alternator to charge your second (auxiliary) battery simply by connecting the positive terminals of both batteries so that they’re in parallel. But paralleling your batteries means that when the engine’s off, your electrical loads will also drain the starting battery – not good if you want to start your van in the morning!

    So you need a device that allows you to charge a second (auxiliary) battery from your van’s alternator without draining your starting battery when the engine isn’t running.

    There are two kinds of devices for this: DC-DC chargers and Battery Isolators.

    We’ll go over both in this post, but in general we recommend that most people get a DC-DC charger for their rigs.

    What is a DC-DC Charger?

    A DC-DC charger (also known as a battery-to-battery charger, or b2b charger) is a device that takes the input from your alternator/starting battery and uses it to charge your aux battery.

    DC-DC chargers are able to charge just about any type of battery (including lithium), they work with modern variable voltage alternators, and they employ multi-stage charging to fully and properly charge your battery bank.

    DC-DC chargers come in two varieties: single input and dual input.

    Single Input DC-DC Chargers

    Single input DC-DC chargers do one thing, and one thing only: charge your aux battery from your alternator. This is what you want to get if you already have your solar equipment, or if you want the flexibility to pick and choose the exact specs you need for each component.


    • Variety of amperages available to suit your specific requirements
    • Easy add on to solar panel kits or existing solar setups


    Charges your auxiliary batteries from your alternator. Also available in 20A and 60A sizes.

    • 20A size is best for 40Ah LFP or 100Ah AGM batteries
    • 40A size is best for 100Ah LFP or 200Ah AGM batteries
    • 60A size is best for 120Ah LFP or 300Ah AGM batteries

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    Smart DC-DC charger from Victron with Bluetooth connectivity. Comes in models ranging from 12A to 30A.

    Dual Input DC-DC Chargers

    Dual input DC-DC chargers, on the other hand, also function as solar charge controllers. So with just a single unit, you can charge your batteries from your solar panels and from your engine. This makes installation a whole lot easier, and it makes your electrical system look a bit cleaner.

    However, combined units like this take away the flexibility to really customize your solar setup independent of your engine charging, since you’ll be locked in to the specs of your DC-DC charger (For example, Renogy’s DCC50S can only accept 25V solar input, which means you must wire your panels in parallel to stay under that voltage).

    But, if you were planning on wiring your panels in parallel anyway, then the DCC50S allows you to have one less component in your system.


    • One unit handles both solar and DC-DC charging
    • Easy to install (usually no ignition tap)
    • Also tops off your starter battery


    • Less flexibility with charging parameters
    • Need to assemble your own solar components vs buying a kit

    One unit for all your charging needs. Charges your aux batteries from solar and your van’s alternator. (Bonus: it also tops off your vehicle starting battery from your solar).

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    40A dual input charger that allows you to charge from both solar and your alternator. Also available in a 50A version.

    What is a Battery Isolator?

    A battery isolator is a device that allows you to charge an auxiliary battery from your van’s alternator, while keeping your starting and aux batteries “isolated” from each other.

    Battery isolators are inexpensive, and they’re generally pretty easy to install. However, they are not always the best choice for your van’s electrical needs, and in most cases a DC-DC charger is what you should go with.

    Battery isolators may not work properly with modern variable voltage alternators, won’t work with lithium batteries (unless you pay through the nose for a lithium-specific isolator), and may not maintain the proper voltage to fully charge your aux batteries.

    There are three types of battery isolators out there: solenoid battery isolators, solid state battery isolators, and voltage-sensing relays (or “Smart” isolators). Voltage-sensing Smart isolators are far and away the best choice, so we’ll FOCUS our discussion on these.

    Smart battery isolators work by automatically sensing the voltage of your starting battery. When the voltage reaches 13.3V (meaning the engine is on and the battery is fully charged), the isolator “cuts in” and sends 100% of the alternator’s current to your auxiliary battery. When the starting battery voltage drops to 12.8V (meaning the starting battery is no longer charging), the isolator “cuts out” to prevent your starting battery from draining.

    Rugged and durable Smart battery isolator for charging your aux battery while driving. Easy to install, and IP65 certified.

    The KeyLine Chargers Iso-Pro140 Smart Battery Isolator has worked out great in our van. It’s small and compact, it’s very simple to install (the hardest part is running battery cable from the engine compartment to the rear of your vehicle). And it’s IP65 certified, which means you won’t have to worry about it failing after driving the dusty road to Burning Man.

    Everything you need to install your Smart battery isolator. Includes the Iso-Pro 140, battery cable, crimp terminals, and lugs.

    The KeyLine Iso-Pro 140 is also available as a kit that includes wiring, rings, terminals, etc, which should help make installation a whole lot easier.

    When to Use a Battery Isolator (and when not to)

    Battery isolators will work in your rig if all of the following are true:

    • You have an older van with a fixed voltage alternator. Battery isolators need a consistent voltage to work properly. If you have a newer vehicle (about 2015 or newer) with a variable voltage “Smart” alternator, an isolator probably won’t work for you.
    • Your auxiliary batteries are lead acid (AGM, gel, flooded lead acid). Most isolators won’t function properly with lithium batteries. (There are lithium-specific isolators out there, but they’re super expensive and thus kind of pointless.)
    • You’re on a tight budget. Battery isolators are cheaper than DC-DC chargers, but that’s about the only advantage they have. If you’re not on a tight budget, you’ll be better off with a DC-DC charger.

    If all three of the above apply to you, then awesome – get a battery isolator for your rig.

    However, if any of the above do not apply to you, then you need a DC-DC charger.

    DC-DC Chargers vs. Battery Isolators

    On the surface, DC-DC chargers seem very similar to battery isolators. Both allow you to charge your auxiliary battery while driving, and both prevent your starting battery from draining when your engine is off. But the difference is in how they charge your aux battery.

    Battery isolators simply parallel your starting and aux batteries together, which puts them at the same voltage. So if your alternator is sending 14.4V into your starting battery, the battery isolator connection will put your aux battery at 14.4V also (meaning it’s charging).

    There are a few issues with this:

    • With modern variable voltage alternators the voltage output can fluctuate, preventing the battery isolator from kicking in.
    • If your alternator isn’t putting out enough voltage, your isolator may only partially charge your aux battery. This can lead to battery degradation over time.
    • Voltage drop can be an issue if you have a long wire run connecting your isolator to your aux battery.

    DC-DC chargers, on the other hand, take voltage input from your alternator/starting battery and boosts it to the proper voltage for charging your aux battery. They do this by putting a “load” on your alternator, so that you alternator treats it like it would, say, a light bulb, and sends power to it. No matter what voltage your alternator is putting out, a DC-DC charger will send the proper charging voltage to your aux battery.

    There are a few advantages to ths:

    • DC-DC chargers can handle the fluctuations of modern variable voltage alternators and still charge your aux battery properly
    • DC-DC chargers can employ multi-stage charging, so you know your batteries are being properly and fully charged.
    • DC-DC chargers can work with different charging profiles, meaning you can use them to charge different types of batteries (including lithium).

    What are the downsides to DC-DC chargers? Mainly that they are slightly more expensive than battery isolators, and they may be a little more difficult to install (since some DC-DC chargers require you to tap into your ignition circuit).

    But DC-DC chargers are way more flexible and capable than battery isolators, and we think they’re the best overall choice for vanlife.

    What Size DC-DC Charger or Battery Isolator Do You Need?

    DC-DC chargers and battery isolators comes in different sizes, indicated by amperage (i.e. a 60A DC-DC charger, or a 140A battery isolator). How do you pick the right size for your van?

    Sizing a DC-DC Charger

    When selecting a DC-DC charger, you want to size it based on the charge rate of your aux batteries. This is based on your battery chemistry – so an AGM battery has a different charge rate than a lithium battery.

    Here’s the general rule of thumb for battery charge rates:

    • Lithium batteries (LiFePO4, etc.) can be charged at 0.5C (or, 50% of capacity). This means that a 100ah battery can be charged at 50A.
    • Lead acid batteries (AGM, gel, FLA, etc.) can be charged at 0.2C (or, 20% of capacity). This means that a 100ah battery can be charged at 20A.

    Note: These are general guidelines only. Check the specs of your specific batteries before selecting charging components.

    DC-DC Charger Sizing Calculator

    Keep in mind, this is the maximum charge rate. You could undersize your charger, but don’t oversize it (some DC-DC chargers, like the Renogy models we recommend, have the ability to set a lower charge rate if needed).

    Again, double check your specific battery’s specs to make sure you’re getting the right size DC-DC charger.

    Sizing a Battery Isolator

    The general guideline is to size a battery isolator based on the maximum output of your alternator. You should be able to find this number either in your vehicle’s spec sheet, or stamped onto the alternator itself.

    So, if your alternator max output is 175A, then in theory you would need at least a 175A battery isolator.

    However, although your alternator may be capable of outputting 175A, not all of that is available for charging your aux battery. Some of that is being used to power the other systems and electronics in your van, so the amperage actually being sent through your battery isolator may be substantially less.

    On top of that, most battery isolators out there come in sizes ranging from 125A to 150A. While there are larger isolators available, they get pretty expensive above 150A, and at that point you might as well get a DC-DC charger anyway.

    Long story short, if you’re going the battery isolator route a standard 125A to 150A Smart isolator should have plenty of capacity in most situations.

    Installing a DC-DC Charger or Battery Isolator in Your Van

    What You Need

    • DC-DC charger or battery isolator
    • Deep cycle battery
    • Battery cable (size cable based on specs for your specific unit)
    • Battery terminal lugs (size for your cable) and crimping tool
    • (2) Inline ANL fuses (one for each battery – see fusing specs for your specific unit)
    • Cordless Drill
    • Mechanic’s Toolset
    • Multimeter
    • Zip Ties
    • Cable sheathing/flexible conduit (sized for your cable)


    • Disconnect the negative battery terminal from your starting battery. This is an important safety step that isolates the starting battery so you won’t get shocked.
    • Mount the charging unit. Find an easily accessible spot. Battery isolators are typically mounted within the engine bay (you may need to temporarily remove your starting battery to make room). DC-DC chargers are typically mounted back by the auxiliary battery so they are out of the elements.
    • Run battery cable from the engine bay to your van’s electrical hub. You may need to run this underneath your van. Cover the battery cable with sheathing or flexible conduit to prevent shorts. Use zip ties to keep it out of the way. Make sure there the cable is tight and that there is nothing loose hanging down. Drill a hole up through your van’s floor to route the wire inside. Seal this with silicone caulk.
    • Ground the charging unit. Attach the DC-DC charger or battery isolator to a common ground point on your van’s chassis. It’s best to use an existing ground screw.
    • If needed:Tap the charging unit into your vehicle’s ignition circuit. Some DC-DC chargers (and battery isolators) require that you tap into your van’s ignition circuit.
    • Attach the charging unit to your starting battery. Cut and crimp battery cable to the size that you need. Run a cable from the DC-DC charger or isolator to an inline ANL fuse, then another cable from the fuse to your starting battery (for DC-DC chargers, this is the long cable you ran under your van. Battery isolators are mounted in the engine bay).
    • Attach the charging unit to your aux battery. Cut and crimp battery cable to the size that you need. Run a cable from the DC-DC charger or isolator to an inline ANL fuse, then another cable from the fuse to your aux battery (for battery isolators, this is the long cable you ran under your van. DC-C chargers are mounted near the aux battery)
    • Reconnect your starting battery and make sure everything works. Fire up your van, wait a few minutes, and check to make sure your aux battery is charging. DC-DC chargers should give you a readout. Battery isolators will have indicator lights, and you can also check the voltage at your aux battery terminals using a multimeter.

    Step 1: Disconnect the negative battery terminal from your starting battery.

    Find an easily accessible spot. Battery isolators are typically mounted within the engine bay (you may need to temporarily remove your starting battery to make room). DC-DC chargers are typically mounted back by the auxiliary battery so they are out of the elements.

    Step 2: Mount the charging unit.

    Find an easily-accessible spot to mount your charging unit. DC-DC chargers typically mount back by your aux battery. Battery isolators are typically mounted in the engine bay (you may need to temporarily remove your starting battery for this step).

    Step 3: Run battery cable from the engine bay to your van’s electrical hub.

    You may need to run this underneath your van. Cover the battery cable with sheathing or flexible conduit to prevent shorts. Use zip ties to keep it out of the way. Make sure there the cable is tight and that there is nothing loose hanging down. Drill a hole up through your van’s floor to route the wire inside. Seal this with silicone caulk.

    Step 4: Ground the charging unit to a metal point on your vehicles chassis.

    Attach the DC-DC charger or battery isolator to a common ground point on your van’s chassis. It’s best to use an existing ground screw.

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    Step 5: If needed: Tap the charging unit into your vehicle’s ignition circuit.

    Some DC-DC chargers (and battery isolators) require that you tap into your van’s ignition circuit.

    Step 6: Attach the charging unit to an inline fuse then to your starting battery.

    Cut and crimp battery cable to the size that you need. Run a cable from the DC-DC charger or isolator to an inline ANL fuse, then another cable from the fuse to your starting battery (for DC-DC chargers, this is the long cable you ran under your van. Battery isolators are mounted in the engine bay).

    Important Note on Fuses

    The in-the-box instructions for some battery isolators may not call for any fuses. But adding two inline fuses (one as close as possible to your starting battery and another one close to your auxiliary battery) is an important safety feature.

    The purpose of a fuse is to break the circuit in case of an electrical short. When you install an isolator, you’re likely running electrical wire underneath your van. If that wire somehow shorted out and both of your batteries were not fused, you could have a serious problem on your hands.

    So – it’s a good idea to fuse both batteries when you install a battery isolator. When in doubt, add a fuse!

    How big of a fuse do you need? Unless it’s outlined in the instructions for your battery isolator/DC-DC charger, it’s a good idea to fuse based on the charge rate of your battery.

    Step 7: Attach the charging unit to your aux battery.

    Cut and crimp battery cable to the size that you need. Run a cable from the DC-DC charger or isolator to an inline ANL fuse, then another cable from the fuse to your aux battery (for battery isolators, this is the long cable you ran under your van. DC-C chargers are mounted near the aux battery).

    Step 8: Reconnect your starting battery and make sure everything works.

    Fire up your van, wait a few minutes, and check to make sure your aux battery is charging. DC-DC chargers should give you a readout. Battery isolators will have indicator lights, and you can also check the voltage at your aux battery terminals using a multimeter.

    Electricity on the Road in Any Conditions!

    We think a DC-DC charger (or a battery isolator) should be one of the first things you add to your van’s electrical system. Sometimes solar isn’t enough, or you may not have the budget for solar right away. In either case, a DC-DC charger is a great solution.

    No matter if you’re traveling in overcast climes, in the deep forest, or other areas where you may not get enough sunlight, charging your batteries while driving ensures that you can have the power you need in all conditions.

    John is the co-founder of Gnomad Home. He researches and writes the in depth guides on our site, and his goal is to make vanlife, alternative living, and dream chasing accessible to all through the democratizing power of free information. He’s also passionate about creating, both hands on and digitally. he’s the driving force behind our vehicle builds, and he’s also in charge of the web design/development around here.

    DC-DC Solar EV Charger

    The key component to transform the solar car from a backyard science experiment to cost effective practical transportation.

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    This project was created on 10/04/2022 and last updated 8 months ago.


    I’ve added solar charging to my Chevy Volt with near-OEM performance. This means charging the high voltage drive battery directly by means of a step-up DC-DC charge controller. Details like Maximum Power Point Tracking and a trickle charger for the 12v battery are needed too. A Programmable Logic Controller is needed to operate the contactors for safe high voltage battery charging. This project incorporates all of the needed components on a single circuit board, minimizing cost and weight, and maximizing reliability and efficiency.

    Submitted for Hack-a-Day Prize round 5 (Save the World Wildcard)


    Installing a moderately sized solar array on a vehicle’s roof can collect enough energy to drive 5 to 10 miles a day. When compared to the 37 miles a day that the average American drives, it may seem insignificant. Everyone wants to say the glass is three quarters empty. But we should think of it being one quarter full. A 25% reduction in vehicle “energy consumption” is huge.

    Many areas still do not have good EV charging infrastructure. Workplace chargers would be ideal for managing the Duck Curve. The EVs could charge during the day from the plentiful solar energy. But many companies are still not willing to install chargers. A vehicle mounted solar charger will work anywhere there is sun. This is a practical and tangible way for drivers to reduce their environmental impact. And it has the potential for an economic return on investment by supplying clean, low cost electricity directly to the vehicle. The cost of a solar charger might be offset by choosing not to install a home EVSE for vehicle charging. Or it could allow an urban dweller who does not drive much to get an electric or plug-in hybrid electric vehicle even if they can’t install an EVSE.

    This project aims to add solar charging to a Chevy Volt in a manner that does not require any special work by the driver. Well, it will need to be parked in a sunny location. But the driver will not need to plug a cable into the J1772 port for charging like the majority of solar car projects. This project also avoids an additional battery for temporary energy storage and the losses from multiple AC to DC conversions.

    Project Progress

    ☑Solar array mounted on vehicle.

    ☑High voltage DC-DC charge controller.

    ☑Maximum power point tracking

    ☑Also charge the 12v battery during the day.

    ☒ Relay coil economizer. Currently disabled due to malfunctioning in the morning.

    ☑Automatic switching between charging during the day and low power standby mode at night.

    Future Directions

    ☐Avoid check engine light without manually switching off charger before driving.

    ☐Charging while charging. (Combined grid and solar charging)

    ☐Larger and/or more aerodynamic solar array.


    The DC-DC converter firmware source code is licensed GPL v3. Some of the underlying libraries whether written by myself or others are released under MIT license.

    The roof mounted solar array is nearly the maximum size possible before it starts to interfere with normal vehicle usage. The car currently has Hightec Solar 210w panels. (200w bifacial shown) Radio reception, especially satellite, is compromised. The rear hatch can be opened without interference. The solar panels are barely visible through the windshield when seated in the driver’s seat. This solar panel setup should not be considered ideal. It was just an easy way to get a good array mounted without permanent vehicle modifications. That was important at the beginning of this project when it was uncertain whether the DC charging would be possible.

    A Raspberry Pi receives data from the high voltage management CAN bus and uploads it to

    The solar energy collected should correlate with Global Horizontal Irradiance. The GHI is measured at a test station about 10 km away. Sometimes the charger may be down for maintenance or rejecting energy because the battery is full.

    Under the hood is not the ideal location for the DC-DC converter, but it is easy to access and makes for good photos. Two manual shutdown switches are accessible with the hood closed.


    Input: 30-43vdc, MPPT intended for 72 cell solar array, should work with 60 cell panels but may not reach maximum power point at high output voltages.

    Main Output: 300vdc-400vdc 1A, maximum continuous power about 300w, CV/CC modes, isolatedAux Output: 13.8vdc 3A, CV/CC.



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    Project Logs

    Additional Considerations

    The PCDB1910 met most of the minimum requirements with copious jumper wires installed. Most importantly, it proved that it was possible to DC charge the vehicle without damage or constantly setting the “check engine” light. My experience with this board led to a list of improvements for the next revision.

    • Maximum power point tracking is desirable for all solar electric systems. Well, Electrodacus might disagree. But with a small vehicle mounted solar array, the vehicle will consume all the power it can generate. I eventually added MPPT to the software for the first board revision after running without it for a while. It is particularly frustrating to see reduced charge power at low state of charge.
    • 12v auxiliary output. 12v charge controllers are a common off the shelf item. But the marginal cost of adding a 12v output to the main board would surely be less than a separate 12v charger. There is also the issue of running two MPPT controllers off one solar array. They may conflict. Many charge controllers expect the solar negative connection to be floating with respect to the battery negative. I was lucky to find a charge controller that worked in this situation. The first board revision using the Propeller 1 was intended to have this feature but it did not have enough current sensors or processor cores.
    • 12v adjustable output. The Chevy Volt operates its factory DC-DC converter (replaces the alternator) at a reduced voltage sometimes to save power. The off-the-shelf charge controller I used with the first board revision output a constant 14.4v due to the load of the contactors and battery management system. Reducing this to 13.8v or below may save some energy.
    • Energy logging. It’s important to monitor the amount of energy collected to detect problems This data will also be useful for promoting this unusual solar car system. The first board revision used the battery backed RAM of a DS1307 to maintain a kilowatt-hour count. Now, I use a Raspberry Pi that logs data from the solar charger board as well as the vehicle’s battery management system. It even uploads to the website.
    • Automatic day/night switching sounds trivial at first. But when it comes to programming the microcontroller, it becomes complicated. Most charge controllers can cycle on and off at dawn without issue. That is a big issue when charging a high voltage drive battery. The high voltage charger should be turned on only when there is enough available power to overcome the overhead of the contactors and battery management system. And the number of on/off cycles should be minimized because that involves closing the contactors and a high voltage precharge.
    • Contactor coil economizer. Contactors require a certain amount of voltage to close. But once closed, they will stay closed with much less voltage. If the voltage can be reduced during contactor operation some power can be saved. The Chevy Volt does not economize the contactors. This may be a bad idea while driving; the vibration could cause the contactor to open unexpectedly. And there is not much motivation to economize the contactors when charging from grid power.
    • Electromagnetic interference. Since the solar panels are mounted extremely close to the radio antenna, any electromagnetic interference from a solar charger could have a significant impact on radio reception.
    • Function as a logic analyzer for development work. The best way to figure out the how to operate the vehicle’s contactors is to put the vehicle in different states and observe what it does.
    • Designed for an enclosure. Since dust and moisture is common in the automotive environment an enclosure with an IP68 rating would be ideal. However, the space available in the vehicle is fairly restricted. Also, the board needs to dissipate heat well. So a plastic enclosure would not be as desirable. Most power inverters use an extruded aluminum enclosure for this reason. As a compromise I designed the board to fit into an IP66 rated Bud EXN-23366.

    Read more »

    Charge Controller Minimum Requirements

    • Output voltage regulation is one important safeguard against overcharging the lithium-ion battery. Voltage regulation is also necessary to prevent damage to other vehicle electronic should the contactors open unexpectedly for any reason.
    • Isolated high voltage output. While solar panels are commonly connected in arrays capable of generating 400v DC, it would be best practice to have the solar panels isolated from the high voltage drive battery. This proved to be a minor burden. The standard non-isolated step-up converter is not well suited for a 10:1 voltage ratio anyway. I used a full bridge converter which provided the necessary voltage gain and isolated output.
    • Contactor control output. It seemed much easier to access the battery pack using the existing contactors instead of opening the pack and making a new connection inside. on this in another update, or check the Real Solar Cars YouTube channel. It would not work to simply turn the car on to charge. The Chevy Volt uses about 250w at idle. The 420w array on the car usually collects about 200w in realistic conditions. In any case, 250w is a lot of overhead. To minimize the overhead, it’s necessary to charge the car with all systems off except the contactors and battery management system. The battery management system on the Chevy Volt is enabled by a 12v signal on the same connector as the contactor signals.
    • A CAN bus interface is needed to receive data from the vehicle’s factory battery management system.

    The automotive environment adds unique challenges that are not often encountered in DIY projects:

    • High and low temperatures were addressed by choosing automotive grade parts when possible. I also spent a lot of effort making the board operate efficiently to minimize the temperature rise. Multiple temperature sensors help ensure that the board can shut down before reaching damaging temperatures.
    • Moisture may eventually lead to corrosion. This is likely to affect connectors first. So no unnecessary connectors. It may be desireable to apply conformal coat to the circuit board.
    • Vibration is another reason to avoid unnecessary connectors.
    • Serviceability. The circuit board needs to be removable for repairs or modifications. I ended up using a 40 pin IDE connector for this.
    • Safety critical. It’s not likely that rouge data on the Chevy Volt high voltage management CAN bus would cause a collision. This bus is separate from the main CAN bus. What is more likely is getting stranded at the side of the road. The solar charging board should not impede any important vehicle operations. It must be possible to switch off the solar charger board and have the vehicle operate as before. This was accomplished by adding diodes which allow the vehicle’s contactor control signals to pass through. In the event that these diodes interfere with vehicle operation, the solar charger can be quickly disconnected and replaced with a bypass board. The bypass board connects the input signals directly to the output signals.

    Charger board minimum required features:

    • 400v DC regulated and programmable output voltage.
    • 400v DC output to be isolated from solar panels and vehicle chassis.
    • CAN bus and contactor control outputs for the vehicle interface.
    best, dc-dc, chargers, battery, isolators

    Charger board design guidance:

    • All important functionality incorporated on a single circuit board.
    • Preference for vibration resistant SMT parts when possible.
    • A single board with mostly SMT parts is preferable for mass manufacturing as well.
    • A connector to allow the solar charger to be quickly replaced with a bypass board.
    • Pass-through diodes mounted on the vehicle side of the interface connector.
    • A high quality highly flexible interface cable rated for water and oil.

    The PCDB1910 board was designed to meet these minimum feature requirements.

    There’s more than one way to. build a solar car.

    • The easiest way is to add an off-grid solar system to the trunk. Many people have done this. It requires no electrical modifications to the vehicle. There are many downsides.
    • A vehicle is a hostile environment for lithium batteries and inverters. Adding a cooling system adds more cost and parasitic energy losses.
    • The added batteries add weight to the vehicle. Although 12 kg for a single LiFePO4 shouldn’t matter much. The additional energy on board should more than counteract the range loss.
    • Battery degradation ruins the economics of solar charging. Even a cheap LiFePO4 that might last 4000 cycles adds 0.06 per kwh.
    • The charging cable must be plugged into the vehicle’s J1772 port. Charging while driving is not permitted.
    • The overall efficiency of this setup is hurt by converting low voltage DC into 120v AC and then converting the 120v AC into 400v DC. Also, the MPPT charge controller is an additional conversion from 17v to 13v for the battery charging.
    • The vehicle’s on-board charger typically has a maximum power of 3000-6000w. The efficiency of these chargers at 50-300w is likely to be low.
    • This method might also require plugging into the vehicle’s J1772 port, preventing charging while driving. But maybe that interlock could be hacked around?
    • The J1772 standard only allows current down to 6 amps. Maybe the voltage could be reduced to 100v and still charge. An array capable of producing 600w won’t easily fit on the roof of a car. Efforts to reduce that charge current on the Chevy Volt were not successful. The charger output power is controlled by varying the output current. The Volt’s computer adjusts the output current in order to control the AC input current. It is possible to override the output current via CAN bus. But then charging will soon stop when the computer notices a large difference between the commanded current and the measured current. This effort was abandoned due to concerns over point 2.1.
    • Connecting the new charger into an existing vehicle battery is its own can of worms. on that in another update.
    • There is not a lot of suitable electronics on the market to do this. Perhaps a microinverter could be hacked to function as the required DC to DC converter. Remember that microinverters have a complex anti-islanding algorithm that is necessary for safe grid connection. I felt that it was better to put effort into designing a custom converter. The GZF inverter modules seem ideal at first glance, but those have no output voltage regulation. With the high open circuit voltage of a solar panel the converter can output 900v. No way is that thing going on my daily driver! Also, they are wound for a 12v input, not the 17v maximum power point of a 12v solar panel. And they operate at a fixed voltage ratio, preventing maximum power point tracking.

    Build Instructions

    • Solder the 40 pin female connector to the BCI2103 pcb.
    • Cut a 6 foot piece of 25 conductor 20 awg cable. The CF5-05-25 cable has numbered wires.
    • Remove 4 inches of sheath from one end and 6 inches from the other.
    • At the end with 6 inches of sheath removed, strip wires 1-24 leaving 1/4 inch of bare copper.
    • Attach the 33001-3004 terminals to wires 1-12.
    • Slip a cable gland over the cable from the other end which has 4 inches of sheath removed. The exterior end goes towards the connectors. The interior end goes towards the wires.
    • Solder the wires to a BCI2103F pcb according to the wire numbers shown. It might be best to cut, strip, and solder one wire at a time. Some wires remain unconnected. They are needed only to seal the connectors from water.
    • Solder the 1N5819 diodes.
    • Connect the two connectors together and check for continuity across the diodes.
    • Add a small jumper wire or solder bridge to connect the two CANL lines together. And connect the CANH lines together as well. This will ensure the most reliable operation since there is no software to make use of the CAN bridge feature yet. The jumpers allow CAN data to pass through the cable even if the 40 pin connector is disconnected. The diodes allow the contactor control signals to pass through from the vehicle to the battery pack.
    • Wrap the connector end with electrical tape for protection.

    Overall view of the completed cable assembly.

    • Raise the vehicle on a lift or ramps and jack stands.
    • Remove the blue circled nuts on the heat shield. It’s common for these bolts to break, so we will try to not remove all of the heat shield bolts. Fish the Battery Interface Cable down from the top. Connector end goes down. Use the main high voltage supply cables to the inverter as a guide.
    • Unplug the black connector from the battery. Connect the Battery Interface Cable to the matching connectors on the battery and vehicle wiring harness. This connection is shown on a spare contactor module for clarity.
    • Reinstall any nuts removed from the heat shield.
    • Wrap the PCB end of the Battery Interface Cable with an insulating material to prevent the diode leads from shorting to other underhood components.
    • Install the Yakima Jetstream roof racks according the instructions.
    • Get 8x 8×7/8 bracket, 4 for each solar panel.
    • File out the end hole to fit the square part of a 1/4×1 carriage bolt.
    • Drill out the next hole to fit the round part of a 3/8×1 carriage bolt.
    • Slide a 1/4×1 carriage bolt through the bracket and through the frame of the solar panel. Secure with a washer and nut inside the panel frame. It should be tight enough that bracket can be easily rotated by hand but tight enough that it does not rotate under its own weight.
    • Orient the brackets like shown.
    • Slide 4x 3/8×1 carriage bolts through the channel of each roof rack bar. One bolt towards each end of the bar and two bolts near the middle.
    • Place a 1-1/8×0.54×1/8 nylon washer over each carriage bolt. The washers should sit flush on the roof rack bar.
    • Carefully lower each solar panel onto the carriage bolts. The bolts can be slid along the channel and the brackets rotated to find the right positioning.
    • Carefully open the hatch to check for clearance between the hatch and the solar panels.
    • Secure the solar panel brackets with a washer and nut.
    • Tighten all nuts firmly. Remember to tighten the nuts inside the solar panel frame as well.
    • Cut a piece of 14/4 SJOOW cable to reach from the solar panels to the mounting location of the DC-DC charger board.
    • Attach MC4 connectors to one end of the cable.
    • Route the cable under the solar panels but above the roof racks, then down the side of the windshield. Keep it towards the outside of the wiper pivot and run underneath the foam block where an existing wiring harness runs.
    • Optional: Slide a 2 piece of 14/4 SJOOW cable sheathing over the radio antenna to prevent antenna wear against the solar panels.
    • The PCDB2105 was designed for a 72 cell solar array. Since these are 36 cell 12v panels, connect them in series.

    Dcdc charger with solar

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    What is a DC-DC Battery Charger: All You Need to Know

    A stable supply of electricity in your van is vital, especially for long trips. It lights your van, powers up your switchboards and sockets, and activates your fridge, heating system, and water pumps. There are several ways to charge your campervan batteries. The main ways to do that are:

    • Alternator (DC-DC)
    • Solar, and
    • Shore Power (Plugging it in); this requires you have an inverter/charger.

    One component that raises a lot of questions is the DC-DC battery charger. What is a DC-DC battery charger and why do you need it?

    In this article, I’ll cover the following topics:

    • What a DC-DC battery charger is, its function, and its importance.
    • A quick comparison between the DC-DC battery charger and other alternatives.
    • Several popular brand choices for DC-DC battery chargers.

    So, without further ado, let’s get right into it!

    What is a DC-DC Battery Charger?

    Your vehicle’s alternator is what creates the electricity and charges the vehicle battery while you’re driving.

    When you have a campervan, you use that same alternator to charge your house batteries. These are the batteries that are used to power the components inside your campervan (lights, etc) and generally, these will be Lithium or AGM batteries.

    By default from the factory, your alternator is set up to know when your vehicle battery is charged and how much power the alternator needs to put out. It’s not designed to know about the campervan conversion you have going on in the back.

    That’s where the DC-DC Battery Charger comes in.

    Why do You Need a DC-DC Charger?

    The reason you need a DC to DC charger is that most of the time your vehicle battery is a lead acid battery, so your alternator is designed to charge a lead acid battery. The charging profile to charge your house battery is different. So the DC to DC charger tells your alternator:

    In short, the DC-DC Battery Charger is the brain that tells your alternator how to properly charge your house batteries.

    Alternator. DC-DC Battery Charger. House Battery

    Direct Current (DC) Explained:

    Let’s also talk about DC (direct current) in more detail. Direct current, more commonly known as DC, is known for its constant voltage flow. In contrast, AC (alternating current) has a changing flow of voltage.

    While most of our home appliances still work on AC, DC is more efficient and popular in small cars, boats, and vans. With the soaring popularity of solar power in vans, DC and DC-DC battery chargers have emerged as important players.

    • A DC-DC charger (also known as a battery to battery charger) converts the output from your primary battery and charges your secondary battery using optimal charging.
    • Most typically, a single battery or a system of batteries is used to store the converted power.
    • You can use the secondary batteries powered by a DC-DC charger for minor purposes (charging cellphones) and running major appliances such as your fridge.

    Pro-tip: If you are an on-the-go van lifer travelling miles on the road, you can charge your secondary battery via the DC-DC converter quite efficiently.

    How Does a DC-DC Battery Charger Work?

    The DC-DC battery charger uses your van’s alternator (an electrical generator) to convert the available power. It then converts that power to a higher voltage (Ah) for your secondary battery (i.e. your house battery).

    Here’s how the DC-DC charger uses a 3-step process to charge your battery optimally.

    • Bulk: In this step, the DC-DC battery charger converts the current from the alternator and fills in the secondary battery almost to the maximum.
    • Absorption: Here, the power levels off and stabilizes so the battery doesn’t ‘overcharge’.
    • Float: This occurs when the battery is fully charged with its optimal capacity reached.

    What are the Benefits of Using a DC-DC Charger?

    Now that you have a good idea about DC-DC chargers, let’s look at a few benefits of installing one of these.

    Overcome Issues With Smart Alternators

    Most vans now come with Smart alternators designed to minimize power output. This means they cannot charge a secondary battery with their load restriction. A DC-DC converter takes care of this problem by isolating the main battery from the alternator.

    Maximizes Main Battery Charge

    Another benefit of installing a DC-DC battery charger is its ability to maximize the charge of the main battery. The charger can convert an amperage of as low as 9 volts up to 13.5 volts to charge the main battery quickly and efficiently. You can get close to 100% charge on your main battery with a good day of driving.

    Works Without Solar Power

    DC-DC chargers are also a blessing in disguise if you mainly travel in areas without a lot of sunlight. DC-DC chargers can help charge the auxiliary battery to power your gadgets without worrying about solar power or other energy backup options.

    Adapts to Different Batteries

    One of the most important benefits of a DC-DC battery charger is that it adjusts for different battery types. This is useful as it can save you the time and cost of buying a different charger every time you replace your battery.

    A DC-DC charger also adjusts the power based on what the battery is used for, minimizing damage to the battery through overcharging.

    Can I Use a DC-DC Charger with Lithium Batteries?

    Yes, you can definitely use a DC-DC charger with lithium batteries as it can optimize your battery life. A DC-DC charger can also extend your lithium battery life.

    • Lithium batteries absorb the maximum amount of power available which can quickly become an issue if you are charging directly from an alternator. This is because if the alternator already has a significant load, the lithium battery will add to this load, causing the alternator to burn out.
    • A DC-DC charger effectively manages the power input in a lithium battery, making sure it doesn’t heat up when overcharged.
    • These batteries also have a different restart process and specific battery chemistry, making it difficult to charge them through alternative means such as an alternator.

    If you are still deciding between AGM v Lithium batteries, this informative article can help you make the right decision: AGM vs Lithium, Which Battery is best for Van Life?

    What Size DC-DC Charger Should You Get

    Most commonly, batteries up to 200Ah require a DC-DC battery charger of around 25Ah. For ampere-hours exceeding 200, a 40-ampere DC-DC battery charger will work better.

    If your alternator has a 200 amp rating, you’d want to take that number, and cut it in half and that would be the charged power. The reason it’s recommended to run it at 50% is that you never want your alternator to be running at its maximum output load because it’s really hard on the alternator and it wears them out.

    To select the best size for your DC-DC charger, you should consider the following:

    • Alternator Size: Typically, alternators range between 60 to 150Ah while DC-DC chargers vary between 6 to 40Ah. You need to get a larger charger for optimal usage if you have a high-powered alternator with more capacity.
    • Battery Type: A DC-DC charger rated 20% of your battery’s amperage would work fine for conventional batteries such as AGM and lead-acid batteries. With a lithium battery, you can go higher, to almost 30% of your battery’s rated amperage.
    • Voltage: It is recommended to match your charger with your van’s electrical system. For example, if you have a 12-volt system (which is most common), you should go for a 12-volt DC-DC charger.
    • Usage: Your energy usage also plays a part in determining your DC-DC charger size. If you use several appliances with your auxiliary battery, you will need a DC-DC charger.

    Popular DC-DC Charger Brands and their Cost

    Now that you have an idea of how DC-DC battery chargers work, you may wonder which is the best brand to buy. To give you a heads up, several good brands are out there catering to different customer needs.

    Here’s how they measure against each other.

    Red Arc (Our Recommendation)

    In my opinion, Red Arc is the brand that you should go for. There are a few key features that set this brand apart.

    • It works smoothly with several battery types, including GEL, AGM, and lithium.
    • Includes additional features such as solar regulation, allowing users to prioritize charging options from different power supplies (solar vs. battery).
    • It has a reliable built and can stand up to extreme temperatures and climate.
    • Works with both 12 volts and 24-volt system


    Victron DC-DC chargers such as the Orion-Tr Smart isolated/non-isolated are one of the most popular brands in the market right now with the following features:

    • Works well with both 12-volt and 24-Volt systems and lithium and lead-acid batteries.
    • Includes Bluetooth so you can control the power settings from the comfort of your cellphone via an application.
    • It is durable and can adapt to high temperatures.

    Price: The Victron Orion-Tr Smart 12 V 30 Amp Non Isolated costs around 230.


    Sterling is another popular name that many van enthusiasts choose when it comes to DC-DC battery chargers. Here are its key features:

    best, dc-dc, chargers, battery, isolators
    • It comes in three variations: 40 A, 70 A, and 120 A with a 12 Volt option, hence catering to a large variety of customers
    • Works well with Smart alternators with an in-built vibration sense mode.
    • It is Lithium compatible and includes a low-temperature trip for lithium-ion batteries.

    Price: The Sterling Power Pro Ultra Charge costs 350 with a 5-year warranty.


    Renogy is known for its cheap yet decent quality in the market. Here are some of its best features:

    • Its flexible design ensures the safety and improves usability in different conditions.
    • Renogy offers several layers of safety, including over-voltage and reverses polarity protection, safeguarding the batteries from overcharge.
    • It is compatible with lithium, lead-acid, and AGM batteries.

    Price: The Renogy 12V 40A DC to DC costs around 160, while the Renogy 12V 60A Dc to Dc costs approximately 200.

    Key Takeaways

    Here’s a brief overview of what this article discussed:

    • The DC-DC Battery Charger is the brain that tells your alternator how to properly charge your house batteries.
    • A DC-DC charger can maximize charging to 100% and optimize your auxiliary battery’s life.
    • Lithium batteries work well with DC-DC chargers as it efficiently manages the power input.
    • A DC-DC charger size depends on your usage, voltage, and battery life. As a general rule of thumb, a 200 Ah battery requires a 25 A DC-DC charger, while bigger batteries require a 40 A charger.
    • Recommendation : You should choose RedArc to buy the best DC-DC charger suited for your needs.

    Now that you have sufficient knowledge on this subject, you can confidently choose the best DC-DC charger that suits all your needs!

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