Q&A: DC to DC Battery Chargers FAQ (Frequently Asked Questions)

Q&A: DC to DC Battery Chargers FAQ (Frequently Asked Questions)

Wagan Tech3/29/23

by: Justin Gray

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:

25A DC to DC Battery Charger (#7410)
40A DC to DC Battery Charger (#7411)



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, please 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 work
These 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.

1 - 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.

2 - 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.

3 - 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.

4 - 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.

5 - 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.

6 - 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.

7 - 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.
Dc charger light chart troubleshooting

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.
DC charger mounting plate dimensions size

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

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.

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)wagan.com or 1.800.231.5806


Meet the models:

25A DC to DC Battery Charger

40A DC to DC Battery Charger

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