Thursday, June 8, 2023


Ask Dave: Can I just swap my RV’s Interstate batteries with lithium?

Dear Dave,
Can I just remove my RV’s two Interstate 12-volt batteries and install 2 new lithium 100 Ah batteries? —Paul, 2018 Cedar Creek Hathaway 5th wheel

Dear Paul,
It is not wise to just replace the old lead acid or AGM batteries in your rig with lithium without checking to see what type of charger you have. According to the owner’s video Forest River has on their site, they use a WFCO converter that is a standalone model and can be several places inside the unit. We just upgraded a Thor Challenger with lithium and had to do some research to find where it was. It was finally found under the bed pedestal.

We started underneath the bed and removed the false panel and only had access to the water heater. Then we pulled off the mattress and found this access panel and still had to remove the hinged platform to get access to the converter.

This converter simply charges the batteries at 13.6 volts for several hours until they reach 12.6 volts and then drops to a maintenance charge of 13.2 volts. This will not hurt your new lithium batteries. However, it will not charge them sufficiently and will take a long time. So you will pay $1000+ for each battery and only get 65% usage. I have also found these under kitchen cabinetry, so plug the unit in and listen for the distinctive hum of the fan.

Does the RV have a larger inverter?

Another consideration is if your unit has a larger inverter. I believe it does for the residential refrigerator that is in some of the units. The larger inverters will also charge the batteries and may have a multistage charger that starts with a bulk charge of 16 volts to break up sulfation in lead acid batteries. That will not be good for your new lithium batteries. Ours had a Xantrex Pro 1800, which we found in one of the outside compartments. But it did not charge the batteries; it just powered the two TV outlets and a few more. We unplugged the rig and found the refrigerator light went off, so we knew it did not power the refrigerator.

The next thing to check is if you have a solar panel system and charger. These can also provide either a bulk charge or insufficient charge.

Make sure the cable is heavy enough

We elected to replace the WFCO with a Progressive Dynamics model designed for lithium. We worked with Dennis in the technical department to verify the correct charger as well as the right gauge wiring from where our converter was located running to the batteries. Since we had over 20 feet, we needed to make sure the gauge would be sufficient for the higher voltage. Luckily, Thor had used a heavier-gauge wire, so we were fine.

It’s important to verify your cable is heavy enough to handle this, as well. Here is the new converter in the rat’s nest that Thor has under the bed pedestal. This model also has a charge wizard that allows the owner to set the desired function, including storage.

The last consideration is a quality lithium battery, as there is some real junk out in the market. We have been researching for a couple years now, as lithium has gotten more popular, and went with the Expion 360. We came across this through Zamp Solar, who we have been working with for more than 6 years. The founder of Zamp Solar sold the business to Dometic, and started Expion 360, as his own RVing trips were not going well with some of the poor-quality batteries.

Their batteries use only high-quality cells that are connected mechanically. They are not soldered, as the solder will not hold up with the rigors of the RV road. Many of the cheaper lithium batteries are made overseas and designed to sit in a climate-controlled residential setting. Do your homework and check out Expion 360 here.

Before and after the lithium battery

Here is the set of Interstate 6-volt batteries connected in series that were shot and the new lithium batteries with 200 Ah capacity!

Oh, and one more thing. Do you need a DC to DC charger that will protect your engine alternator or, better yet, protect your lithium batteries from a large alternator in your tow vehicle going down the road? To find out if your vehicle needs this, visit Expion 360 and check out the technical section.

For further information watch this video from electricity expert Mike Sokol: RV Electricity – Just Ask Mike (J.A.M.): Can you just “drop in” lithium batteries?

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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4 months ago

You can upgrade your WFCO to accept Lithium…I installed two battleborn 100amp and upgraded my converter…it’s just a plug in and not hard to do…also do look into a dc to dc charger…I run a Mercedes sprinter and did not want to toast my alternator..

Steve K
1 year ago

Short answer to the question: Yes, providing the charging unit will work with Lithium batteries. A new charger isn’t expensive. Top of the line Battle Born Lithium batteries are now priced below $900 and are one of the best on the market. Expion 360 units are more expensive and Zamp Solar is an expensive way to go solar. Do more research.

Wayne Thomas
9 months ago
Reply to  Steve K

And the Battleborn batteries will fully charge at the 13.6 volts the converter puts it, so you would only replace that IF you wanted them to charge faster.

1 year ago

Try Battle Born brand batteries as they’re made in Reno, Nevada. All lithium cells come from China but the quality of the battery comes from the way the company manufactures the end product. 95 percent of the China made batteries are GARBAGE. Choose wisely.

David V
1 year ago
Reply to  Crowman


Roger Spalding
1 year ago
Reply to  Crowman

I conversed, via email, with a Dragonfly/Battleborn service engineer just a couple of weeks ago. He assured me that Battleborn now sourced all of its lithium from mines in Nevada, and elsewherein the US. It still had some empty cells in inventory from China which it was going to use up shortly. Afterwards, all cells at Battleborn would be assembled in America with American mined lithium. The “Made in America” stickers are very important to BB ownership and management. Genocide of the Uyghurs, child slave labor and oppression of Hong Kong are enough to stop many American companies, like BB, from doing business with the Chinese Communist Party. Nike, the NBA,General Motors, Ford and Microsoft are just a couple of American companies which condone human exploitation and suffering.

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