Saturday, September 30, 2023


Can lithium batteries start my RV’s onboard generator?

Dear Dave,
I just read your article about dead batteries not starting an Onan 6500 diesel generator. You said you replaced them with TWO lithium batteries. I have an Onan 5500 LP generator and the spec calls for batteries that can supply 440 CCA [Cold Cranking Amps] to start the generator. I have read articles where people have replaced their RV’s batteries with lithium batteries, and they are not able to start a generator. What capacity lithium batteries did you use to start the 6500 KW diesel generator? What would you recommend for a 5500 KW LP generator? I don’t want to install lithium and find out they can’t start the generator! Thanks. —Charles, 2015 Cardinal 5th wheel

Dear Charles,
The article you are referring to was referencing a 6500 diesel generator that quit running while driving and the two lithium batteries I replaced were in a 2015 Thor Challenger with a 5500 Onan gas generator.

Interesting responses from lithium battery companies

Thank you for the question, as it required more research and some interesting responses from different lithium battery companies and forums.

Battle Born Batteries, from Dragonfly Energy whose batteries are used in all Keystone RVs, has a video on their FAQ website that has a guy standing by a workbench that states their lithium batteries do have enough Cold Cranking Amps (CCA) to start an onboard generator. However, they provide no data or other verification.

Here is what I received today from Expion 360:

Our lithium batteries are deep-cycle batteries. They are not cranking batteries. If you are wanting to replace the house batteries in a motor coach that has an onboard generator, we suggest keeping one of the AGM or Lead Acids to start the generator or moving the generator to pull from the starting battery. If you have any other questions, please let me know and I will get you the information you need.

Dakota Lithium Batteries claim to have 1000 CCA and will start an onboard generator, according to their website. But there is no data to back it up or verification.

RELiON goes a little deeper into the data:

Do Lithium Batteries Use Cold Cranking Amps?

Generally speaking, most lithium batteries rely on ratings related to peak current (20°C/68°F for 5 to 10 seconds), as opposed to CCA. The RELiON RB100, for example, is rated at 200A for 5 to 10 seconds. The CCA rating is mainly used to understand how much current a battery can provide when rapidly starting or cranking an engine in cold temperatures, while still maintaining the requisite voltage. For ratings related to deep cycle storage or long-term use and storage, the CCA rating is not as useful or relevant.

It is important to note though that some lithium batteries are actually dual-purpose, providing both cranking and deep cycling. The RELiON HP Series lithium battery does just this, as it has the ability to act as a source of power for the trolling motor and electronics on a marine vehicle and also provides the power needed to start the motor.

Lion Energy sent this response;

Thank you for writing in. The UT1300 BT batteries can easily start the 5500 watt generators used in RV’s. No specific data collected other than the engineering team, employees and customers using the UT1300 batteries in their RV’s. When the battery gets low, the UT1300 still has enough energy to start the generator.

It depends on the Battery Management System

So what I found is that it depends on the Battery Management System (BMS) within the battery, which may or may not allow full cranking power to the generator. The dual purpose ones like the RELiON seem to be the best. The two Expion 360 batteries we installed in the Thor Challenger are working fine. Most BMS will only allow 100 CCA, so you would need to connect several parallel to get 450 CCA.

Do you really need 450 CCA for a 5500 LP generator? From what I found on most Onan sites is the 10KW diesel pulls that much power, and the 5500 should only need about 360. But you still might not be able to start it with only two 100 AH lithium batteries. Every generator is different in how well it turns over and how fast it starts. I can tell you the Generac in my father’s old Vectra needed a ton!

A workaround

What I also found on several forums is that most who are having an issue starting the onboard generator simply start the engine and the power coming from the alternator works fine. Or just press the booster button. Not the most ideal situation, but a workaround.

So here is another question that came up. If the lithium battery has poor CCA power available, how can it/they be used in a motorhome situation to “jump start” the engine, especially in the case of a diesel?

I’d love to hear what others have to say.

 You might also enjoy this from Dave 

Do’s and don’ts when replacing RV batteries

Dear Dave,
We’re beginning our 5th year full-timing in our Vilano. I suspect we may soon need to replace our two 12-volt batteries. I would like to know what to look for in choosing replacement batteries. I’d also like to know the correct procedure to remove the old batteries and install the new ones, including the do’s and don’ts and things to watch out for. Thanks. —Bob, 2018 Vanleigh Vilano 325RL

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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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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Dan Haumschild
1 month ago

I installed 2 Battleborn 100ah lithium batteries and they start my 4k generator no problem. They seem to start it quicker than my AGM batteries did.

1 month ago

You’d think that for the price they’d be capable of much more.

Walt G.
1 month ago

I replaced my 2 6 volt agm deep cycles with 2 – 12 volt Redodo lithium self heating and they do start my onan 4 kw gas gen.
My gen takes a bit of cranking to start and after a few short tries it fires up. So far so good.

Neal Davis
1 month ago

Thank you, Dave! I plan to only replace the house batteries with lithium and only when the house batteries begin to quickly lose their charge. I plan to always (?) run AGM batteries as the chassis batteries. Thank you for raising the question of boosting the chassis batteries with the house batteries. I hope to keep the weight and footprint of the chassis batteries similar after replacement, implying greater house battery capacity. Also I regularly check the chassis batteries to avoid being surprised by dead starting batteries.

Last edited 1 month ago by Neal Davis

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