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;

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. 

HAVE A QUESTION FOR DAVE?

We have a popular forum for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.

##RVDT2182