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Old 03-24-2022, 12:39 PM   #1
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Lithium battery won't crank my Onan generator

I bit the bullet and purchased an Expert Power 200 Amp Hour Lithium (LiFePO4) battery to replace the two 100 AH wet cell batteries that came with my Leprechaun 260-D. In addition, I upgraded my converter to accommodate the higher voltage required for the Lithium battery. I connected the motor home to shore power for a couple of weeks, the voltage now is 13.29 volts. Today I go to start my Onan generator on battery power only and the generator starter doesn’t turn the generator over and the lights flicker. To start the generator, I had to start the motor home engine. I called Expert Power and they claim this is normal, the BMS is limiting the current to the generator starter. Is this what I should expect?

Thanks in advance for your replies.
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Old 03-24-2022, 12:59 PM   #2
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That sounds like it's possible. What is the amp rating on your BMS as well as the discharge rate on your lifepo4 battery? To be perfectly honest I never even thought it would be an issue but I did hear of another person on another Forum have the same issue. Just can't remember which forum.
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Old 03-24-2022, 01:57 PM   #3
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yes, i have read the same in a couple of posts. your 200 amp hour battery may well be limited to 100 amps max discharge by the internal bms. i'm not saying this will work but see if you can exchange it for a couple of 100 amp hour batteries wired in parallel. this will give you the same amp-hour capacity but will probably give you a max of 200 amps of max discharge.

I'M NOT SAYING THIS WILL WORK. YOU'LL NEED TO CHECK THE BATTERY SPECS AND THE GENERATOR STARTING AMP RATING.

this is a concern for lithium batteries. they have lots of capacity but not as much max discharge capability as lead acid batteries
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Old 03-24-2022, 02:16 PM   #4
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Smile

Thanks for getting back to me.
The maximum discharge current is 150 amps. Maybe the generator pulls more than this when starting.
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Old 03-24-2022, 02:19 PM   #5
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Originally Posted by CHICKDOE View Post
yes, i have read the same in a couple of posts. your 200 amp hour battery may well be limited to 100 amps max discharge by the internal bms. i'm not saying this will work but see if you can exchange it for a couple of 100 amp hour batteries wired in parallel. this will give you the same amp-hour capacity but will probably give you a max of 200 amps of max discharge.

I'M NOT SAYING THIS WILL WORK. YOU'LL NEED TO CHECK THE BATTERY SPECS AND THE GENERATOR STARTING AMP RATING.

this is a concern for lithium batteries. they have lots of capacity but not as much max discharge capability as lead acid batteries
Yes two 100 Amp hr batteries would work according to Expert Power the LiFePO4 supplier. Only problem is my battery box is an inch too short to accommodate two 100 Ah batteries.
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Old 03-24-2022, 03:18 PM   #6
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i don't know what generator you have. we have an onan 5500 and the specs for it say it should have 450 amps to start. i have tried to monitor this and i only see it using a couple hundred amps when it tries to start. but probably the colder it is the more amps it will take to turn it over. plus ours is lp fueled so there is no load from a fuel pump which is probably included in their spec.

also many lithium batteries can provide a high current for a shot period of time before they cut the current down. i'd look real hard at you battery and see if you can exchange it. a couple in parallel that can provide a high current for 10 seconds or so might work.

BUT AGAIN I CANNOT GUARANTEE THIS!

i know there are people out there that start generators with lithium batteries. i just don't know what generator, what batteries, and how many.

the battery company should be able to give you a better idea than 'this is normal'! what do they suggest as a solution?
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Old 03-24-2022, 03:24 PM   #7
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Now you've got me wondering if the battery I am building will have enough power to start my generator. I have an Onan 4000 I am building a 12-volt lithium ion battery with 304 amp hours. It says it's discharge rate is .5c which should give me somewhere around a hundred and fifty amps. My bms is 200 amp. Fingers crossed, I guess. I guess worst case scenario I have to buy another set of cells to make a 608 amp hour battery.
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Old 03-24-2022, 03:39 PM   #8
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how many cells are you using to make the 304 amp hours? do you have the option to make 2 152 amp hour batteries and connect them in parallel? all it would require is a 2nd bms and case. that would give you 300 amps between the two.
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Old 03-24-2022, 05:52 PM   #9
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I just got the cells so kinda stuck with them. after I top balance I'm going to see if it works. If it doesn't, I might need to look at a second set of cells and arrange them either them 2p 4s (1 bms) or 4s 2p (2 bms's).
I think I worded that right.
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Old 03-24-2022, 07:50 PM   #10
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One option would be to install a L/A battery just large enough to start the generator then steal a trick from plug-in hybrid cars.

My Volt has an AGM 12v battery that starts the engine when needed and powers the 12v accessories. It's charge is maintained by the main 360 volt lithium battery through a DC-DC charger. A battery for a riding mower, small farm tractor, or "Harley-" should start the generator.
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Old 03-24-2022, 07:52 PM   #11
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Most Lithium battery manufacturers flat out state that their deep cycle Lithiums should not be used for starting generator engines. Some manufactuers (such as Dakota Lithium) make dual purpose Lithium batteries that can be used for deep cycle and starting.

Easiest way to determine if a Lithium is "dual purpose" is the manufacturer will list both Amp hour rating and Cold Cranking Amps rating. Otherwise look at spec sheet and most 100 amp hour Lithiums will only list max discharge of 100Amps.

Typcial Onan generator you should probably plan on having at least 450 CCA.
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Old 03-25-2022, 12:33 PM   #12
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Does this make sense...small Lithium jumper box

There are a bunch of small Lithium Emer car jumpers boxes out there that I have to believe will start a generator. Wonder if you could install one permanently in parallel or on a relay to solve this.

I don't know at all. Does anybody have enough familiarity with these things to educate us???
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Old 03-25-2022, 01:00 PM   #13
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There are a bunch of small Lithium Emer car jumpers boxes out there that I have to believe will start a generator. Wonder if you could install one permanently in parallel or on a relay to solve this.

I don't know at all. Does anybody have enough familiarity with these things to educate us???
Currently to crank over the Onan 4000 I just start the motor home engine, so I don't plan to hook up an auxiliary battery just to crank over the generator. My surprise is the 200 AH Lithium would not crank the generator. Live and learn.
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Old 08-06-2022, 12:26 PM   #14
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This thread is educational. According to these comments, changing my Forester's house batteries to LiFePo would allow longer boondocking but would eliminate the emergency start feature if the engine battery died. I suppose I could carry a boost box.
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Old 08-06-2022, 12:52 PM   #15
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Hmmmmmm..... Makes me rethink Lithium batteries.

After reading this thread, I looked again at the Coachmen Crosstrails that I've been looking at. They have a 400AMP AGM or an optional 800AMP Lithium Ion. I wonder if the higher AMPs are required to start their generators with lithium.

(and in a 'back to the future' moment, they are installing 3 way refrigerators in the rigs) and they have inverters and Renology 'state of the art' which can operate everything, including A/C from the battery.
Not ready to buy, but the upgrades are interesting.
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Old 08-06-2022, 09:48 PM   #16
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Originally Posted by Reverse_snowbird View Post
Hmmmmmm..... Makes me rethink Lithium batteries.



After reading this thread, I looked again at the Coachmen Crosstrails that I've been looking at. They have a 400AMP AGM or an optional 800AMP Lithium Ion. I wonder if the higher AMPs are required to start their generators with lithium.



(and in a 'back to the future' moment, they are installing 3 way refrigerators in the rigs) and they have inverters and Renology 'state of the art' which can operate everything, including A/C from the battery.

Not ready to buy, but the upgrades are interesting.
The issue isn't so much the lithium battery's capacity as much as it is the BMS. Depending on the starter current, especially on a cold engine) the current may well exceed the max discharge current alliwed by the BMS.

More a priblem with single batteries which may have <200 amp discharge BMS's. Not so much with multiple batteries in parallel.

Similar to what some experience with 200 ah batteries with BMS limitedvto 100 amp continuous discharge when attempting to run a microwave.

If a generator mfr recommends a 400 cold cranking amp battery I think I'd want a minimum of 400 amp max discharge rated BMS ability. Enough LiFePo4 batteries in parallel should do the job. Too few and overcurrent shutdown is likely.
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Old 08-08-2022, 04:50 PM   #17
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I have a Cummins/Onan 5500 Watt Propane Generator. I bought a NOCO NLP9 400 CCA Lithium Starter Battery from Walmart. I think it was $86. Also the NOCO 1 AMP Charger that I leave plugged in all the time.

Works great!

FYI, there was a guy that did a test and measured the current to start the generator at about 40 degrees F. It was a little over 100 amps. At 0 degrees I think it would be much higher.
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