RV Onan 5500 LP Starting with Lifepo4 Batteries

[Partimewages]

Has anyone used their Lifepo4 batteries to also start their on board generator? My assumption would be that the BMSs would need to be rated for a short amount of surge current.
Any experience would be helpful.

 

[0truck0]

It might do it, but some say it can damage the battery over time. 450 cranking amps might be what your 5500 ask for. A lot for the typical lithium to put out at once.

For a motorhome you could connect it to the vehicle starting battery, should be no danger of depleting the vehicle starting ability, and gen will trickle charge the battery when running too.

Have you seen the lithium jump start emergency packs? They are small brick sized lithium packs that will jump a dead vehicle. I just did a friends Ford v-8 Explorer and it did not even struggle. You could use one for the gen battery, and they are cheap on ebay.

 

[Partimewages]

It's a 5th wheel. But the jump starter idea is one I've been thinking about.

 

[BobH]

The generator cranking draw & my hydraulic levelers are the reason I kept my AGM battery connected to the 12v side in my RV.

 

[fmeili1]

My Onan QG 4000 cranks with about 80A and the inrush is 280A with my 12V DIY LiFePO4 battery, 280AH using a 200A JBD BMS.

 

[eXodus]

Has anyone used their Lifepo4 batteries to also start their on board generator? My assumption would be that the BMSs would need to be rated for a short amount of surge current.
Any experience would be helpful.

Yes, I am starting my 2002 Onan 5500 from a single 100AH 12v LFP battery with 100A BMS which supports 200A for 5 seconds. So I just be mindful when it does not start right away to stop and wait.

On the Bluetooth BMS it usually stays under 100A for cranking.

You might just want to get a clamp on meter and crank your generator from you current lead batteries and see what it draws.

 

[Partimewages]

Yes, I am starting my 2002 Onan 5500 from a single 100AH 12v LFP battery with 100A BMS which supports 200A for 5 seconds. So I just be mindful when it does not start right away to stop and wait.

On the Bluetooth BMS it usually stays under 100A for cranking.

You might just want to get a clamp on meter and crank your generator from you current lead batteries and see what it draws.

Thanks,
I'm changing my 10 year old Fullriver DC224s to lifepo4s. I'll have 2 in parallel but could go up to 4. I'll try with the two and post results.
Figured I'd ask first and get an idea of maybe what to expect.

 

[eXodus]

450 cranking amps might be what your 5500 ask for.

those amps are always related to lead batteries which drop in voltage (8-10V) quite a bit when cranking. LFP stays much more stable - thus need less cranking camps

A starter has a total amount of Power in Watt - the highest I saw for the Onan 5500 was 350 CCA and depending on the model as low as 200 CCA Not sure where the 450 CCA are coming from - that's as much as 4 cylinder car engine needs. And not that tiny 2 cylinder generator.

Lets to some rough math - a 350 CCA * 8V = 2800W starter motor,

Now assuming the LFP stays at 12V instead of dropping to 8-10V like lead tends to do.
2800W / 12V = 233A

My Onan QG 4000 cranks with about 80A and the inrush is 280A with my 12V DIY LiFePO4 battery, 280AH using a 200A JBD BMS.

your values check with my general math on generator capacity.

 

[eXodus]

Thanks,
I'm changing my 10 year old Fullriver DC224s to lifepo4s. I'll have 2 in parallel but could go up to 4. I'll try with the two and post results.
Figured I'd ask first and get an idea of maybe what to expect.

worst case the BMS shuts you down, Not sure how often you start your generator - but for me it's like every couple of weeks - so I am not worried about longevity of the battery.

 

[justinm001]

It's dumb to have your house batteries start your generator anyways. If they're dead then you can't start the generator to charge and get power.

My coach has its own 12v battery and so do all Prevost and other large ones. Keep the system separate with its own 12v battery then babe a 120v to 12v charger to keep the battery topped off.

This way if your house is dead you can start. If the generator 12v is dead you can use jumper cables and hookup to your truck.... Probably use the lithium and let it charge the sla battery.

 

[fmeili1]

It's dumb to have your house batteries start your generator anyways. If they're dead then you can't start the generator to charge and get power.

My coach has its own 12v battery and so do all Prevost and other large ones. Keep the system separate with its own 12v battery then babe a 120v to 12v charger to keep the battery topped off.

This way if your house is dead you can start. If the generator 12v is dead you can use jumper cables and hookup to your truck.... Probably use the lithium and let it charge the sla battery.

This does not happen if coupled with a solar array on the coach... I'm very happy with the replacement of my two 12V 100AH lead acid house batteries with my 12V DIY 280AH LiFePO4 battery. The generator starts without any issues and in case they would really sucked empty in the night, I just need to wait a bit in the sun. Even with a bit of charge, the LFP's can start the generator with nice fast crank (because of low voltage drop).

At the beginning of my coach conversion to LFP, I also was a bit skeptical about the generator cranking... but after some tests I've decided to get rid of the old lead acid completely for the house batteries.

 

[Partimewages]

worst case the BMS shuts you down, Not sure how often you start your generator - but for me it's like every couple of weeks - so I am not worried about longevity of the battery.

I should start every month. Reality every 6 months to exercise.

 

[Partimewages]

It's dumb to have your house batteries start your generator anyways. If they're dead then you can't start the generator to charge and get power.

My coach has its own 12v battery and so do all Prevost and other large ones. Keep the system separate with its own 12v battery then babe a 120v to 12v charger to keep the battery topped off.

This way if your house is dead you can start. If the generator 12v is dead you can use jumper cables and hookup to your truck.... Probably use the lithium and let it charge the sla battery.

It on a 5th wheel.

 

[justinm001]

This does not happen if coupled with a solar array on the coach... I'm very happy with the replacement of my two 12V 100AH lead acid house batteries with my 12V DIY 280AH LiFePO4 battery. The generator starts without any issues and in case they would really sucked empty in the night, I just need to wait a bit in the sun. Even with a bit of charge, the LFP's can start the generator with nice fast crank (because of low voltage drop).

If you have solar running then the generator isn't really needed and you'd have to wait until either there's enough solar and charge to start or preemptively start the generator. I wouldn't want to wait all night then all day on a stormy day to get power.

Also our generators might be a bit different. Mines a 20kw diesel powered from a Kubota engine that's in tractors and skidsteers.

 

[Partimewages]

FYI
This is a no solar system right now.
The post was just too see if anyone had a similar setup and what they had to do.
Thanks for all the comments!

 

[fmeili1]

Also our generators might be a bit different. Mines a 20kw diesel powered from a Kubota engine that's in tractors and skidsteers.

ok this is a different league

 

[Checkthisout]

It's dumb to have your house batteries start your generator anyways. If they're dead then you can't start the generator to charge and get power.

My coach has its own 12v battery and so do all Prevost and other large ones. Keep the system separate with its own 12v battery then babe a 120v to 12v charger to keep the battery topped off.

This way if your house is dead you can start. If the generator 12v is dead you can use jumper cables and hookup to your truck.... Probably use the lithium and let it charge the sla battery.

Kind of.

RV's have always been setup so the alternator charges the house batteries and have an emergency start button so the engine can be started off the house batteries if needed.

Did yours come different?

 

[justinm001]

Kind of.

RV's have always been setup so the alternator charges the house batteries and have an emergency start button so the engine can be started off the house batteries if needed.

Did yours come different?

Some have that and it uses a relay to turn on the connection when either side has a charging voltage. They also use the house battery to start the generator. It's a dumb cheap way to just connect everything together, but if one dies then they all do.

No mine didn't come that way. I did have a gen merge option to connect my generator battery to the house battery but that was more for storage. My coach is commercial so has a bunch of redundancies, some entertainer ones even have dual 20kw generators just incase one doesn't work.

I have a separate chassis, generator, 12v house and 48v house system. Even have a shunt on the generator battery to monitor its voltage and use that aux to monitor my chassis. Have separate 120v chargers for them all.

 

[Partimewages]

@justinm001
You need to post some pictures of your rig!

 

[justinm001]

@justinm001
You need to post some pictures of your rig!

They're on here scattered. BTW I live just north of Columbus in Delaware and work in Worthington, so if you ever see a big shiny metal bus it's likely me

Here's the listing when I bought it a year ago

2008 Prevost XLIIDouble Slide # 49482

prevost-stuff.com

Current build info

Captains 08 Prevost XL2 renovation build - iRV2 Forums

Bought this coach back in May and am working on a slow full rebuild. https://prevost-stuff.com/2008Prevos...ley032022.html We do a ton of weekend and day trips, mainly to auctions and various other

www.irv2.com