Single high amp BMS or two BMS in parallel?

[Visionquest]

I'm going to build a 280aH Lifepo4 battery using sourced cells and BMS. Remaining concern is cranking power for the ONAN5500 genny in my RV. The cells can do 2C (560amps) for 30 seconds which exceeds the expected 350amp max cranking amps that the 5500 might want.

Anyone have experience with a 12v BMS that can do 350amps for 30 seconds? Alternatively, does anyone have experience putting two BMS's in parallel to pull more amps from a single battery? If I use 200amp BMS's it would theoretically support 400amps cranking power. My thought is that two BMS's is much cheaper than building a second battery, plus I have space constraints.

Thanks in advance.

 

[k490]

Why not use a lead acid start battery to start the generator they do a much better job of that. Probably could get a smaller one. I don't know much about RV generators how they start up. I just assumed it has a small starter uses a lead acid battery.

 

[BentleyJ]

A BMS that controls an external contactor rated for 400A is a simpler, cleaner solution for high current use cases.

 

[Ampster]

Alternatively, does anyone have experience putting two BMS's in parallel to pull more amps from a single battery?

My first experience with a high Amp BMS was with an EV conversion which used a contactor. That is the only way to deal with high currents because the FETs in BMSs do not do well with high Amps. Also I think the balancing circuits would not work well with two BMSs in parallel because when one BMS is shunting current the other parallel BMS would get confused and they may not be able to effectively do their job to keep the individual cells balanced.

 

[MacGyver]

Why can't you use the RV starting battery to start the ONAN5500 genny?

 

[Checkthisout]

Like others have said, just use a 12V battery and charge it using any number of devices that convert 120-12 or 48-12.

Your existing 12v converter is overkill but would do the job just fine for free.