Starting my Onan 4k with my LIfepo

[GSXR1000]

I am building 2 batteries (272AH) with 2 120A BMS. How much stress will it put on my BMS? It does pull 245A for a split second. then quickly goes way below 100A.

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[snoobler]

Assuming it can be distributed between the two BMS evenly, it might be fine. Of course, that depends on if the BMS can handle its rated current. They also have a surge current, but it's likely a much shorter duration.

I also don't know that I'd trust that the peak is only 235.8A since a meter NOT in inrush mode likely won't capture the inrush peak with the MAX function, and I don't know if the inrush function in AC mode would capture the peak current either.

The inrush on a motor is typically 4-10X the run current, so my gut says the low end of your actual peak current is > 300A based on a running current of about 77A. I wouldn't expect the BMSs to handle it.

 

[GSXR1000]

115 A was in rush.. so the DC motor might be acting differently ?

 

[GSXR1000]

my plan is to put a 200A fuse strait to battery to generator starter solenoid. then i separate wire to the generator controls so if bms opens it won't engage the solenoid

 

[GSXR1000]

also I bet the amps will be lower in Lifepo due to lack of voltage sag and 3x AH

 

[snoobler]

also I bet the amps will be lower in Lifepo due to lack of voltage sag and 3x AH

That's a good point.

Note that a 200A fuse may not blow even with much higher current as it's a function of overload and time. It might handle 300A for a few seconds.

 

[GSXR1000]

That's a good point.

Note that a 200A fuse may not blow even with much higher current as it's a function of overload and time. It might handle 300A for a few seconds.

yes but I will have 550A @ 1C and they can handle 2C for short duration...

 

[GSXR1000]

nevermind max is 1C

 

[HRTKD]

The Overkill Solar version of that BMS can be ordered with three wires instead of two and 8 gauge instead of 10 gauge. That should help with the throughput.

I'm running a synthetic 0w-30 in my 5500w generator. It seems to start a little easier with that oil than what Onan specs out.

 

[GSXR1000]

The Overkill Solar version of that BMS can be ordered with three wires instead of two and 8 gauge instead of 10 gauge. That should help with the throughput.

I'm running a synthetic 0w-30 in my 5500w generator. It seems to start a little easier with that oil than what Onan specs out.

way too hot here in Texas for a 0 weight oil... lol.
I run royal purple 10-30
I am thinking with lifepo lower internal resistance it will start much easier.. also 550 AH of battery

 

[GSXR1000]

The Overkill Solar version of that BMS can be ordered with three wires instead of two and 8 gauge instead of 10 gauge. That should help with the throughput.

I'm running a synthetic 0w-30 in my 5500w generator. It seems to start a little easier with that oil than what Onan specs out.

mine has 3 x 8 guage.. works great no heat at 85 amps for 3 hours even the heat sink

 

[GSXR1000]

**** UPDATE ***

2-130a bms starts the generator no problem.. cranks faster with lifepo... and current drops much quicker.. amps never went over 205 for a split second

 

[HRTKD]

That's great to hear! Was that max or inrush?

 

[GSXR1000]

That's great to hear! Was that max or inrush?

inrush shows lower then max

 

[HRTKD]

What do you mean, "current drops much quicker"?

 

[GSXR1000]

What do you mean, "current drops much quicker"?

on my 2x100ah agm batteries it took a second for the starter to get to full speed. now pretty much instant.
and before I could hear the compression stroke now not really

 

[HRTKD]

I might have to give this a try. What size wire are you running from your battery/bms to the generator?

 

[GSXR1000]

I might have to give this a try. What size wire are you running from your battery/bms to the generator?

3 x 10 guage on each bms

 

[mkaye]

i have 280Ah LFP - Chargery BMS - starts my 4K Generac w/o problems
i have 250A fuse from battery to + busbar

 

[HRTKD]

i have 280Ah LFP - Chargery BMS - starts my 4K Generac w/o problems
i have 250A fuse from battery to + busbar

What size wire is going to the generator? The existing wire I have to work with looks to be no more than 8 awg. It's not the wire that was providing juice to the generator from the original lead acid battery. Despite the high amp startup being short term, I think I'm going to have to run a new wire from the LiFePO4 battery bank to the generator.