Questions about charging a lifepo4 battery with a generator.

[Deegore]

I'm planning to put together a 16s 48v 304ah battery with a 200amp 20s JK bms.
What would be an appropriate size battery charger to run off of a 3000 watt inverter generator?

I'm asking because I have a 12 volt 100 amp powermax battery charger that I cannot run off my 2000 watt generator, and it makes my 3000 watt generator bog hard.
My math says that it should only be pulling around 1410 Watts, but seems to be pulling much more.

 

[Supervstech]

Usually, .02C, or 40A for a 200ah bank.

 

[Brucey]

I'm planning to put together a 16s 48v 304ah battery with a 200amp 20s JK bms.
What would be an appropriate size battery charger to run off of a 3000 watt inverter generator?

I'm asking because I have a 12 volt 100 amp powermax battery charger that I cannot run off my 2000 watt generator, and it makes my 3000 watt generator bog hard.
My math says that it should only be pulling around 1410 Watts, but seems to be pulling much more.

Could be losing several hundred watts of power at the higher end, also potentially a big inrush when you first turn it on tripping the generator offline

 

[Deegore]

Thanks, I'm also wondering if I can buy some cheap 10 amp 48v chargers and hook four of them up together to get 40 amps.
Would the BMS know how to handle that?
What would be the advantage of a $500 Smart charger compared to $160 for some dumb chargers?

 

[Rednecktek]

Thanks, I'm also wondering if I can buy some cheap 10 amp 48v chargers and hook four of them up together to get 40 amps.

I've had to do that before, using 2 battery chargers and the onboard converter to get a battery bank full in a day. It's a hassle with all the clips and cables but it does work. The BMS didn't know anything about what I was doing, all it saw was 70a of charging coming in.

What would be the advantage of a $500 Smart charger compared to $160 for some dumb chargers?

I'd like to know too, you're not the only one.

I'm asking because I have a 12 volt 100 amp powermax battery charger that I cannot run off my 2000 watt generator, and it makes my 3000 watt generator bog hard.
My math says that it should only be pulling around 1410 Watts, but seems to be pulling much more.

Was it a Predator generator bought in the last few years? I've had a real hard time getting those to carry 50% of rated capacity. Your math is correct, your generator isn't doing its job. One thing you can do is grab a Kill-A-Watt and throw that on the generator and see what it's actually providing to the charger.

 

[Steve_S]

Real Use Case info: (just for comparison & clarity)
I use a Champion 4650W Inverter Generator (Dual Fuel model) which has an L5:30 (120V/30A) outlet.
This is connected to my Samlex EVO Inverter/Charger which "can" do up to 100A Charge for my 24V System. I have this set to a MAX of 80A so that AC Passthrough is handled without stress and to handle any surges if they come up.

While charging from Inverter/Charger ONLY (no solar input), the Samlex is pulling 120V/23A (+/- 3A as it floats a little as it should).
This leaves the Generator running with 2700-2900 Running watts so it is not even stressed and ample room to handle incoming demands without issue.

Note that I am running Battery Packs in Parallel, so the Incoming Charge Amperage is divided between the entire bank and is proportionate to the battery Pack AH Rating as well. Too Many forget that LFP works proportionately. Simplified Example below:
Assume you are pulling OR pushing 60A from/to the Battery Bank.
Also assume a 100AH, 200AH & 300AH packs in Parallel. (YES this is fine with LFP)
At the battery pack level you would see IN/OUT of 10A, 20A & 30A for that total of 60A.
This of course is slightly affected by the Internal Resistance of the packs so it will float a little between then as they handle the charge/discharge.

 

[Deegore]

My 2000watt was a champion. And my 3000watt is a generac. The generac overload light flashes for about 5 seconds when I plug in the 100 amp charger, but it always runs great. I guess with inefficiencies it is pulling over 2000 watts.
Maybe another factor is I'm using a 50 foot 12 gauge extension cord.
I should get a kill-a- watt meter.
I think I will get 10 amp chargers so if my generator doesn't like 30 amps I can go to 20.