Using multiple AC to DC chargers

[burnerskooolie]

I have 600 AH of LiFe Po batteries. I'd like to charge them with my 3800 Watt generator, but I can only find 100 Amp AC to DC chargers, which means that I'm only using 1200 Watts, and that it will take 6 hours. Can I use 2 or 3 chargers in parallel, to charge 300 Amps per hour?

 

[Rucker]

I don't think so. It's not like they will blow up, but chargers rely on voltage to determine state of charge, and the two chargers may think (because of the other charger) that the battery is at a higher state of charge than it is. they may flutter or behave in unexpected ways.

I have both solar charging and a shore power charger, and they run in parallel. But I suspect the solar charge controller may see the higher voltage from the charger and simply not feed from the solar.

Maybe borrow a friend's charger rather than buy a second one, and closely monitor? If you learn more, let us know.

 

[Jono14]

In general this should work.

Both chargers will look at the downstream voltage of the battery and respond as that voltage rises. LiFePO4 batteries have such low internal resistance that the voltage should stay low until they get closer to full.

You should be careful to only use chargers that can be programmed for LFP batteries such as absorption around 14.0 - 14.4V and float at 13.5V (the specific battery should have specific recs for these levels) - you don't want to rely on the battery BMS to shut charging down if the charger voltage is too high.
A few chargers out there (like Victron) can be networked so they function as a single charger. But that is not required.

You also want to be careful not to charge the batteries faster than their recommended max rate. Typically that is 0.5C meaning that a 600Ah battery can charge at 300A - so you should be OK there. Overall however, that max rate of charge may wear the batteries out a bit faster (a bit more heat stress) than slower charge rates, so that is another trade-off of the high charge rates.

 

[cessna175]

I would go with Rucker. two chargers at the same time will most certainly cause problems. You might want to seek out a charger that handles your charging needs. Batteries are expensive!

 

[Rucker]

I think Jono is right in theory-charging devices are looking at the voltage and LiFePo voltage doesn't rise until the battery is pretty saturated. Having said that, any voltage/current input into the system will in some fashion large or small distort the voltage and complicate the charger's job.

My thinking is you really need to just test under various conditions between the DCDC charger, the Solar Charge Controller (if you have one) and Genny.

Did a little digging and here's a link that discusses Solar Charge Controller and DCDC interaction (for example): Understanding the working of an MPPT solar charger

 

[Cheezewhiz]

Ahh.. way lower amperage, but when I plug both trickle chargers in at the same time, the batteries charge much faster than one alone.

They seem to play nice

 

[Mat7783]

I have 600 AH of LiFe Po batteries. I'd like to charge them with my 3800 Watt generator, but I can only find 100 Amp AC to DC chargers, which means that I'm only using 1200 Watts, and that it will take 6 hours. Can I use 2 or 3 chargers in parallel, to charge 300 Amps per hour?

I have a 80amp DC charger for my 600AH 12V setup and it charges fine.cant say exactly how long to get full charge from 50% drain.

 

[LargeMarge-TC]

I suggest running your situation by the nice folks at MAC'S BATTERIES AND SOLAR in Eugene Oregon.

Mac's Batteries

Mac's Batteries specializes in lead & lithium battery solutions: cars, RV, forklift, and off-grid power solutions. Solar panels and components available.

macsbatteries.com