Homebrewed Electricity > Storage
Charging a 24v bank from a 48v bank...or vice versa...how to do it? Can it done?
Scruff:
You can play with LVD on the controller maybe to set thresholds or use voltage triggering to disconnect the charge source.
Depends on the batteries too, I usually assume the higher voltage would be bigger so more capable of finding a natural regulation. Eg. if 48V is 200Ah and 24V is 100Ah unlikely the 24V will every drain the 48V to 50%SOC.
Dump controller would work too but I'm not sure if that's healthy to have batteries on both sides.
Whatever it is has to have current limiting.
PWM generally speaking doesn't like a Voc >170% the battery voltage...it often can do it but not for as long as one that isn't asked to.
makenzie71:
That's the issue, the bigger bank is going to be the 24v bank...I think. I haven't decided which way to go yet. The issue I'm having is I have one 48v turbine, and everything else runs 24v, and the inverters run off the 24v...so it is possible the 24v bank can draw the 48v bank down. I think it's something so unorthodox that I'm going to have to just try something and see how it works and adjust from there :/
Scruff:
Not that unorthodox I was tooling for 48V then I realised HGV was 24V and that'd be a better investment aside from the intrinsic problem of big cables and expansion cost-prohibitive hardware.
Swings and roundabouts. There's more availability of used gear at 24V but less competing buyers at 48V.
It depends on the controller you are using even the (larger) ones without load terminals will often still have LVD that opens the FETs so you could set the 48V to MPPT but only to 50.5V.
MPPT controllers usually have current limiting as standard, PWM usually not.
Scruff:
Thuther option is use transformers upstream of the 48V rectifier.
makenzie71:
So that actually seems to work...I ran my 48v bank to the PV side of this cheap 60a controller and it's dropping the voltage down to 29vdc and hitting my 24v bank.
https://youtu.be/yUHF3Re622U
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