I've got a 2-unit Aolithium rack battery set coming soon, and I'm reading up on charging. Right now, I have a Victron 150/35, and was planning on using solar to charge. I noticed that most people seem to have a dedicated charger for getting their batteries initially charged up. Is solar still a reasonable way to charge a new rack battery? If not recommended, what chargers or methods do you recommend?
Assembled packs by AOLithium, SOK, EG4 etc are all top balanced & charged & tested prior to assembly, so this is generally not a problem. The only GOTCHA is that the packs may be a slightly different voltage when they arrive, most likely just above 3.2V per cell (51.2V for a 48V Pack) so when you first install them into the rack,
before turning anything else on, turn on the battery packs and let them balance out between themselves. If you have the ones that can be controlled with a phone APP, you will see power being transferred back & forth as they balance out, once they have settled (showing same voltage & no amps being used) then power up your solar charger controller followed by your inverter/charger.
Note I am assuming you have a separate Inverter/Charger as you are using a Victron SCC. You can also use the Charger in the Inverter which can be Generator or Grid Power. You CAN charge with the Inverter/charger AND the SCC simultaneously "provided" that you do not exceed the Max Amps the battery packs can take.
AOlithium 48V/100AH Rack Packs have an EndAmp/TAILCURRENT of 5A (see settings in SCC) When packs reach Tailcurrent, they flip to FLOAT mode (constant voltage / variable current) from ABSORB (should be a max of 60min, will kick off earlier as Tailcurrent is reached).
!! WARNING !! Correct for Voltage Differential !
When
charging from Solar AND/OR Inverter/Charger:
Use a Multimeter and check the voltage at the SCC or Charger and again at the battery pack terminals, note the difference. There is always a bit of difference because every lug, wire, connection like fuse/breaker adds resistance & a bit of loss results. LFP unlike Lead Acid is MILLIVOLT & MILLIOHM sensitive (not brute force). Adjust your Solar Controller & External Charger (as applicable) so that the Battery Packs are getting what they are supposed to get and not more.
-- Now the part everyone hates....
You have to do it AGAIN when there is NO Solar Input and the inverter is powering normal loads. The "bias" is different when discharging and it can be enough to cause issues... You NEED to ensure that the Low Volt Shutdown of the inverter is accurate or else it may disconnect too late with the batteries being too low causing the BMS to shutdown and not take a charge.
Good Luck, Hope it helps.
Here is a quick reference you may find helpful