diy solar

diy solar

AIMS Charger And SOK Batteries

KenH

New Member
Joined
Apr 7, 2022
Messages
5
I just bought 2 SOK 12v 100ah batteries to use with my solar system. I read that the two batteries should be charged individually on initial hook up to balance them. I bought a AIMS converter/charger based on Will's recommendation that this is a good charger for lithium batteries. When I hooked one of the batteries to the charger with both switches set to "0" it goes to what appears to be float mode; solid green light and flashing yellow. I had the battery connected for about 3 hours and it didn't seem to increase the charge at all. both batteries are showing 13.2 volts. From what I understand I should get them to 14.2 volts before hooking them together in my system. I don't understand why the charger is not increasing the charge on the battery. Thanks!
 
13.2V is 3.3V per cell which is most likely above the recharge threshold where a new charge cycle is initiated. Is there a way to manually start a charge cycle on the AIMS?
 
13.2V is 3.3V per cell which is most likely above the recharge threshold where a new charge cycle is initiated. Is there a way to manually start a charge cycle on the AIMS?
Not that I can see. I had the batteries hooked into my system before I knew that I should balance them. According to SOK they ship at 30% charge but I probably charged them above that by having them hooked to my array. Maybe I need to draw them down in order to get a full charge with the AIMS charger?
 
Not that I can see. I had the batteries hooked into my system before I knew that I should balance them. According to SOK they ship at 30% charge but I probably charged them above that by having them hooked to my array. Maybe I need to draw them down in order to get a full charge with the AIMS charger?
So if your array already charged the batteries they should be good to go. With the following clarification.
If your system is 12V and the batteries are going to be connected in parallel you can just connect them both to the AIMS and let the system run. Parallel batteries will self balance, if one battery is at a higher state of charge its internal voltage will rise faster forcing a larger percentage of the current to the other battery. Eventually they will both balance out at whatever the charger voltage is set at, as long as its at least 3.45V per cell.
In a 24V system where the batteries are connected in series, this is a completely different scenario. Each battery has to be top balanced individually to achieve 100% SoC, then they can be connected together in series and placed in service.
 
I am connecting them in series for a 24v system.

The BMS in each 12V battery should keep the cells balanced but cannot keep both batteries balanced. You may need to periodically top balance both batteries with one 12V charger connected to each battery in parallel. This should be possible without disassembling any of the 24V cabling and preferably during low to zero other input/output to the batteries from the AIMS.
 
Not sure I understand how I can charge the two batteries in parallel if I have them wired in series. Do you think that wiring them in parallel will allow the AIMS charger to increase the charge when there are currently at 13.2v? I'm still not having any luck getting the charger to increase charge. It just goes to solid green and flashing yellow and shows 13.2v on the positive wire from the charger to the battery.
 
Not sure I understand how I can charge the two batteries in parallel if I have them wired in series. Do you think that wiring them in parallel will allow the AIMS charger to increase the charge when there are currently at 13.2v? I'm still not having any luck getting the charger to increase charge. It just goes to solid green and flashing yellow and shows 13.2v on the positive wire from the charger to the battery.
Sorry, if my explanation was confusing. The batteries are in series for 24V. The AIMS is connected to the to the batteries in series at the most positive and most negative connections so all the AIMS charger/inverter settings are for 24V operation.
I was suggesting that IF an occasional top balance is needed you could use a completely separate 12V charger (connected to both batteries in parallel) and charge them both at a fixed voltage, for example 14V, which would top balance both of them without disconnecting any of the 24V wiring. This is exactly how a BMS balances individual cells in a battery pack while its in use. This why the BMS has so many wires, it has a connection each cell + & -. Thus the BMS "sees" the individual cells in parallel.
 
Thank you Bentley, I ended up drawing the batteries down with a small inverter that I have. Got them down to around 30v then tried the AIMS charger and it worked great. The first one just topped out at 14.4 and I'm working on the second one now. Seems that your initial comment about being above the charge threshold was correct.
 
Back
Top