I have a small system with two matching 12V 100 Ah batteries connected in series. I've taken good care of them, but recently I noticed that one battery is a full volt lower than the other (12.8V vs. 11.8V). Since this is a backup system that doesn't get cycled often, is this level of imbalance normal? Should I be looking into getting a balancer? Also, is it possible to swap the positions of the batteries temporarily until I can get a balancer? I tested the system under moderate load yesterday to check if it was functioning properly.
2 Answers
Swapping the batteries around won't solve the issue. You definitely need a balancer, especially since the internal resistance of the batteries can differ slightly, causing imbalance. It’s kind of a must-have when using 12V batteries in series instead of a pre-made battery set. For now, take them apart and charge each one fully before putting them back together again.
If your system isn't in active use, an old car's 100W headlight bulb can help! Put the batteries in parallel using the bulb in one connection and let it sit for a day. Then you can reconnect them in series. It’s a temporary fix that might save you some money compared to buying a balancer, but keep in mind this method may need to be repeated fairly often depending on how you use the batteries.
That’s an interesting idea! I was thinking about adding two more batteries soon, so I figured I’d need a balancer regardless.
Thanks, that makes sense. I’ll keep the system off until I can get a balancer. Do you have any recommendations for one?