Hey everyone! I'm trying to enhance the battery capacity in my off-grid system. Currently, I have two 125ah 12v lead acid AGM batteries that are about two years old and have bravely survived two Canadian winters. They seem to be working fine, but since they're used, I'm considering adding four new batteries of the same exact type and size. I've read that mixing batteries of different ages and conditions isn't recommended, so I'm thinking about using a bank selector switch along with a marine bank switch. The plan is to run the smaller two-battery bank most of the time and only switch to the larger bank when I need extra power, like for charging tools during long visits. Am I missing anything important here? I'm not very knowledgeable about wiring and solar systems, so I'm open to any suggestions!
2 Answers
There's definitely mixed opinions on this! If your demand doesn’t exceed what one of the banks can handle, you can just run them in parallel without issues. It's all about how much power you’re pulling at any given time.
Will Prowse mentioned that it's usually fine to run mismatched batteries in parallel, but never in series. So, in your setup, you could consider keeping one string for the old batteries and two for the new ones, connecting them all in parallel. That way, you keep the usage more balanced!
Gotcha! So you're saying I can have one bank of old and two banks of new, all working together? That sounds manageable.