Hey everyone! I'm a first-time poster here. I have a 4KWh 24v off-grid system set up at my remote cabin in Germany. Previously, I used four 6v lead acid batteries, but they died a few years ago. I then switched to cheaper 12v 90Ah car batteries in a 2s2p configuration. Unfortunately, two of those batteries are really underperforming now, to the point where I can't even keep the lights on overnight. I decided it's time to upgrade to LiFePo4 batteries, so I just bought about 10KWh (24v 100Ah, four in parallel) and I'll install them this weekend.
Now, my question is about the old lead acid batteries; two of them are still somewhat functional. Is there any way I can integrate them into my system, maybe for a small water feature or a pump for watering my vegetables? I assume I'd need a separate charge controller and probably a panel for that, but I'm hesitant to invest more money into keeping these old batteries alive when I could just buy more LiFePo4 instead. Has anyone here dealt with old batteries after upgrading? What did you do with yours?
4 Answers
You might consider a DC/DC charger for the lead acid batteries. However, I'd suggest just cutting your losses and using a DC/DC converter to run your 12v loads instead. Keeping it simple is key here!
Honestly, it’s not the most efficient use of resources. It's probably best to recycle the lead acid batteries and be done with them.
Yeah, I figured as much. It wouldn't make sense to invest in extra equipment just for those old batteries.
When it comes to new batteries, you want to prioritize proper charging. It's best to fully charge each of your new LiFePo4 batteries individually before connecting them all to the charge controller. This helps keep them balanced!
Totally agree! Full charge initially is the way to go before we link them together.
For anyone looking at solar systems, I'd recommend over-specifying your battery needs. If you need 10 kWh for the night, shoot for around 20kWh instead. This way, you reduce wear and enhance lifespan by not cycling them too hard. If you're going to leave your system unused, it's smart to keep the batteries at 50% for longer life!
I actually have a DC/DC buck converter (24 to 12v) that I'll keep using. I may research DC/DC charging if I think it's feasible.