I've been having some frustrating luck with my battery setup and I'm not sure if it's working properly. I'm using two 175w solar panels, a 40amp controller, a 12v 100ah lithium battery, and a 700w inverter. Currently, my battery's at 100% but the monitor shows 13.1v and 1.9a (26.6w). I use this system to charge tool batteries and Bluetti batteries, which I then use to power my fans and lights. However, when I switch on the inverter, the voltage drops to 12.6 and keeps falling. It seems like the battery isn't performing as expected, and I'm wondering if it should allow me to use it for lighting at night. Plus, during sunny days, it struggles to keep up with charging a small Bluetti.
3 Answers
Any draw on the battery will cause a voltage drop. You need to check the resting voltage of your battery after it's been idle for an hour. If it doesn't hold a stable charge, you might have a damaged battery or cell. Additionally, your setup might be too small for your needs. You could be draining the battery too deeply, which can affect its ability to hold a charge later.
Your 100ah battery can only hold about 1200 watt-hours, meaning it could be drained in about 2 hours if you're pulling significant power. If you're looking for longer usage, consider adding more batteries to increase your capacity to around 5000 watt-hours. That way, you should be able to get through the night without issues.
Getting a shunt-based battery monitor is a wise move. Monitoring the remaining capacity through voltage alone isn't reliable. Also, if you're using a LiFePO4 battery, it should ideally charge to around 14.2v. Right now, at 13.1v, you might be somewhere between 90% and 40% charged.