When we set up the solar system (I love saying that, I know it’s technically a photovoltaic (PV) system, but I will forever use this one) we were able to obtain 60 batteries for free. A company that had used these batteries as a server backup had gone under and left them to be disposed of. We knew when we got them that 1) they weren’t really designed for solar and 2) they were 10 years old. We knew we had a maximum of 5 years of use out of them. We knew this. It doesn’t make the fact that they are currently going bad any easier to handle.
For those that are unaware of our setup, we connected four of these 12 volt batteries together in series to create a 48 volt. Then we connected the 48 volt batteries together in parallel. This essentially gave us 15 48 volt batteries. At full capacity we could potentially charge them all and retain enough electric to last about 4 days without any sun. On a nice, bright, sunny summer day we could charge these to full capacity. Unfortunately, over the past year, we were not getting this kind of battery capacity. Even during the summer we were still needing to utilize the generator to get us through the night. Not good, not good at all.
We finally decided it was time to check all 60 batteries and pull the bad ones. We knew we had a few bad ones that were draining them prematurely (even one bad battery can drain good batteries so you should never have bad batteries mixed with good ones. This goes for all batteries, even your AAAs). After unhooking the them from each other we used a multi meter to check the voltage on each of the 60 batteries. Then moved each of the bad 80lb batteries outside to be used to trade in when we replaced them (hopefully later this year) with new solar capable 12 volts. We were hoping for no more than 12 bad ones. We unfortunately ended up with only 7 good 48 volt batteries (7 x 4 = 28 12 volts), meaning that more than half (32 12 volt) batteries were bad and need to be replaced. EEEK. No wonder we couldn’t hold charge.
Fortunately we can replace the batteries 1 48 volt at a time (4 12s again) but the ones we are looking at actually have the holding capacity of 3 of our current 48s, which will be very helpful. Also, since eliminating all the bad batteries we can currently get through the night, during the winter, with a heater on the water lines and pump and the pellet stove going, and NOT have to run the generator if we had sun that day, and if we didn’t we only need to run the generator for about 3 hours. I would call that a win. At least we aren’t spending $10 a day to run the generator anymore.