I just installed a 3-panel system along with (2) Deka 12V 245Ah AGM batteries. The system is working great.
I did notice that when I first took a reading of the batteries it showed 14.1V. I used the system for a few days to power my computer and TV and saw that it got down to a 11.7 reading. Since then (approximately 7 days) I have not put any load on the system and have been checking the batteries each night to see that they are recharging properly/fully. They now seem to be stuck at a 13V reading and haven't gone up at all in the past 3 days.
Do these results make sense? Is there anything that I should be looking at to make sure that everything is operating correctly and that I'm protecting the long-term life of my batteries?
Thanks for your help.
Comments
Sorry to hear that; that's a common problem with severely discharged batteries (80-90%).
The combination of a severe (90%) discharge and letting the discharged battery sit for some time may have killed the battery due to sulphation.
For extending the battery life; there are three key rules:
1) Do not discharge it below 50%.
2) Recharge the battery as soon as possible after use.
3) Make sure you use a charger designed for your battery.
These new batteries are not sulphated. They do come from most suppliers, not fully charged. Without knowing what size array you are charging with, we cannot determine if the batteries are being properly charged, also what type of charge controller and what are the settings ?
Since you over discharged the battery, it may take many days of no use to fully recover the 400-500 AH's that you removed. You did not say how much PV power the 3 modules are so no one can tell you how many AH's of power you can make each day. If you are making 80AH per day then it will take 4-6 days to recharge IF you are not removing (using) any more power during those days.
Once the battery is fully charged, the PV solar should raise the voltage each day to the acceptance set point of 14.4 volts adjusted for temperature. Then after sundown the battery will quickly drop to around 12.8 volts.
You should calculate how many AH's you can make daily so you know how much you can consume and still recover the each day.