I've set up a 100-watt solar panel with a basic controller and two 9Ah 12V deep cycle batteries. The controller runs 6 LED lights for 4 hours after it gets dark. For the first 6 months, everything worked great, but now the lights only last about an hour. Even after a sunny day, I checked the batteries, and while they were fully charged, they dropped to 10.4 volts when the lights turned off. Is the quick discharge caused by battery degradation or could it be a problem with my controller? I haven't changed anything in the lighting circuit, but I wonder if moisture from recent rain could have affected anything. Any advice would be really appreciated!
4 Answers
Also, consider that your location could be impacting the sunlight hours. If you're situated more north, you'll get less sunlight during winter. Adding more solar panels could help improve your situation!
Definitely check your voltage cutoff settings. I suggest you raise it to at least 12.5V; a lower cutoff will shorten your battery life significantly. Keeping it around 12V should help your batteries last longer!
It sounds like your cutoff voltage is set way too low. For lead acid batteries, the safe cut-off should be around 12.05V for regular use. Going down to 10.4V can really damage your batteries over time. If you have a good charger like the CTEK MXS 5.0, you might be able to recondition them!
You might want to install a shunt to monitor your battery usage. It works like an electric meter, showing how much power goes in and out. That way, you can compare your usage to the original capacity (2x 9Ah). This could give you a better idea of your batteries' health!