Solar Panel not charging battery

[louise_374474682]

I had a solar panel fitted to the caravan two years ago, and have not had to charge the battery since. I also have a tracker fitted which allows me to send and receive warning and information messages from the van about GPS lock on/power source and whether the van is being moved or not. I've now received a daily message from the van, warning of a low battery reading (under 12v), sent daily for the last 10 days. If I return a message asking for a battery strength update, the caravan returns values between 13 and 14v.
Anybody got any ideas - the low battery warning happens around 17:30 - is it as simple as sunset causing some sort of charge drop?

 

[JTQ]

If you get an answer of between 13 and 14 volts then something is charging your battery or the measuring equipment is duff. A fully charged battery after resting two or four hours will be about 12.7 volts so do a check it in the middle of the night. If the measuring system is working ok then you should get that sort of value. Seeing the rested, non charging voltage at 12.7 ish and over 13 during the day indicates that at least the solar system and battery are okay, of course accepting the measuring system itself is not telling porkies.

 

[louise_374474682]

Thank you for your help, that makes perfect sense.