Gdetrailer wrote:
13.8V is barely charging and 13.5V is "maintaining", that is the difference.
.
.
.
Your solar panel voltage rating is pretty low for charging a 12V battery. Typical old school solar panels designed to charge 12V batteries will typically have a no load output voltage of 17V or a bit better.
More modern panels now days have voltages over 19V open circuit.
Concur !
I think your voltage is low because you are using smallish portable panels. Check their spec sheet for open circuit (not connected to anything) voltage. It might be time for an upgrade !!
