13.5 volts tells me it is charging. Voltage would drop to 12.7 (full charge) pretty quickly if not being charged. I Assume
you are not on shore power?
What charge controller do you have. Any read outs other than LEDs. (red, green, orange, blinkly) digital?
If you are on shore power, the panels would not be charging unless it is set to charge higher than the shore power charger.
'01 National RV Tropi-Cal, Ford V10, '01 Suzuki GV 4X4 Blue Ox Tow Bar,300 Watts Solar, 2500 Watt '458' Inverter, NO TVs, Most light fixtures upgraded to LEDs