PWM or MPPT.

[Bidja]

I recently had my auxiliary battery fail while away camping. It dropped a cell reducing the battery voltage to 10volt. While checking out the battery I checked the panel's output and found it fluctuating between 7 - 16volts. Not good, and obviously faulty and possibly the cause of the battery cell failure over time.

You state that you

checked the panel's output and found it fluctuating between 7 - 16volts

OK, guess you checked panel outputs with array disconnected from controller. If not, good idea to check the PV array output (full sun) when isolated from the controller: open circuit voltage and the current flow with a multi meter. Then if all is good, connect your sys up. PV output specs should be on the back of panel. Note: open circuit voltage of panel will vary depending on sun exposure.