Calling all solar panel gurus

[MOAK]

I have a 125 watt synergy solar panel with the cheapo kit controller set at 14.1 volts. I have an Engle MD 14 for freezing and an ARB 63 qt for refrigeration. On average the fridge and freezer supposedly draw about 4-5 ah combined
The solar panel supposedly makes, on average 6-8 ah. Yet, when in full sunlight my 66ah battery was drawn down to 10.6 volts with both fridges running. ?? In theory at the very least it should have broken even steven and kept my battery topped off even considering a 15-20% loss in efficiency. Do I need another panel or do I need a better controller? All answers will be appreciated and thanks in advance

 

[rtexpeditions]

I would look at all 3 items there Battery, Panels and regulator.

Panels are never as efficient as the optimum wattage stated. There would need to be strong light on a clear day (noon in the desert conditions).

Cheap regulators drop the voltage but maintain the same current so effectively drop the wattage by 12/19 fraction. MPPT regulators give better performance but they're not perfect. You could also check that the regulator is actually capable of delivering enough Amps (allow some leeway, even double the Amps probably doesn't cost that much more).

Those battery voltages indicate the battery is quite discharged so probably not enough capacity there either (you should not discharge to below 80%).

For an optimum build, that would run without charging the battery from the engine etc., I would multiply the required load (60W) by 6.
50% panel and regulator loss and for 1/3 of a 24hr period you need to deliver 3 x the load, 1 load (60W) so you don't discharge the battery for 8 daylight hours and 2x load (120W) to charge the battery to cover the other 16 hours when the panel is not producing power, so 360W. You also need the battery capacity to store that power.

Of course on a vehicle, you are always limited by available space, weight and cost so you will probably need to compromise.

So more panels, an MPPT regulator with a high current rating and more battery capacity are all good.

 

[MOAK]

You’ve confirmed my assumptions- it is a brand new battery and the two combined batteries give us a total of 126ah or about 60 usable AH. I’m thinking another portable panel and MPPT regulator. I’ll be doing more tests at home before choosing.. I know solar panels have come a long way since I mounted ours over 6 years ago.