Thread: Upright Compressor Fridge - Solar

According to the cheap but US-made Watt meter, the cheap MPPT controller attached to my 120W panels is doing a very poor job, producing on average 2A at 14V with the power jumping between nearly 40W and below 20W when charging 2 N70 size calcium batteries in bright sunlight. The panel voltage is being maintained just above 17V which is where the maximum power is produced but its not being converted to battery charge. Connecting the meter directly between the panels and the battery for a short period shows 15V, 5.5A and over 80W but as 15V is well below the panel voltage for maximum output, the panel max o/p cannot be inferred. A decent MPPT controller is needed.

That seems to reflect my experience as well - might be good for recharging the batteries over a longer period of time but when there is a load like a fridge on the battery, the MPPT I have does not put enough ah back into the battery to cover the use overnight so the battery capacity is slowly reducing.

I put the Watts meter between my 240v smart charger and a battery and I get the same result - most of the time high volts but not a lot of amps but near the end of the process amps ramp up - not an issue when you are not relying on the sun but when the Mppt wants to do the same it is dark.

I also found disconnecting the MPPT and connecting the panels direct to the batteries for an hour at a time really puts the Ah back into the battery and then the MPPT seems to go well and keeping the batteries up.

Garry

Originally Posted by Graeme

According to the cheap but US-made Watt meter, the cheap MPPT controller attached to my 120W panels is doing a very poor job, producing on average 2A at 14V with the power jumping between nearly 40W and below 20W when charging 2 N70 size calcium batteries in bright sunlight.

Could it be that the MPPT controller is limiting it's output to 14V so as to not over charge the battery? What happens if you put a load on the battery? If you draw two amps from the battery, the MPPT controller should supply an additional two amps of charge, assuming there is enough power available from the solar panel.
Aaron