Solar dump load after batteries charged

[Mike90250]

How many solar panels of 150w and inverter require to run an ac refrigrater of approx 170watt

How many hours of sun will you have? Assuming the fridge runs 30% of the time @ 170 watt (ouch, this is not going to be good)
Starting surge of the fridge motor is going to need a 1Kw pure sine wave inverter, and it "should" work most of the time.


8hrs x 170w = 1360 watt hours consumed by fridge
Assume 4 usable solar hours summertime, and 2 hours winter time ?
rule of thumb is array has to harvest 2x the daily use (this accounts for system losses of about 50% total)
Winter - you need a 1400 watts of array (will vary if you have more or less solar hours) (10 panels)
Summer - you need a 700 watts of array, but will have dead batteries in winter with less sun (6 panels - can't use a odd number like 5)

Battery requirement is 1360 x 4 = 5440 watt hours of storage, gives you 1 cloudy day before battery dies.
24V battery would be 226ah, or 4ea, 6V Golf cart batteries would do the job (wired in series)

[asdex]

Hi, I use a 24volt DC 900w element in my hot water cylinder. When the SOC reaches 100% the aux relay on my Midnite Classic turns on a 24 volt relay. This relay is also controlled by the cylinder thermostat. The relay switches a 80amp solid state relay which puts battery current onto the element. When SOC reaches 98% it turns off. I have on/off time delays programmed in too. Often with more than 26amps going to the batteries, the element just stays on alot of the day.It works very well. I just need to fit a timer to turn off the relay an hour or two before sunset to go into the night with 100% SOC. the panels are 2kW. The cylinder 44 gal and it takes about 9hrs to heat the water from cold.