Seeking Opinion on Off Grid set up

[WDSMITH]

Hello Forum. I am new to the forum and new to solar.

I recently set up a small off grid solar power system to provide the basics for our 240 sq ft cabin. SET UP: 2 Canadian Solar 215W 24V panels wired in series; 2 Canadian Solar 250W 24V panels wired in series (930W total). Each solar panel string runs to its own Midnight Solar 20 amp breaker contained in a Midnight Solar Combiner Box. I split the din rail in the combiner box to run each pv string positive separately. All pv negatives run to the negative buss bar in the combiner box. Each pv string has its own EPSolar 40amp MPPT charge controller, and both charge controller charges 4 Rolls S-605's in series parallel to make a 12v system (900+Ah).

I am just looking for any assistance/opinion on my system set up. The cabin is tiny, so a 12v system is fine for our needs. However, I wonder if the set up is efficient.....and whether the system is sufficient to charge the batteries. Is there a better configuration I should consider. Any advice is greatly appreciated.

Power Needs: 5 cu ft freezer converter to a fridge with a Johnson's Control; a small new bar fridge; 12v water pump; 4 led lights; and a 600W microwave (used for 2 mins couple times a week during daylight).

I live in Nova Scotia, Canada.

[sensij]

You are probably a little bit light on PV. At STC and no losses, you'd be generating a C/12 charge current. More would be better, but that is getting to be some serious charge current.

Short days in winter there will be a harsh adjustment, and I think you could find yourself falling behind if you are regularly discharging much more than 100 Ah (1200 Wh) in a day. Do you have any ability to better measure the actual energy consumption for the appliances you listed?

At what azimuth and tilt do you have the panels mounted?

The big battery gives you some autonomy and can handle the load surges better than a small battery would, but you've got to find a way to get back to 100% SOC regularly. Do you have a generator and fuel stored to fall back on?

Also, it may not matter much, but I'd suggest keeping the DC- from each of the PV strings isolated in the combiner like you did with the PV+.

[WDSMITH]

Thank you Sensij,

This is very insightful and helpful. I think you are spot with respect to whether my pv array will sufficiently charge my battery bank. Even on good sunny days it seems the charge control monitors show a 100% charge on the batteries, but even with the smallest of loads on the batteries in the evening drops the SOC to 60% SOC. I have no way to manually equalize the batteries, and I fear I am damaging them without sufficient charge (sulphate etc). Is this possibly a symptom of the batteries not becoming fully charged? The voltage highs during bulk charging reach between 14.1 v to 14.2 v. Would there be any benefit to wiring the individual pv strings in parallel as opposed to series (higher amps vs higher voltage - I never fully understood the implications of this wiring concept when it comes to battery charging?).

The amp draw on the freezer is about 30amps (Johnson Control). The draw on the new mini bar fridge is about 90amps. The lighting consists of 4-60 watt led bulbs.

Thanks again.