Non technical solar off grid person

Welcome to the forum Lardeaulad,

The panels you are using?

https://dir.indiamart.com/items/vikram-solar-315-w-eldora-grand-ultima-silver-polycrystalline-solar-panels-s685.html

Electrical Data at STC

Maximum Power (Pmax)	315 W
Maximum Power Voltage (Vmpp)	37.5 V
Maximum Power Current (Impp)	8.4 A
Open Circuit Voltage (Voc)	42.5 V, 45.8 V
Short Circuit Current (Isc)	7.22 A, 8.92 A

And I am guessing that you are using the Schneider/Xantrex C35 controller?

https://www.solar-electric.com/tracc35solch.html

Your going to be getting into a little specmanship issue here... Your PWM type charge controller (the C35) is rated for 35 amps continuous and 85 amps intermintent. Your solar panels on a clear day and pointing at the sun should produce upwards of:

• 8.5 amps Imp * 4 parallel connected panels = 34 amps Imp-array

That is very close to the 35 amp rating of the controller.

With PWM controllers, they do not have the ability to regulate their output current (MPPT type controllers, more expensive) do... So, we would normally apply some deratings to the wiring and controller. For this controller:

• 34 amps * 1.25 NEC derating for continuous current * 1.25 NEC solar derating = 53 amp branch circuit and breaker (round up to next standard wire size and breaker/fuse rating)

There is a good chance that your C35 can overheat and shutdown on some days... There is something called the "edge of clouds" effect. This is where it is possible to get "more solar energy" than is normal under certain partially cloudy conditions--As a cloud passes by the sun, it can magnify the amount of solar energy and can get 1.25 to (1.25*1.25=) 1.56x the normal output current from your panels (Imp--Current Maximum Power).

So--I would be too suggesting in the >=53 amp rated controller (and cabling/breaker/fuse rating) range.

Also, with 3 or more solar panels in parallel, you should use a Combiner Box--Basically a reverse fuse/breaker box. Each + wire from each solar panel (or series string of panels) connects to its own circuit breaker (or fuse). In your case you have 4 panels, so 4 breakers/fuses. This is done for safety--If one panel becomes shorted, the other three panels can backfeed current to the one shorted panel and start a fire (the actual fuse/breaker rating--Check the 315 Watt panel spec. sheet) or:

Maximum Series Fuse Rating

15 A

The remote battery temperature sensor is a good idea when the solar charge controller is in a different location vs the battery bank--The remote temp sensor tells the controller the actual battery temperature (cold batteries need higher charging voltage. Hot batteries need lower charging voltage).

https://www.solar-electric.com/schneider-130-0004-03-01-35-foot-temperature-sensor.html

Regarding something better than blinking lights... There are a whole bunch of different battery monitors. From simple voltage only monitors:

https://www.solar-electric.com/midnite-solar-mnbcms.html

To more complex units that use a "shunt" (a precision power resistor in the battery negative cable) and a meter (measure shunt voltage to find the charging/discharging current):

https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html
https://www.solar-electric.com/victron-energy-bmv-712-smart-battery-monitor.html

https://www.solar-electric.com/search/?q=battery+monitor (Bunch more from our host NAWS)

It depends on what you are looking for, how much work/price to install, other options/features.

-Bill