Solar Controller question

Voltage Compensation is, in all likelihood, referring to Temperature Compensation, (T.C.) as said. See page 32 of 64, in the manual linked above.

A hot battery must be charged at lower voltages, to avoid over-charging and excessive gassing. Cold batteries require higher charging voltages to achieve a full charge. So, on a hot battery, one might charge at say 14.6v, whereas on a cold battery, one might charge at say 15.1v. T.C. does this automatically... which is good because it also compensates for the battery warming up during charging.

This is one of many charts illustrating the effect of deep cycling on a 12v battery:

DOD vs Lifespan Chart

Do not confuse DOD with SOC. DOD (depth of discharge) is what's been used, while SOC (state of charge) is what's remaining. So, 20% dod = 80% soc.

The problem is, 50-80% SOC charging is, by far, way faster than 80-100%. Many boondockers, therefore, operate in the 50-80% soc range, for +/- a week or so, but then they must fully charge up to 100% to avoid progressive capacity loss and heavy sulftion. This is usually done, once hooked back up to shore power, at home or a campground.

Solar is very helpful, in that it has all day to do that much slower top 20%. So one can charge up to say 80% soc, in the morning, with their genset, and let solar finish things off throughout the day. And enough solar eliminates the need for gen charging, altogether.

Hope this helps.

4aSong wrote:
The readout on my Viewstar VS1024BN Solar Controller has an item called State of Charge (SOC) and Voltage compensation (VC) can anyone explain these In simple terms. :h

Did you read This?

SOC shows how full is the battery. I wouldn't trust this reading, it's never accurate.

Voltage compensation is - I think - the temperature compensation coefficient. In other words, how much the voltage of set points will increase or decrease per 1 degree Celsius when temperature goes up or down from 25C. Refer to your battery manual to set the temp coefficient. If you are not sure, set it to 5mV/C per 2V cell, i.e. 0.03V/C per 12V battery.

There is no "safe percentage" for SOC. Normally, people are trying to keep it above 50% at all times. The lower it gets discharged, the shorter is battery life. On the higher end, you should try getting it to 96-98% every day. 90% is not good enough. If solar doesn't cut it, you need to add more solar or run a generator for 30-40 minutes in the morning and then solar would finish it off by the evening (hopefully). Or - reduce your energy consumption, so that the battery won't get too low by the morning and then solar will be able to get it to 98%.
But, like I said, you can't trust SOC readings on controller.

What is a safe percentage range for SOC?

SOC ..on a solar controller is usually percentage of the amp hour capacity..
Sometimes stated in amp hours, Sometimes stated in percentage of full capacity
The amp hour numbers of a full set of batteries, has too be entered, aka set with batteries fully charged

Some controllers just take a voltage reading and give approx SOC