Solar Charger Controller questions

[grega]

I have a few basic questions regarding battery charging via solar panel. I Currently have one 85W panel rated to 4Amps (I think).

For curiosity sake and to understand whats going on I've been watch/reading the Controller display during the three different types of methods to charge the house batteries on the RV: solar, Generator, and Running the Chassis Engine.

During these times I have noticed the Chassis shows a SOC% of 100%, the Generator 94%-96% and the Solar only anywhere from 15%-ish to 40%ish

Also, when I flip through the display I've noticed aH display. Latley is was at 30aH for a long time and never went up (days)... then 7o.. then 90 increasing to about 115aH after I was actually plugged in to shore power for a few days.

I'm pretty sure I've seen something like 600aH in the past...

.. now to the point:
Question 1- what is the SOC%? Is this the rate at which the batteries are BEING charged or the ACTUAL charge of the batteries? This is confusing because when I turn off the generator or engine te SOC% may be lower than what the display shows during charge

Question 2- What does the Ah display mean? Is this the estimated amount of charge the batteries actually have? Namely, is this a better estimate than the SOC%?

Wew... sorry for the long winded question..

[RPAspey]

What charge controller are you using? Is there a shunt in line with the battery ground?

2000 Cherokee, LEDs, solar, inverter, etc. '07 Tundra 5.7L DC-LB, modded as well.

[grega]

It's a Nature Power 28amp. What's a shunt?

[RPAspey]

Its a electrical device that creates a mili volt signal from dc current flow. I'll look into your charge controller once I get back to my office.

2000 Cherokee, LEDs, solar, inverter, etc. '07 Tundra 5.7L DC-LB, modded as well.

[RPAspey]

OK, here's what I found out, the downloaded manual is worthless. But what I could determine is that charge controller is a PWM style without battery current input/monitoring. So, no shunt.

The battery AHr is based on a battery "capacitance" setting, which you will have to determine and enter yourself. This value would be the manufacturer's published 20 hour rate. The AHr you see is worthless without a shunt to actually measure the current usage both in and out of the battery.

The state of charge (soc) seems to be nothing more than a voltage reading from the battery. This value is calculated as a percentage of full charge volts (13.7) to low volts (10.5). The soc will give you an idea of the battery condition, but is by no means accurate. Case in point..your chasis alternated should be charging at 14.5 volts or so. The coach converter should be charging around. 13.6 or so. Using the manual's specified settings, anything >13.7 would be 100%, just under that would be just under 100%.

Now, for your charge controller.. this CC is a PWM style...basically a fancy switch that turns on when the solar panel voltage is higher than the battery voltage. If your batteries had a low SOC and the solar panel wasn't getting direct bright sun, there wouldn't be enough current made (you said you have an 85 watt panel which is 6.8 amps at perfect conditions) to offset parasitic load. Thus your battery won't actually charge.

Any questions? I hope this is clearer than mud.

2000 Cherokee, LEDs, solar, inverter, etc. '07 Tundra 5.7L DC-LB, modded as well.