Please help me understand solar readings

[iamunique127]

I have two 6V lead acid batteries and Escape-installed 160W solar panel and GoPower PWM-30 solar controller.

I haven't been sure if the solar panel would get enough light through the new CalMark cover to maintain the batteries over the winter so I added a small, 18W solar panel outside the trailer. I had trouble with the solar controller that came with the small panel so it hasn't been connected yet. I left the house solar system turned on in the meantime to see if it would get enough light.

I checked the battery condition yesterday by reading the GoPower readout and I'm somewhat confused by what I saw. In the past the voltage has been in the 13.somethingV range but yesterday, even though the SOC said 100%, the voltage was only 12.8V. Solar input read 0.0A.

I topped up the electrolyte with distilled water in the fall. The water was barely needed as the levels were all nearly full. The voltage showing on the GoPower solar controller has been in the high-13.V range all summer.

A week or two ago I looked at the trailer and there was snow covering the solar panel but when I went there yesterday the majority of the snow had melted. I brushed a little bit off the solar panel and removed a little bit of ice but the cover over the panel was mostly clear.

Does anyone have an idea of why the voltage would show so low now?

 

[vermilye]

12.8V is normal for the pair of 6V lead acid batteries when full. If no current is flowing it is for 2 reasons, 1 the batteries are full, or 2, not enough sun to turn on the controller. With 12.8V showing, it doesn't indicate that sun is getting through the cover, but it also doesn't indicate that it isn't. If it drops to the neighborhood of 12.5V - 12.6V with the sun shining, I'd suspect the cover is blocking the panels, but it doesn't look like a problem at this point.

 

[SRS]

The resting voltage of a flooded battery is 12.6, AGM is 12.8, so depending on which type you have the voltage seems correct to me. And that would be your correct SOC in that situation. You probably have minimal or no loads at the moment. Full batteries don't need a charge so the controller has stopped charging and shows 0 amps. FWIW, a Victron shunt would give you better information regarding you SOC.

I'm not sure what setup your using for the 18W panel but if its plugged into the Zamp port then you should disconnect that panels controller. The Zamp Port should be wired to the Go Power controller and can handle both panels. It appears the roof solar is maintaining you batteries. I'm sure others here will chime in.

Happy New Year.

 

[iamunique127]

Thank you for the replies.

It was a dark, cloudy day here yesterday when I did this check. With the batteries showing 100% I wasn't surprised that no current was flowing.

They are flooded batteries. The battery disconnect is off so there is no load.

I was surprised and a little alarmed at the 12.8V because I have seen mid-13 volts in the past. I'm relieved that 12.6 or so is normal.

The 18W maintainer panel is on it's own SAE port coming in to the trailer and I have a seperate small controller for it which I haven't hooked up and actually may not now that I know the covered panel is getting enough light to keep the batteries topped up.

 

[John in Santa Cruz]

mid 13V is charging float voltage for lead acid, like your solar panel has sun, but the battery is already 100%

 

[vermilye]

Check the wiring inside the trailer that goes from the SAE Zamp port and see where it goes. Escape usually wires it to the input of the GoPower solar controller, but they have sometimes connected it directly to the batteries. If it goes to the solar controller, you do not need or want an additional solar controller at the 18 Watt panel. A second check - Be sure the polarity is correct between your 18 Watt panel and the batteries or GoPower controller. Don't go by wire color - the Zamp folks use the opposite polarity from standard for a SAE connector - there are too many places where the polarity could be reversed to take a chance. Use a volt meter to check.

 

[iamunique127]

Thanks John in Santa Cruz. I guess I've looked at the readout in the daytime when the batteries were charging.

Vermilye:
-I added the SAE port for the maintainer myself. I plan to check polarity as I go about adding the small solar controller that came with the panel. It has ring terminals to connect to the battery posts.

-the main, roof mounted solar panel goes to the GoPower solar controller which is then connected to the batteries. I have added a disconnect switch on the positive cable from the solar panel, before the controller. I had intended to turn it to Off when I plug in the maintainer.

Does that all sound correct?

 

[CE Vogel]

Thank you for the replies.

It was a dark, cloudy day here yesterday when I did this check. With the batteries showing 100% I wasn't surprised that no current was flowing.

They are flooded batteries. The battery disconnect is off so there is no load.

I was surprised and a little alarmed at the 12.8V because I have seen mid-13 volts in the past. I'm relieved that 12.6 or so is normal.

The 18W maintainer panel is on it's own SAE port coming in to the trailer and I have a seperate small controller for it which I haven't hooked up and actually may not now that I know the covered panel is getting enough light to keep the batteries topped up.

I think you are fine. Most lead-acid controllers will provide a 'boost' voltage of about 13.5 volts during initial charge, then when the batteries are fully charged, the controller will drop to a 'float' voltage of about 12.8 volts. Your reading indicates fully charged batteries. As long as the reading stays above 12.6 volts, your solar panels are doing their job. The reason the controller drops from 13.5 volts to 12.8 volts is to reduce battery gassing and water consumption.

 

[John in Santa Cruz]

a 1 stage lead acid charger (most older converters, including the WFCO 8955 are pretty much a constant 13.5-13.6V, this bulk charges the battery then maintains it. 3 stage 'smart' chargers will bulk charge around 13.6V, then run an 'absorption phase' of 14.2V or so, then drop to 13.2V or so as a maintenance charge.

12.6V or so is a charged lead acid at rest without any charger or load

 

[iamunique127]

Thanks guys.