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Old 12-04-2023, 01:27 PM   #1
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Brand: Thor Motor Coach
State: Missouri
Posts: 24
THOR #31274
Dometic power controller and battery charge question

I am at work and have some information, other info I will need to get when I get home.

I have a 2 year old Thor Coleman 22eqf (3000 miles) with a dometic gp-pwm-10-sq solar charge controller. I do not have solar panels installed. It's a new acquisition, we have done one trip with it and the rest of the time it has been in storage at home with 120 volts plugged into the 30 amp connector. I can get voltages on charge and voltages when the power disconnected when I get home. I am not sure of the battery but it appears to be the origional one.

The solar controller shows the charge of the battery and has 4 lights to the side, with each light representing an approximate percentage of battery charge. My question is that the charge indicator never reads as full; instead it stays at the 80% (guess) mark. The battery does not appear to be overheating or to be overcharged but the fact that it never shows full is a bit of a concern.

My initial guess is that the battery has been abused a bit too much in the last couple years and is of questionable capacity, however as I am new to RV'ing and don't want to throw parts at something that may not be an issue I'd like to get other opinions. We have a trip coming up in a couple weeks and I want to make sure I understand what is going on before we head out, especially as it's a tad cold out and I don't want the battery to die on us when we need it.

Any assistance would be greatly appreciated.

Dave

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Old 12-04-2023, 03:58 PM   #2
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Brand: Thor Motor Coach
Model: ACE 27.1
State: Florida
Posts: 13,876
THOR #7035
Get a voltmeter.
Read the battery voltage when "not at full"
Disconnect from SP
Wait 1 hour.
Read the battery voltage.

You could also stop at Harbor Freight and get a battery load tester but probably not necessary yet.

Using the solar controller as the "judge" for battery status when it is not charging is not the best line of reference. It may be set for the wrong type of batteries or it could just be unhappy that your converter is in float mode at 13.1 to 13.6 VDC when the "Full" LED really wants to see 14.5 to 14.9 VDC.

To actually know the health of your batteries you would have to load test them and measure the actual capacity vs their rated capacity. The HF load tester above will point out a bad cell issue (under load) but doesn't really measure capacity. To do that you would need to invest in a shunt based battery monitor system. There are several cheap ones available om Amazon but it would be better to invest in a quality system like this Renogy one:
https://www.amazon.com/gp/product/B07RP5B5P7/?th=1
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Old 12-04-2023, 04:11 PM   #3
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Brand: Thor Motor Coach
Model: Axis 24.1
State: Connecticut
Posts: 1,733
THOR #20289
I will second adding the Renogy shunt based battery monitor. It gives you real state of charge info that you cannot get any other way besides a specific gravity meter. If you have fill ports on your batteries you could use a Sp Gr meter but it won’t be as accurate.

I suspect all is ok and the 80% light just indicates the float voltage. The 100% light probably comes on at a higher voltage while in the final stage of charging.

Battery voltage is almost worthless unless you let the system rest for at least an hour as Ted suggests above.

David
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Old 12-04-2023, 07:27 PM   #4
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Brand: Thor Motor Coach
State: Missouri
Posts: 24
THOR #31274
Quote:
Originally Posted by 16ACE27 View Post
Get a voltmeter.
Read the battery voltage when "not at full"
Disconnect from SP
Wait 1 hour.
Read the battery voltage.

You could also stop at Harbor Freight and get a battery load tester but probably not necessary yet.

Using the solar controller as the "judge" for battery status when it is not charging is not the best line of reference. It may be set for the wrong type of batteries or it could just be unhappy that your converter is in float mode at 13.1 to 13.6 VDC when the "Full" LED really wants to see 14.5 to 14.9 VDC.

To actually know the health of your batteries you would have to load test them and measure the actual capacity vs their rated capacity. The HF load tester above will point out a bad cell issue (under load) but doesn't really measure capacity. To do that you would need to invest in a shunt based battery monitor system. There are several cheap ones available om Amazon but it would be better to invest in a quality system like this Renogy one:
https://www.amazon.com/gp/product/B07RP5B5P7/?th=1
Thanks, thats really good information there and it confirms some of the suspicions that I had. I'll do some evaluations on the battery itself and use that to compare against the info the controller is presenting until I can invest in a better monitoring system.

Dave
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Old 12-04-2023, 09:10 PM   #5
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Brand: Thor Motor Coach
Model: Chateau 24F
State: Ohio
Posts: 3,980
THOR #16721
IMO many Renogy products are simply repackaged versions of other products with a markup added. Very suspect that Power Queen and Renogy shunts look very similar - just rebranded graphics. Shop carefully. When you get outside the Victron umbrella, most products of this nature roll out of the same Chinese factory. You may as well buy the cheapest one... otherwise you're just paying a "name brand" markup for the exact same item. For details watch a few Will Prowse YouTube videos of teardowns/reviews.

Shunts all basically work identically... they measure power going into and out of the battery. All you really need is available amp hours in the battery. All the other stuff will eventually get old as information overload.

With a lead-acid battery, start with it fully charged. Wire the shunt to the negative terminal, and the power lead for the display to the positive battery terminal.

Connect the shunt and program in the amp hour capacity of the battery. Then set the display to 100% state of charge. The shunt will measure amps into and out of the battery and convert to "state of charge" percentage.

With lead acid, you should consider 50% SOC as being empty... you might cheat occasionally, but that will degrade the battery and shorten it's life.

Also with lead-acid, you should occasionally recalibrate as the battery ages if you want better accuracy.

A shunt that does the job without the bells and whistles is less than $35 on Amazon...
QWORK Battery Monitor Voltmeter Ammeter, Voltage Current Range 8V-80V, 0-100A Voltage Current Meter with 13 ft Custom Cable https://a.co/d/hDDHKGf
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Old 12-09-2023, 08:43 PM   #6
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Brand: Thor Motor Coach
State: Michigan
Posts: 19
THOR #19346
new batteries only last 2 years now adays. does your rig have a use switch? if so it needs to be on when on shore power to charge the batteries. does your rig have an inverter? if it is not off tutn it off to maintain batteries.
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