Solar panels Mystery

Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
Hello All,


The facts are:


1. 3 new AGM batterys, rated at 110 Ahr each. Normally charged by a multi stage charger


2. The power meter reads 390 Ahr for the 3 of them (not 330 as expected), and is very accurate measuring the load in and out


3. Above 295 Ahr, the batteries do not charge by the engine alternator

Below 295 Ahr batteries charge OK by the engine alternator


4. The Solar Panels (2 x 100W) do not seem to charge the battery at all, no movement from the meter


That’s the real concern.


They are connected properly, when connected directly to floodlights (to test them) they work. They increase the voltage of the batteries up to 13.6 on a sunny afternoon, but have no effect on the Ahr reading. How can this be?


Any clues on resolving this would be greatly appreciated.
 
Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
an intelligent PWM, by www.ecosolarpanel.com (its Chinese). I don't think the fault is with the controller because I've independently tested the voltage it reads with the multimeter, its correct
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
It could be that the connection of the solar controller to the batteries is bypassing the shunt that is used to measure the battery IN/OUT Ah. This shunt is usually on the negative side of the battery bank.

If the solar panel is raising the battery voltage, it's charging the batteries. I've seen mine much higher than that, FWIW. It could be that the solar controller is detecting that your batts are charged, and is just entering float mode, which would align with 13.6V.
 
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Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
Let's assume...

On a bright sunny day at solar noon local time the sun is due south and at its zenith. This will produce from your panels the maximum voltage and current to the controller. Since I don't know the make of the panel I will also assume it to be around 17vdc. With that, the current assumed to be 5.37 amps (generic voltage and current of average solar panel).

So both panels are now produce combined 17vdc and 10.7 amps. If the batteries are not discharged deep enough, there would be no reason to charge them. So maybe the controller is not seeing a low enough voltage for it to kick in. It could be producing a trickle charge or, like you see, nothing at all.

Have you tried just putting a single battery with low voltage (like a motorcycle battery) on the panels to see if it will charge it? I know you said that the charger is working because it burns a light on the load outputs.
 
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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
WHY DO YOU HAVE 390, NOT 330- THE POWER OF THE THREE BATTERIES. YOU ARE TRYING TO CHARGE TO 390, WHICH THE BATTERIES CAN NOT ACCEPT. Do you have a smart charger on the alternator?
 
Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
It could be that the connection of the solar controller to the batteries is bypassing the shunt that is used to measure the battery IN/OUT Ah.

Yes. I think thats the most likely scenario
 
Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
Let's assume...
So maybe the controller is not seeing a low enough voltage for it to kick in. It could be producing a trickle charge or, like you see, nothing at all.

Have you tried just putting a single battery with low voltage (like a motorcycle battery) on the panels to see if it will charge it? I know you said that the charger is working because it burns a light on the load outputs.
The voltage was way down at about 12.5 and rose to 13.6 so I think its safe to assume its charging. No, I haven't yet tried a low voltage battery
 
Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
WHY DO YOU HAVE 390, NOT 330- THE POWER OF THE THREE BATTERIES. YOU ARE TRYING TO CHARGE TO 390, WHICH THE BATTERIES CAN NOT ACCEPT. Do you have a smart charger on the alternator?
I really don't know why it reads 390! Yes, the alternator charger seems smart, its a recent model 2012 Yanmar and seems to regulate the voltage and incoming charge OK.
 
Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
alternator charger seems smart
What brand of alternator seems smart?
It is not the alternator but the regulator that controls charging. Some alternators have internally built regulators. These are generally dumb (not programmable or temp sensing units).
 
Jun 14, 2010
2,081
Robertson & Caine 2017 Leopard 40 CT
I think jviss has the right answer.

Also, I'm not clear about why you think a battery monitor would measure the AH capacity- that's something that you need to input on setup, after that all it can do is measure amps flowing in and out, and calculate an estimated AH reading. The reference to Mainsail's post mentioned above explains why these meters are inaccurate.
 
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Jan 4, 2010
1,037
Farr 30 San Francisco
Seems like the alternator and the rating of the batteries agree. The alternator won't charge past 295 Ahr because that is the limit of the battery. Your monitor needs to be told the actual capacity.
 
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Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
Thank you all for all the advice, I'm satisfied that the meter is not including the readings from the solar panel, only from the alternator.
 
Dec 28, 2016
37
Beneteau Oceanis 400 Auckland
I think jviss has the right answer.

Also, I'm not clear about why you think a battery monitor would measure the AH capacity- that's something that you need to input on setup, after that all it can do is measure amps flowing in and out, and calculate an estimated AH reading. The reference to Mainsail's post mentioned above explains why these meters are inaccurate.
Agreed, jviss has the right answer and AH capacity- that's something that you need to input on setup.
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
Is the meter new also? If not, did it previously work well with an older bank of the same AH capacity?

Beware readings on multimeters, especially digital ones, when checking a PWM outputs. Sometimes they are sort of accurate. Sometimes they are very much not even in the ball park. Unless you have a meter with an oscilloscope function, you can't really know what a PWM output is doing.

I don't know what AH meter you have & I don't know what solar controller you have, but if the solar charge feed to the battery bypasses the AH meter sensor, then it would not be beyond the realm of my imagination for some automatic algorithm in the meter to calculate that your bank has more capacity than it really does after the meter sees good voltage remaining after it saw more power going out than it saw go in.
 
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