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Old 10-25-2017, 06:05 PM   #1
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Insufficient Solar?!

Unfortunately, it seems Iíve put the cart before the horse meaning I fear I have a solar setup installed on my camper van that is not sufficient for the size of battery bank.

Hereís what I have:
-2x Eclipse 100W monocrystal panels in series
-20 Amp Commander MPPT solar charge controller
-MT-50 Tracer Meter
-2x Lifeline 4D AGM 210 Ah batteries in parallel (12V, 420Ah)

After living in the van for 10 weeks now I realize that the batteries never reach full charge due to the fact that the solar output is not sufficient for a battery bank with 420 Ah. The average charge the system will achieve is about 12.7V. So, never do the batteries reach a full state of charge.

2 question for your imaginative input:

1. How could I add to the existing solar setup to achieve the charge needed for this battery bank? Space is the biggest constraint being there is only an additional 42Ēx15Ē area to work with behind the other 2 panels. And the controller is a max of 20A.

2. Would I be better off downsizing to just one 210Ah battery? The existing setup should sufficiently charge just one correct?

Any help and insight is appreciated. The van will be home for another year so having a properly working solar and battery setup is pretty important. My apologies for being a bit ignorant on the subject and obviously not doing the thorough homework I should have in the first place.

Thank you!


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Old 10-25-2017, 06:23 PM   #2
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Why are the panels in series? (This might be a dumb question, but it might also be THE question)

But I would think that you are pumping in 30+ volts which is great for a 24 volt system, but unnecessary for a 12 volt system. I am not familiar with how the controller handles that but it does say it auto senses 12 or 24 volt systems. Something just sounds wrong here, I think you should be paralleling those panels into the controller unless the instruction manual tells you otherwise.

And remember, solar panels really only give off max charge when the sun is right on them, so most times you are getting a lot less.

Keep both batteries. Another thing to understand is that much capacity will really only be finished off by the charger for the most part.

What kind of charging profile are you using on those batteries? You should really only be using a bulk and float charge and only equalizing according to what Lifeline recommends, which is not until battery shows some signs of wear.

I quickly breezed the settings for that monitor, you should check to make sure the controller is set up for 12 volts as it might have defaulted to a 24 volt system or, if it sensed the battery voltage and set up properly it may be simply cutting out because you are sending more volts to it then it's cutoff voltage (~16). This goes back to having those two panels in series. Voltage adds in series, amps in parallel. So you may be causing your controller to simply cut out pretty much all the time.

What would be helpful is for you to let us know what your parameters are from the monitor.
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Old 10-25-2017, 06:50 PM   #3
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Quote:
Originally Posted by Flux View Post
Why are the panels in series? (This might be a dumb question, but it might also be THE question)

But I would think that you are pumping in 30+ volts which is great for a 24 volt system, but unnecessary for a 12 volt system. I am not familiar with how the controller handles that but it does say it auto senses 12 or 24 volt systems. Something just sounds wrong here, I think you should be paralleling those panels into the controller unless the instruction manual tells you otherwise.

And remember, solar panels really only give off max charge when the sun is right on them, so most times you are getting a lot less.

Keep both batteries. Another thing to understand is that much capacity will really only be finished off by the charger for the most part.

What kind of charging profile are you using on those batteries? You should really only be using a bulk and float charge and only equalizing according to what Lifeline recommends.
From what Iíve read series connections are used for smaller systems with a MPPT Controller. Connecting the panels in series does increase the voltage level while keeping the amperage the same. According to Renogy, ďThe reason why series connections are utilized with MPPT controllers is that MPPT Controllers actually are able to accept a higher voltage input, and still be able to charge your 12V or more batteries. Renogy MPPT Controllers can accept 100 Volts input. The benefit of series is that it is easy to transfer over long distances. For example you can have 4 Renogy 100 Watt panels in series, run it 100 feet and only use a thin 14 gauge wire.Ē

The MPPT controller has a 3 stage charging profile that goes through boost, float and equalization charging stages. This should be the correct way to charge, maintain and desulfate the batteries but, I think the 200W solar panel setup is not enough to properly achieve these charging stages. Thatís what Iím trying to confirm and remedy.
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Old 10-25-2017, 06:51 PM   #4
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Basic rule of thumb is 100 watt for each 100 ah .
I too am under wattage but not nearly as much.
I have 200watts for 310 ah but the 7622 helps to bring up the SOC.
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Old 10-25-2017, 07:50 PM   #5
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Why does the panel wattage matter?
I’d think with the alternator and a battery separator the batteries would get full charge when you drive anywhere. But assuming you don’t have one wouldn’t, worst case, it simply take a few days to bring the batteries to full charge?

I don’t see why they would “stop” charging at 12.7V unless something is misconfigured?
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Old 10-25-2017, 08:04 PM   #6
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Wiring solar panels in series simpy reduces the size wire you have to run, the controller takes care of the rest. The total number of amp hours you get from the panels remains the same in series or parallel. As for your first question, you have two choices as I see it. First, add more solar, or reduce your amp hours consumed. You could put a switch between the batteries, charging one at a time, but you won't get any additional amp hours in total. I have 300W in total, and 220amp hours of battery. Under solar alone, the batterys never come up to full charge until I drive for a bit, but the panels will run my refer non stop. It's all the other loads I add that exceedes the total output of my solar.
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Old 10-25-2017, 08:28 PM   #7
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It seems you are in fact reaching full charge. At rest, meaning when the van is not running, the 12.7V you are seeing from the batteries would be a full charge. Only when you run the van will you see the spike into the 14.--V range.
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Old 10-25-2017, 08:34 PM   #8
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Do you have a location where you can add a second alternator dedicated solely to the house battery?
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Old 10-25-2017, 08:52 PM   #9
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It seems you are in fact reaching full charge. At rest, meaning when the van is not running, the 12.7V you are seeing from the batteries would be a full charge. Only when you run the van will you see the spike into the 14.--V range.
It would help if we knew exactly what the charger model is.
I downloaded this:
https://www.renogy.com/renogy-20-amp-commander-mppt-solar-charge-controller-w-mt-50/#tab_prd-downloads

The table on page 21 implies that it would charge to 15V. Is that right?

In which case B350 should expect to see more than 12.7V, I'd think.
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Old 10-25-2017, 10:15 PM   #10
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As far as I understand, an AGM battery charges quite slow. That said, just idling the van will give a short charge peak with very little actual charging done to the battery. For a full charge from an alternator a van would have to be driven for anywhere from 4 to 8 hrs.
I can attest to this seeing a short charge spike into the 13V range after idling or even a short 1 or so hour drive. The battery voltage then falls back off to the 12.7V range.
And that is with a larger than stock alternator rated at 135A and 14.5V. I then also have the Blue Sea 7622 automatic charging relay which combines the van and house battery anytime 13V is sensed for 90 seconds and disconnects the two when voltage drops below 12.75 for 30 seconds.

And yes, the solar charger is the Renogy 20 Amp Commander MPPT solar charge controller.

I guess the lack of overhead sun at this time of year plays a big factor too which I didnít consider. So maybe that is playing a significant role in the equation?
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