Noob solar problem... no bulk charge state!

Masonsky

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Oct 11, 2021
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My setup on my off grid RV is

4 x 100w renogy panels, connected in parallel
Rover 40a mppt controller
Single 12v sealed battery

There is some moderate shading on the panels at any given time, but typically at least one panel is in full sun. I've taken readings at the terminal ends of the cables from panels to the controller before hooking the controller up, and I'm getting a solid 20v, but only 3 to 6 amps at any given time. After hooking up the system, however, the controller is only ever showing 12 to 14v from panel, which, as confirmed by renogy tech support, is not enough to allow the charge controller to enter a bulk charge state. I'm also confused as to why the controller shows a different panel voltage than I'm getting with the multimeter. The controller also only ever shows 0.0A going into the battery. I tried to measure the current going to battery today and blew the fuse in my multimeter :(

Another thing i notice is that the battery voltage (as displayed by charge controller) fluctuates based on incoming panel voltage. If the battery is down at, say, 12.3 before the sun is up, after we get some light it can increase to typically between 12.6 and 13.4, even though that is not the actual voltage state of the battery. Should I be concerned?

Can anyone help me figure out what I need to change to get my batteries charging? I'm completely in the dark about what the problem could be and I'm going to need this solar system to work to run my heater at night.
 
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12VoltInstalls

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Panel voltage on the display is not what the battery gets, and the battery voltage displayed is not either, because the battery load ‘weights’ the voltage input from the SCC to basically the same as or a halo above battery volts.
Unless the rover rover is busticated
 

Masonsky

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Oct 11, 2021
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Panel voltage on the display is not what the battery gets, and the battery voltage displayed is not either, because the battery load ‘weights’ the voltage input from the SCC to basically the same as or a halo above battery volts.
Unless the rover rover is busticated
Ok. That makes sense. I gather that the battery voltage will show in the 14v range during a bulk charge and the 13v range during a float charge, which will be different than both the input voltage from the panels and controller. What I can't figure out is why the controller won't charge the battery.

Do I just not have enough direct sunlight hitting the panels? To what degree can partial shade affect a solar array? Enough that the system won't charge a battery at all? Or is it more likely that there is an equipment malfunction or an error in the setup?
 

Rednecktek

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MPPT controller or PWM? Have you thought about going with a 2s/2p setup so the controller has more to work with?

Also, if it's sending 0a to the batteries, maybe they're just full? Sounds like you need a DC amp clamp.
 

Masonsky

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Oct 11, 2021
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MPPT controller or PWM? Have you thought about going with a 2s/2p setup so the controller has more to work with?

Also, if it's sending 0a to the batteries, maybe they're just full? Sounds like you need a DC amp clamp.
It's mppt. The battery isn't full as far as I can tell, I've taken voltage readings at battery, and as soon as the sun goes down the battery drops down to a low soc. The DC amp clamp sounds like a good idea, as I blew the fuse on my 10a multimeter earlier.
 

Rednecktek

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If you've got MPPT, give the 2s/2p setup a go. Your controller will have more to work with through the day and be able to charge up the batteries a little quicker in lower light. Remember, being in parallel the panels have to get enough sun to get over 14v before they start charging anything and those 100w panels usually top out at 18-20v so not a lot of head room. If you had a set in series each panel would only need enough sun to break 7v (7v+7v=14v min) to start charging the batteries.

Granted the math is probably a little more complicated but you get the idea. :)
 

12VoltInstalls

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got MPPT, give the 2s/2p setup a go. Your controller will have more to work with through the day and be able to charge up the batteries a little quicker
Exactly
FWIW I have 7 100W panels. As an experiment back in may or April I did 4 panels 2S2P with mppt and SE and SW facings. This was a remarkable change. I had an idea I might benefit but it worked so good I never got to adding two more panels or the seventh on my old pwm.

This morning, sun was just blipping up over the eastward mountains and my solar panels were reading ~14V. The charge side was 12.6V at ~2A. Basically not much at that point but if I were parallel I would be getting nothing at all. Now- 45 minuets later- panels are ~34V 2.x Amps and battery side is 13.2V and 4.5ish Amps
Big benefits demonstrated real-time.
 

Masonsky

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All right, I'm going to hop up on the roof and switch my setup to 2s2p today. I'll report what kind of numbers I see. Thank you for your help!
 

Bud Martin

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Aug 27, 2020
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OP: "There is some moderate shading on the panels at any given time,"
How moderate is the shading? 1/4 of the panel, 1/2 of the panel?
Is there away for you not to have shading so you can see how much power you are producing without shading?
 

Masonsky

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Oct 11, 2021
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The shading is around a quarter of total panel surface usually. The shade is from tall alder trees, so it's splotchy. Once in a while one or even two of the panels will be in full sun.
 

acdoctor

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Oct 5, 2020
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If you blew a 10 amp fuse, and were between the SCC and battery it seems you are charging some of the time. Maybe your consumption is just larger than your recovery with the shading. Move it to a new spot for a day. Or grab a saw.
 
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