diy solar

diy solar

Can’t get a charge

Jaketx22

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Dec 24, 2021
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I have a van with 2 100 watt solar panels that I modeled off of will prowse’s small 12 volt system. When I first put it together it worked great all summer when I just had it hooked to one panel. I just unhooked everything and moved it all to a more secure spot in my van and hooked up a second solar panel. I have not been able to get a full charge on my 100 ah battle born lithium battery. I cleaned my panels and parked my van in the full sun(I live in Texas) my remote meter keeps reading that it is nighttime and won’t charge. I don’t see any loose wires or anything. What could be wrong?
 
Did you connect the panels to the controller before connecting the battery? If yes, you may have confused the controller. Are the two panels wired in series? 36V coming into the controller would be very confusing. I would fully physically disconnect all the wiring, and start over, connecting the wire from the battery to the controller first. Let the controller boot up, and only after it's booted reconnect the solar input wires.

What controller do you have? Is it MPPT or PWM? Are your panels wired in series or parallel? There are some fake MPPT controllers out there that say MPPT on the cover, but are actually only PWM. It could have worked just fine with 1 panel, putting out voltage appropriate for a 12V battery, but not two in series.

Also, keep in mind that the winter sun is lower in the sky now then in summer, so the panels are getting lower solar input.
 
I think I connected the battery first. I wired my panels in parallel. It is an mppt controller, good quality.
 
I think I connected the battery first. I wired my panels in parallel. It is an mppt controller, good quality.
Do you have a volt meter that you can put on the contacts and see if there's actually power coming in? It might be a broken wire that you can't see because the insulation is covering it? If you do see voltage, try tilting the panels over to better face the sun. It is just two days after the solstice. The sun is just about a low in the sky as it can get right now. If it is a true MPPT controller, try wiring the two panels in series.
 
So I unhooked it and rewired it all back in. It now is showing that it’s daylight but not charging, it is showing 4 volts from the panels
 
So I unhooked it and rewired it all back in. It now is showing that it’s daylight but not charging, it is showing 4 volts from the panels
I would disconnect the panels and test open short voltage across both. Maybe the new one is dragging the other down? If both test out good, I would ohm the wires with the panels disconnected, breaking everything down into the smallest possible sections for testing.
 
Ok thanks, I’ll have to get a volt meter. I did see that the hot wire from panels wasn’t seated in the charge controller very good so I redid it and when I did the voltage dropped to 2 from 4.3
 
Well the connector I bought only allows it to plug in the one way so it shouldn’t be reversed
 
Ok thanks, I’ll have to get a volt meter. I did see that the hot wire from panels wasn’t seated in the charge controller very good so I redid it and when I did the voltage dropped to 2 from 4.3
Has solar panels, CC, batteries but no VOM.?
I’m just messing with you but a VOM is essential when troubleshooting this stuff.
 
Well the connector I bought only allows it to plug in the one way so it shouldn’t be reversed
Murphy's Law Mistakes get made. The connectors could have accidentally put on backwards. This is where the voltmeter comes into play for troubleshooting. You can get one off ebay for less than 10$.
 
We've seen 2V before, and that time it was reversed polarity from panels.

Don't assume everything you buy is correct.

A VOM, DMM, etc. is essential for troubleshooting, connecting things correctly, evaluating operation and condition of batteries ...

Dont need one when it works!

But it doesn't. So Quit arguing and buy one.
 
Wasn’t arguing, definitely need one now, just explaining why someone would have all that stuff and no volt meter. I did unhook it and hooked back into the original panel they way I had it before and it’s still just showing 4.3 volts
 
I did crimp some 10 gauge wires to the solar wire to get enough length to go to the new spot where I have The charge controller, I wouldn’t figure that would result in such a drop though.
 
Can you separate your panels with your wiring right now? Have you tried just plugging in 1 panel, check the voltage, swap panels and re-check? If both panels give you the 20-ish volts you're expecting then when they're together you should be reading real voltage. If one is dead it'll mess with the other one. If one is flipped on accident then your voltages will be backwards and there's your culprit.
 
Dont need one when it works!

Yes you do. You need it to know what you're doing, before it works or not.
You'd want to at least check polarity, you can't just go trusting labels.
Check it before you connect things, double-check it after, then triple-check it before you power it :·)

In the case of you panels, you would probably also want to measure current (A) to get a read of what they're actually putting out.
Most meters have a 10A plug you put your lead into to measure anything more than milliamps.
Still, 10A, at 12V, isn't much.
Make yourself a field ammeter like mine :cool:

fieldamp.jpg
 
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