Making hardly any watts

alexmichaelx · June 2019

Hey ,

ive recently installed 2 50w flexible solar panels onto the roof of my campervan and wired them up parallel to my mppt charge controller and from there to the battery. I’m confident that the wiring is no issue and I’ve spent a while checking that and making sure of it. My digital meter tells me I am making roughly 22w of power from the pv’s but shouldn’t I be making at least 50-80w on 2 50w panels on an average sunny day? Right now it’s saying the pv voltage is 15.6v and a current of 1.4A. I can take a picture , make a video for anybody interested in helping me solve this issue. Some days I make 1a an hour then other days I make 2.4a to 3.5a an hour. But today is the best day of the year for sun and today I’m making 1.4a. Something doesn’t ad up and I’m a very confused cookie right now. Any insight would be greatly appreciated.

littleharbor2 · June 2019

Two things,
You need to series wire your panels if you have a REAL MPPT controller.
2nd, Is your battery already nearly fully charged? If so it wont accept much current.

alexmichaelx · June 2019

I started off my setup with both panels hooked up in a series. But later I read that I could damage my battery by doing so. When I hook it up in a series the voltage jumps to 36v. Then the mppt kicks in and it shows a lower voltage of 15v again but with a much lower ampage. Im using a 12v acid leisure battery on a daily basis which also runs my diesel heater. It’s never full unless I leave it to charge for a few days in the panels. if it was I wouldn’t be so bothered about this current issue with a low wattage input from the pvs. I have two liesure batteries and they both need a constant charge. I live in my van so I use a lot of electricity. But let’s be clear here. I do not use the liesure batteries when they are on charge. I use one at a time until it’s barely got any juice in it.
i really want to know why the wattage is only showing 22w when I have 100w on the roof. Whether I hook it up series or parallel I get the exact same wattage reading from the pvs. Thanks for you response. A

mike95490 · June 2019

alexmichaelx said:

.... But later I read that I could damage my battery by doing so. ...

You can damage the charger if it's connected to solar and not to the battery.

And if your charger is really MPPT, it should be able to handle 40V input, down convert it at 95% efficiency and charge your 12V battery.

100 w of panels is not in real danger of overcharging a battery that's in daily use. Maybe if you left it charging for a week with no loads....

littleharbor2 · June 2019

alexmichaelx said:

. But let’s be clear here. I do not use the liesure batteries when they are on charge. I use one at a time until it’s barely got any juice in it.

Why are you doing this? There's a good chance you have already ruined your batteries.

Can you enlighten us as to what brand and model charge controller you are using.

Estragon · June 2019

If the controller is really an mppt type, it not only can handle higher voltage and buck it down to charging voltage, it actually requires higher voltage to do so. Generally speaking, on the order of 20-30% higher, so charging voltage of say 14v needs 14v x 1.25 = 17.5v minimum. 15.6v is likely too low.

Also, if the batteries are being deeply discharged regularly, they may have lost a lot of capacity. If so, they would get to the controller absorb voltage fairly quickly, and take little current to stay there. They'll provide little current for loads, and take little current to "recharge" to the diminished capacity.

alexmichaelx · June 2019

I’m not going to reply to everyone here because nobody is sticking to the actual question at hand. The question is why are my panels only making 20w of power when I have 100w on the roof. I’m starting to think the flexible panel should I’ve bought aren’t as good as they say they are.
Ive explained my setup. There has been no damage to any batteries or charge controller. The wiring is fine and wiring them up in series or parraellel makes no difference. I would like to point out this is for a campervan not a house. Series wiring is commonly used on house sized charge controllers as my house has panels too. Series makes a higher voltage and parallel makes more ampage current. I need amps not voltage. Voltage is what it should be at but watts is not. Which is why I am lead to believe my panels are just cheap and worth replacing with more reliable ones.

alexmichaelx · June 2019

Don’t worry about it guys. I’ll But a new set of panels. These Chinese ones are the problem I think.

BB. · June 2019

Flex panels--If they last 2-5 years, you are doing well. And they have been known to die sooner.

If you have an Amp Meter (DMM with 10 amp full scale), you can just short out one panel in full sun and see if you get >50% of rated output Isc/Imp in full sun... If not, then the panel (or connections) are probably bad.

And with a light load (use a small 12 volt rated bulb) and see what the Voltage of the panel is (bulb should be less than 1/2 of panel output current in full sun for this test).

-Bill

Making hardly any watts

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