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MPP 24V Solar Inverter Troubleshooting

CandaceBlair

New Member
Joined
Jul 3, 2021
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39
Hello all,

Newbie day 3 here ??I’m trying to figure out why my solar panels are dead. Upon testing with multimeter, there are good readings at the panels themselves, going into the inverter but not coming out of it.

I’m not sure what to do besides maybe buy a new inverter. It was purchased last fall and hasn’t been used more than a month on the road (it’s in my camper conversion). Is there something else I should test or scrap it for a new one?

More context: when I bought the camper it worked fine. There was an arch at the negative wire, happened when I dropped it off to be painted, I assume they were inside trying to check things out. Cleaned all that up but it hasn’t been right ever since. Before it died, it would charge when plugged up to shore power but still not from the panels. I went out of the country for two weeks and unplugged it, it was dead when I got back and will not charge when plugged up.
 
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Hopefully a solar charge controller rather than your inverter. If you have an "all in one" it could be both, plus a shore power charger.

Do you know what model you have? Arcs are never good for electronics.

Wires from the solar panels should go into a box. Make sure you have voltage there. It could be as simple as a blown fuse.

Your description sounds like an all in one.
 
Hopefully a solar charge controller rather than your inverter. If you have an "all in one" it could be both, plus a shore power charger.

Do you know what model you have? Arcs are never good for electronics.

Wires from the solar panels should go into a box. Make sure you have voltage there. It could be as simple as a blown fuse.
It’s an all-in-one. I’ll check the wires from the solar panel box also.
 

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Hopefully a solar charge controller rather than your inverter. If you have an "all in one" it could be both, plus a shore power charger.

Do you know what model you have? Arcs are never good for electronics.

Wires from the solar panels should go into a box. Make sure you have voltage there. It could be as simple as a blown fuse.

Your description sounds like an all in one.
I’m also not sure what all I should be checking, there wouldn’t be a video on this by chance anyone could link for reference would there? I’m trying to find everything I can between Google and YouTube but an all in one explanation would be great. Especially knowing what the voltage should be at each point.
 
It’s an all-in-one. I’ll check the wires from the solar panel box also.
I know nothing about the unit or more importantly how to diagnose it.


They may have spare parts for it, or be able to help diagnose it. They are good units by reputation. Certainly an 80 amp charge controller is above average. Actually quite a nice price as well, you would have a hard time finding a solar charge controller with 145v input and 80 amp output much cheaper.
 
I’m also not sure what all I should be checking, there wouldn’t be a video on this by chance anyone could link for reference would there? I’m trying to find everything I can between Google and YouTube but an all in one explanation would be great. Especially knowing what the voltage should be at each point.
We have multiple people on here with the same unit, we just need to get them involved. @Will Prowse has a video on the unit, but it is not a "diagnose the problem " video.


He has multiple about the all in one units.
 
We have multiple people on here with the same unit, we just need to get them involved. @Will Prowse has a video on the unit, but it is not a "diagnose the problem " video.


He has multiple about the all in one units.
Ok thank you for your input and the link. I’ll watch a few more of Will’s videos. They have been my go-to troubleshooting resources for the last three days.
 
Ok thank you for your input and the link. I’ll watch a few more of Will’s videos. They have been my go-to troubleshooting resources for the last three days.
If nothing else, it tells you what wire goes where and how to access the terminals to verify that the solar output makes it to the unit. Also make sure the battery power makes it to the unit.

At that price you can probably replace it cheaper or almost as cheap as repairing it. MPP is based in Taiwan, so you can probably get better support than from mainland China. You may want to send them an email, like I said, maybe as simple as a fuse.
 
If nothing else, it tells you what wire goes where and how to access the terminals to verify that the solar output makes it to the unit. Also make sure the battery power makes it to the unit.

At that price you can probably replace it cheaper or almost as cheap as repairing it. MPP is based in Taiwan, so you can probably get better support than from mainland China. You may want to send them an email, like I said, maybe as simple as a fuse.
Yes, that video and the solar forum search for my specific unit has helped steer me in the right direction for checking everything I didn’t know to check/where to check already. Thanks for those quick tips!
 
Does anything work on this all-in-one? Inverter? Charger? Transfer switch? Solar?

I prefer separate components for these things to avoid days like this.
Consider if you need a new solar controller just get a separate controller.
 
Yes, that video and the solar forum search for my specific unit has helped steer me in the right direction for checking everything I didn’t know to check/where to check already. Thanks for those quick tips!
If wired correctly, there should be a breaker somewhere to disable the solar panel input, so if you don't have voltage going in, start looking for it.
 
Sounds like you fried your solar charger controller. Both the the pv and batteries connect to it. Easy board swap. Literally 20 minutes. Have you confirmed your inverter is fine by running loads via shore power through it? As a poster above said there are fuses in the system that you should check as well. (Inside) Did you buy this from Ian Roux? If so contact him via USA mpp solar and he'll point you in the right direction
It's the long board pictured below. I have the 24v hybrid units. I'd assume this part is the same
 

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Sounds like you fried your solar charger controller. Both the the pv and batteries connect to it. Easy board swap. Literally 20 minutes. Have you confirmed your inverter is fine by running loads via shore power through it? As a poster above said there are fuses in the system that you should check as well. (Inside) Did you buy this from Ian Roux? If so contact him via USA mpp solar and he'll point you in the right direction
It's the long board pictured below. I have the 24v hybrid units. I'd assume this part is the same

I would assume he has spare parts, or can order them. Thanks.

This looks like the manual, which always helps.

 
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Does anything work on this all-in-one? Inverter? Charger? Transfer switch? Solar?

I prefer separate components for these things to avoid days like this.
Consider if you need a new solar controller just get a separate controller.
I may not fully understand but if I’m following you, nothing works right now because my entire system is dead. The all-in-one won’t even come on the way it’s connected at the moment. And I do understand why you say separate components would be better here.

Sounds like you fried your solar charger controller. Both the the pv and batteries connect to it. Easy board swap. Literally 20 minutes. Have you confirmed your inverter is fine by running loads via shore power through it? As a poster above said there are fuses in the system that you should check as well. (Inside) Did you buy this from Ian Roux? If so contact him via USA mpp solar and he'll point you in the right direction
It's the long board pictured below. I have the 24v hybrid units. I'd assume this part is the same
Got it! it got dark on me and I’ve been troubleshooting all day trying to figure this out so I took a break but I will check the inverter via shore power first thing tomorrow. Thank you for the insight.
 
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Here we are ten days later and I think I’ve figured out my issue. Solar panel tech said I needed a new inverter. Power was going in but none coming out. So before I bought one, I plugged it directly to the lithium batteries and bypassed the BMS. The inverter came on ??

Crazy thing is, my BMS was working ten days ago. I’m wondering if the solar tech put something back together wrong when he took all the wiring a loose?? But if it’s the BMS, that’s much cheaper than buying a new inverter!

Thank you all for your help and guiding me when I was lost!!
 
Here we are ten days later and I think I’ve figured out my issue. Solar panel tech said I needed a new inverter. Power was going in but none coming out. So before I bought one, I plugged it directly to the lithium batteries and bypassed the BMS. The inverter came on ??

Crazy thing is, my BMS was working ten days ago. I’m wondering if the solar tech put something back together wrong when he took all the wiring a loose?? But if it’s the BMS, that’s much cheaper than buying a new inverter!

Thank you all for your help and guiding me when I was lost!!
It's certainly possible that the BMS could be bad.
It's also possible that the BMS is just doing its job and shutting off power for a reason.

You may wish to post some screenshots of the app for the BMS, it might tell us.
 
It's certainly possible that the BMS could be bad.
It's also possible that the BMS is just doing its job and shutting off power for a reason.

You may wish to post some screenshots of the app for the BMS, it might tell us.
Yes, I am optimistically thinking that is what’s happening also, the BMS is doing its job! My batteries are wired correctly but my BMS is showing incorrect readings. Is there a way to reset it? I tried shorting the negatives coming out of both ends of the BMS but that didn’t work. Saw it on a YouTube video.

the batteries are wired in series and still charging. Voltage is set to 28.8. It’s still charging very slowly but charging none the less and almost done finally!
 

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Yes, I am optimistically thinking that is what’s happening also, the BMS is doing its job! My batteries are wired correctly but my BMS is showing incorrect readings. Is there a way to reset it? I tried shorting the negatives coming out of both ends of the BMS but that didn’t work. Saw it on a YouTube video.

the batteries are wired in series. Voltage is set to 28.8. It’s still charging very slowly but charging none the less and almost done finally! The app reading and voltmeter reading are not the same and I can’t figure out why!
 
Yes, I am optimistically thinking that is what’s happening also, the BMS is doing its job! My batteries are wired correctly but my BMS is showing incorrect readings. Is there a way to reset it? I tried shorting the negatives coming out of both ends of the BMS but that didn’t work. Saw it on a YouTube video.

the batteries are wired in series and still charging. Voltage is set to 28.8. It’s still charging very slowly but charging none the less and almost done finally!
You should not charge without a BMS, you will soon ruin your batteries.

Yes, it certainly looks like the BMS has been fried. The BMS looks at individual cells that make up the battery and protects (shuts off) if an individual cell would be damaged by more charge or discharge. If all of the individual cells are above 3.0v and below 3.5v, I would stop charging until you replace the BMS. The cells that make up the battery have a charge curve that is interesting, and makes it very difficult to control manually, that's why everyone uses a BMS.

Identical BMS (I think):


One that is actually rated high enough to run your Multiplus:


Never mind, I looked back, you have a 2000 watt inverter, the 100 amp model is fine. You may wish to contact Overkill, they have a good warranty.
 
You should not charge without a BMS, you will soon ruin your batteries.

Yes, it certainly looks like the BMS has been fried. The BMS looks at individual cells that make up the battery and protects (shuts off) if an individual cell would be damaged by more charge or discharge. If all of the individual cells are above 3.0v and below 3.5v, I would stop charging until you replace the BMS. The cells that make up the battery have a charge curve that is interesting, and makes it very difficult to control manually, that's why everyone uses a BMS.

Identical BMS (I think):


One that is actually rated high enough to run your Multiplus:

The BMS was working so I’m definitely not purposely charging without it. It’s connected but I don’t know why it’s not working anymore. The power supply is about to stop charging the batteries and I’m repeatedly monitoring as well.

Thank you for the link, I will check it out.
 
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