PowMr - 24v Off-Grid Solar Inverter MPPT and 120A charger - issues with it! Can it be repaired

[lycaki]

Hi Everyone,

Bit of a strange one, just to give some background; Purchased this cheap PowMr 4200W 24V Solar Inverter Pure Sine Wave Off-Grid With MPPT 120A Charger from eBay.
Everything was good, system installed well, no issues - can't really fault setup and initial use. System was powering 2.5kw easily max and running 500 watts house idle, again didn't seem to be under any stress. I never ran more than kettles/PCs/ low energy ligths - no heavy loads. System ran with zero faults!

Roll on 30 days of continuous use without issue (soon to end).

I was using the AC charger at night to put 60-80 percent back into the batteries 24v Eve 8S1P (using cheap rate electricity we have at night). System again worked perfectly, charged batteries to required percentage... system happily carried on. No solar here in UK as yet (it's winter, no sun here in UK).

Then after about 30 days of use I noticed it was not coming on, did a power cycle - went to power it on ... heard some relays clicking to come on (as it does) and then it would click off again (as I was running it in offline mode on batteries only). While standing there, I heard a very loud pop noise.

Rather than check anything, just contacted my ebay seller, they immediately without question gave me a full refund! I was expecting some back and forth regarding what had happened. They just agreed to refund. Bizarre but very nice outcome... Can't really complain about the process there.

So now I'm left with an inverter that doesn't work and I would really like to repair it, rather than junk it.

I contacted PowMr direct and explained what had happened and I now wanted to repair it for myself, no obligation for them as I had received a full refund and could they help. Unfortunately, they've been particularly unhelpful ... they said they offer no parts for resale, I asked about replacement motherboards for sale. They said, no they don't offer!

So final ask - Would they be willing to send me a circuit diagram/ schematics.
They said they don't know what that is and they don't do that anyway.

I know they are not obligated to help me as it was through a third party seller but it's such a shame they don't offer anything other than 1 sentence emails to questions. I'd love to repair it! Inverters are within my skills and I'm well aware of the high voltages that are in them etc...

Anyway cover is off, all capacitors have had more than enough time to discharge (and will be checked). Annoyingly there is no visible signs of damage from Mosfets or Capacitors. No scorching or any burns whatever (visually inside - I enclose picture). I'm pretty sure the issue is on the DC side as it had AC power and was showing a fault 9 (overload but nothing was running at that time and had no load). The system was running mostly in off-grid mode (except for 4 hours at night).

The pop/bang was loud, I was expecting to see a capacitor had launched it's soul to outer space but nothing is out of place in first level inspection.

Anyone have any experience with fixing these... it's basically free and such a shame to junk it - even if it was crappy and only lasted 30 days.
I'm going to start measuring the 35v capacitors on DC and seeing if they register the right microfarad as that's an easy win. The Mosfets will be next ...

Anyone have any obvious clues as to what might have gone bang (it was more of a loud POP) after some clicking of relays.

Thanks for any help - not sure I can recommend PowMr unfortunately if this is how the quality of the product is and especially how PowMr support people, who offer zero support! I'm lucky I got a full refund.

 

[JCSchwarb]

Sorry to hear about your dilemma. I would want to know about your AC input synchronization and startup configuration. Is your inverter set to solar, battery then grid? How are you handling the physical Neutral-Ground bond? It sounds like there was an unbalanced load entering the inverter that caused it to pop. I had a similar situation between inverters that were not properly load balanced with current sharing cable.

As for repair, search out local electronics repair shops to see if they can isolate and fix.

Hope this gives some ideas.

 

[lycaki]

Thanks for replying JCSchwarb,

Basically, yes - I think mine was battery/solar then grid (although battery was set to charge from Grid)

It's a much simpler system setup, It was not attached to the grid as such, it has a simple AC in (not in phase or synchronisation) and separate AC out.
The AC in powers the charger and will power the load if required ... or charge the batteries. It's more of a glorified UPS - it was not really on except at night only to charge from AC side, not in use. The charge would be switched off and then full offline-battery mode used

The neutral bond is similar to some UPS/Inverters - it does tie into the casing of the inverter and use the house earth bonding (which is not ideal in my opinion in terms of earth grounding).
The setup was incomplete though, as I was going to setup a complete separate earth bond to a rod in the garden and setup an off-grid board to power the electrics. I wanted it fully separate from the AC/Grid and only have a charger on it at night. This will feature in my final setup. However it was just used as a UPS type battery to power my room electrics (simple PC/Lights etc).


At night it was on a smart timer plug which turned the AC part of it on at night, the AC was set to charge the Battery immediately (Util first) on AC about 50amps into the 280 amp battery. That part worked without any issues.

The pop bang came in the day, while I was in there, I think I had powered the battery side off - there was no AC/grid on into it at the time. When I turned on the battery DC side, that's when it start clicking on and off (only battery side) and then the pop.

Thanks, regarding local repair, I will do, I just fancied the challenge of fixing it... will go that route if I can't find any obvious issues (or beyond my abilities).

 

[JCSchwarb]

Sounds like you have thought out the fault condition pretty well. It still sounds like something caused a back feed or in rush or something to cause this failure. Do you have a CB or fuse between battery bank and inverter?

 

[lycaki]

Sounds like you have thought out the fault condition pretty well. It still sounds like something caused a back feed or in rush or something to cause this failure. Do you have a CB or fuse between battery bank and inverter?

I do, although that's set pretty high at 200amps - which was at roughly rated to not exceed 4800watts - I think the inverter can handle 6000watts short load. However, the BMS for the battery was set at 175 amps max output so should have dropped a load bigger than roughly 4200. I put them all well within tolerances of the inverter... Mainly for a surge that could bypass the BMS.

You would think the inverter must have it's own fail-safe internal fuses ... I can rule out PV inputs as I had the PV turned off with a DC isolater. So there was no PV overvoltage.

I can't see anything obvious that looks fuse at the DC side of the inverter but can possibly rule out surges from fuse and BMS failsafes?

Seems strange not to have something as simple as a fail safe fuse internally?

 

[JCSchwarb]

I do, although that's set pretty high at 200amps - which was at roughly rated to not exceed 4800watts - I think the inverter can handle 6000watts short load. However, the BMS for the battery was set at 175 amps max output so should have dropped a load bigger than roughly 4200. I put them all well within tolerances of the inverter... Mainly for a surge that could bypass the BMS.

You would think the inverter must have it's own fail-safe internal fuses ... I can rule out PV inputs as I had the PV turned off with a DC isolater. So there was no PV overvoltage.

I can't see anything obvious that looks fuse at the DC side of the inverter but can possibly rule out surges from fuse and BMS failsafes?

Seems strange not to have something as simple as a fail safe fuse internally?

I agree and was shocked when my inverter fried. The only fuse is the positive battery terminal. The issue on mine was unbalanced or unsynchronized phasing on the output stream. I did not have my AC input breaker on. Why the inverter didn’t sense the sine wave irregularities or the load imbalance and shutdown. Curious, when the inverter fried, did your battery CBs immediately trip? That could be another clue about the load imbalance.

 

[lycaki]

Seems like an easy win for them to put some circuit protection inside inverter - your inverter sounds like a more advanced model. I wonder why it didn't shut down like you said. Were you able to repair?
My friends model does the grid-tie in synchronisation but I was going to do that at a later stage. Now, I wanted a more simple almost off-grid UPS while I was getting it all setup and then spend some money later - now I wanted to take advantage of our cheap night rate electricity tariffs.

No nothing tripped via CB - it went to zero power. There wasn't even anything more than the inverter load on it at the time (which is 35 watts being drawn from the battery). It was such a weird failure like as though the part just wore out...

 

[mikeyoungvcu89]

I would just take the win - you got your money back. I had nothing but trouble. Tried to contact support a couple times but they are zero help.
The manual is a joke, they are probably dangerous as well. I breathed a sigh of relief when I got that thing off my wall.

 

[lycaki]

I would just take the win - you got your money back. I had nothing but trouble. Tried to contact support a couple times but they are zero help.
The manual is a joke, they are probably dangerous as well. I breathed a sigh of relief when I got that thing off my wall.

yeah you're probably right, just feels such a waste of it to junk it... when it worked, it performed well - for 30 days!
Sometimes they use cheap capacitors in bulk and it's easy to replace them with some newer better ones.

Can't say I'm impressed with the response from support. I appreciate they may not be interested in helping but it would have been nice to just engage a little. Definitely put me off buying any type of PowMr replacement due to the support response.

It was more of a side project to fix it