Repairing a failed Enphase iQ7 Microinverter
for fun and profit?
Last year, I bought some IQ7 microinverters on eBay that were advertised as used, good condition. As it turns out, most of them were non-functional but by the time I tested them all a return was no longer possible. When provided DC power and connected to the grid (on the same trunk cable as other working microinverters), they power up, show 6 green LED flashes, and then start flashing red. They do communicate with the Envoy:
But they don’t seem to see any AC power. That has to be wrong since they’re communicating with the Envoy!
My suspicion is that the Power Line Communication, microprocessor, etc are all good, but maybe something’s wrong in the sensing circuit.
I poked around on the internet and found these:
Interesting to see that IQ7 and IQ8 seemingly use the same internals!
Those videos helped me see what’s going on inside - there’s a 3A fuse and a MOV, together acting as an overvoltage protection/crowbar. I suspect these micros were exposed to a lightning or other high-voltage fault at their previous location. Using those teardowns, I located the fuse position and drilled the housing to expose it:
I initially hooked up a resistor there in case there was a short internally, and powered up with 120v. No smoke, so I moved to 240v, no smoke, and then 240v no resistor. I hooked up a power supply to the DC side, and success! The microinverter can report AC voltage/frequency, and push power into the grid:
I also found this video which shows this failure (blown fuse/MOV)
And there was a comment from someone who had repaired them:
Couple last thoughts:
The housing is sealed well! I know that Enphase mills the housings off to open them up. I don’t see any other way if you want full access. In my case I just needed access to the fuse so drilling a hole worked, though I should have used my drill press with the travel stop set so I didn’t overdrill (which happened, you can see I touched the PCB)
I think its possible to replace the fuse and re-waterproof, by epoxying over the hole. Of course I understand this is Very Not Endorsed by Enphase! Not sure I’ll bother, mostly wanted to know what happened and whether it was a software (fixable) or hardware fault - and now I know.
If this was useful, please leave a comment!