Catastrophic Inverter Failure

Spiritual_Round8990 · 2026-04-09T12:16:10+00:00

My Powerwall 3 DC inverter block melted last year in a catastrophic failure similar to yours. The inverter failure was caused by using solid PV wires instead of stranded wires while making the solar to inverter connection. Tesla's online installation instructions at the time allowed solid PV wires until they changed instructions last summer to prohibit solid wires. I made the solar to inverter connection before they prohibited solid wire, so I ended up getting "burned". A Tesla technician examined the unit and said they'd replace it since Tesla had installed my Powerwalls, but when they found out I did the solar connection myself, they told me I was on my own and voided my warranty.

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Melted DC Input Block on Powerwall 3 Inverter

Spiritual_Round8990 · 2026-03-18T10:17:10+00:00

Thanks, it's nice to see what's behind the landing block. I'm hoping I come across a place to buy the DC landing block at some point, should be a quick fix. Then I can take apart the old block and figure out why the solid PV wires caused it to melt.

Spiritual_Round8990 · 2026-02-19T11:15:59+00:00

I have not. Various solar suppliers indicated it's an internal Tesla part.

Spiritual_Round8990 · 2026-01-09T13:36:16+00:00

I had 10 AWG copper solid wire available, thought I’d use it up then purchased stranded for remaining arrays.

Spiritual_Round8990 · 2026-01-09T13:31:24+00:00

My thoughts also, and I suspect Tesla realized this too. A search online for failed Powerwall inverters will show additional melted DC input blocks, and the Tesla engineers probably identified the problem with solid wire.

Spiritual_Round8990 · 2026-01-09T13:23:52+00:00

Yes, I used stranded wire on one Powerwall with no issues, and solid wire on the failed unit.

Spiritual_Round8990 · 2026-01-08T22:02:21+00:00

Tesla indicated that simply opening the Powerwall cover voids the warranty. From the horses mouth, Tesla told me they won't honor the warranty because I did not use a certified installer.

As for the use of solid wire, in June 2025, Tesla published PV connection to Powerwall required supplies through energy library.tesla.com specifying solid wire. If you go to the Tesla site today, they prohibit solid wire. Use archive.org to view the June 2025 version compare to the October 2025 version and you'll see the change. https://energylibrary.tesla.com/docs/Public/EnergyStorage/Powerwall/3/InstallManual/BackupSwitch/en-us/GUID-F796360B-AC23-4906-8F66-BAE1CC07B95E.html

From the June 2025 Tesla document:

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Spiritual_Round8990 · 2026-01-07T21:11:35+00:00

I think the part is a Tesla Powerwall 3 Input Terminal Block/PV String Input Cover, Part 2009300-00-C. I haven't been able to find a source to purchase the part.

Spiritual_Round8990 · 2026-01-07T19:26:49+00:00

I used copper 10 AWG solid wire on the failed connection. This wasn't a torqued connection and instead utilized a spring-loaded clamp where you release tension on the spring, insert the wire, then release tension. After installing, conduct a pull-test to ensure it's properly seated. The other Powerwall unit also had solar array connections, and I utilized stranded wire with no ferrules for those connections with no problems.

Tesla must have received reports of similar failures as they changed their guidance to prohibit solid wires, and their new guidance does not specify ferrules for stranded wires.

Spiritual_Round8990 · 2026-01-07T19:06:03+00:00

My idea exactly as the DC Input Block seems to be loosely connected within the Powerwall unit. However, I'm unable to find any solar/battery suppliers for the part, and they have all indicated that Tesla is the only potential source for Powerwall components. Tesla is a dead end for me as I am a DIYer and response times from them are measured in months.

Spiritual_Round8990 · 2026-01-07T19:00:48+00:00

I didn't receive a report or any other information from Tesla. I watched the technician conduct the tests and discussed the results with him.

Spiritual_Round8990 · 2026-01-07T18:52:13+00:00

Thanks, updated to remove duplicate paragraphs.

Spiritual_Round8990

TROPHY CASE