KWeld Reversze polarised

[WaynesWorld]

Got myself a KWeld spot welder last year and was working well till I connected the power cables to my source battery (100AH AGM) in reverse, and killed it... Well not completely. It blew a track off the back which I repaired. It still appears to weld but they do not hold, even when set to over 100 joules, using 0.2mm nickel. They just pull off.

I suspected I killed the FETs, so I desoldered the 5 drain legs of each, and they all tested about 20.v forward and 2.8v reverse if memory serves. Is this right for these?

I can see no other obvious damage. Anyone got schematics or know what i should be looking for next?

[m k]

Maybe adding some pictures would help.

https://www.eevblog.com/forum/projects/guesses-on-what-i-am-attempting-here/25/

[WaynesWorld]

Not much to see. There is no obvious signs except the blown track I repaired. I just took the little strip off so you can see the damage caused by the polarity reverse. And I removed the display to expose the main board.

Let me know if you need anything else?

[static333]

Did you find the datasheet for these MOSFETS?
Here is how to test MOSFETS: https://www.homemade-circuits.com/how-to-check-mosfet-using-digital/

Still wrenching on the 720 SD?