PD9245C-14.8

KJINTF wrote:
BLF

A while back you posted a thread regarding a blowup thermistor on one of your converters.

Was that Converter a PowerMAX PM3-100?

The reason I ask, Just received one requiring service and noticed an aftermarket thermistor was soldered in from the top. Remembered you mentioned your soldering ability and wondered if it was your old converter.

The real problem was a shorted FET which is a simple low cost fix for a 100amp converter.

Yes it was. I still have mine though. PowerMax says they have since upgraded their thermistors. Haven't heard of any troubles since.

The prototype adjustable 100 they cobbled together in 2012 had the big 5R25 thermistor's fat "legs" attached to the thin legs of the original smaller thermistor that had been clipped off.

My repair job was to drill through the circuit board and poke the legs of the new thermistor through to get the thing down to the right height to fit under the lid, and then solder above and below, and clip off the legs sticking out underneath. I am really bad at soldering so I was lucky the thermistor was located where I could get at it by itself on the board.

I have also used a 2R25 thermistor with thin legs which seems to work as well as the big 5R25 with the fat legs, so I don't have to drill such big holes for the fat legs. Problem solved so far.

The big 5R25 thermistor in the prototype was bigger than the regular PM3-100 had back then, but I still managed to blow its thermistor. I blame "hot restarts" and also clamping on the 12v after turning on the 120v input was mentioned by guys here as a possible cause, where that is harder on it.

Now I make sure the 12v is attached first, and if the Honda gen conks out right after starting, I don't immediately restart it and so get the converter back on while the thermistor is still warm. (I have revised my Honda start to prevent that too--now let it warm up for a couple minutes before plugging in the 100 amper so now it doesn't conk out. If it is cold out like 35F, I also start with eco off then turn eco on a bit later after it is all running ok. No more conking out and no more fried thermistors either.)

I reported on my thermistor tests some time back. What was strange to me is that the converter still worked ok even though the thermistor was partly damaged. I got several starts out it before it got so damaged the converter would not start any more. The big black disk first gets a crack or two and it can even show a red hot spot glowing before shutting it off. Pieces fall off. It still works! But when enough pieces fall off, that's it. :)