Re: (ET) Charger failure with very interesting data....

[g k <oasis654 gmail com>]

An electric Detective

On Sat, May 16, 2026 at 1:27 PM Chris Zach via Elec-trak <
elec-trak cosmos phy tufts edu> wrote:

> This morning I was using the "newer" E15 tractor and putting it on
> charge between runs. No biggie, runs fine.
>
> However after about 30 minutes I noticed that the transformer was
> humming when I walked by it. Odd, but didn't make the connection that
> things were "wrong"
>
> A short time later I was sitting in the hammock, looked over, and saw a
> wisp of smoke coming from the charger (lid was open). Ran over, AC cord
> was hot, unplugged it, pulled the cage over the charger and yep, the
> transformer windings were smoking on the primary side.
>
> Bad. Drove it over to the hose, hosed it down to cool it off, took a
> picture, still hot even with water on it. Very odd.
>
> WHAT HAPPENED?
>
> The good news is I have it plugged into a Third Reality outlet which
> logs all data to my Home Assistant. So I was able to pull up the charge
> profile to see what the heck happened. It's.... interesting and kind of
> explains what went bad.
>
> Normally when charging the charger goes to 11 amps/1000 watts/PF 90%
> then quickly drops to around 8a, 800 watts, PF 92% as it bulk charges.
> Then as the battery voltage hits 42.5 or so the AC power input drops,
> power factor stays about the same. Ok.
>
> Not this time. As the charge current tapered down the power factor began
> to drop 80%, 70%, 60% then it dropped like a rock to 20%. At the same
> time the wattage went up sharply from 116 watts (fully chargedish) to
> 600 then 700 watts then 480 and was climbing back to 600. The power
> factor was 23% and the amperage went from 1.4 to *19* amps. (all at the
> AC plug values)
>
> WOW!
>
> This was not good. While the watts drawn was within specs, the current
> had skyrocketed and would probably have popped the breaker in a few more
> minutes. And while it was only pulling 400 "watts" it was probably
> pulling 2000+ volt/amps.
>
> So what happened?
>
> Not sure yet, but I'll bet the capacitor went to a dead short. I'm
> wondering if that was the winding that was smoking; if so is quite
> possible the transformer is toast. Oddly enough the wires to the
> capacitor (pretty light ones) were not smoked, so what I may have seen
> in the graphs was the capacitor failing, then the PFC windings heating
> up and shorting then all hell breaking loose.
>
> Very interesting. I THINK I have a spare transformer; but I don't think
> this was a diode failure. Diode bridge was cool and batteries are
> charged and working.
>
> Interesting data point.
>
>
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