Thanks for the suggestion. I wish I could contact the mfr but it's the weekend
and the grass need mowing. Also, Ryobi also no longer makes this mower, so many
parts are no longer available. The local mower shops don't have the time or
expertise to troubleshoot this kind of problem. That's why I'm having to
troubleshoot it board-level.

So.... here I am back to where I started.

Here's some more info...

After going over the voltages again after dinner, it looks like the charger is
only putting out 18-21VDC, which is too low to give a decent charge. Seems like
I remember troubleshooting something else on this mower a few years ago and it
was putting out 27VDC.

So, I went back and look at the little rectifier board, which is just 4 diodes.
The input there is 35VAC and the output is 107VAC and 46VDC. Does this look
weird? I'm wondering where the AC is coming from and why it's up so high.

The diodes all checked out OK with an ohm meter, but I’m wondering if one of
them is breaking down when AC is applied (?)

Polar

Can one assume that you have contacted the manufacturer?

[...]



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Polar