Honestly I don't think the charger has anything to do with his problem. He made an assumption, but from all he's described it seems to be a battery issue. Panasonic also offers a 4a charger for his battery and it's a simple 2 pin connector so his initial thinking that 4a is too much current doesn't hold true.
For charging Li_Ion batteries all you require is a CC-CV power supply set to the correct charge voltage. It's not rocket science or anything that requires $100's dollars in hardware as this tech' has been around since before Li_Ion batteries were even invented.
This is true.
XLR connectors mainly used for audio connections have been used for years as charge connectors as well as they can handle the low current and are a quality connection. The 3rd pin is utilized in charging things such as golf carts as a safety device (lock out) to prevent anyone from driving it away while charging...though I haven't seen that safety feature utilized with ebikes.
And though you might be able to get away with 3 pins for communication by doubling up on the Negative wire... Much better practice is 2 separate wires for communication, hence 4 pins or more.
Three pins is passive communication. Tells people not to mess with it, even though 99% of the time, it's a dummy pin. It is in the XLR.
One exception is, if my memory hasn't failed again, is the Stomer 3 pin charger. Someone grafted a Stromer plug onto an expensive charger (Satiator?) using only the +/- and it wouldn't charge the bike. Per pictures posted in a thread here, the third pin appeared to have a resistor between it and the negative. Maybe Tom J. remembers.
And I think it's a connector issue. I have a bunch of adapter cables I made to allow my various chargers with 5.5mm plugs to use XLR plugs, or XT60 and XT90 connectors. With my tiny 3A charger. I note my 5.5 connector mounted on a cable. which hangs in the air and doesn't have a case/cabinent to transfer heat, getting a bit hot over time.
Excellent! I love happy endings.
Did you get an explanation of the failure?
Not that 4a is excessive.. But unless you have a time constraint charging slowly with a 2a Charger is a little better for the battery as it generates less heat within the pack.