Like many people here i’ve been using my BT-C3100 for around 10 years. It’s been an absolute workhorse and never gave me any issues until recently.
A few months ago slot no.1 started giving false readings and even overcharged a battery to 4.5V. After that i stopped using that slot and continued with the remaining three.
Not long after slot no.4 began showing similar problems. At that point i decided it was time to open it up and see if it could be saved or if it was ready for the bin.
By then slot no.1 was reading around 0.4V even with no battery inserted so something was very wrong.
The issue became obvious about three seconds after opening it. There are several electrolytic capacitors on the positive rail (not entirely sure of their exact role) and all of them were bulged and likely dried out.
They are low esr 10V 220µF capacitors. I ordered replacements from aliexpress swapped them in today and so far everything seems to be working properly again.
Given that these chargers are getting close to a decade old, it might not be a bad idea to refresh them especially if you are still relying on one as your main Li-ion charger.
I should check mine, too. My usual #4 slot started going mental with the display, “flickering” between 2… “screens”? Like really rapidfire, 3-5 times per second. The other slots seem okay.
With all the other chargers I got, you’d think I’d have a spare at the ready if this one goes teats-up. Pfffft.
Thank you very much for posting regarding this issue, as well as the related info you included!
Perhaps particularly given the pulsed (vs continuous/steady) charge & discharge current going on in these units, I wouldn’t be surprised if those caps perhaps don’t lead the easiest of lives;-)
Mine is similarly ~10 years old, and is still doing what it does consistently / well; although it has had a relatively ‘easy life’ compared with some, and is no longer the primary device I use.
Again, thanks for the potential failure point to keep in mind!
