Panasonic cordless phone shows charging but actually it's discharging

"There is a diode on the circuit board, if this is faulty the phone will show to be charging- but the charger will actually drain the hand-set batteries. I de-soldered this off the board and re-placed with a small diode off a defunkt circuit board that I happened to have, any small value diode should fix this. The old diode must be removed. Mine now works fine.

-David"

"I don't know enough to replace diodes or repair my phone or base. I have the same symptoms of the original poster. Is it more likely the problem is with the handset or base? I'll just replace the culprit.

Thanks"

"Have a slightly different problem. 1 out of 4 handset is forever charging even though battery is full. I can put a known full battery (shows full in other handsets) into this one and it will show 1 bar. If the handset charging circuit think battery is not full. All of this without the charging station. The charging station is fine as I can put other good handset in there and battery charing behavior is correct (shows charge complete when full)

So obviously if the handset thinks a full battery is not full, then its always charging and generating heat like what I am seeing. Going to probe the circuit board (pic below) for voltage readings. Looks like there are diode on the battery side also. Wondering if others have had this problem.

I have 4 handsets and using a known good fully charged battery, I get 2 handsets showing 1/3 bars, 1 showing 2/3 bars, and only 1 handset showing 3/3 bars.

Dug a bit deeper into the schematic (didn’t find exact but perhaps close) Battery voltage is fed to the IC (likely pin 58 of basedband IC SC14430). IC reads voltage and make decision to trigger the external charge circuit (transistors + diode system). 3 Voltage islands on the handset board (3.3V, 2.5V, 1.8V) identical readings between good handset and bad one.

On the good handset, had the handset opened up with alligator clips on battery post for 2xAAA power supply. The alligator clips accidentally touched the 2 charge terminals as its easy to do with the back cover off. Battery and charger terminals next to each other are reverse polarity and the good handset also shows 1/3 bar on full battery after touching. There was no spark or noise. Something must be really easy to damage with such low voltage and current."

I am having the same issue. You a very technical person. Can you state in layman's terms how to fix?

"hi,

i have a somewhat similar problem with my panasonic handset.

my handset is 110v and i live in a country with 220v. i usually just get an adapter 220v to 5v and splice them up. this time i accidentally switched the wires while splicing.

when i put the phone on the dock, it somewhat reversed the phone. meaning when i remove it from the dock. it says that its charging and i cant use it. and when i put it on the dock it thinks that it is out of the dock and i can use the phone.

i tried the dock again with another phone, and it did the same. it somehow reversed the phone. after that i doubled checked my splice and found out the i reversed the wires.

is there a way to fix this? not sure if the polarity is the issue. for now i cant use the phone.

thanks in advance

Update (08/02/2020)"

There are 3 possibilities - bad batteries, bad charging base, bad contacts. It's clear that bad charging base (defective diode) has happened to a number of people and is probably the main reason people come here (after all, you will have replaced the batteries before you get to this topic). Why not just close this topic - it's been solved!