Trying to repair/hack logitech diNovo Edge keyboard ....

[scince!]

I am a big noob in electronics but I like to thinker a lot and watching EEVblog.

So I have a keyboard Logitech diNovo Edge for 8 years and my original battery died it can hold charge for 2-3 hours. I bought a new replacement battery. I installed the new battery but it`s not charging. When I put my keyboard on the charging station its blink once green and after that it blinks red. I switch it with the old battery and it works so I was sure the problem was in the battery. I emailed ElectroPapa.com and received a second battery for free but it has the same problem...

My theory : The battery for the keyboard have 3 pins (+,- and T) and the "T" on my new batteries is not working properly so the keyboard protection decides not to charge them so I want to bypass the protection. Pictures bellow show my idea will it work, will it explode , what do you think I have to do?

Greetings from Bulgaria and cheers to the professionals!

[PA0PBZ]

DON'T DO IT!

There is most likely a charging circuit between the charger connector and the battery connector, bypassing that will almost certainly kill the battery in no time 

[scince!]

I think the charging circuit is in the charger ?

[Rasz]

dont know about this keyboard, but logi mouses have charging circuit inside them, charging base is just a holder with connector

quick test if its the thermistor - wire up old battery ground and T  + new battery ground and vcc at the same time

[PA0PBZ]

This could be the charger circuit:

[scince!]

Rasz i dont fully understand you...
you want me to connect the new battery + , - and only connect the old battery T and see if its charging ?
I made some photos hope they are helpful close up of the suspected charger board on the keyboard and two photos of the insides of the docking station charger.

[PA0PBZ]

The fact that you have a T connection going to the board points to at least some part of a charge circuit there, it is supposed to stop charging when the temperature rises too high. when you measure the voltage on the T for both for the old battery and the new one (while under charge) it could provide a clue why the new battery isn't charging.

[Rasz]

Rasz i dont fully understand you...
you want me to connect the new battery + , - and only connect the old battery T

and ground

looks like your holder has smoothing cap and diode bridge

[scince!]

      I wrote an email that the second battery was defective and got a refund ... so now i am wondering to buy a new battery from a different manufacturer or buy a cell phone battery same Voltage but 2x the capacity and half the price? Will it start working and if not maybe I can modified it to use the +,- of the cell phone battery and the T of the original? Will it charge correctly or explode 

thanks for the help so far

[Rasz]

why are you asking us? you have all the parts to test it
+ I didnt suggest connectoing thermistor of original battery as a permanent solution, just to check if your 'new' chinese batteries are ok

[scince!]

I connected the T of the old battery and tested with the two chines batteries its works ... got refunded and order from a different manufacturer now I will wait for two weeks and post an update