Cellphone Battery Connections

[Trevors]

Hello everybody,
I am trying to keep my old cell phone powered by a power supply instead of having a battery in it. There are 4 connections on the cell phone. I tested the battery and got 3.7v across two of 4 contacts. Does anybody know why there are 4 contacts on the phone? Nokia 6110 (old model)

 

[Nigel Goodwin]

Probably connections to the electronics in the battery, for monitoring charging rate and degree of charge.

 

[HS3]

I am speaking from memory but I believe the Nokia 6110 uses the same battery as the Nokia 5110 of which I have one. These are older NiMH batteries and the battery pack does not have control circuitry like the newer LION packs do.

In this case

(1) negative
(2) 47 Kohm to ground
(3) 10 Kohm to Ground
(4) Positive + 3.6 V

The resistors are variable with temperature and sense the temperature to control the charging process. I have used fixed resistors in dummy batteries and they work well. You can test your own battery to see how it fits into this scheme.

 

[Diver300]

You need a power supply that can deliver a large peak current.

Cellphones take up to 1.9 A at 3.8 V

They only take that much current for 1/8th of the time (1/4 if using GPRS), and the cycle of taking current and not lasts 1/216 s.

If your power supply dips when 1.9 A is taken, the cellphone will turn off.

 

[Trevors]

Hello people,
Txs for the replies. My cell phone battery is a Li-ion (BLS-2). (I think it was a later model of 6110 which came with an extended Li-ion)I was planning on leaving it in the phone with the charger always plugged in. Unfortunately, an error 'Not Charging' comes up shortly after the charger is plugged in. I've bought a new generic battery, with the same result. I therefore would like to connect the phone directly to another power source. Guess I'll have to break the battery open and see whats inside and then try to 'fool' the phone.