Li-ion battery at 0.00 volts on a mobile phone

[Steppy]

I was just given a spare mobile phone, but it was totally flat and wouldn't switch on. It hadn't been used for some time.. over 6 months.

I took the battery out and measured it.. to my suprise I found it measured 0.00 volts.. not even one 1mv? I put the battery back in the phone and plugged the charger into the wall and stepped back from the phone half expecting to go up in smoke!!

To my suprise it started chargeing after 20 minutes of thinking about it.. Now it works fine.. holding charge and the talk time is perfectly usable.. 3-4 days of standby and 2 hours of talk time..

Now, I thought Li-ion don't like being drained all the way down to zero volts? They break or short inside.. Is this true..? and why is the battery now working normally... back to a normal 4.20 voltage charge reading?

Anyone? Can a Li-ion be used after being sitting at 0.00 for months on end? Any data or web links to read?

Cheers,

Steppy

 

[Brum]

Probably some protection circuit that kicked in. When you connected the charger, the circuitry resetted itself and it works again. The circuitry doesnt allow discharging to 0,00 V, it will cutoff the power at 2,4V or so.

 

[65535]

How many contacts were there? Only 1 pair actually conducts others I don't know what they do yet. But only 1 - and 1 positive others are nilche. Either that or a latch so it doesn't get over discharged.

 

[TJZ]

The over-discharge circuit activated.
That is why you got the 0.00 volts reading.
If this didn't have the protection, your battery
would be ruined if it is discharged too low.
When you put it back in the charger, the circuit will
reset itself in a short time and the battery will charge again.

 

[Leow]

I had this happen once on a newish non-oem battery. It wouldn't turn on or even charge.
I managed to reset the protection by shorting the terminals + to + and - to - with a spare charged battery.
LeoW

 

[Steppy]

The battery has three connections... + & - & T

The T is a temp resistor... this measures about 10k ohms and charges with hand Temp..

I didn't think there was any room inside the mobile phone battery casing... has anyone ever opened one to confirm the protection circuit...?? I can understand having a short-circuit protection circuit but a voltage disconnect circuit too?? because I have hear that some new laptop computer batteries have the shut-off voltage circuit on the laptop charge circuit side rather than the battery pack... This allows them to get more power out of the cells.. lower resistances..

Steppy

 

[legtu]

I didn't think there was any room inside the mobile phone battery casing... has anyone ever opened one to confirm the protection circuit...?? I can understand having a short-circuit protection circuit but a voltage disconnect circuit too??

I've opened and played with a couple of batts... Some of them only have short-circuit protection, others have short-circuit/over-voltage/under-voltage protection and the cheap/imitation ones have none.

 

[Vbeez]

The protection circuit definetely kicked in. Most mobile phone batt have protection circuit against under/over voltage-over discharge- short circuit.
I use Nokia battery BL6C protection circuit to charge Lithion unprotected cell for my flashlights, so it will terminate charging when full.