[Thinkpad] TP600 Battery Pack problem

[James McKenzie]

Bryan:

I have not been able to confirm/deny the existance of a counter in any 
Li-Ion battery to include the Thinkpad series or my two cell phones.

However, if a Li-Ion battery starts to draw too much current, thus 
'warming' up the battery, charging the battery can go from a long time 
to not possible due to internal charge control circuits.  With the 
batteries supplied with the Thinkpad, a simple overheat circuit 
consisting of a temperature sensor and current limiting circuitry are 
employed, thus slowing or stopping charging until the battery cools 
down.  With some batteries, a bi-metal interruptor is used, some with a 
permenant open-circuit stopping any further attempts to charge the 
battery until the circuit is reset (much like the overheat circuit on 
most AC motors). 
I have discovered that the battery used in the 600 Thinkpad series could 
be rebuilt and used just like new batteries, which leads me to discount 
the 'counter' theory and to believe as one 'set' of batteries goes 
'south', the entire battery fails to charge and once a 'set' loses the 
ability to charge fully, the entire battery is effected.  The solution 
at this point is to either replace the battery or replace all cells in 
the battery.  With reliable, low-cost replacements it is less expensive 
and safer to replace the entire battery than to attempt to replace cell 
'sets' as Li-Ion batteries can and have caught fire when overheated or 
can be rendered inoperable during soldering due to internal overtemp 
circuits.
BTW, when Dell incorporated Li-Ion batteries, it was not unusual to read 
of a laptop catching fire due to problems with the batteries.  A whole 
series of Dell Li-Ion batteries was recalled due to this problem. 

James McKenzie

Bryan Daum wrote:

>   As we really don't hear of laptops or cell phones. etc lithium batteries
>blowing up doesn't that make it likely that the "lithium recharge cycle
>counter" might be a pretty common hardware/software gizmo?
>
>Bryan
>
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