Archived from groups: comp.sys.laptops (
More info?)
"mike" <spamme0@netscape.net> wrote in message
news:421E079C.1040904@netscape.net...
> Electrical Fan Club wrote:
> snip
> > The problem is that the manufacturers will not part with information
such as
> > this, and as a result, many a person has attempted to recover
overdischarged
> > batteries, through ignorance of what is actually happening. Many get
away
> > with it, but not all. There is a correct procedure to be followed, not
to
> > ensure the greatest chance of success, but to ensure that any failure
causes
> > the minimum damage. If anyone is interested, I'll post the procedure,
>
> Post the procedure.
> mike
>
The following procedure for recovering overdischarged Li-ion batteries is
not recommended either by myself or the battery manufacturers.
The correct procedure for an over-discharged Li-ion battery is to dispose of
it in the correct manner. I accept no responsibility for any undesired
results from following this procedure. I provide the information, only
because in its absence, attempts at recovery are likely to be made in less
than safe conditions.
[BEGIN]
WARNING: Lithium-ion batteries contain an electrolyte that is highly
inflammable. Lithium-ion batteries can under conditions of over-charging
also contain Lithium metal that will spontaneously ignite on contact with
oxygen or air. Lithium-ion batteries can under these same adverse
conditions generate internal oxygen gas. Thus over charging will eventually
result in explosive rupturing of the case. The resultant fire is impossible
to extinguish. Fire fighting activity should be limited to preventing any
flammable material in the flame path from burning.
NOTE: Lithium Polymer (more correctly Lithium-ion-Polymer) batteries have
dispensed with the flammable solvent for the electrolyte, and although any
fire will be smaller, the risk has not been eliminated.
This procedure can only be applied if the battery has been overdischarged
for a few days at most. If the time period of overdisharge is not known or
in doubt, DISPOSE OF THE BATTERY.
Otherwise:
1). Find a fire proof location where the battery can be charged, that is as
at least 2 metres from any combustible material. Note that it may be
necessary to charge the battery in its parent device. Note: that any
rupture point will produce an oxygen fuelled jet of flame several feet long.
2). While monitoring the individual cell's terminal voltage, charge the
battery in the location mentioned in para 1, at 0.1 CmA (e.g. charge a 1 Ah
battery at 0.1 A), while monitoring the terminal voltage. Terminate the
charge when the terminal voltage of any cell is 3.1 volts. Wait 15 minutes
and then note the cell voltages.
3). Leave the battery in this location for 24 hours. If the battery is
still in one piece at the end of this period, compare the cell voltages with
those noted in para 2. If any cell voltage is significantly lower than the
previously noted value (by 0.2 volts), then dispose of the battery.
4). The battery should now be charged using its normal charger in the
location referred to in para 1. Note that if this parent device is
something expensive, there is a risk that a battery rupture will destroy
that device.
5). When the charger indicates the termination of the constant current part
of the cycle, terminate the charge. DO NOT wait the extra hour for the
constant voltage part of the cycle to complete. Leave the battery in the
fire proof location for 24 hours. Bear in mind, that should you wish to
remove the battery from the expensive charging device, that there is a risk
of rupture while handling it.
6). If the battery is still intact, it may be discharged and recharged
normally, and then returned to service. The battery must be indelibly
marked that it has been subject to this procedure. This procedure must
NEVER be carried out again on the same battery.
It may be noted that the battery indicator may show a fully charged battery
as being only 75-80% charged (dependant on the accuracy and resolution of
the indicator), but almost full capacity should be available. This is a
quirk of the chemistry. The useful life of the battery will be shortened
however.
This information has been compiled from many sources, none of whom wish to
be credited with any endorsement.
[END]
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