Re: Laptop Battery Problem

On Mon, 24 Apr 2006 09:04:16 +0100, "The Electric Fan Club"
<ian.shorrocks@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:

This sounds exactly like a dead battery. The charging circuit has detected
that the battery is discharged below the minimum limit and has (correctly)
refused to charge the battery. There is no method of recovering the battery
and indeed, it is extremely dangerous to try.

Don't know where you get that extremely dangerous stuff from.

(Presuming Lithium-Ion,) when the pack protection circuitry isolates the cells
from the load/charger due to undervoltage (typically at 3v0/cell), there remains
a high impedance charge path for the very reason of avoiding a permanent
lockout. Proper CLCV Li-xx chargers actually acknowledge this condition and
maintain a charge voltage to effectively "trickle" the pack back into the
safe_to_charge zone. None of that has any particular danger associated with it,
as the cell SOA usually has a 0v5 margin below the shutoff voltage, and a pack
that has been isolated on undervoltage will take considerable time to reduce by
a further 0v5/cell.

Even cracking the pack and charging individual cells is fine as long as the
charger used recognises the low-voltage condition and treats the cells
accordingly. (Whether this is successful depends on the need to reset "smart"
protection circuitry if present.) The only down-side of this type of treatment
is that the user needs to take care to ensure all the cells are brought to
closely matching SOC before reconnecting load, or the protection circuitry may
lock out again on cell differential.

The key to safe charging of Li-xx technologies is a proper charger, and an
understanding of their proper care and feeding.
.

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