[Power] Unbalanced charge after storage

[James Cameron]

Failure while stored is caused by self-discharge.

Inside the battery case are cells and several protection devices.

The devices reduce the chance of fire, and increase the life of the
battery, by turning off the battery if the voltage is too high, too
low, or if the temperature is too high.

One of the devices consumes a small current (35 microamps), which will
eventually drain the battery.  For a fully charged battery, this
should be a few years.  For a drained battery, it could be weeks to
months.  The cells also self-discharge on their own anyway.

Once a cell falls below a critical level the device will disconnect.

This is a latching state.  Nothing the laptop can do will fix it.  The
device must be reset, and it can only be reset if the cells have
stored energy.  No energy will be stored because the cells are
unreachable behind the device.  A dilemma, chicken or egg, or
catch-22.

Nathan's procedure resets the device by charging each cell.  The
device then reconnects the cells to the connector.

Another method is below.  In some countries, both methods require a
qualified or certified technician, who must be suitably insured.

1.  use an electrostatic discharge protected work environment,

2.  gain access to the negative terminal of the cell furthest from the
connector,

3.  while providing a charge current to the connector, briefly connect
the P- pin on the connector to the negative terminal of the cell,

4.  continue charging as normal,

5.  reseal any damage made in step 2.

Normal charging in the laptop should be resumed once both cells have
reached 3.1V.

The cells in the battery will have been damaged by the self-discharge.

We do not have specifications or experience in the nature of the
damage, and so the long term results and safety outcomes should be
considered unpredictable.

Hope that helps.

On Mon, Dec 07, 2015 at 02:41:23AM -0500, Nathan Riddle wrote:
> Unbalanced charge after storage
> XO-1 Batteries
> 
> More XO-1‘s received for service have failing batteries after long term
> storage. The battery LED is green (full charge), but the battery will not power
> the XO-1. The batteries were / are NOT defective. One or both of the two cells
> in the battery were discharged. The battery as a whole may have read 0 V at the
> connector, but the cells showed residual charge.
> 
> If the cells are directly charged / discharged to equal and set values (+/-
> 0.02 volts at about 3.100 volts is convenient near the bottom of operating
> voltage range) and then charged normally, the battery again becomes
> operational. An external 3.2 V cell with 30 ohm resistor can be used for
> charging and a 30 ohm resistor can be used for discharging at about 100 ma.
> Such recharged batteries have continued to operate normally in day to day
> charges / discharges and were stable over several days storage. Long term
> (months) stability is unknown.
> 
> It is not necessary to open the case to directly charge cells. Small holes can
> be drilled in the plastic battery case to access charge points. Since the cells
> are connected in series, only two holes (to B2+, B2-) and connector Power+ are
> needed.  B2+ is the common point.
> 
> Apparently, several different charging circuit boards have been used in battery
> production and charging points vary, so the type of board must be known or
> discovered. The boards are located in the narrow section of the battery case,
> 
> Early batteries had circuit boards with test point pads on the bottom of the
> board ( 0.3 inch [7.5 mm] center to center and the board is centered in the
> narrow section and 1.5 mm in from B2 compartment wall ). An alternative , using
> center points (both ends) of B2 cell compartment as a reference, is 4 mm down
> (toward curved side) and 4 mm away from narrow section This catches the B2-
> lead which crosses horizontally (after fusible link) in the lower half of the
> case.   B2+ is on the battery end , which is the outer can of the B2 cell . 
> Caution:  The drilling through the plastic case was done manually with a pin
> vise and drill stops.  NO drilling on any metal !!
> 
> The serial numbers at production changes in the charging circuit board are
> unknown; however, to this point, examined batteries beginning with serial
> numbers 001 and 002 have contained the original board. May not be true for all.
> 
> On a trial basis, the Michigan Community Repair Center ( http://wiki.laptop.org
> /go/Repair_center_locations ) is accepting such NOT DEFECTIVE batteries (serial
> numbers beginning with 001 or 002) for such recharging.
> 
> Battery rebuild also seems possible and is being explored
> 
> SAVE your old XO-1 batteries -- they may have a second life.
> 
> N. C. Riddle
> 

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-- 
James Cameron
http://quozl.netrek.org/