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</head><body><div><p>Unbalanced charge after storage <br>XO-1 Batteries</p><p>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.<br> <br>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.</p><p>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.<br></p><p>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,</p><p>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 !!<br></p><p>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.</p><p>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. <br></p><p>Battery rebuild also seems possible and is being explored<br></p><p>SAVE your old XO-1 batteries -- they may have a second life.</p><p> <br></p><p>N. C. Riddle</p></div></body></html>