Editing Psion netBook Battery Service (section)

== Rebuilding the pack ==

The community procedure below is the one published by OpenPsion, contributed by a rebuilder who did it on a Series 7 and reported '''12½ hours of runtime with 2200 mAh cells, against 7 hours from the tired originals'''.<ref name="libatt" />

'''Read the whole procedure, and the soldering caution, before starting.'''

=== What you need ===

* '''Three 18650 Li-ion cells''', matched. 2200 mAh or higher is the recommended and cost-effective choice; the originals were 1500 mAh.<ref name="libatt" />
* A '''multimeter'''.
* '''A spot welder and pure-nickel strip''' — see the caution below.
* Thin wire, good liquid flux, solder and a soldering iron, if you are following the original method.
* Thin screwdrivers and a thin knife.
* Glue or tape for reassembly.

=== 1. Check the cells before you fit them ===

'''Confirm every new cell sits at the same voltage''' before connecting them in series. The original rebuilder measured 3.78 V on each.<ref name="libatt" /> Cells at different states of charge will be forced into balance through whatever connects them, which at the currents involved is not a gentle process.

Buy cells you can trust. The 18650 market is full of relabelled and overstated cells; [[Battery Refurbishment]] covers how to tell.

=== 2. Open the pack ===

'''The case is not designed to be opened, and you will break the internal locks getting in.''' Work the seam with thin screwdrivers and a thin knife. Plan to glue or tape it closed afterwards.<ref name="libatt" />

Inside are the three cells, welded together, and the white controller board.<ref name="libatt" />

=== 3. Make the interconnects ===

Prepare four connection pieces before touching the cells, and '''keep them short'''. The two middle connections bridge cell to cell; the outer two go to the controller board.<ref name="libatt" />

=== 4. ⚠️ Joining the cells — spot weld rather than solder ===

'''The published procedure solders directly to the cells. This wiki recommends spot welding instead, and you should understand why before choosing.'''

The original method is: sand a small patch of the terminal to give the solder something to key to, apply a drop of flux, and tin it '''in half a second, no more''', cooling the cell immediately afterwards with a cotton pad soaked in alcohol. The author is explicit that overheating a Li-ion cell may damage it.<ref name="libatt" />

That works, and people have done it successfully. But it puts a soldering iron against a live lithium cell for a period judged by eye, and a cell's internals begin to degrade well below the temperature at which solder flows. A '''mini spot welder and pure-nickel strip''' delivers a 1–10 ms pulse that heats only the surface, and it is the method [[Battery Refurbishment]] recommends for exactly this reason. A collector re-celling a netBook Pro pack in 2023 reached the same conclusion independently: "Since there are 3 batteries in there, I'm going to try using a spot welder this time."<ref name="hpcf-recell">[https://www.hpcfactor.com/forums/forums/thread-view.asp?tid=21108&start=1 HPC:Factor forum thread], September–October 2023, in which a collector re-celling one of these packs states the intention to spot weld rather than solder, and notes 18650 sourcing.</ref>

If you do solder anyway:

* '''Half a second on the cell, then cool it.'''<ref name="libatt" />
* '''Watch polarity on every joint.'''<ref name="libatt" />
* '''Keep the solder flat.''' File down any raised blob. This is not cosmetic — a solder spike is what pierced a neighbouring cell's wrap in the incident described above and nearly caused an explosion.<ref name="libatt" />
* Buy '''tagged cells''' if you can, to avoid soldering to the cell body at all.<ref name="libatt" />

=== 5. Transfer the controller ===

Remove the old wires and old cells, and solder your new pack to the controller board. Keep the wires short.<ref name="libatt" />

=== 6. Reassemble ===

Check for anything that could bear on a cell wrap before you close the case — a proud joint, a wire end, a burr. '''Insulate generously.''' Close the case with glue or tape, since the locks are gone.<ref name="libatt" />

=== 7. First charge ===

Fit the pack and charge from the mains adapter. Remember that '''the charge LED goes out at about 70 % capacity''', so let it run the full three hours rather than trusting the light.<ref name="faqpower" />

Then run the machine down and watch what you get. A successful rebuild with 2200 mAh cells should comfortably beat the original 8½-hour figure.<ref name="libatt" />