On the bench today was a set of good multi-function hair clippers with all the accessories. The motor had been running slower and slower, finally not starting at all - even after full charge.
Initial Inspection
First suspect was the motor, so the case was removed and a spot of thin plastic-friendly oil (obtainable from model shops) to both motor bearings.This brought a slight improvement, but the clippers were still rather poorly.
As seen from the photos, the battery is a pair of 600mA AAA Ni-MH cells strapped together and spot welded with metal tags. These are readily available, but are often provided with ordinary wires and a plug - these would be OK as long as the cell rating is similar. Double-check the physical measurements to be sure!
I preferred to use an exact replacement, so ordered from a specialist battery supplier - £10 inc postage (2108 price). If you're prepared to use a wire-ended pack, it'll be a bit cheaper. Much better than £25 for a new unit, and keeps it out of landfill too.
Battery Replacement
Once the new battery had arrived - only 2 days - the job of replacement started. It proved to be fairly straightforward, taking about an hour - tools required are:- 15-25W soldering iron
- 18swg core-fluxed solder
- solder wick
- small Phillips and flat bladed screwdrivers
- small craft knife.
Caution: even small batteries may have enough energy to spark, short circuit and/or overheat. Take care when working.
Carefully remove the two screws from the motor and the two screws holding the charger socket in place. Gently press the LED from the case front - it's a snug fit, gentle pressure should extract it. Gently pry the PCB from the retaining clips - easiest to do at the motor end, some flexing of the case may be needed but don't overdo it.
Carefully ease the LED from the case, then the whole electronics assembly with wiring should lift out.
Beware of a spring under the motor - mine stayed in place - yours may fly off!
Using the solder wick, gently heat the battery tag joints to remove as much solder as possible. Avoid dwelling the iron on any joint for more than a few seconds in case the copper land lifts from the PCB.
(I confess I used a solder-sucker - this is not advisable because it removed some of one PCB land from the board! Hence the recommendation to use solder wick.)
Once all solder is cleaned away, the battery should just fall away from the board.
Remove the two pieces of foam from the old battery by gently peeling, and stick them on the new battery in the same positions. They should peel away easily and still be quite soft and pliable - replace if brittle and/or flaking. They're quite important as they help clamp the battery in place when the covers are on.
Before it causes any damage, Tape the live ends of the old battery and dispose via recycling.
Clean up the PCB ensuring no short-circuits, stray solder or excess flux are present.
Being very careful not to short the contacts of the new battery, cut or peel any protective/retaining tape away from the connecting tags.
Ensuring correct polarity, gently insert the tags through the PCB until the battery is a snug fit against the board. Hold or clamp them in place, then solder the tags to the PCB, cut off surplus tag metal and tidy the new joints.
Carefully re-assemble parts, ensuring the LED is pushed fully home, then tidy wires away to the side of plastic pillars, finally gently clipping the PCB back into place.
Replace the two pairs of screws holding the charger socket and the motor - do not over tighten in plastic!
Check for protruding wires and rectify as necessary.
Replace the cover and gently tighten the three securing screws.
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