I have standardised my cordless tools (drills, saws, etc) on a particular manufacturer's 18V range, and I am 
well pleased with the quality of the equipment.  However, the batteries are *darned* expensive!  I saw some 
for sale on eBay and won one for about half the price in the shops, but when it arrived I found it wasn't 
actually made by the firm themselves, it was a no-name copy (this wasn't mentioned in the eBay auction!).  But 
it seemed to work and I carried on using it in rotation with the genuine ones I have for a while.

But after about 10 cycles, I found that it was taking less and less charge each time, and before long the 
charger was indicating "dead battery".  I had lost track of who I bought it from, so sending it back wasn't an 
option so I decided to look inside and dismantled it.  It used Panasonic NiMH 3000mAh cells, which was a bit 
of a surprise, and I measured their voltages.  All were good except one that was showing signs of slight 
leakage, and no voltage whatsoever!  It was acting pretty-much as a dead short.

I bought a replacement (tagged) cell, and just as I was cutting the tags from the dodgy cell I noticed 
something - its flat end was connected to the next cell's flat end, its centre-contact end was connected to 
the centre-contact of the next one in the other direction - it had been fitted in reverse!  So for all of its 
short life it had been reverse-charged, so I'm not surprised it finally gave up.

It shows that not only was the assembly shoddily done, but there can have been no quality control, because 
surely they would have spotted the problem, and/or the voltage would have been lower than expected (I imagine 
that before the first charge the voltage would have been about 2.4V too low, since the problem cell was 
pushing the wrong way).

Anyway, I carefully soldered in the new cell (wishing that Phil Pemberton lived closer so I could have asked 
to use his spotwelder! :-) and charge-balanced the cells, and reassembled it into its case.  I seem to have 
saved the pack and it's now operating as it should have.  In future I'll make sure I'm buying the 
manufacturer's own products, not a no-name copy!  But I may get them from the 'States, where they cost about 
half what they do here...

Cheers,


Howard Winter
St.Albans, England


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