Howard Winter wrote:
> 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
>
>
>   
This fake battery business is a serious problem. If moved from NiMH to 
LiIon, it is the cause of laptops exploding all by themselves, and cellphone
batteries catching fire. It is caused by China's lack of quality 
control, made extreme by Chinese manufacturers not honoring copyright laws.

If it isn't corrected soon, I think the IEEE committee will recommend 
eliminating the use of Li-Ion cells for safety reasons.

--Bob

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist