Ni-Mh/Ni-Cd charger repair

[Peter Orban]

Hello Everyone,

I was given a faulty battery charger that was DOA when bought, except they
never bothered checking it, and now it is too late to return.
The charger is an "Ultra Rapid Charger":
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1487814
It also looks like that it is equivalent to the following Sayma charger:
http://www.samyatech.com.tw/eportal...?main_page=product_info&cPath=5&products_id=9

I did find a cold solder joint inside that I fixed. I tested the charger
with four AA size Ni-Cd batteries, but after about two hours I disconnected
as it was getting so hot. The batteries were also quite hot, a lot warmer
that with other chargers. Two of the batteries were flat before charging
while the other had some juice left in them, though not sure how much. The
batteries now seem to be fully charged.
I am reluctant to declare the charger repaired, I am concerned about safety.

Any comment on the above?

Thanks, Peter

 

[mc]

Some circuitry relating to current limiting or time-out seems to be faulty.
Is there a solder bridge anywhere?

 

[t.hoehler]

Some circuitry relating to current limiting or time-out seems to be
faulty. Is there a solder bridge anywhere?



Hi Peter, it's really hard to say if there is something wrong with the
charger or not. My experience with fast chargers is to leave the cells in
them for only two hours or so. Put the charger on a timer so if you
forget, the cells won't suffer and your house won't burn down. Really, 10
or 20 bucks doesn't buy much charger, especially when they throw in the
cells too! I bought a 10 buck whiz-bang NIMH fast charger, complete with
4 - AA NIMH cells from MCM electronics. As you say, the charger and the
cells get pretty warm after a short time. But with a two hour charge, each
pair of cells runs my digital camera for days on end, and a cd player for
about 10 hours. So I know it's working, but you can bet I have that puppy
on a timer!

Hope this helps,
Tom