14.5 VDC @ 200 ma circuit needed for NiCad charger.

[Bill Volz]

I have a Black and Decker cordless power drill. The charger quit working
- the transformer is putting out 0 volts. For the cost of a new charger
unit, I can just buy a new drill (about 50+ bucks).

I tried to use a 15 VDC @ 1000 ma transformer from Radio Shack and a 3
watt 25 ohm rheostat. It worked (at least the charging light lit up),
but the rheostat started to overheat and smoke and I noticed the charger
was getting warm in one spot too, this after about 1 minute of working.
Obviously I've got something wrong.

What kind of circuit do I need to supply the appropriate voltage and
amperage? Can I just use 15 volts for the recharger? Would the extra 1/2
volt hurt the batteries? Would there be too much current? Start a fire?

Thanks,

 

[Rolavine]

Subject: 14.5 VDC @ 200 ma circuit needed for NiCad charger.
From: Bill Volz wrvolz@earthlink.net
Date: 1/11/05 9:12 PM Pacific Standard Time
Message-id: <4l2Fd.4946$C52.2185@newsread2.news.atl.earthlink.net

I have a Black and Decker cordless power drill. The charger quit working
- the transformer is putting out 0 volts. For the cost of a new charger
unit, I can just buy a new drill (about 50+ bucks).

I tried to use a 15 VDC @ 1000 ma transformer from Radio Shack and a 3
watt 25 ohm rheostat. It worked (at least the charging light lit up),
but the rheostat started to overheat and smoke and I noticed the charger
was getting warm in one spot too, this after about 1 minute of working.
Obviously I've got something wrong.

What kind of circuit do I need to supply the appropriate voltage and
amperage? Can I just use 15 volts for the recharger? Would the extra 1/2
volt hurt the batteries? Would there be too much current? Start a fire?

It's been my experience with these things that bad batteries blow up the wall

warts for the chargers. This makes sense in light of what happened to your
kludge replacement? You would think they would design better protected wall
warts, but nope!

Rocky

 

[paddy_21]

Previous posts although inciteful do not answer the question at hand. The
wall wart does say 14.5 VD @ 200ma, however the circuit inside the charger
base is made for an AC wall wart. I'm assuming my old transformer was
simply a 14.5V AC module. The DC rectification happens in the 4 diodes
inside (full wave rectifier) the charging base. The 200 mA limitation is
through R2. However mine is burned out and I can't tell what the color
code is. Can someone tell me please, then I could verify if my batteries
are bad, and which ones.