Resistor value for battery charger

R

R Farris

Guest
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't work -
because both batteries are discharged. Turns out the problem is with the
battery charger. It is composed of a transformer that plugs into the wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is with
the base unit. When I took it apart I found a single ceramic resistor that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace the
burned one?

rf78801x.att.net
 
"R Farris" <rf76309@worldnet.att.net> wrote in message
news:jAbnd.931755$Gx4.36595@bgtnsc04-news.ops.worldnet.att.net...
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't work -
because both batteries are discharged. Turns out the problem is with the
battery charger. It is composed of a transformer that plugs into the wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is with
the base unit. When I took it apart I found a single ceramic resistor
that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace the
burned one?

rf78801x.att.net


Mine has a 4.7ohm 1Watt. (there's a IN4001 rectifier diode in there as
Click to expand...
well).
 
Great, thanks much!


"john jardine" <john@jjdesigns.fsnet.co.uk> wrote in message
news:cnjh2l$vah$1@newsg1.svr.pol.co.uk...
"R Farris" <rf76309@worldnet.att.net> wrote in message
news:jAbnd.931755$Gx4.36595@bgtnsc04-news.ops.worldnet.att.net...
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't
work -
because both batteries are discharged. Turns out the problem is with
the
battery charger. It is composed of a transformer that plugs into the
wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is
with
the base unit. When I took it apart I found a single ceramic resistor
that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace
the
burned one?

rf78801x.att.net


Mine has a 4.7ohm 1Watt. (there's a IN4001 rectifier diode in there as
well).
Click to expand...
 
Sometimes you can get lucky by finding a parts diagram. Who makes the drill
and what model?

Are there any readable numbers/symbols on the old part?

Mike

"R Farris" <rf76309@worldnet.att.net> wrote in message
news:jAbnd.931755$Gx4.36595@bgtnsc04-news.ops.worldnet.att.net...
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't work -
because both batteries are discharged. Turns out the problem is with the
battery charger. It is composed of a transformer that plugs into the wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is with
the base unit. When I took it apart I found a single ceramic resistor
that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace the
burned one?

rf78801x.att.net
Click to expand...
 
Well, its a Ryobi HP1201 drill and the charger is part 1400674 but I could
find no schematics for it (the charger). I did find a parts diagram for
the drill but not a breakout for the charger.

Ron


"Mike" <no_spam@comcast.net> wrote in message
news:l7adnR5h_oaE_gDcRVn-iA@comcast.com...
Sometimes you can get lucky by finding a parts diagram. Who makes the
drill
and what model?

Are there any readable numbers/symbols on the old part?

Mike

"R Farris" <rf76309@worldnet.att.net> wrote in message
news:jAbnd.931755$Gx4.36595@bgtnsc04-news.ops.worldnet.att.net...
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't
work -
because both batteries are discharged. Turns out the problem is with
the
battery charger. It is composed of a transformer that plugs into the
wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is
with
the base unit. When I took it apart I found a single ceramic resistor
that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace
the
burned one?

rf78801x.att.net
Click to expand...
 
Some of the charges are smart-chargers, in that they have a third wire
connected inside the batterypack that senses the pack voltage as it is
charging.

You can tell if yours has this because there will be a third contact on the
pack and in the charger connection well.

It sounds like yours may be a simple constant voltage charger with a current
limit resistor.

I suspect the reason the resistor is damaged is your battery pack's nicad
batteries has one or more shorted cells. This causes the pack to draw more
current than it would normally.

If this is the case, it's time to get another batterypack. You could open the
pack and measure which of the cells have a voltage and which are at zero
volts. You will likely find some are dead. Replacements are available, but, the
other cells are likely to fail soon as well.

I've tried the capacitor "shock" method to revive some nicads, but with limited
reliability. The "shock" is a current surge from a capacitor that removes some
of the internal crystaline structures that develop in a dead battery which push
through the battery separator material.
 
I was also unsuccessful locating a parts diagram for the charger. Although,
I did find many results of people having the same problem..

Perhaps someone that reads this group has the same drill and can give you
specs by disassembling theirs..

Mike

"a" <a@email.com> wrote in message
news:n9end.35173$7i4.8797@bgtnsc05-news.ops.worldnet.att.net...
Well, its a Ryobi HP1201 drill and the charger is part 1400674 but I could
find no schematics for it (the charger). I did find a parts diagram for
the drill but not a breakout for the charger.

Ron


"Mike" <no_spam@comcast.net> wrote in message
news:l7adnR5h_oaE_gDcRVn-iA@comcast.com...
Sometimes you can get lucky by finding a parts diagram. Who makes the
drill
and what model?

Are there any readable numbers/symbols on the old part?

Mike

"R Farris" <rf76309@worldnet.att.net> wrote in message
news:jAbnd.931755$Gx4.36595@bgtnsc04-news.ops.worldnet.att.net...
Okay, I think this is a basic question...

Bought an rechargable drill at a garage sale. Of course it doesn't
work -
because both batteries are discharged. Turns out the problem is with
the
battery charger. It is composed of a transformer that plugs into the
wall
and a base unit that holds the 12VDC battery.

The wall unit works okay and produces 17VDC @ 400mA. The problem is
with
the base unit. When I took it apart I found a single ceramic resistor
that
was wired in series - but it was burned beyond recognition.

Okay, my question: what value of resistor do I need to buy to replace
the
burned one?

rf78801x.att.net
Click to expand...
 
Only two contacts and the series resistor.

Thanks to all.

Ron

PS There are some smart folks out there!



"Kent Regal" <kentregal@aol.com> wrote in message
news:20041119050628.21518.00000684@mb-m11.aol.com...
Some of the charges are smart-chargers, in that they have a third wire
connected inside the batterypack that senses the pack voltage as it is
charging.

You can tell if yours has this because there will be a third contact on
the
pack and in the charger connection well.

It sounds like yours may be a simple constant voltage charger with a
current
limit resistor.

I suspect the reason the resistor is damaged is your battery pack's nicad
batteries has one or more shorted cells. This causes the pack to draw
more
current than it would normally.

If this is the case, it's time to get another batterypack. You could open
the
pack and measure which of the cells have a voltage and which are at zero
volts. You will likely find some are dead. Replacements are available,
but, the
other cells are likely to fail soon as well.

I've tried the capacitor "shock" method to revive some nicads, but with
limited
reliability. The "shock" is a current surge from a capacitor that removes
some
of the internal crystaline structures that develop in a dead battery which
push
through the battery separator material.
Click to expand...
 
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