need help ID'ing resistor please!

[fatboymedic]

I am trying to repair a charger for my electric drill, and I found a burned up resistor.... dog boned, ceramic?, BROWN bands on both ENDS, and 2 black bands... picture attached.... any help please??

 

[duffy]

10Ω, looks like 1 watt.

 

[fatboymedic]

why is it so large?? and whats the last band? is it temp?? I guessed it was 10 ohm, but 4 bands??

 

[duffy]

It's large because it's 1 watt instead of 1/4 watt. The 4th band is tolerance, that one is 1% (Brown = ±1%; Red = ±2%; Green = ±0.5%; Blue = ±0.25%) You have to go by the gap between the bands on these, the gap is near the tolerance band.

More importantly, did you find what burned it out? Resistors don't usually just burn out on their own.

 

[fatboymedic]

i have NO idea... just found it not chargin one day... i dissassembled the case, and while plugged in inserted a drill battery and wiggled it around... the LED lit breifly, then out.. that resistor was quite warm, and when i poked it with a dowel, the LED again lit breifly... checked with a multimeter, and no voltage across it....

 

[duffy]

Could be a bad battery pack. Sounds like this is a current limiter resistor, maybe. You leave the batteries sitting in the charger days on end?

 

[fatboymedic]

that battery, yes - i was out of the house for @ 3 months going through the "Big D"

 

[colin55]

The way to work it out is this:

Put in a 10R 1watt resistor and feel hot hot it gets after 10 minutes. Remember, a 10R resistor will allow the battery to charge at 300mA.
What is the mAHr rating of the battery.

 

[Boncuk]

Put in a 10R 1watt resistor and feel hot hot it gets after 10 minutes.

What does that mean please? Obviously my language barrier problem?

Boncuk

 

[colin55]

Try a 10R (brown black black silver or gold) resistor of the same size or larger than the one on the PC board. Turn on the circuit and feel the resistor with your finger after 10 minutes of charging the battery in the drill. It you cannot hold your finger on the resistor, it is getting too hot. If the resistor smells or smokes it is getting too hot.

If it gets too hot, put another 10R in series with it.

 

[Jirka46]

It it gets too hot, put another 10R across it.

You should not do that. This will double your charging current. To lower heating with same current you could use two 20 ohm resistors in parallel or use 10 ohm with higher power rating.
Jirka

 

[colin55]

I have made a correction to my posting, thanks Jirka46.

 

[Hero999]

It might have been undersized.

I recommend replacing it with a ceramic resistor which is the same size but double the power rating.

 

[duffy]

I agree. Put the biggest 10Ω resistor that will fit in there.

 

[wcsur]

Or the battery pack you are trying to charge is bad and causing it to draw too much current.

 

[colin55]

You may have one shorted cell. Blow it open by connecting it to a 12v car battery.