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Can anyone explain how this battery charger works?

TCSC47

Mar 7, 2016
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In the diagram the yellow disc component has been assumed to be a capacitor. However, as you say the circuit would not work if it was. The yellow disc has to be something else like a thermal fuse, or a current limiting device of some sort. I am writing this late at night and I am too tired to analyse the rest of the circuit, I'm afraid.
 

Harald Kapp

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Nov 17, 2011
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Where is the image from? The original website could help solve the riddle. I agree with @TCSC47 that this is possibly a current limiting device, e.g. an NTC.
The symbol in the schematic diagram is incorrect in any case.
 

Sunny Rio

Feb 13, 2022
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Where is the image from? The original website could help solve the riddle. I agree with @TCSC47 that this is possibly a current limiting device, e.g. an NTC.
The symbol in the schematic diagram is incorrect in any case.
It's my drawing and my photos of my cheap cordless drill NiCad charger. I agree it's a current limiter. I didn't know those existed pretending to look like capacitors!
 

Harald Kapp

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Take a picture of the component from the side so we can see the inscription.
 

cjdelphi

Oct 26, 2011
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It's my drawing and my photos of my cheap cordless drill NiCad charger. I agree it's a current limiter. I didn't know those existed pretending to look like capacitors!

that's definitely a thermistor ntc or ptc, is it there to prevent an inrush or is it there to decrease current are you positive your circuit is correct?
 

cjdelphi

Oct 26, 2011
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try measuring the resistance before when cool then switch off and measure again

probably limits the current when hot
 
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