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Why do three AA batteries inline get hot?

 
 
Reply Mon 3 Nov, 2014 06:47 pm
I was rigging three AA batteries inline to duplicate a #703 Eveready Battery for a WW1 flashlight and I left it switched off. I came back a couple of minutes later and it was hot as heck. What happened?
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Type: Question • Score: 4 • Views: 1,335 • Replies: 6
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roger
 
  1  
Reply Mon 3 Nov, 2014 06:55 pm
@adlearned,
Does 'rigged' mean they were physically in the flashlight? Sounds like you managed to find a direct short from positive to negative, but it's kind of hard to guess how.
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adlearned
 
  1  
Reply Tue 4 Nov, 2014 07:35 am
I was attempting to reach 4.5 volts by using a plastic three-AA battery holder from a toy that I wired in line. It's possible it may have made contact with the brass outer body. But still I could use an explanation beyond that.
engineer
 
  1  
Reply Tue 4 Nov, 2014 07:40 am
@adlearned,
You shorted the batteries. When you have a short, you get a very high current, energy = voltage * current and energy is expressed as heat. You probably also killed your batteries.
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timur
 
  1  
Reply Tue 4 Nov, 2014 07:48 am
@adlearned,
The other explanation is that the 703 battery, aka lantern battery, can deliver 3-4.8 amp/h.

The AA battery, or LR6, can only deliver 0.4-1.8 Amp/h.
If you connect them in series their total current remains the same.

Which means that if your WW1 lantern's consumption is greater than 1.8 amp/h, your AA batteries are going to heat.
adlearned
 
  1  
Reply Tue 4 Nov, 2014 03:08 pm
@timur,
A very lucid explanation. Thanks!
timur
 
  1  
Reply Tue 4 Nov, 2014 03:12 pm
@adlearned,
My pleasure.
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