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Battery Pack

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watersteps

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Hello, I'm building an externial battery pack for a metal detector. At present it uses a stick type battery pack with 8 AA batteries, they are 1.5 volts and mounted in series giving the pack 12 volts of power. These 8 batteries will operate the detector for about 13 to 15 hours.
In the front of the pack there is one capacitor mounted between the terminal that the battery touches and the terminal that is in the metal detector. I think it is the positive side the other side (negitive) has no capacitor.
I looking for the value of the capacitor and the reason why they use a capacitor. There is no value printed on the capacitor.
I do know that a rechargeable pack only has 9.6 volts of power and the AA pack has 12 volts so I would think that any power from 9.6 to 12 volt should be good.
I also know that other detector owners would rather use the the AA pack and not the rechargeable
because the AA lasts longer.
If I build a battery pack I would like to add a capacitor so it works like the factory pack.
 
I'm not too sure with your capacitor but it is common in TV remotes to have a capacitor in parrallel with the batteries to stabilize the voltage as the battery ages.

In your 12 volts case get a 16 or 25 Volts 2200 uF capacitor and see how it goes.

If your metal detector is designed for 9.6 Volts and you put 12 volts on it be sure that it doesn't fry your detector.
 
Caps just add supply stability. they're IMO crucial for microcontroller supply, but usually any electronics product (I assume you bought it?) should have a regulation on the supply internally. Otherwise, AA batteries or not, a fluctuating supply renders a lot of compromise in quality, and in my case, my PIC main board becomes nearly useless without caps to stabilize the supply. :)
 
The way you describe it, that component is probably a resettable fuse or a thermal fuse... not a capacitor.

creakndale
 
As you describe it one lead goes from the + terminal of the battery to the metal detector? That definitely can't be a capacitor a capacitor would be wired in parallel to the + and - leads, if it's in series with the + lead it's likely a fuse as creak said, if it were a capacitor it would be impossible for current to flow from the battery.
 
Here is a sketch of the battery pack with the numbers of the cap or whatever it is. I'm still not sure it is a cap, any ideas?
 

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  • AA Battery[1].pdf
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An idea has already been given, it's probably an inline fuse. Find out what the maximum running current of the detector is and chose an appropriate fuse, or simply confiscate the fuse from the old battery pack. Or if you're not too worried about simply ignore it's existence.
 
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