Why does my 12v charger output 24v?

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Dec 31, 2017
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I have a black and decker 12v drill, and I wanted to use it’s charger for a custom 12v battery pack I built. I measured the voltage with my multimeter, and it shows and output of 24v (same as is labeled on the charger).

Why is this? Is there some way this is safe for my battery?
 
NeedForSpeed said:
I have a black and decker 12v drill, and I wanted to use it’s charger for a custom 12v battery pack I built. I measured the voltage with my multimeter, and it shows and output of 24v (same as is labeled on the charger).

Why is this? Is there some way this is safe for my battery?
What chemistry is your battery? What chemistry is the charger designed for? It may be a nicad charger that terminates differently (i.e. negative delta V or something similar.)
 
many such devices use proprietary chips to ensure only the makers products are used
 
I've heard of batteries you can readout the details of every charge / use cycle
 
The "charger" may not be a complete charger, but just an unregulated "linear" (transformer style) power supply. In those cases, without the designed-for load on them, their voltage may be very much higher than when it has the proper load on it.


Another possibility is that the charger is designed for multiple-voltage systems whose batteries have a BMS that will shutdown input once at HVC. That's a dangerous practice, because if the BMS FETs fail shorted, they'll continue to overcharge to the full input voltage. :/
 
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