12v vs 6v

[Jamie123]

The small rechargeable sealed batteries like the ones in emergency exit lights.
How much longer will a 12volt battery last than a 6 volt battery with the same Ahr rating say 7 amp hours. Using this for a remote still picture camera that uses 6 volts. But I have a cable from camera that allows u to hook it to a 12v and steps it back down to 6v. I would assume is way more that double. But exactly how much more ?
Thanks.

 

[amberwolf]

It's all there in the numbers you already have:

12V / 6V = 2

6V * 7Ah = 42Wh

12V * 7Ah = 84Wh

84Wh / 42Wh = 2

The only number you don't have is the efficiency of the "cable" that converts from 12v to 6v, which will waste some of the power. If it doesn't list it's efficiency, you can assume it's 70-80%, meaning you'll only get 70-80% of the total capacity of whatever 12v source you use.