Thread: 12 volt Battery
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Old 11-04-2013, 07:29 PM   #7 (permalink)
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Originally Posted by RobertISaar View Post
if you want to make any noticable difference to the electrical system, expect to measure capacitance in F, not uF.
Adding a little to this thought...
Each farad can store about 100 joules at battery voltage (about 14.5 volts) 1 joule is 1 watt-second. So 1 F could store 100 watt-seconds. That's if you can convert the whole charge down to 0 volts. I guess you'd better assume you could use the top 30%, 14.5 volts down to 10 volts - you need 3 times as much capacity.

There is a hybrid cap called the Stinger available from car audio sources, it seems to be a combo capacitor & lithium battery which emulates 50 F. They cost about $200 each.
If you attached one of these in parallel with your battery, you'd gain 50 farad If you could use about a third of that (14.5 v down to 9.6 v) it would provide about 1,666 watt second. About 20 amps for 7 seconds to run your lights and radio.

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