Thread: 1 Farad CApacitor Tank?

The problem is...someone came up with that 1F capacitor idea...never came back to give us the report on what has happened. Even those who followed never reported back. Look at some physic/electronics book and you find how to calculate the decay time of a 1F capacitor under a 5A load

If we assume :

The PC drains 5A then we can say the load resistor = 12/5 = 2.4Ohms

So :

Battery supply = 12V
Minimum supply volatge = 10V
PC Load = 2.4Ohms
Capacitor = 1F

t = RC log[e] (Vi/V)

t = time ( how long it take to drop to minimum voltage )
R = resistor ( PC load, 2.4ohms )
C = capacitor ( Tank capacitor, 1F )
Vi = Initial Voltage ( Battery supply, 12V)
V = Voltage at time t ( Mimimum supply voltage, 10V )

Therefore :

t = 2.4 x 1 x log[e] (12/10)
= 2.4 x log[e] 1.2
= 0.44 seconds

0.44 seconds is not exactly enough...at 10V supply your PC would have crashed by then. You will get 0.77sec if the capacitor was charged to 13.8V. And how about the voltage drop by the diode required?

OK heres a quick summary :

1F tank circuit :
Expensive, bulky, 0.44 second crank survival...maybe they look cool perhaps?

Seal lead acid tank circuit :
Cheap, smaller size, 30mins or more crank survival (depending on rating)

I hope this is the last time the big expensive 1F capacitor non-functional tank circuit question will come up

A Cap won't but this would or one like it

http://www.batcap.net/MegaCap.htm

Originally Posted by adrian_uk17

Well i already have a huge 1 Farad capacitor in my amp circuit that is wired in series through my distribution block, if i run the ITPS through this will it be able to handle cracking etc?

Wow!
I suppose it might work, though I could get an Optima red or yellow top and lots of carputer goodies for that price! Not cheap!

I suppose there's no easy way around the extra battery that doesn't cost three times that.


Cheers,

Kris

50F for $469.00 to survive a 22 sec crank, thats sure more than enough. I think Ill give that a pass

lol maybe i can hook up 10 or 15 of these guys

Not to worry kids, I am indeed just kidding.

You could use a small, cheap motorcycle battery and a dual-battery isolator to isolate the car computer. It would last long enough for cranking and then some, and they're cheap compared to 1F caps.

My suggestion was never ment to be a soluation for everyone, 469 is spendy, even to me, but if you drive a Micro car that batcap is much smaller then a extra battery, an Isolator and all the other junk.

Originally Posted by Ricky327

50F for $469.00 to survive a 22 sec crank, thats sure more than enough. I think Ill give that a pass