solution to cranking power probs?

Jamez_Warner · 05-23-2003, 01:03 PM

what about putting one of these farad capacitors in the +line between batt and your computer? anyone tried this? does it have enough stored power to keep PC running?
James

Jamez_Warner · 05-23-2003, 01:18 PM

ok lets work this through

1 farad

Q=CV

1x12 = 12 columbs of charge stored

1 amp = 1 coloumb per second

start engine 3 secs max

this means the capacitor can output 4amps for the 3 secs it takes to start a car...

55W low power supply for VIA EPIA m/b draws 4.5amps at full load, running at less than full prob be about 4 amps

i dont have any farad capacitors handy, but someone that does might wanna have a go !!
ps. tell me if any of my maths is dodgy lol
James

cproaudio · 05-23-2003, 02:18 PM

supplying the amperage is not a problem. Voltage is what the problem is. inverters shut down when the voltage drop below 10.5 volts. Even if you put a cap in, the voltage will still drop below 10.5 volts during crank. You need to isolate the cap from the battery so that when you crank the engine, the voltage on the cap doesnt drop at all. You have to put a high amperage diode between the battery and the cap. Diode has a voltage drop of .7 volts. A weak battery at 12.3 volts will actually feed 11.6 volts to the inverter after the power passes through the diode. This is what a tank circuit is. this topic has been discussed and done many many times. And yes it does work if installed correctly.

Jamez_Warner · 05-23-2003, 02:21 PM

:S, still should be simple with a small circuit to switch across when voltage drops below say 11v...
James

TruckinMP3 · 05-23-2003, 02:25 PM

Yup, should be simple.... we have several egghead electronics types on this board.... go ahead and build one that is not much money, small and reliable.....