boot battery-> capacitor -> starter?

[barryogen]

I just want to bounce this idea off you guys.

Just wondering about my current battery to boot relocation project(need some more space), and I was thinking of using something like the Stereo 1 farad between the battery and the starter, meaning that I could (semi-) skimp on the power cable(cost saving?*).

As I see it, the big wire is only really needed for the big current draw for starting it, the rest of it is pretty much just small power back and forth depending on whats running.

The only thing I can see where it would be an issue, would be if the car didn't start on the first go - the cap may be empty for a minute or so, or however long it takes to pull enough through.

Or if the battery gets unplugged from the car for some reason, although, again, not really an issue, as it would be known about.


your thoughts please?

*cost saving as I already have one with no use for it.

[Alex B]

1 farad probly wouldnt be enough, forget the cap, 2 runs of 4 gauge worked for hrt.

[barryogen]

1 farad probly wouldnt be enough

Holy sh|t, I mean 1 farad is a lot.

*edit*
2 16ft runs of 4 gauge should be good for between 400 and 1200W RMS according to http://www.the12volt.com/info/recwirsz.asp

The cap is rated for 1000W RMS(from it's spec sheet), so I'd imagine it would be borderline... will probably just get the decent cable.

forget the cap, 2 runs of 4 gauge worked for hrt.

k, sounds like a plan.

[Mr.Phreak]

As Alex said, sell the cap on TM, and put the money towards cable

[sergei]

and make sure you have good earth wiring connecting starter/engine to chassis, otherwise you might light up the loom (had bad experience forgetting to connect back the earth wire to body, with battery in the boot). Beacuse when you remove battery from front, main earth wire just hangs there, in most of the cases, with secondary not so fat going to body, wich is not fat enough to support starter current).

[evil_si]

35mm cable is all you need, go to a welding supply shop, kendalls, weldwell, weld tec, Not BOC, they sell it buy the meter and are generally cheaper than electrical shops etc.

i wouldnt use the cap, make sure you have an earth of at least equal size as your power feed, one from block to chassis, and one from battery to chassis.

[Lloyd]

Dude, the cap will do nothing at all. 1F is big for a cap, but by the time you hand stops moving turning the key to start it'll be empty. And if you haven't got a resistance in the line it'll charge near enough to instantly with no load on it. Best bet is get some wire rated up to a couple of hundred amps (the 4ga I had was 100-odd amps and there was 2 runs of it). Your starter is going to draw up to about 120A or so (maybe more) and it isn't really something you want to be going cheap on.

[dotdog]

Dont bother with a cap, cause your cable is still going to have to carry the current to the starter motor, all the cap will do it hold the voltage up while starting. Ive run 25mm for mine, and put some good earth straps on the block to the chassis and never had a problem

[barryogen]

Ta muchly guys... like I said, I just wanted to run it by some people... to me it seemed like a "good idea", so I wondered why no-one had done it prior.

Now I know why, it wouldn't work as expected.

now if I had a 5 or 10 Farad cap mumble mumble

[Stealer Of Souls]

Okay...
From personal experience... The cap does help... But I suspect that it was more from the fact that it kept the voltage at the ignition coil from sagging rather than current to the starter.
Also, if you did wanna try (best way to see what happens after all), don't get a cap with any sort of digital meter or auto on/off device... Stuffs things up since the cap is disconnected till after the first crank anyway.
On a similar note, this idea does exist in a retail product... or at least it used to... I found some group that was selling cap banks (about 5 Farads I think) that they used to re-inforce a tiny battery to crank reasonably large motors...

At the end of the day... Use more cable. Cheaper, easier, more reliable. But it was a great experiment, and the cap can provide other useful benefits...