Cranking amps? (Mega fuse selection)..
Turbo Mini Forums

Anyone know what a typical cranking amperage is? I want to put a mega fuse adjacent to the battery for the main battery cable.

I think I've got a 200 amp on mine. I've got it on the ground strap.

In all honesty, i'm only really protecting against a dead short (Pinched or trapped battery cable), so anything substantial will do. A dead short produces thousands of amps and fuses blow instantaneously.

What's the battery and battery cable rated to? those are the bits you need to protect

I think Mr. Sprocket got it right.
As i recall the starter uses 160 amps. A bit more if it is Cold. A bit more if it is low on voltage. + 10% is the rule of thumb.
200 amp fuse sounds just about right.

If i have more toys than you when i die, I WIN

You really need a slow blow or a motor fuse. The peak current of the starter motor will be quite high, but the steady state will be more reasonable.

What type of starter do you have. The built in solenoid or geared type typically have lower current.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I'm still using inertia starter, but changing to the geared type over winter when I redo the wiring again.
I'm just wanting to run this as a safety measure in case of an accident or whatever else so the fuse pops before some very bad stuff happens.

Buy a cheap DC current clamp meter and test.
Handy tool to have and very inexpensive these days.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Worst case I=V/R

I thought clamp-on meters only worked with AC?

I think that's the same as the one I have, would need to check part numbers.
But DC versions are cheap now.

http://www.ebay.co.uk/itm/Signstek-UNI-T-U...qkAAOSwyWZZS-X~

Or if you have a scope, you can buy various versions for that

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

http://www.ebay.co.uk/itm/Hantek-CC-650-AC...119.m1438.l2649

http://www.ebay.co.uk/itm/Hantek-CC-65-AC-...119.m1438.l2649

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Most clamp meters you see on ebay are hall probe type that measure AC and DC.

They're useful occasionally, but not really a fault finding tool. More a system checking tool.

For the question Dave asked, 200A should be sufficient. I've measured the current in the past with a clamp meter and never seen much over 100A.

But I never checked the surge as the motor started.

I've got a 200A on my single seater (or is it 300A?) anyway, it works!

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Well Strip me naked and call me Susan .
I've never bothered buying a clamp on meter because I thought they were all AC only, which I guess was correct 20 years ago LOL.
That is great info and will be purchased forthwith

fat thumbs.....

Edited by Sprocket on 6th Jul, 2017.

Dc inrush is different to ac inrush as there is no real reactance in dc motors. Current draw is proportional to torque so as torque increases to overcome the load, current increases quickly and then levels off. So DC peak current of a motor is I=V/R

I've fitted a 200a breaker in mine, didn't fancy getting stuck somewhere with a blown fuse. Makes a handy isolation point too

Edited by stevieturbo on 10th Jul, 2017.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will