Car been garaged for 7+ years. What's the liklihood it could be made a runner?

Joe_Horner

Phil_L wrote: »

I think you will find that 100A is rather on the low side. I have seen test results peaking at over 1000A and cranking at 400A to 600A.

Not on an "average" small petrol engine. The peak is possible, but it's for fractions of a second from starting, but typical car batteries have a CCA rating of around 350A.

You can get a rough idea of what your starters drawing with a voltmeter.

The internal resistance of your battery is approximately equal to 7.2 divided by the CCA or "starting power" rating - say 360A. That would give a resistance of 0.02Ω.

When the car's cranking, this resistance will cause the battery terminal voltage to drop by an amount equal to the current times the internal resistance (good old Ohms Law).

Just checked mine and I have a "no load" voltage of 12.6v and a cranking voltage (HT lead disconnected to stop it firing) of 10.8v, so that's a drop of 1.8v

1.8V across a resistance of 0.02Ω gives a current flowing through the battery of 90A. Seeing as the starter is in series with the battery, that's also the current flowing in the starter (+ the ignition circuit but that's small enough to ignore for an "envelope" calc)

With a big engine, especially a diesel, it'll obviously be a lot more.

As for 10mm² leads, yep they'll probably do the job for a car like this, Mikey, (although, remember you'll get that voltage drop on EACH lead so the starter may be a little slow with them) but the bigger ones just look so much more businesslike

espresso

The so called pedants are simply correcting the usual posted by Strider590.

Strider590 wrote: »

DO NOT use jump leads if the battery is dead (10v or less), it'll draw so much unregulated current through the leads that they'll melt and weld themselves to both cars.

gilbert_and_sullivan

Strewth its hard work here.

In car compounds they nearly always have mini bus full of yardies...not the ones who deal drugs...the mini bus will often have a set of good quality leads permanently attached to the battery and clipped to a rubber covered pole at the front.

These leads will be used every day of the working week to jump start dozens of vehicles of all descriptions with flat batteries, those lads don't have time to ponce about making calculations about resistances, they simply connect up and fire up.

Good jumper leads work.

Now for goodness sake OP will you get someone with a proper jump pack (not a toy one from the accessory shop) or good jumper leads (same) to connect up and see if this flippin car will start.

mikey72

I wouldn't spend a lot for a one off though.
Cheap leads have saved me a few times, when I've been caught out.

pendulum

Strider's gone quiet, ha!

Joe_Horner

mikey72 wrote: »

I wouldn't spend a lot for a one off though.
Cheap leads have saved me a few times, when I've been caught out.

Eh? A well-considered money saving opinion in the motoring section??? Come on,Mikey, play by the rules!

TrickyWicky

I wouldn't spend anything on jump leads. I'd find someone who has a decent set of motoring skills and leads and get them to do it for me.

s_b

TrickyWicky wrote: »

I wouldn't spend anything on jump leads. I'd find someone who has a decent set of motoring skills and leads and get them to do it for me.

post 16 again then:D

Delivery_Driver

I tried to help someone get started who'd broken down on a roundabout.They just had crappy leads and the combination of a 2.5 diesel trying to start a 1.9 diesel melted them.Then they remembered they might have run out of fuel:D.


I thought Strider's work was something to do with car batteries?

zappahey

Strider590 wrote: »

You'd need a cable of no more than 2m length, with a cross sectional area of 25mm². Anything less would get very warm indeed......

Apart from huge, do you have any idea how big that is?

A bit less than 6mm diameter. Doesn't seem that huge to me.