Poll: what size battery cable? [View Results]
170 amp (25mm2)
240 amp (35mm2)
300 amp (40mm2)
345 amp (50mm2)



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Author: Subject: what size battery cable?
MikeR

posted on 15/7/18 at 11:07 AM Reply With Quote
what size battery cable?

So I'm looking at battery cables. I want to take a cable from the battery to the fia switch, then back to the starter solenoid, then on to the starter. Total length is close to three meters for the positive cable.

Looking at the starter (according to Haynes) it's 2400w at 12v or 200amp by my calculations.

Taking into account amps i think I need flex 35 (11.8mm od, 35mm2 cross section). However adding in voltage drop I'm looking at 50mm cross section or 13.3mm od.

Does this sound right?
What have you fitted?

Engine is a venerable xflow.

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furryeggs

posted on 15/7/18 at 07:08 PM Reply With Quote
Buy a set of 400A jump leads and cut the clamps off. It should be more than enough and alot cheeaper than battery cable.
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ianhurley20

posted on 15/7/18 at 07:46 PM Reply With Quote
In my case no idea what I fitted - nicked it all of my MX5 donor car - OK for Mazda it will do for me





My build blog http://ianhaynes20.wordpress.com IVA passed 3/10/16

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SJ

posted on 16/7/18 at 09:48 AM Reply With Quote
Nowhere near that size on mine. I had some what I think are 110a cables kicking about and used those. No issues so far.

Never noticed the cables even getting warm.

ebay link

Stu

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907

posted on 16/7/18 at 12:38 PM Reply With Quote
I used 35mm copper welding cable. Used crimp on lugs to connect to the starter and to the chassis for earth.
Used QR battery terminal connectors.


3m would be under a fiver.

Paul G


p.s. Good for making up quality jump leads as well. Beware cheap aluminium jump leads.





The one and only member of the Suttol Owners Club. Now also the MX5 Owners Club. A few more in that one.

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loggyboy

posted on 16/7/18 at 12:55 PM Reply With Quote
35mm2 (2awg) should be more than adequate.

[Edited on 16-7-18 by loggyboy]






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furryeggs

posted on 16/7/18 at 03:23 PM Reply With Quote
I had some 200A leads and they got hot when cranking, which would slow after a few turns. Swapped for bigger 400A leads and it cranked alot faster and they don’t get hot.
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907

posted on 16/7/18 at 09:15 PM Reply With Quote
Do you mean to say that your engine doesn't burst into life the instant you turn the key ?


What you need is an ultra reliable Lotus engine.











Got a feeling I might regret saying that.





The one and only member of the Suttol Owners Club. Now also the MX5 Owners Club. A few more in that one.

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Angel Acevedo

posted on 17/7/18 at 03:37 PM Reply With Quote
What is the purpose of your car?
That may lead you to the right answer...
Are you looking for extreme lightness?
Or reliability is a more worthy goal?
Voltage drop coupled to cold weather may lead to extended cranking which is not a good thing on a thinner than desirable cable.
I would go for thickker unless I was racing the car.
HTH.
Angel Acevedo





Beware of what you wish.. for it may come true....

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MikeR

posted on 17/7/18 at 10:09 PM Reply With Quote
Purpose is to pass IVA and get driven for a few miles before I'm too old / broken to do it

35mm cable is going to be bought - just trying to decide if i get it pre-made or buy a 20 quid hydralic crimper ebay special and cable....

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907

posted on 18/7/18 at 12:12 AM Reply With Quote
quote:
Originally posted by MikeR
Purpose is to pass IVA and get driven for a few miles before I'm too old / broken to do it

35mm cable is going to be bought - just trying to decide if i get it pre-made or buy a 20 quid hydralic crimper ebay special and cable....





No need for special crimpers.

Buy the lead and lugs and use a dot punch or blunt chisel to crimp them.
One supplier even includes a length of heat shrink in the deal.

eBay lugs & cable
eBay lugs & cable






The one and only member of the Suttol Owners Club. Now also the MX5 Owners Club. A few more in that one.

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big-vee-twin

posted on 22/7/18 at 09:15 AM Reply With Quote
I just bought a set readymade up from Halfords, much less hassle. Been on two years no issues.





Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016

http://www.triangleltd.com

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rusty nuts

posted on 22/7/18 at 09:37 AM Reply With Quote
quote:
Originally posted by 907
quote:
Originally posted by MikeR
Purpose is to pass IVA and get driven for a few miles before I'm too old / broken to do it

35mm cable is going to be bought - just trying to decide if i get it pre-made or buy a 20 quid hydralic crimper ebay special and cable....





No need for special crimpers.

Buy the lead and lugs and use a dot punch or blunt chisel to crimp them.
One supplier even includes a length of heat shrink in the deal.

eBay lugs & cable
eBay lugs & cable



I find the above method works well especially if you lay the cable and terminal in a piece of decent angle iron supported in the jaws of a vice

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40inches

posted on 22/7/18 at 01:51 PM Reply With Quote
I made a crimper from bits of scrap, works well.
Crimper bits
Crimper bits
In action
In action
Finished
Finished

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