DIY jumper leads

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mrmisior

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Accidentally pulled a wire of a clamp of a "Heavy duty jumper leads".
I was shocked to find that the wire is ~<1mm packed in a 10mm thick coat of PVC...
What a ripoff.
Anyway looking at google, it suggests that a 4mm wire should start a diesel no problems.
Since I have decent clamps of that dodgy set.
I found a cheap 6mm earth wire in screwfix:

https://www.screwfix.com/p/nexans-6491x-green-yellow-1-core-6mm-conduit-cable-10m-coil/7000t

It's 10m so I can make a 5m jumper leads.

Anything against that?
 
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I used 16 mm² welding cable, and braid between the two sides of the clamp, as in the main they fail because too much current goes through the spring and gets spring red hot so no longer a spring, these would start a D8 but you don't really send full start amps down the lead, you run donor vehicle for few minutes first, so as a result even 6 mm will work, just need to wait longer before turning key.
 
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The thinner and the longer the leads, the higher the resistance, so as short and large as possible is best. The higher the resistance the less chance of being able to crank an engine over.

Having said that - you should leave the leads connected for a while, with doner car engine running, to put some charge in the flat battery. The longer it is left charging, the more the likelihood of it having enough power to start.

By default, I carry a pair of home-made leads, made with crock clips and proper copper coax cable transmitter cable, which is quite light and better than you might buy. I don't expect them to be able to crank immediately, but give them a couple of minutes..
 
Harry Bloomfield said:
The thinner and the longer the leads, the higher the resistance, so as short and large as possible is best. The higher the resistance the less chance of being able to crank an engine over.

Having said that - you should leave the leads connected for a while, with doner car engine running, to put some charge in the flat battery. The longer it is left charging, the more the likelihood of it having enough power to start.

By default, I carry a pair of home-made leads, made with crock clips and proper copper coax cable transmitter cable, which is quite light and better than you might buy. I don't expect them to be able to crank immediately, but give them a couple of minutes..
Click to expand...

Indeed, the cable doesn't need to carry the cranking current. The safest way is to leave the donor car running and allow it to charge the flat battery for several minutes. Stop the donor engine and crank the other. Disconnect leads.
 
I got some heavy duty jump leads from motor world years ago. They are 35mm² tri rated. I changed the clamps after a while as the supplied ones were a bit crap.
I used them just last week. Buy cheap buy twice.
 
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The flex on my mother's ancient iron went bang where it exits the appliance. I bought a length of replacement flex from ebay & fitted it (nothing appeared odd wrt conductor size).
It went bang in exactly the same place the very first time she used it.
As a result I will never buy cables, switches, sockets etc. from ebay - too much cheap sh!te & not worth the risk.
 
johnny2007 said:
Buy proper leads.
Click to expand...
Link please to a genuine 4mm-6mm leads.
Please do not send me to ebay, amazon, halfords (where i bought heavy duty <1mm leads), eurocarparts as they are all seems to be selling the same junk.
 
Gordon equipment or Durite seems to be one of the main suppliers of auto electrical stuff, but don't think they have a retail outlet, Ring is the other big one, I tend to find what I want on their website then google the part number to find a supplier.

When I worked in Algeria and we had a problem with stolen batteries I had a set of 60 mm² jump leads with welding connectors one end and crock clips the other end and with the Chevy modified to charge two 180 Ah batteries I could start a D8 well 583 side boom with no battery connected to the crane, however that is rather extreme, and my 12 Ah battery pack with 16 mm² leads with forklift plug on end and crock clips other end will start most cars.

Yes just 12 Ah and it's a VRLA (AGM) battery at that. But normally there is some power left in the vehicles battery, so not really using just the 12 Ah battery. The problem is you want the donor vehicle engine running before you try starting the vehicle with discharged battery, but not during cranking or you can damage the donor vehicles alternator. The worse the jump leads are, the less likely it is you damage donor vehicle, also less likely to do damage if put wrong way around, the power pack has a relay which does not connect if connected wrong way around, with those 60 mm² make a mistake and your looking at flying acid and moulded rubber as the battery explodes.

I have had my fair share of batteries exploding even without mistakes, I saw it starting to flash across with a Landrover and quickly tried to drop the bonnet, it lifted it back up complete the the spare tyre on the bonnet there is that much force. With a old 966 a pair of 180 Ah batteries were under the seat, the seat catches were broken and the loading shovel was over charging I was just arriving to change the alternator, it was like an ejector seat, lucky is stalled in the earth pile and the driver landed on soft earth and I was able to empty a carboy of distilled water over him to wash off the acid. But jump starting is dangerous, and I had jump leads with a welding connector in centre so I could clip onto battery with no spark then connect leads. Well not only for that, it allowed me to put welding leads in the middle when I could not get near the earth mover. Connecting chassis to chassis last can also get one away from firing line.

I have seen jump leads melted, had they been good jump leads connected wrong way around I hate to consider the outcome.
 
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