TECHNOFILE
LRM workshop
by Lindsay Porter
in association with Mobile Centre Limited
5
6
7
8 JUMP START FACT FILE
Jump To it
1
put to the test
Why waste money on expensive jump leads when you can buy them for a song on eBay? Well, here’s what happens if you take the cheap and nasty route. And by contrast, here’s how you can fit permanent, pro-quality, jump lead connection points to your Land Rover.
For many years now we’ve got used to
the idea of goods becoming cheaper and cheaper. But some things simply can’t and won’t, not unless you accept a cut in quality. Jump leads are a perfect example. Their main cost lies in the expensive copper core of each cable. If a manufacturer reduces the size of the cable, it reduces the ability of the jump lead to do its job. Cheap jump leads have one advantage, and one advantage only. They don’t take up much storage space in your vehicle. On the other hand, they’ll be sure to let you down when you need them. Which means, you’ve spent your
2
82 June 2011 LAND ROVER monthly
money on pretty decorations and a false sense of security. Tim Consolante of MCL came up with the idea of trying to find out just how much use cheap and nasty jump leads would be if you put them to the test. I think you’ll agree that the results were quite spectacularly interesting. PicTURE 1 Tim’s initial plan was to make jump lead connectors permanently fitted to front and rear bumpers using Anderson connectors. This is the grade of cable he selected. It’s 40mm2 cable, rated at
3
anti to £8.99. These eBay leads were rated at 600A, used 8mm2 cable and were classed as Extra Heavy Duty in the description. As a rule of thumb, each 1mm2 will carry 8A. So, using our rule of thumb these would be capable of actually carrying around 65 Amps continuous and definitely not 600. The croc clips are only rated at 250A anyway!”
300Amps continuous, similar to that of the jump leads that MCL supply. PicTURE 2 Tim, who is a leading vehicle electrics expert says, “The battery clamp is a vitally important link in the chain, the one on the right in the picture is rated at 600A, the one fitted to the jump leads is rated at 150A. These leads cost £3.99 and are laughably classed as ‘Heavy Duty 200A’. These were made using 6mm2 cable which is actually rated at 42A continuous, and NOT 200A!” PicTURE 3 Again from Tim: “We upped the
4
PicTURE 4 In order to simulate what would happen if a fully charged battery was connected to the flat one on a stranded vehicle before cranking the engine, Tim connected my Defender’s battery to his battery tester with a cable from the set of slightly heavier duty cheap and nasty jump leads in the circuit. PicTURE 5 He wound the tester up to 225 amps (by no means the maximum amount that you could expect to use when cranking a Land Rover with a flat battery) and within less than a minute, this is what happened. PicTURE 6 We let it singe for perhaps 60 seconds, turned off and gave it all time to cool down. In this location, the insulation simply burned away. PicTURE 7 Here, and this wasn’t preplanned, where two cables crossed each
9
other, the insulation melted and allowed the cables to touch. If we had been using both positive and negative cables and this had happened, we would have had a dead short which, Tim tells me, frequently happens when people try to start a vehicle using these dangerously inadequate jump leads. The result is very likely to be a fire or an exploding battery, or both. PicTURE 8 When you come to compare the cheap jump lead cable with one of MCL’s safe and acceptable ones, you can spot the difference in an instant. Not only is there much less copper in the cheap one but the strands of cable are much coarser. The cheap cable contains around 40 strands whereas the MCL cable has 565 strands, each 0.30mm thick. More, lighter strands are far more flexible than fewer, thicker strands and so are less prone to breaking. PicTURE 9 And then there are the clamps themselves. This one has taken up smoking at an early age… PicTURE 10 …while results are similar at the other end. But in both cases, note that only one side of the clamp has overheated which means that only one side of the clamp is conducting electricity.
10
More pearls of wisdom from Tim Consolante: “All batteries have ratings on such as ‘650 CCA’ This would mean 650 Cold Cranking Amps, so the battery is able to deliver 650 Amps for a pre-determined amount of time. As a battery becomes discharged and voltage drops, current rises. In a jump start situation you will be trying to start the flat-batteried vehicle and charge its battery at the same time using current running down the set of jump leads. As a rule of thumb, if you have a set of short jump leads, for example 2.5m long, the cable should always be at least as thick as the earth lead on the vehicle. To see an inrush of current in the region of 500A is easily possible for the first few seconds as your starter motor starts work on a cold engine while the battery is powering up glow plugs and other areas.” PiCTURE 11 The clamps fitted to heavy-duty jump leads, such as MCL’s, should have an integral strap to carry the electrical current equally to both sides of the clamp. Cheap and nasty ones can only conduct current through the hinge holding the two halves together. the right connections PicTURE 12 Grey Anderson connectors are, I’m told, frequently used for the charging connections on electric fork-lift trucks in the
11
LAND ROVER monthly June 2011 83