 | Home > Maintenance & Modifications > Beware "heavy duty" jump leads |
 
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
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My primary starting battery has come to the end of its useful life starting my Defender after 7 years, which I don't think is unreasonable. It's now going in to retirement powering a gas banger.
As a result of this, after work on Monday, my Defender wouldn't start. The battery was at the stage where it would still spin the engine over but the fuel and temperature needles were doing a merry dance and the engine wasn't firing. The night before I'd left the battery on charge, and it had started in the morning. I linked the auxiliary battery (which should be plenty to start the Defender by itself) and the starter turned over noticeably quicker, but it still didn't fire and the needles carried on dancing. I then borrowed a colleague and his Ford Mondeo (it was the biggest car available!) which has a 70ah AGM battery in it. Connected my "heavy duty" jumper leads to the running Mondeo, got in the car, turned the key and it still wouldn't go. It was now turning over very quickly but the needles were still doing their merry routine. Even after leaving it connected up for ten minutes or so, it still wouldn't go. So I called the breakdown service, fifteen minutes later a man turns up, gets in and the Defender starts on the second try with him not doing anything other than turning the key. 
Anyway, I got home and fitted the new battery that I had, and whilst I was at it I had a look at the cables linked to my aux battery. When I was fitting the battery I'd forgotten to buy cables for it so used a spare set of jump leads that I had lying around, same as the set I keep for emergencies. The total cable run is less than 30cm. I now have some 16mm2 cabling for a different project, and the 16mm2 cable has much more copper than the jump lead cable. The jump leads have more rubber so they're thicker, but in terms of useful electricity capacity they're not so good. With just the new battery fitted my Defender is back to starting as it always used to. It doesn't turn over any quicker but the needles don't flap and it starts very quickly. I've also changed all the wiring to the second battery to use the 16mm2 cable I had, and in due course will upgrade that some more. My guess is that on a compression stroke the voltage drop along the cables and from the battery was enough to confuse the ECU, but because there was more capacity available on the non compression strokes it sounded like it was turning quicker. So anyway. Beware Silverline's heavy duty 600A rated cables suitable for use with large vehicles. They're not. I don't know how the 600A rating of the jump leads can be justified, 16mm2 is rated at 110A and the leads are less than that. http://www.silverlinetools.com/en-GB/Produ...ncy/456956 |
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3rd Mar 2018 5:34pm |
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| Clive Member Since: 21 Mar 2014 Location: Littleborough Posts: 467 
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600 Amp fusing rating more like
Excessive optimism seems a common problem with a lot of stuff these days, so many things are made to "just do" the job while phrases like "heavy duty" are unjustifiably banded about to boost a buyers confidence and get them to part with some extra hard earned. Whenever I've looked at jumper cables, I always make a point of pulling back the insulating sleeve at the clip ends to try to gauge the size of the cable, also the weight of them is a bit of a giveaway. Personally, I wouldn't bother with anything less than 35mm cable. Having said that, and especially with lightweight cables, there's a lot to be said for connecting the cables between the cars with the engine running on the "donor" car and leaving it for maybe 5 - 10 minutes to give the flattened battery a chance to accumulate a bit of charge, it helps to take the strain off the cables when the heavy current starts to flow. |
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3rd Mar 2018 7:14pm |
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| BogMonster Member Since: 05 Feb 2008 Location: Stanley Posts: 400  
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"Heavy duty jump leads" are a bit like "mud and snow tyres", meaningless marketing bullsh! Copper is what counts!
35mm2 is what you want for jump leads and winch cable. Maypole make some decent leads. The ones I have in the garage are these: https://www.partsinmotion.co.uk/electrical...355-detail Having spent many hours over the years starting flat Td5s when I used to sell vehicles, they can be particularly obstinate with a totally flat battery and I eventually just always used to give them 5 minutes connected to a running vehicle before trying to start them. --- 2006 Defender 110 SW 300Tdi • 2011 Ford Ranger XLT crewcab • 2015 Defender 110 Station Wagon Utility TDCi Last edited by BogMonster on 3rd Mar 2018 9:24pm. Edited 1 time in total |
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3rd Mar 2018 9:20pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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I think they'd probably have been fine if it was a problem along the lines of I'd left my lights on and I'd have done as you say. The battery was basically fully charged, just not working properly.
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3rd Mar 2018 9:21pm |
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| ChrisCM Member Since: 10 Jun 2013 Location: Cornwall uk Posts: 572 
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A lot of cheap jump cables are constructed from CCA (copper coated aluminium) which, of course, looks nice and beefy but does not have the current carrying capacity of pure copper, beware!
The same warning is good for automotive wiring cable in general, another problem with CCA is getting a good solder connection.  2010 Defender 110 Station Wagon, Santorini Black. |
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4th Mar 2018 9:24am |
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| Screbble Member Since: 26 Apr 2015 Location: Lancashire Posts: 2079 
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Have a look at the 35mm2 jump leads at Mobile Centre and you won't go far wrong - particularly their 'kits' for the Anderson set up.
There's also a link to a magazine article/feature which pretty much sums up what others have said |
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4th Mar 2018 9:35am |
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| ChrisCM Member Since: 10 Jun 2013 Location: Cornwall uk Posts: 572
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Hi Screbble - I second that. I have a set of the Mobile Centre ones with Anderson Connector, great bit of kit! 2010 Defender 110 Station Wagon, Santorini Black.
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4th Mar 2018 9:45am |
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| Screbble Member Since: 26 Apr 2015 Location: Lancashire Posts: 2079
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Can't seem to find the article now but I shall keep looking
https://www.mobilecentre.co.uk/search?search=Jump+leads |
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4th Mar 2018 9:53am |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8580
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Aluminium v copper?
Conductivity of aluminium is about 2/3 of copper, about 1/3 of the weight of copper and about 1/3 of the price of copper. Now looking at that last statement you can see why aluminium is used in cheap jump leads. IIRC American houses use aluminium conductors and high voltage power lines are aluminium. OK slightly larger transmission losses with aluminium but weight is extremely important in high voltage lines. Use copper would need pylons either closer together or different cable supporting system. Current carrying capacity depends on cross sectional area (CSA) of conductor. 35mm2 CSA for jump leads is a good size to use in 4x4 area. A solid 35mm2 copper rod will have the same current carrying capacity as standard 35mm2 jump leads but major problem is flexibility. For flexibility of leads with same current capacity you would need a cable with larger number of copper strands but of small strand diameter. So there are differences in useability of jump leads of same CSA. Yes the more flexible cable does cost more! Crocodile clips are all the same? Again no, they may look the same on first looking, i.e. 180 clips look the same as clips rated at 300 amp clips. The 300 amp clips have a braided strap between the two arms of the crocodile clips. I do not quite understand the physics of the use of a braided strap between the two arms of the crocodile clips unless they are using thicker metal in the clips. So look carefully at the specification of the jump leads. Brendan |
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4th Mar 2018 11:48am |
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| ARC99 Member Since: 19 Feb 2013 Location: North Yorkshire Posts: 1831 
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Brendan...............I asked about the braided strap and was told that it allows current to pass through both halves of the clip and prevents arcing on the pin that forms the hinge between both halves of the clip. Hope that makes sense. Don't make old people mad.
We don't like being old in the first place, so it doesn't take much to  us off.
Richard |
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4th Mar 2018 11:56am |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8580
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Whilst I can see the braid spreading the load between the two arms of the clips. What I do not understand is surely the current limiting factor is contact area between clips and battery terminal?
I tend to wiggle the clips when fitting them to try and get better cleaner contact area between terminals and clips. Brendan |
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4th Mar 2018 12:46pm |
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| ChrisCM Member Since: 10 Jun 2013 Location: Cornwall uk Posts: 572
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Yes, if you consider the contact area of the SB175 Anderson connector (rated for 300A max) the contact area between even the biggest clips is minimal considering how difficult it is to get the large clips on some battery terminals. It would be interesting to know what the current carrying capacity of these clips is?
But I suppose its a bit academic really as the quality ones seem to work fine. 
As an aside I recently purchased one of the small lithium emergency jump start packs, the cable and clips on that are far smaller than my mobile centre jump leads but it still managed to start my sons 300tdi which had a flat battery. Electricary or Magic? 2010 Defender 110 Station Wagon, Santorini Black. |
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4th Mar 2018 4:09pm |
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| Justtellme Member Since: 23 Nov 2015 Location: Ottawa Posts: 310  
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Aluminum was used in houses for about 10-15 years in the 70s/80s in Canada until it was determined that they cracked at the terminations and oxidized as well when they were terminated with other metals causing high resistance and fire hazards. Not sure about the US, but it hasnt been allowed or common for a few decades in Canada. They do still sell special oxidizing preventing paste at most homestores when doing renovations with older aluminum wired houses for when you have to combine aluminum with copper on new runs... Alumium wiring...another good home idea that wasnt thought through, just like formaldehyde insulation or asbestos in your gypsum.... |
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4th Mar 2018 4:18pm |
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| kmac Member Since: 07 Oct 2009 Location: Middlesex Posts: 1308 
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These halfords leads are 35mm^2 - not a bad price especially with the trade card.
http://www.halfords.com/workshop-tools/gar...jump-leads |
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4th Mar 2018 4:49pm |
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