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MG MGB Technical - Battery connections

I need to make up a battery lead from an isolator switch I've just mounted on the rear heelboard. I have some suitable lead (37/1.0) where the OD of the unsleeved copper is about 7mm in diameter. I was thinking I would solder this to a suitable 10mm eyelet at the isolator switch end and have found several on the Autosparks site. However, I'm a bit unsure what size the solder 'bucket' should be. Tight fit or loose before soldering? Is this the way to go? Any other ideas?
Richard Coombs

Not sure how long you need, when I did the same to my old B and now midget I got premade cables from a motor factor up to about 450mm (even Halfords sell them) - they are usually crimped.
I use crimped connectors on the boat batteries - made up by the local marine electrical engineer - you do need the very large professional crimping equipment to do this correctly.

Soldering is good but care required not to melt insulation as a lot of heat required with thick copper - connecters need to be an 'easy' push on,
pre tinning them makes it easier.

R.

richard boobier

Halfords is a good idea. I'll check it out.
Richard Coombs

I recently needed to make a battery cable for an isolation switch so while I was at it I renewed the rest of the cables. I purchased the cable from local battery suppliers and the eyelets from a marine chandlers. I crimped them myself with a crimping tool and then covered the ends in heat shrink tubing, and just to finish them off I added a few Lucas stickers to give them that old school look. This saved me pounds and looks great.(See photo) This is a good if not better alternative to solder. I only go to Halfords if I really have no other option!

Dave MGB

I wrapped wet cloth round the end of the insulation when soldering cables into terminals for my cut-off switch. I also fitted rubber boots which cover the whole of the terminal including the threaded studs and and some of insulation, so any slight shrinkage etc. at the end of the insulation is completely covered.

PaulH Solihull

A good friend of mine who was a marine electrician told me that crimping large cables is always a better bet than soldering them, providing you can make a really strong crimp. Do it in your bench vice. The problem with soldering these large cables is that you need an awful lot of heat to ensure the solder flows through the cable strands properly, and it is very rarely achieved. If you crimp it really well, you squash all the strands together and make a first class connection. I followed his advice with my V8 battery cables and have never had a problem despite the heavy electrical load. There is no way you could ever pull my crimped connectors off!

If you are going to solder, you want the fitting to be as tight as fit as possible. Even crimp it before you solder it.
Mike Howlett

Crimping done properly does beat soldering, for the several hundred amps thst can flow in an MGB starter cicuit I would take care to use the proper kit. This will ensure you get the cold weld you need and it will last indefinitely. You will find the tool will not release before it has applied full pressure, so once done, it stays done. When I replaced my earth strap I soldered it and it was hard work, even using a borrowed high power iron I couldnt flow the whole terminal at once and solder kept wicking into the braid which concerned me as it made it less flexible, got there in the end but crimp would ahve been better.
Stan Best

I was expecting to have to solder using a gas torch to get the heat and the flow correct. However I would prefer to crimp but didn't have the correct tool (which tool was it Dave?). I do have a decent vice so could try that, although I'm dubious about getting a good crimp that way. One problem is the main cable in the car. There's no way I'm going to remove it in it's entirety (very neat job Dave) to get perfect access. So, to get good access to the isolator switch end I guess I would have to release the rear cable fixing (shown in Paul's photo) and do the work under the car. This might restrict the options. The other cable is 'free' so can be done anywhere.
Anyway, thanks for the inputs so far.
Richard Coombs

Richard,
The normal rule with electrical connections, is to make a good mechanical joint first, then solder.

Belt and braces, I guess, but I have never had any failures with this approach.
G Ward

I remembered overnight exactly how my electrical friend crimped the battery connections. He didn't do it in the vice as I said up there, he had a V block of steel in which he laid the cable and connector, and then using a blunt punch (say 3 or 4mm tip) he hammered a groove along the connector forcing it into the cable strands. No solder was used. As I said earlier, they certainly won't come off and have never given a moment's bother. If you don't have a V block, you can use a short piece of that Dexion angle bracketing that is used to build factory warehousing racks.
Mike Howlett

I looked at some heavy duty crimping tools.
http://www.cabletooling.co.uk/Cable-Crimping-Tools/?gclid=CI2H_72C-KUCFUYe4Qod0jV9pA/
I can see that hiring or paying an expert who owns one to visit might be the way to go. I dislike using a torch under a car on axle stands and paying £700 for a tool you use once doesnt add up.
Stan Best

Richard
I'm with GWard crimp then solder this eliminates the chance of corrosion in the joint
Just be alert when purchasing you fittings -- there are a lot of alloy crimp on fittings about now which need high pressure crimpers to get a good permanent connection and can't be soldered, or not with normal solder. Make sure you get the pretinned ones to make the job easier if you are going to solder
Willy
WilliamRevit

Thanks all. As usual a straightforward "five minute" job when first looked at becomes a good learning exercise. I'll go for crimp then solder.
Richard Coombs

"The problem with soldering these large cables is that you need an awful lot of heat to ensure the solder flows through the cable strands properly"

This is true. Many years ago when replacing the push-button starter on my Mini with a key operated solenoid (probably considered sacrilege now, although I do still have the push-button) I had a motor mechanic make up a cable for me and he just melted solder in the terminal cup then plunged the cold cable in. That worked for a few months. Since then I've tinned the cable end as well as part filling the cup with solder, and left the heat on for a few seconds after joining the two, and haven't had a problem. As I say above wrapping wet cloth around the end of the insulation greatly limits the scope for damage to it. As well as redoing the Mini cable I've done this for both MGBs (two terminations each) and haven't had a problem in the several years since. For the ZS I opted to buy a length of cable from Halfords with the terminations already on as the existing cable already had a bolt-up terminal and could be swung round onto the switch but I needed a new length to get from the switch to the fusebox.
PaulH Solihull

Richard thanks for the complement regarding my battery cables. The Ďcrimping toolí I use is a heavy duty wire stripper(car boot sale)£2.00. As you can see by the picture I place it in a vice and swing off it. It produces a really strong crimp and no amount of pulling will move it. I then religiously cover the ferrule with an inch of heat shrink to finish off. I have looked into other heavy duty crimpers for battery cable; you could go mad and buy the best! But due to the small amount of use it would get it didnít warrant me getting one. There is one on the net which looks good and is cheap, itís called Big Buck and is a small blue cradle-and-punch type of crimping tool. You put the ferrule in the cradle and hit the top with a big hammer. See my next post for photo of Big Buck.

Dave MGB

Here is a photo of Big Buck. I think itís about $30 or cheaper in your finest English Pounds! Undertaking work on an MGB is as expensive as you want to make it. If youíre resourceful and do good work you can reduce the cost tenfold. Everyone will have their own opinion, and thatís the good thing about this great site.

Dave MGB

This Big Buck looks as though it will work. Someone said earlier that the angle in some Dexion might do it. I think the solid constuction of this tool shows you how you need to hold the work piece firm, snd not let it flex when you hit the punch. I have made perfectly good low current crimps with a pair of sidecutters crimping in 2 or 3 places. Key thing is to get past the elastic limit and get a cold weld. I wouldnt do this on the MGs, joints may work but dont look nice!
Stan Best

After looking at that simple design, a nut splitter might do a fairly decent job. They can be had for under $20 and used for splitting rusted nuts as well. RAY
rjm RAY

This thread was discussed between 17/12/2010 and 21/12/2010

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