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Battery Cable.... SPLICE ??

Posted by edross 
ed ross
Long Island, USA   usa

Hi all,
Doing interior for my son,1980 MGB USA, GVVDJ2AG509439.
PO had put kill switch in paasenger rear footwell, just anterior to the battery. The key stuck out into the footwell, and the body & terminals was occupying space in the battery rack area, making it difficult to remove or replace battery.
I have hence removed it. However, it appears that the PO had cut, shortened, & replaced battery terminal with a "eye" type terminal that was attached to the now gone killswitch.
OKAY, I should clean up and paint the battery rack area, correct. I should eliminate kill switch, right ??
Can I splice the battery cable? I'd rather not have to replace it, I'd rather not have to get under car in winter & deal with road grit, grime. oil, etc & have to replace clips, clamps or whatever I need to undo in order to remove cable, cause whatever I try to screw in or out will undoubtedly break due to corrosion, rust, grit, etc.
Also, there will now be an additional 2 cables that will be needed to be attached at the ground and Positive terminals for an audio amp that I am installing in the trunk. ( Plus that pre-existing RED wire that is already attached to the ground cable. I dont know what this is, but I think I'll have to do something about that thing, at least change its color.) any suggestions on how & where to attach?? I suppose that I can just attach them to the bolts on the battery terminals themselves, as I suppose most people due, But since I am doing the trunk, and I need to do something about the battery cable, and I have to do something about that weird red wire on the ground terminal, should I do something like a terminal bank in the trunk or something ??
So any advice on these items, or routing of these cables would be appreciated
Please see pics below.
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ed ross
Long Island, USA   usa

Re: Battery Cable.... SPLICE ??

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ed ross
Long Island, USA   usa

Re: Battery Cable....
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100_0045.JPG (53.6 KB) –

ed ross
Long Island, USA   usa

Re: Battery Cable.... SPLICE

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Jack Long Avatar
Forest Hill, Maryland, USA   usa
1955 MG TF 1500 "Harriet"
1974 MG MGB "Lucy"

It's not so much a "kill switch" as a battery isolator, but I have them on both my cars in that same location and think they are a good idea. However, I recommend that you break the ground wire, not the hot wire, for said switch. Its easier, since the ground wire terminates in the battery box area anyway, and safer.

I'll defer to others here as to the wisdom of splicing the positive wire but personally I'd probably bite the bullet and replace it, just for the peace of mind. I've dealt with DPO wiring enough times to make me resolve not to create any of my own.
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ddubois Avatar
Dave DuBois
Bremerton, WA, USA   usa

Ed - IF you splice the cable, only do so using a proper crimp barrel splicer, using the proper splice tool and insulate it well with at least two layers of heat shrink tubing - DO NOT use electrical tape! You would be much better off bitting the bullet and replacing the entire cable - much less chance of something going wrong or moisture getting into the splice, causing corrosion that could bite you later on. Personally, i would keep the kill switch. If for nothing else than the convenience of being able to disconnect the battery when working on the car without having to dig into the battery well.

Dave DuBois
1953 MGTD
1966 MGB

Member Services:
SU fuel pump restoration and conversion to solid state. Information and technical articles on SU fuel pumps.
Simon Austin Avatar
Surrey, BC, Canada   can

I'll vote for replacing the cable and keeping the battery switch as well. The fewer the connections, the better. The cable is relatively easy to replace and you can buy long lengths of cable (72" comes to mind) and add terminals as required.

"Speed fast you want to spend?"

Edited 1 time(s). Last edit at 12/10/2009 09:54PM by Simon Austin.
bleteaches6 Avatar
Lee Orphan
Sumner, WA, USA   usa

Sorry Ed, but if you have the switch, relocate it using the ground side of the battery, not the hot side. As for the cable, buy a new one. Splicing the cable is only asking for trouble IMHO.

As for the other ground wire, you'll have to trace it and determine if it is necessary.

Regardless, it sounds like you have a little homework to do with the wiring.
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Jim Barker
Northeast, IL, USA   usa
1970 MG MGB GT "The Bearcar"

In reply to a post by Simon Austin I'll vote for replacing the cable and keeping the battery switch as well. The fewer the connections, the better. The cable is relatively easy to replace and you can buy long lengths of cable (72" comes to mind) and had terminals as required.

Yeah, I'll second that motion. The fewer the splices the less chance of a problem/trouble in the future. Perhaps you could re-locate the cutoff switch to the trunk area, although I rather fancy being able to get to it in the case of an emergency situation. You'll have to get under the car and trace out where the mystery cables go, as DPOs are notorious for hacking things up to make things work instead of going the distance and performing a proper modification.

Jim B.
Car Prep Inc. Avatar
Chuck Methven
Corona, CA, USA   usa
1997 BMW Z3

I agree with replacing the cable! Keep it clean Ed!! Also, the kill switch on the ground side is a good thing for these cars.


Sinewave Avatar
T. Keith Vezina
Kenner, LA, USA   usa

New cable. Besides the saftey issue, one of the biggest problems with the MGB is voltage drop. A spice could potentially (no pun intended) introduce more resistance into the system.

T. Keith Vezina
British Motoring Club New Orleans
1976 MGB, 1976 MGB Trailer & 1967 MGB MK. I
frank0936 Avatar
Frank Stabler
Fairhope, So. Alabama, USA   usa
1975 MG MGB "Miss Scarlett"

Keep the battery switch on the ground side and replace the positive cable. I use the battery cutoff switch every time I get out of the car for any length of time. It's also an anti-theft measure of sorts.


A legend in my own mind....
75 B with HIFs, Pertronix, K&Ns
pooch2 Avatar
aussie 1968 MK 1
By the Beach, south coast NSW, Australia   aus

A soldered or crimped splice will be fine with insulation.
Redwind Avatar
Charlie Hopek
So. Cal, USA   usa

Replace the cable. 72" will most likely be too short, seems the one I made up was 80"- 82". Make it a bit longer so there will be some play for future terminal replacement. You can have good quality cables made up at an automotive electrical shop or marine supply. I purchased marine cable because it was finer strand wire which in theory will carry more juice. Not so sure if it is that important. Absolutely reinstall the isolator switch. I use mine all the time. I would lower the mounting point so that it does not cause problems removing or installing the battery. Purchase a battery terminal end made for amps like this: "Tin" the ends of the cable and amp power supply wires with solder before installing into the terminal. If use a terminal like this you will only need to get the correct size lug crimped on the other end. Seems that I purchased #4 cable as a replacement so that it would fit in the holders under the car. Don't take my word on the wire size, my memory sucks anymore. Use the neg side for the switch. You can pick up appropriate size premade cables up at any parts store to wire the switch.
herkdriver Avatar
George Pelech
Georgia, USA   usa
1963 MG MGB "Maggie"

No-just use a bolt to hold the two wires together and wrap some duct tape around it, that way someone can call you the DPO (just kidding). Another vote for the isolation switch. As for the wiring to the amp-use a spade connector and attach it to the battery clamp, pass through the hole for your fuel pump wiring. Make sure you put a fuse in the circuit.
I replaced a shortened battery cable-recommend you replace all the rubber grommets on the way with new.
Get dirty and have fun.
ingoldsb Avatar
Terry Ingoldsby
Calgary, Alberta, Canada   can
1971 MG MGB

The effort of a proper splice is greater than the effort (and cost) of replacing the cable.

A kill switch is not much use unless you can get to it quickly. If you can't locate it somewhere accessible then get rid of it. I personally would prefer to use fusible links in key locations (such as the connection at the starter solenoid that powers the rest of the car). They are automatic and will work even if you aren't around.

Terry Ingoldsby
mac townsend Avatar
Fairfield, CA, USA   usa

That lashup was not a proper kill switch. Such a proper kill switch would take into account the alternator output as well...otherwise trying to kill the engine with this switch will not turn it off but will likely damage the rest of the charging circuit as well.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks:
zzzinger Avatar
Greg Stroop
Santa Maria, CA, USA   usa
1964 MG MGB "Blondie"

I say keep the kill switch, move it to a better location if necessary. It is very handy to have for electrical emergencies, simple disconnect during repairs or battery isolation during storage.
If the cable is good and the eyelet has been properly installed with minimal resistance ,<1 ohm, I'd keep it with the eyelet.
If you install another connector it has to be done right. Resistance there will burn the insulation back quite a ways and melt anything it touches, leaving you stranded. I used a torch and soldered a crimped eyelet to be sure.
You will find some debate on which side (+ or -) to switch. Either way is better than completely removing the switch from the car IMO.
scotabbott Avatar
Scot Abbott
Pittsburgh, Pa 15216, USA   usa
1974 MG MGB "Bee"

An isolation swwitch is worthwhile, and it's already there. Iwould recommend you make cables-a new ground and a new positive cable-and that you run the ground up to the engine itself,as well as to the body. The stock ground arrangement is awful in most B's. It is usually a flex cable held with a rusty bolt to a rusty section of the battery box angle stock. I made my own cables by soldering ends on very heavy cable (maybe #4) about the dimeter of my little finger)..
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