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MG MGB Technical - BATTERY & CABLES

Battery in my 79 MGB packed up. Had quite a struggle to get the cables "out of the way" to remove the battery. A larger struggle ensued to mate the cables to the new one.

It's a Class 56-3. Specs are as follows: measurements 9-3/4"-L, 6"-W, 7-1/2"-H, 590 Cold Cranking Amps,and 725 Cranking Amps @ 32-F / 0-C.

Questions:

Just what is the correct size battery for this car? Other than getting the car started, just how much demand is placed upon the battery??

Next item: How long are the battery cables supposed to be and where on the car do they terminate? Not knowing how many owners turned wrenches on this car before I got it, I strongly suspect there has been "some cobbling" performed here.

Cheers

Gary
79 MGB




Gary Hansen

Gary,
we use a different code for battery sizes over here (and the measurements are in mm overall) but in the Archives will be the single 12v Vitra battery that DaveO recommends (for the two 6v to one 12v cage).

Moss over here have images of type 069 batteries so have a look at the various ones in the link below, but after reading my notes in this post and always cross-reference check on the battery manufacturer's sites for specs.

You want a good battery as the cables are longer on a MGB because of battery location and the space is restricted. But just CA and CCA are not all, and there's 7? lots of different specs for the figures, see attached PDF for four types used over this way.

But again these figures are just test figures and don't tell you how long the battery can keep to spec with time passing and use.

How much the battery uses depends on what you've added to the car but as standard little compared to a modern car. What's the AH of the battery you have?

60 - 70Ah looks standard-ish, 75Ah more heavy duty.

Tayna 069 - https://www.tayna.co.uk/car-batteries/types/069/

For the cables I can't remember but you definitely don't want the original style screw-on helmet battery clamps on them.
Nigel Atkins

Gary,
As Nigel says... your battery looks to be about the right size for the car. And yes they can be a bugger to get out if it doesn't have a handle in the top.

Peak demand will be when it's cold, dark and wet LOL. That's when you have the headlights, heater blower, wipers and ICE turned up! So a normal UK summers day LOL

Add to this by being in traffic when the alternator output is at it's lowest and you get a net drain on the battery. How long it lasts depends on the AH storage capacity. That's why we have HD as you want the biggest AH number you can find (well in the UK anyway!). For you, in a warm climate with big open roads, any battery that delivers a CCA of 500+ should be enough.

Cables on your car should be quite straight forward.. One from the +ve terminal to the starter motor and one from the -ve to the body inside the battery box.

Best of...
MGmike
M McAndrew

For cables I was thinking of routing and holding.

500+ (depending on what type of 500) sounds plenty but it depends on environment, weather, state of starter, earths, etc. but more consistently good and long lasting of sufficient CCA and Ah is best. Quite often you do get what you pay for regardless of printed numbers, the highest numbers are not always on the best battery. As lead is heavy comparing same lead construction batteries by weight can give a clue sometimes. As can warranty years as a rough guide, well over here anyway.
Nigel Atkins

Nigel:

Thanks for the Tayna spec sheets. It is true, the USA and the UK are separated by a common language.
I'll work on the "translation"

Mike:

Thanks for the advice on the cables.

Yes, it is a tight fit. Another coat of paint and it wouldn't fit.

I'll work on it and get back with results.

Cheers

Gary
79 MGB
Gary Hansen

Once the engine is running the alternator should be supplying all the power with some left over to keep trickle-charging the battery, even at idle, especially with the 45 amp 18ACR. If the system voltage drops below 12.8v then the battery is being discharged.

As such the only time the battery supplies power is when cranking and while parked if things are left on.
paulh4

Gary,
do bear in mind the Tayna battery measurements are to the most extreme parts of the battery, so the height is to the top of the terminals etc..

If 069 batteries are a bit too tight you can search by your measurements (mm), on the Home page click in the 'Search' box and this gives a drop menu with 'OR: SEARCH BY BATTERY DIMENSIONS'. - https://www.tayna.co.uk/

The bigger the battery generally the more it can hold, but a bit smaller battery might have lower CCA and Ah numbers but could be better by being more consistent and long lasting than the bit larger battery with its higher but less consistent and long lasting numbers. 500 CCA and 60Ah is a lot for a standard MGB. My midget is 340 CCA, 45Ah and I'd expect 10 years use out of it at least.

Do remember to check the type of posts and position The battery can be turned of course).

Nigel Atkins

Nigel, I fitted a new battery a year ago as it gave up the ghost during lockdown. From recommendations on a thread from this forum I fitted a Varta B36

https://www.varta-automotive.com/en-gb/products/varta-blue-dynamic/544-401-042

Its a 44AH battery with a CCA of 420 Amps, and has proved that its up to the job on my roadster (although I do have a high torque starter).

It is a bit smaller than the Yuasa battery it replaced, but will fit easily in a battery box. I did have to turn the battery 180 deg to get the -ve post in the right position, but that was not a problem.

Andy
Andy Robinson

12v batteries with the terminals in the corners along one long side are usually available in both types, Type 1 would have been correct.
paulh4

Andy,
thanks, I think(?) that's the one I'm thinking DaveO recommends for the one 12v instead of two 6v.

I'm sure your 440/44 would still be fine with standard starter, just IIRC Gary travels quite a bit in his B, and to high altitudes and hot places, so he'd know better if his use of the car needs more margin in battery power.

Bit annoying on that Varta link they have UK code 202 and Tayna list it under 002L (I looked it up under battery brand on Tayna site). This is the problem with all the different codes and descriptions and interpretation of dimensions. My neighbour bought a Halfords battery recently and it was a different code to the two I found, and had a different foot clamp arrangement which my neighbour didn't want me to modify so much more time taken looking for bits to modify the clamp.

Something I've wondered is whether the battery box is different for the later 12v battery cars, I ought to know as I had a r/b but it's too long ago now for my memory (well that includes this morning for me).

Of course Gary being in America needs a battery with the biggest numbers. 😁

Nigel Atkins

Nigel,
Battery box for RB car with correct orientation of battery terminals although i had just removed the clamp prior to lifting the battery out(This was disconnected during my recent re-furbs). Battery since cleaned up & put back together with a well ventilated plastic box which is a pig to get it to adapt to fit the cables & use a new method of clamping the battery. (Although it does seem to reduce the amount of road noise etc,) I have had the lid for a couple of years which is a great improvement on the original.
Cheers,
Charles






Charles9

Gary. I purchased a new 79, in Bitburg, Germany, in November of 1979 and owned that car for something over five years. The battery to be used was a group 24. I do not remember whether it was a Group 24 or a Group 24F (the battery terminals are swapped between the two styles). Today, however, I use the red Optima battery which is slightly smaller, more powerful, sealed, and has demonstrated very significantly longer battery life than the common lead-acid batteries I have used over the last 20 years in my MGs. In addition, the Optima has a handle making inserting and removing the battery from the behind the seat compartment significantly easier.

As to the cables, the one from the negative terminal (ground) is attached to one of the downwards sections of the battery box. The positive cable is a long run from the main terminal of the starter back to the positive terminal of the battery. It is secured by several cross pieces which also secure other wiring going to the rear of the vehicle securely to the chassis to prevent dragging and possible damage.

As a side note, the long (positive) cable will, over time, deteriorate and cause starting problems. (Best test is to check starting voltage at the starter while trying to start the car. If the voltage drops at the starter terminal, but remains high at the battery itself, the cable is not capable of carrying a full load and needs to be replaced. Best replacement is to have one custom made, just about four inches longer than the factory one you have removed.)

The combination of a custom cable and the red Optima battery will make for a long lived system which, if you ever need to change out the battery, will be a quick and painless (literally) job.

Les
Les Bengtson

Charles,
thanks, I'm glad you put about your lid as I didn't remember it at all, especially the Dzus. 😀

And you have some bragging rights with 600 EN as Google tells me that's equivalent to 650 SAE CCA (all when new of course.
Nigel Atkins

Les,
thanks for info too and very much agree with checking the long cable if starter drops off, often forgotten about, especially if there's the extra cable for two 6v and those silly helmet post caps (forget the proper name) instead of clamps.

Nigel Atkins

Nigel. On the rubber bumper cars thee is only a single 12v battery with the positive terminal cable running from the battery to the large, lower post on the starter. As to the battery clamps, the helmet system was phased out, at least on the North American specification, by the introduction of the RB cars if not some years before that. The last car I owned that had helmet connectors was a 61 Sprite Mark II.

Les
Les Bengtson

Thanks Les. I was thinking of older cars for the helmet caps but sometimes older parts find their way on to younger cars, I can't remember the last time I saw the caps but do remember being surprised to see it on the particular car.
Nigel Atkins

Nigel, you are correct that the Varta B36 is my favoured battery. I think the ‘standard’ number is 202, but Bosch use 002, just to confuse us.

I purchased my battery about seven years ago, in anticipation of my car returning to the road rather sooner than was reality. Although I did trickle charge it during its four year wait, I haven’t charged it since, despite long periods of inactivity, due to lockdown and lack of opportunity.
Dave O'Neill 2

Currently,I have a 075 battery. All is good but my next battery would be a 078 which is a type 1 terminal orientation. Both 075 and 078 fit snug in the cradle but fitting the positive terminal on the 075 bends the cable a little too much.
1980 car.
Image of 075 enclosed.


Craig M Harvey

OK. Got the battery installed. The positive cable is too short and needs to be replaced. Measured the length from the starter to the battery box, and it's about 7'-8' long. If this cable is stocked at an auto parts store, I imagine it would be on a spool and sold by the foot.

I tried to upload some pix, but not successful.

Cheers,

Gary
79 MGB
Gary Hansen

The hole for the battery in rubber bumper cars is quite a bit bigger than that for CB cars, not surprising since the standard 12v battery is quite a bit bigger than 6v. My roadster came to me with a 12v that was bigger than the hole in the shelf, and as the cradle had been extended I did wonder if it had been welded in place ... until I realised that by tipping it on its end I could get it out, fortunately it was a sealed.

Yes you can get 12v to fit but there is a compromise on cranking ability that won't be noticed until the battery gets older. 6v are commonly 600CCA, some 12v to replace 6v are quoted at 300 which is a big drop, but less of an issue with a geared starter (not all 'hi torque' starters are geared) which take a lot less current.

Whatever you do make sure there is a proper clamp for the battery. Roger Parker has written of a case he attended as a motorway Patrol Officer where the driver of an MGB was burnt alive when an unrestrained battery shorted out in a roll-over and started a petrol fire.
paulh4

Craig,
that looks like you have a Halfords battery there, they seem to offer different battery code numbers, to Tanya at least, or that was the case for my neighbour's battery. They don't seem to offer a HB078 on their website. Nothing wrong with Halfords batteries but if you don't have a coupon, trade card or they're on special offer they tend to be a higher priced or you can get a better battery for the same price.

My neighbour's previous battery was a Halfords and it lasted very well considering the car's low mileage, short journeys and periods of lack of use, especially recently of course. Only this week it was took to my mate's for recycling as it's the first battery I've not been able to revive for light out of car use.

Just my thoughts now.

Personally I'd always go for 4 year warranty Halfords battery especially on a car that not regularly used but if you've fitted a socket for a plug-in battery trickle charger it's not so important.

Yes it's all a bit tight with the battery posts for the HB075 and I'm sure the cables aren't as close as they look in the photo and no doubt you've made allowance for the positive cables not being pinched.
Personally I'd have the battery earth cable under the the retaining bar and the other earth cable angled down more so that both earth cables go under the bar and can have slit'd rubber hose off-cut(s) over them at that point to prevent any chance of rubbing. And it'd look neater having the battery earth cable under the other earth cable.

The retaining bar should really be on edge of the battery which will need consideration if the posts go to the rear, a strip of rubber and/or notches in the bar might do.

Just thoughts.




Nigel Atkins

Dave,
yet another example of different numbers, Tayna don't list 202 but they come up under 002L, but Halfords have a HB202 with slightly different dimensions and not quite as much power listed. As with the power numbers battery code have to be investigated a little and not just taken as read. Same for size dimensions as some batteries fit better than others.
Nigel Atkins

Gary,
at 7'8" (as long as that) you might want to allow a little for loss over length but as I can't remember what and as USA use a different gauge system I won't confuse either of us and let you check there. The factory thickness if still on the car would be right.

But won't the Moss or others made up cable fit?
Nigel Atkins

Ready made will also have the connections, I've known of people buying 'loose' as they had access to an industrial crimper for the solenoid end and it still wasn't enough. The battery end is easy.

Yes it's a long run, but I've never heard of the cable deteriorating, only the connections to the solenoid terminal at at the battery which can be dealt with.

Ampere hour rates are only of relevance if you habitually park it with the lights on, otherwise it's only cranking ability that is significant.
paulh4

Nigel, all good points. My battery is Halfords and 6 years old. I had it in mind to find a piece of rubber to go under the clamp plate. As regards the 078 battery-it would be a Varta Silver D39. Not sure why they have different numbers. Cost £66.50 plus delivery. I have read many good comments on the Varta batteries. Image enclosed.


Craig M Harvey

According to Clausager the plastic packing strip to battery clamp was deleted in December 77 :o)
paulh4

Nigel,

My battery was a Bosch S5004 (per my photo on my last post) obtained from Advanced Battery Supplies £84.95 delivered some 4 years ago. I recall that it was similar in size to the original 063 (?) & was easy to fit. My previous battery was clearly oversize & had the usual cut fingers getting it out. It has a similar profile to the Varta D39 with the same type of handle.

Cheers,
Charles
Charles9

Craig,
it's a star buy. 😀

Being serious don't put too much into paper figures it's how these figures are repeated in the real world use. A good battery is a good battery and will stand up more and longer than a lesser battery of the same figures, test figures are useful as a general guide, think of car manufacturers mpg figures but less malicious obviously.

Note the Vatra shows as 15mm higher than the Halfords, I'm thinking about posts, cables and holding bar positions and wrestling with thick wires.

Another example of different listing and codes, Vatra list that battery as "UK Code: 077", see the attached PDF on the Tayna webpage or here - https://www.varta-automotive.com/en-gb/products/varta-silver-dynamic/563-401-061

Big CCA is good for cold or heavy starting and obviously the higher the figure the greater the margin but if your car is summer use only and all of the car is in good condition especially the starting, ignition and electrical systems the battery figure doesn't have to be that high compared to a car that's used year round and parked outside, like my Midget with it's battery that was used for over 10 years - with only just around 310 CCA (when new).

As most experienced classic owners know you often don't even need the battery to get started, a slope or other(s) pushing the car will do. 😁

AH does matter if you actually use the car or get stuck in the rain in stop/start crawling traffic with the electric cooling fan, blower, wipers, lights, entertainment, ect. all going.

Having 30 years experience of various classics used as dailies throughout the whole year and very rarely having access to a garage, one of the very first items (after safety items obviously) that I concern myself with is that the battery is a good one, fully charged and in good condition along with all of its connections. If the battery isn't good I change it very quickly as a good battery helps with running and sorting the car and a poor battery hinders sorting and running the car.



Nigel Atkins

Just in case anyone gets or has the mistaken idea that I know much about batteries, I don't - I am NOT an expert, in anything, if you look up 'not an expert in anything' you will find my name.
Nigel Atkins

Charles,
a Bosch, I bet you get great mpg then. 😁

I forget the number code for the battery when I had mine and Bosch aren't too forthcoming with details so we'll take from Tayna who have it as an 075.

5 years guarantee, and I think I read they swop for new in first three years. No doubt a good battery, not top of their range for bragging but probably with very or over generous margins for your needs but that gives plenty of mental comfort which is always worthwhile.

https://www.tayna.co.uk/car-batteries/bosch/s5004/
Nigel Atkins

Also, I'm not saying Tayna are the only place to buy from though I've found their prices to be good and the few times I've used them that their service is very good - although I did once get a battery that wasn't fully charged, always check the battery before fitting.

Like all databases do check the the details as errors do occur, I saw a battery spec error once.

Do, as always, carefully read any reviews and bear in mind most men do not read instructions and therefore can balls things up but these types often want to blame anyone else except themselves. Sometimes happens with women too but they're less likely to keep up a pretence of being right when it's pointed out to them they've made an error.

Nigel Atkins

The battery in my car resides in a Moss Motors "poly-plastic" formed battery box. Previous owners inflicted their "turn of the wrench" and it is obvious much of this stuff is not a "factory" install and/or material. That includes the battery cables.

What added to the difficulty was, the car is backed into the garage with the right side parked 6" from the wall. This means I had to climb over the seats and hump to get to the battery.

I'm certain I can find the correct gauge wire and have the ends swaged on to longer cables.

Again, thanks to all.

Cheers

Gary
79 MGB
Gary Hansen

Alternators are designed to deliver all the current needed for factory loads at idle, which is why the output increased twice as loads increased. That includes the V8 with twin electric fans. If they don't then something is wrong that needs sorting.

If loads have been added such that the battery is discharging at idle then the alternator should have been upgraded at the same time.
paulh4

Yeap that's how I have it but for some things can be marginal, fine normally but for whatever and many and various reasons outside of the perfect world and perfect MG (as if!) there could be occasions where the margins are too squeezed so a bit of spare fat is useful to get through the lean period.

I know it's a very rare event but it's good to have a bit of spare in the battery for when the cars have something playing up on them (as if!), and they don't always play up in the garages full of tools and facilities that most owners seem to have.

Some people seem to want or need to keep their battery on a trickle charger so they must have some constant drain and/or over a long periods of the car not being used.

If you have hazards and need to use them then the longer they last without the engine running the better.

Not all start as well as quickly as they should which empties supplies a bit more (must be the reason for those 600CCA 6v batteries) then it's a short journey that doesn't replenish enough.

And it may seem strange to many owners but some with classics also use them in the wet and/or night and may want to or have to use parking lights (I prefer reflective number plates but it's against the law for some not to have b&w number plates on a classic).

Also some people have lots of electrics running when the engine is not.

It's a mixed up, muddled up, shook up world, ... 😁
Nigel Atkins

People have been scared into buying 'maintenance' chargers. If you use one of those constantly you have no idea how your battery is deteriorating and how often the unit is having to 'top it up'. If you use the car and are away from home not being able to connect it then you could well find it won't start next day or whatever.

Using periodically and checking the state at the beginning and how long it takes to complete is fair enough.

A lithium battery pack is all I need.

Since November 2015 'black and white' plates are legal on UK cars that are registered in the 'historic' taxation class.
paulh4

Paul,
I do follow what you're saying and generally agree, depends on circumstances though, and the same applies to the use of SatNavs, I use paper versions to guide me (see outdated photo) but people vary in what they need, and what keeps them happy.

I don't use a trickle charger to maintain the battery and my Midget sits outside 365/6 days a year. During the last few years for various reasons it's had little use and sometimes weeks of sitting there rotting away but even if I left it for months in winter I'd still expect the battery to be able to start the car without assistance.

I don't see the need most times for these big figure batteries but if it keeps the owner happy, and to me importantly actually using the car, then it's all good.

Same with the b&w plates if it keeps someone happy then fair enough but just because it's legal doesn't mean you should and not all are legal, I've seen them on a black BMW MINI and other newer cars. On many classics they're not period correct either, not that "originality" bothers me over much but to see them on a tartaned up 'R' reg classic is jarring to the eye.

It doesn't matter on show or sunny-Sunday afternoon classics but if they're actually used, and gawd forbid, actually used when darker skyies I think the reflective surface adds safety to the often very small (and sometimes very dim) lights of classics, and useful for when parked up.

Another reason to always have a good battery to keep the lights bright. 😁




Nigel Atkins

Paul,
The GB number plate legislation changed on 1 January 2021. Only historic registered cars built before 1 January 1980 will continue to be able to use black & silver plate designs.
Cheers,
Charles
Charles9

Nigel - my 73 would almost certainly have had reflective plates from new (the 75 definitely) and I see no reason to change from that. There have been 'illegal' plates for decades, and will continue to be so.

Charles - that's because the 'historic' classification advances year by year and until Parliament changes the law will continue to do so.

paulh4

Paul,
i extracted the information from an article by Roger Parker in the February 2021 edition of the MGOC magazine. He states that "the new rule breaks the link between number plates & Historic vehicle tax exemptions meaning cars who automatically become exempt cannot use the old designs as standard practice." He goes on to say that "number plate legislation was last changed for the current style of number plates from September 2001."
The changes have come about due to the need to change the 2001 regulations as a consequence of Brexit as those regulations included aspects entwined to the EU so the legislation needed to be changed. The rolling 40 year exemptions for cars where they are moved into the Historic class from 1 April 2021 (as per my August 1980 MGB) no longer includes the ability to be able to display non- reflective plates.
Cheers
Charles

Charles9

Charles,
Paul should know this as I'm sure it's been covered here, with possibly a link to the legislation but don't rely on my memory. Roger might have got that info from here. 😁

But Paul might have been away with the OC forum or perhaps the FB crowd at the time.

Surely you don't want black and silver or black and white plates on your car, yellow plate to rear and white to front is coordinated on your car.

Unless you're going to paint it black with silver (or white) go-faster or Shelby stripes - or match the deckchair seat covers.
Nigel Atkins

Hi Nigel,
I don't want black & silver plates on my car. I'm quite happy with the reflective yellow plate at the back especially given the car's colour. Also much more visible & therefore safer + as originally first registered!
Just wanted to make others aware that the legislation had recently changed!
Cheers
Charles
Charles9

You are a credit to the community for disseminating the information, being mindful of safety





... and having such good aesthetic taste like wot I 'ave.

😁
Nigel Atkins

I hadn’t heard about the change in legislation. I don’t remember reading about it here.
Dave O'Neill 2

Ha! I have both changes in my pages and of course looking for the info found the previous change not the latest change.

Roger also writes that it only affects plates replaced from 1st September 2021, existing plate do not have to be replaced as long as they complied with the legislation when fitted and are clean and undamaged. But as 1980-built cars couldn't be registered in the Historic class until 1st April 2021, and the legislation changed on 1st January 2021, doesn't that mean they couldn't legally have black and white plates anyway? And as cars already in the Historic class before 1st January 2021 can continue to wear them, which cars will have to revert to reflective plates if they are replaced after 1st September this year?

Mind you, birthday drinks last night so still befuddled ...
paulh4

Hi Paul,
That was precisely my point,that 1980 built cars only became eligible for transfer into the historical class category from 1 April 2021 & they were not previously permitted to be fitted with black & white plates for road use (when they were not classed as historic) & that the new legislation applicable 1 January 2021 effectively stops 1980 build vehicles onwards from using them as well.
Cheers
Charles
Charles9

Given all the illegally spaced vanity plates on all sorts of cars on the roads does it really matter, how do they get through MoTs.

Dave,
when I say 'on here' I mean the BBS generally but I did think it was on MGB, perhaps General. I think there was a link to the legislation but as it goes back more than 5 seconds I'm not totally sure.
Nigel Atkins

"The change seeks to prevent any vehicle constructed after 1 January 1980 from the ability to display the black and silver number plate despite being recorded in the DVLA’s historic tax class. Those vehicles with a construction date prior to 1 January 1980 will continue to be able to legally display black and silver number plates to avoid any undue costs of replacement."

https://fbhvc.co.uk/news/article/changes-to-black-silver-number-plates-from-01012021
Nigel Atkins

"how do they get through MoTs"

MOT? Insurance? Tax?

paulh4

"The DVLA will also be introducing a new British Standard for number plates produced from 1 September 2021 which will mean all current style number plates that are first fixed to a vehicle from that date must meet the technical requirements contained in that standard."

"British Standard number (currently BS AU 145d) from 1 September 2021 a new standard will become mandatory for all new number plates fitted from that date (BS AU 145e) but can be used from 1 January 2021"
Nigel Atkins

The vehicles I'm thinking of are often owned by the middle-class or well-to-do, in middle or older age so probably exempt from those rules by virtue of being 'the right sort' and not 'others'. I'm sure generally they have Mots, tax and insurance but if they did let it lapse by mistake they could be let off as they're the 'right sort'.
Nigel Atkins

Somehow we seem to have slipped from batteries & cables to license plates.

OK. I got my 8' cables, one red and one black. It is a "4 gauge" thick wire. Is this the correct wire gauge?? It seems to match the thickness of my other two cars. Just making sure I bought the correct wires.

Cheers,

Gary
79 MGB

PS: still working on Uploading images

Gary Hansen

4 AWG in round figures is 25 mm², 10 mm outer, 170a

I've got that, it looked thin to me but it's the same size as on the modern car. Even at the length it's not a big drop and you've plenty of meat on the battery and good clean, secure and protected connections at the four ends will help too.

Don't oversize the ring connectors for stud and bolt have a good snug fit, plus it helps to tighten them at an angle as you hold the cable (to find you've looped it over instead of under and take it off to try again, knit-one-pearl-one).

https://www.12voltplanet.co.uk/extra-flexible-battery-starter-cable-25mm-170-amp.html

https://www.12voltplanet.co.uk/copper-tube-terminal-10mm-max-cable.html

P.S. What's the problem with images (are you using an i-can't phone or other mobile device).
Nigel Atkins

Gary. The four gauge wire is what I have used over the years. But, the only one that you need eight feet of is the red wire running from the positive terminal of the battery to the starter motor. The second, black, wire is the ground wire and runs from the negative terminal of the battery to the frame of the battery box which forms the chassis ground. Eight inches is sufficient and a foot would be about the longest length that would be practical.

Les
Les Bengtson

Thanx Nigel & Les.

Don't know why, but I imagined the wire to be thicker. As soon as I can get the "Queen's" car out of the garage, I can jack up the right side of the MG and slide under and track the cables.

The negative connector to the battery has two cables attached to it. I'm not sure, but I think there is a negative cable that runs to the top bolt on the starter as well as somewhere else on the body for grounding. That would ground the engine as well as the body.

Cheers

Gary
79 MGB
Gary Hansen

A 79 would originally have had a braided earth strap round one of the gearbox mounts. People do sometimes add one at the engine as belt and braces, and I have heard of one instance of someone running an earth cable all the way from the battery to the engine saying copper is a better conductor than steel. Well, yes, but the CSA of the body is a lot more than that of cables likely to be fitted to an MGB, and a cable would only need to go as far as the gearbox. In either case braided (as originally) is preferable to stranded to cope better with engine/gearbox movement.
paulh4

Gary,
if you can, some photos might help as you put previous owners have drifted from factory installation.

I must admit I missed it if you have 8 foot of black cable for the earth run. As Les and Paul have put it's better to have a short earth cable directly from the battery earth post to a good solid clean connection on the battery holding frame or car body.
Nigel Atkins

Craig,
talk of Gary's earth cable reminds me of something that made me curious but I held off asking before. Your battery earth cable seems to go to a share point before returning to the battery box frame, I wondered why this was?

Also belt & braces as the hole isn't just sheet metal but I'd also put a bit of rubber sleeving over the cables.





Nigel Atkins

This thread was discussed between 24/05/2021 and 29/05/2021

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