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MG MGB Technical - 12v conversion

Hi,

Is it easy to fit a 12v battery under the bonnet coz there seems to be plenty of room near the n/s wing?

It would make it a lot easier for doing routine work and especially at the moment as I have to boost my batteries every morning to start up. Think it's the fanbelt or the starter or the alternator or......

Voltage is reading at just under 13 at high speed so I'm guessing there's something amiss.

Anyway, would it be easy to reroute the wires from the batteries to a battery?

Cheers
Matt
Matt

I am repeating myself, but here is a link to a picture of my car (1964 MGB) with a battery under the bonnet.

http://www.mgcars.org.uk/pics/neuhaus3.jpg

Itīs a 36 or 42 AH battery from a VW Golf oder BMW 3series - they all fit. To fix the battery you need an l-shaped piece of metal and bolt this into the existing thread that is in place on the bulkhead.
I didnīt reroute the battery cable. I just cut the old cable to the rear off and fitted new one that is routed inside the heatshield in front of the heaterbox.
Joern-M.

Hi Matt

Re-routing the wires is easy enough, but I personally wouldn't put the battery there in the long term.

Batteries don't like being cooked, and the area that I think you are considering does get quite hot.
It also moves some weight forward and upward which is not ideal but does give better left / right weight distribution if you usually drive solo.

I trickle charge my battery via the cigarette lighter socket, could you do this ?.

Joern, what have you done to your rocker cover ?, it looks great.

Don
Don

If your battery is draining overnight, you need to find the source of the drain. Moving the battery won't help much.

You probably know that the common way of converting from two six volt batteries to a single twelve volt is to put one in the right hand battery box (the driver's side to you, passenger side to me).

A properly functioning alternator should put out around 14.5 volts at speed. Thirteen volts is not seriously low, but it should be higher.

If you disconnect the ground cable from the battery and bridge the gap between the cable and the battery terminal with a voltmeter or test light, you can see if there is a drain. If the test light glows, you have a drain. The brighter it glows, the higher the drain. Begin removing fuses from the fuse block one at a time until the drain goes away. That narrows the search to only those circuits protected by that fuse.

You're right about the fan belt being a possible culprit. I learned that the belt should be tight enough that you can only deflect the belt about 1/2 inch between the pulleys. That is, if you press on the belt on the long stretch between pulleys, you should only be able to deflect it that much, with reasonable pressure. Any more deflection and the belt is too loose; less and the belt is too tight.

Check all the connections on the alternator and on the wires connecting it to the fuse block.
Paul Noble

Where are you reading the 13v? You should measure at the alt brown, the battery post and the fusebox brown with the engine running at a fast idle and minimal. They should be within a couple of tenths, any more of a gap indicates bad connections which could be affecting charging and cranking. With maximum factory load you should still have more than 12.8v on the battery even if you have less than this on the brown, white and green at the fusebox. If you are connecting the booster batteries to your battery(ies) and it then cranks OK there could still be bad connections between the clamps and the battery posts as well as a drained battery. How old is the battery? Old ones can eventually lose enough charge overnight without any external drain to not crank next morning, particularly if cold. When checking for a drain as Paul Noble suggests (with the analogue voltmeter on its 12v scale) the first thing I would unplug is the alt connector. With it in you should see a few volts and this is the normal reverse leakage of the alternator diodes. If you see a full 12v then you have a significant drain, which still may not be enough to light a test-lamp. You should have zero voltage with the alt unplugged, unless you have a alarm, clock, ICE with memory keep-alive circuit, or a drain from a fault.
Paul Hunt

Don Cornwall wrote:

"Batteries don't like being cooked, and the area that I think you are considering does get quite hot."

While I won't argue with that, I would point out that almost every other car on the planet has the battery in the engine compartment, with, apparently, no problems.

Personally, I think the battery is best off where it's at, but there is a lot to be said for the convenience of having the esier access from the engine compartment. Where it's located now makes it awfully easy to overlook routine checks and maintenance. That's no excuse for not doing them, I know, but.....
Dan Masters

Don,

the rocker cover is a standard item, but it is chromed - I didnīt do it, I got the cover as it is.

I am running my car with this conversion since about 20 years and I never cooked a battery. Itīs definitely not a problem having the battery in front!

About the weight distribution: having 2 or 3 kg more or less front or rear doesnīt make any noticeable difference. Believe me, I know it from experience :-)
Joern-M.

That's a pretty car :) I plan to try to install a battery in the front also when I restore my car as it's a PITA to disconnect the battery and charge it in the stock location. Is it held in place only by the bottom bracket? Did you use a mat under the battery to protect the body from corrosion? Thanks for the picture.
Mike MaGee

Mike,

I donīt have a mat under the battery. Why should it rust there? The battery is located by an L-shaped piece of aluminium, aprox. 1 cm high and 4 cm wide and 6 or 7 cm long. I will make a picure of the fixing and mail it to you in the next couple of days.

Jörn
Joern-M.

Mike,
if you want a picture of the way the battery is fixed I need your mailadress. Just send me a mail with it and you will get the picture.
Joern-M.

This thread was discussed between 24/10/2003 and 01/11/2003

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