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Dear All

I have a bit of a conundrum regarding a 12v battery for a 1622 engined MK1. The car came fitted with a YUASA Professional 063 battery, which though 215mm in length just fits in the o/s battery box, which may have been altered at some stage. The battery has a 45AH capacity and a 380 CCA. Anyhow it expired a couple of weeks ago and I put in on a 36 hour fast charge. Refitted it and a few days later went up to Alfreton to have the car tuned by Peter Burgess. The started and ran well and I had the headlights on on the way back - a journey of around 89-85 miles to where I live.
The car has been converted to negative earth with an alternator fitted.

I came to start the car on Saturday without success. I then looked at the MGA Guru's website and he mentioned batteries that would fit the battery box. These included a VARTA Blue B35.

I visited a local supplier and he had not got one in stock. I mentioned what is was for and that size was critical. He suggested an alternative NUMAX 002L which has a 38AH rating and a 320 CCA.

I fitted it and it hardly turned the starter over so I took it back and it was checked and found to be 'a little low'. He also checked the YUASA battery and commented that that too was nearly dead!

When I got back I did the following:
1 Checked and cleaned the terminals and the pos
and neg connections.
2 Checked, cleaned and refitted the battery to
earth connection.
3. Checked, cleaned and refitted the starter motor
4. Checked all connections once more.

I then fitted the new NUMAX battey and whilst there was a little more urgency it failed to be sufficient to make the engine fire.

As the car has to amp meter fitted I dont know whether the car has been discharging, though at no time did the ignition warning light come on. I retensioned the fan belt a couple of months ago and the alternator appears to be brand new.

I have the YARTA battery (the original that came with the car) on a 'trickle. charge for the next 24 hours.

I am rather bemused as to the problem and would welcome any advice please. My knowldedge and appreciation of electrics is rubbish but I have hopefully followed through the obvious checks I would have thought.

I would be grateful for any comments and advice that you could suggest please.

Many thanks




If you have a lucas alternator fitted the diodes burn out & this causes a drain of the battery. Also check the starter switch, when these fail it has similar symptoms to a flat battery. I use a short battery cable & jumped the terminals of the starter switch to see how freely the starter motor turns compared to using the starter switch.

I Hazeldine

First to be able to fit an 063 battery the battery box must have been modified, I too have a 063 battery fitted and had to modify my battery box for it to fit. I suggest you should stick to the 063 battery as it is probably the most common battery available and is therefore one of the very cheapest to buy. That allied to the fact that no matter where you are a replacement will ALWAYS be available. These exotic batteries are fine until they give up in the middle of France!!!

As suggested a fault with the alternator can cause the battery to discharge overnight so you need to do a couple of tests.

Test 1

With engine unning at slightly above idle (2000rpm) measure voltage across the battery, if it is 13.5 or above charging circuit is ine!! if it is below 12.5 the alternator is faulty.

Test 2
When you stop the engine disconnect the battery overnight, in the morning check if the battery when reconnected will start the car without a recharge, if it does then chances are he alternator again is faulty or something else is using power and draining the battery. Sometimes this can be a radio or other device!

Timing too far advanced or distributor not retarding the ignition can also cause poor starting/turning over.

Robert (Bob) Midget Turbo

Check the ignition warning bulb. In many cars when the bulb fails it stops the battery from charging at all. Not the solution here as you have a new fully charged battery, but may have been a cause of the discharge of the old battery, Diodes, as previous post mentioned, are the most likely culprit here, good luck.
A M Leyva

Check the ignition warning bulb. In many cars when the bulb fails it stops the battery from charging at all. Not the solution here as yiou ahve a new fully charged battery but many have been a cause of the discharge of the old battery, Diodes as previous poste mentioned,are the most likely culprit here,good luck.
A M Leyva

Did you check the engine to earth cable?
N McGurk
Barney Gaylord

I'm planning to fit a Varta B35 to my B

or even a Bosch with a 4-year warranty.

Should drop straight in.
Dave O'Neill2

Just brought a Varta B35 for my 65 B (just like an A) fits easily.

Brought from Comes with 4 year warranty not 3 years as on fleabay. Same basic price next day delivery.

Needed to move earth cable - the drivers side battery box is already drilled to take it - may need to scrape off underseal. Also had to die down the clamping stays a short distance. So far has worked really well should have dome it years ago.
G R Wilder

Thanks for the link, looks ideal.
Dave O'Neill2

A little while ago I started this thread on 12V batteries and outlined some of the experiences that I had had with my battery retaining its charge.

After some horrible weather, which discouraged me from even entering the garage, there was a sudden change and yesterday it was up to 18c in central Warwickshire (UK). Having had the car running briefly in the garage the week before I thought I would try again. Anyhow it started and ran well on a 10 mile run with Peter Burgess's tuning work very much paying dividends.

I was talking about this with a friend of mine and he asked if any lights had been left on and I said 'no' but driving home I switched on the side lights and tried the panel switch - which was 'on' but the panel lights were not working (something I must check) so I turned the switch off. I guess that a small trickling of power would indeed run the battery down over a 24 hour period.

I went out in her today and again it started. One thing I will do is fit a battery master switch and of course sort out the panel light.

I really hope that's it and I have been very dumb on this rather obvious matter! Anyhow many thanks for all the great help which is very much appreciated.



Can I ask please what the voltage should normally be across the terminals?
Mine starts fine. Even did so after a month's hibernation without trickle charging.
The voltage before starting shows at about 12.6 volts but someone has just told me that they thought it should be about 13.25v and it will fail by soon. Do you think that is right and should I change batteries now before getting caught out?
Graham M V

Open circuit voltage on a fully charged lead acid battery is 12.6 volts. Open circuit voltage is measured with battery disconnected from any external circuits, and at rest (no current flowing in or out) for about 5 minutes before measurement.

To charge the battery you must supply higher voltage from generator, alternator, or battery charger. When the battery has a net drain (discharging), the voltage will be lower (even when it is fully charged). This change of voltage with current flow in or out is a result of small internal resistance of the battery.

With a good battery, if you find open circuit voltage of 12.0 volts after sitting overnight (or longer), that means the battery is significantly discharged (not fully charged).

If you think there may be some "leakage" through the car's electrical system while at rest, you can easily test for current flow. Disconnect one cable from the battery (any battery terminal) and connect a low wattage test light between the cable end and the battery terminal. If you get even the slightest glow from the test lamp, there is some electrical load that should not be there in an MGA. The common parasitic drain is a modern electronic radio that takes a tiny current to maintain digital memory, but that is small and should require in excess of 30 days to run the battery down.
Barney Gaylord

Thanks Barney. That is reassuring. I will check it from time to time before starting and with battery cutout switch open, and if I notice the standing voltage drops below 12.5 I will know I need to get a replacement.
Graham M V

This thread was discussed between 31/01/2012 and 26/02/2012

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