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MG MGA - Do I need a new battery

Just tried to start the car for the first time since last October. Motor turns very slow, turns fast with no plugs in, battery reads 12.4 volts at starter switch. Is it because the oil is cold probably not, battery one 12v is about 8 years old, when I think back it was getting slower to start last summer? your thoughts please.
Dave 1500
Dave Swinburne

Sounds like you might!

Was the battery fully charged? Have you checked all the connections, you need to be very thorough doing that. Does shorting the starter switch make any difference?

12.4v is low for a fully charged battery, what does it read at the terminals?

If you have access to a good battery, that can be a quick way to check.

Eight years seems like a typical life for a battery, although they can last longer.
N McGurk

Thanks for the advice will give it another go tomorrow.
Cheers Dave
Dave Swinburne

Been through this myself. Have you charged the battery since October before now trying it?
If so, do you have any accessories , like a radio that could be leaking the power?
I am sure those more knowledgable than me will be along with advice, although as Neil has said, it may be near the end of its life anyway. His suggestion to try it out with a known good battery first is the easiest option, but remember if you have a bad connection at the battery terminals, just fiddling with them may resolve it and it might kid you that the new battery solved the problem, when it was in fact just the connections.
I read once that you can try testing with multimeter across terminals of battery, with wires connected, and then again with them disconnected, so you just test across the terminals. This may indicate whether the terminals are connected up soundly, if the reading is different. But I am not certain if this logic is flawed and that the voltage (though not current) would always be the same?

You should of course check all connections in the starter circuit especially at the battery. You could try disconnecting the earth terminal at battery then connect a wire and bulb from that battery terminal to earth. If you get any glowing in the bulb, something is pulling a drain on battery (eg radio).
Connect earth terminal back, then run jump lead to engine block from earth terminal on battery and try engine. If things improve, engine's earth may be faulty, or battery to earth terminal could be faulty.

Good luck
Graham M V

Dave - Your battery has probably become sulphated from lack of use. This is quite common in vehicles that are not used on a regular basis. Lead/acid batteries need to be charged/discharged on a regular basis to maintain them in good health. Whether or not you battery can be rejuvenated or will have to be replaced is up to a professional, but there is something you can do to protect the battery in the future.

I would suggest that you purchase a battery maintainer, battery tender, battery buddy (these thing are marketed under a variety of names) and hook it up to your battery whenever it is going to sit for more than a week without the car being driven. These units are basically a smart trickle charger, that charge the battery to full charge, then turn off until the battery voltage drops to a predetermined level, the charges it back up. By doing this up and down charge, the battery is kept in good condition and the life span of the battery is actually extended. If you do this when you get a new battery, you will find that the battery will last long beyond it normal life expectancy. Just be careful not to get just a plain trickle charger, which is much cheaper, but will ultimately over charge the battery and boil off the electrolyte over time. Cheers - Dave
David DuBois

Thanks David, I recharged the battery connected up still no good even showing 14v, but soon lost charge, so new battery it is. I will look out for a battery buddy before lay up time. Cheer Dave
Dave Swinburne

I have commented on this topic before. I have an awkward storage system here, with cars nose to tail, and have automatic chargers on all of them (about ten in all, including two MGA's). The automatic chargers are, unfortunately, not cheap (nor are new batteries!)but it means that the cars can be driven straight away! Apart from my M-type (6 volt, now with an automatic charger connected--I have been told that modern 6 volt batteries are designed for constant use in fork lifts and suchlike) I have not bought a new battery in several years.
Barry Bahnisch

A question for those with alternators and using battery conditioners - do you have some way to avoid the need to disconnect the alternator when charging? The biggest disincentive with trickle chargers is the need to re-connnect things before driving. Thanks, Mark
M Wellard

No need to disconnect anything, just plug in. I have 30-40 cars on battery conditioners here, almost all with alternators and have not had any concerns.
N McGurk

I too have a lot of vehicles on trickel chargers, including motorcycles, and no need to do anything other than hook them to the battery. It really a no brainer.
TM Going

Got myself a new battery no problems cranking the engine, battery is from Eurocarparts 12v Lion battery 3 year guarantee cost 37 length 207mm height 175 width 175mm fits snug into the battery carrier.
Dave Swinburne

This thread was discussed between 11/03/2012 and 14/03/2012

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