Hi All,
On Friday I could not start my mini, I believe it was/is a battery problem. I have a 1973 Mini Clubman with a 998cc engine. It has spot lights and the previous owner put in a large stereo system with 2 amps and a 12" sub. Other than those items, it is fairly standard. I have a 600CCA battery which has a charge indicator on it. The indicator is showing red (bad). I recharged it over the weekend and the indicator is still red (bad). I took it into *reputable motoring parts shop* and had the battery tested, with two different testers (not multi-meters), both test devices said the battery was fine.

I believe the battery is running flat over time. The voltage across the battery terminals when the car is running is about 12.5V. The guy in the *reputable motoring parts shop* said I had a battery too large for the mini and suggested a 300CCA battery.

Can someone tell me the correct battery type I should be using for my mini and explain why I should be going down in CCA by half??

I do not know how old the current battery is as I purchased the mini 6 months ago.

Regards and thanks to responders.
Fade77

Apart from it being perhaps physically too large, a large capacity battery won't cause you any problems. It will take longer to charge perhaps, but that is about it.

12.5 volts when the engine is running is too low. Perhaps have the alternator checked.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I think that the bloke in the *reputable motoring parts shop* is a wally. (Hey this big battery won't start the car so why don't you fit a smaller one!)

I think you need to go to a *reputable auto electrician*

What they said..you should have the biggest battery you can fit - a lot of us use 550CCA batteries meant for land cruisers

It's most likely your alternator not charging.

Surprised their test devices said it was OK with 12.5V under load :S

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Starlet Conversion:
http://www.ausmini.com/forums/viewtopic.php?t=15484

If the alternator can't put at least 14.2V into the battery (measured at battery whilst running), either the belt is slipping or the alternator has problems.
As said, that `salesman' is a wally.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Also don't discount that the battery may have sulphated or dropped a cell. Batteries don't last all that long anymore - 2-5yrs is probably AVERAGE depending on usage.

Get it diagnosed by a proper auto electrician before you go spending big money chasing maybes. As others have said, it is more important to see what it does in the car when running under load than on the floor.

Most shops mark the age of the battery (the sale date) at the time you buy it so have a look at the battery (stickers etc) and look for a month and year. That should tell you when the PO bought it.

The battery Doc uses in his mini is listed as being for a landcruiser, so I wouldn't pay too much additional to the first salesman.
KB

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I suspect they tested the SG of the acid, or measured for 12V out of the car (or not running). It might hold 12V under those circumstances, but not when it is put under load.

Edit - just re-read his original post. He said it was under load when tested. Wonder if that was just at idle or with some revs?

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Hi and thanks for the quick responses.

The battery was at 12.5Volts when I re-installed it in the mini. I measured it again when it was connected to the mini (engine not running) and still at 12.5Volts. I started the car and pulled the choke out to increase revs, after about 30sec I measured again, the measured voltage across the battery 12.3V and slowly rising (reached 12.35V in about 1min). I reduced the engine rev speed to idle and measured again, 12.35V and slowly dropping. All measurements taken were across the battery terminals in the boot, not under the bonnet.
Do I need to take the car on a long drive?
Is my Alternator stuffed and require replacing, how else can I check the alternator? if it is stuffed, can you recommend an alternator model/brand.

I prefer to do as much as possible before going to the tradespeople.

Once again, my thanks to responders.
Fade77

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Cheers,

Fade77
Nothing is foolproof to a sufficiently talented fool.

First check that the fan belt is tight.

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Starlet Conversion:
http://www.ausmini.com/forums/viewtopic.php?t=15484

If the alternator/ignition light is going out but it's only giving around 12.3-12.5V (belt not slipping) I'd say the voltage regulator is suss.
On early Minis this was separate, but on Clubbie alternators it is internal. It can be replaced by an auto electrician.

If the alternator light is staying on dull or blinking, it generally means the brushes are worn. These are not hard or costly to replace on most Lucas alternators.

Another option is fit a Bosch or other alternator off a modern car- do a search on here, it is discussed often.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

yeah i had a similar problem, running massive stereo and my alternator wasnt keeping up, upgraded it and the one they installed was dodgy, it's all fixed now.

you can't have too big a battery!

if your read out isn't up near 14 volts then as the guys/ladies have said, check the belt, for slipping then check the output at the alternator itself, (test between output terminal and the body of the car), if thats ok it might be a problem in your wiring somewhere as well, if its not get your alternator checked.

i had a 30amp alternator (original so it was dodgy anyway) and found it to not be enough when i was running everything in the car, (spot's audio, wipers etc) things would just die. possibly think about getting one with a higher output (only if needed)

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1962 850,Frog

People often blame the battery being faulty because a car will not start. I call that the $150. mistake. Many go out and buy a new replacement battery for this reason and after a couple of days new one goes flat too ! Most times a battery goes flat because it is not being given sufficient charge while it is being used. Theoretically when a car is being driven it is actually getting it's needed Electrical power direct from the Alternator to run Engine ignition, lights and in many cases Stereos and other electrical gadgets . The alternator is regulated to keep the Voltage coming out of the Alternator high above the battery surface voltage. Because of this the battery also gets charged while all these things are being used and powered as the Alternator supplies enough to also keep the battery charged. Just remember that most Mini standard Alternators are only only capable of charging about 32 amps at the most. If cars are fitted with extra things that draw power the Alternator should be upgraded to keep up with the demand of power needed to run everything and keep battery topped up. Always get the the alternator output tested before unnecessarily spending money on new batteries.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

Most of your cheapo battery charges barely put out 12 volts some slighlty less - enough to get a car started but not really bring it up to full power. You need one that puts out 15volts to fully charge a battery without relying on the car to finish it off.

I built an autocharger and battery monitor into a cheap charger only to discover it would not drop back to trickle at 13.8 and turn off at 14.2 cause the bleeding output of the charger was only 11.8

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!