5 replies to this topic

[nospamprl]

My car suddenly is very reluctant to start when cold. The starter motor is not as brisk as used to be and if I can't get the engine started at the first or second attempts, then I have to jump start it.

After reading some other posts, today I checked battery voltage before starting the engine. It read around 11.95v. I started the engine for a few minutes and when running the voltage surged to 14.1v. I switched on all the lights (4 spot) and it dropped to 13v (although the car was idling, maybe not enough RPM to show more voltage.

I stopped the engine and battery voltage was 12.4v.

My question is if with those measurements I can be sure that the problem is that I need a new battery (although it has less than 2 years and 2000 miles on it) or maybe something is draining the battery. I don't know if something draining the battery will lower its voltage or if it will remain constant but the amps would not be enough.

I also removed the 4 fuses from the fuse box one by one and measured current between fusebox terminals, but none of them showed any reading.

by the way, car is a 1989 Mini Thirty, 998cc.

Thanks.

[sonikk4]

Do the basics first, make sure all of the earth straps are good and all of the connections on these and the battery terminals are clean and not corroded.

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A quick way to check the engine is earthing with the engine running is to measure the the voltage of the battery. Then add a jump lead to a head stud, and sonewhere like the cross member brace supports on the bulkhead and take another reading. If it increases siginifcantly, then replace your earth strap. If not, look at your other connections

[ibrooks]

To see if something is draining the battery - disconnect it's earth lead when you park it up. Re-connect when you want to drive it again and if it's better than it is now then the problem is something draining it whilst it's stopped. If it's still weary then it suggests that the battery is dud. The fact that it's voltage came back up after a short time running would suggest that it is getting a charge which would imply that the earths and contacts are at least OK (cleaning them is never going to hurt though).

Bear in mind that anything with a memory like a stereo or alarm/immobiliser might be affected by disconnecting the battery so if they are fitted this might cause other problems (I wouldn't think an '89 Mini would have an alarm or immobiliser from the factory though).

Iain

[mackeellan]

Simplest way is to remove battery and charge it up as normal. Let it calm down for a few hours and take a reading. If it is as low as 12volt then its completely dead and useless for starting. A good battery should read 12.8 volts. You have proved your altenator is charging the battery but it still shows 12.4 after running so that will probably get even less after and hour. I lived on a yacht for years and this was a common problem to fault find.
Good luck

[dklawson]

If your battery is holding 12.4V when parked, that is still good. I have not seen batteries stay at 12.8V for very long even on cars that have no accessories running when the ignition is off. What may be of interest is what the battery voltage drops to when you run the starter motor.