Mystery Battery/Alternator Problem

[pena]

Having major problems with the battery.
Old battery keep going flat every 2 days.

Fitted a brand new battery on Wednesday Afternoon

- Alternator checked and giving out 14v
- All connections to the battery were cleaned
- Test carried out when car off to see if anything is draining the battery (No Drain)
- Battery receiving 14v (Car was not moving at the time)
- Dash reads between 12.3 & 13.9 when I drove it for the whole day wednesday & today.
- Drove back from work tonight (About 1 hrs drive with headlights on)
- Dash volt drops to between 11.1 - 12.1v
- stopped at cash point
- Try to Start car & battery is flat

WTF!!!!

Had to get a jump start from someone.

Basically a brand new battery has only lasted a day.

[ronspeedsix]

Earthing problem ? Check battery earth cable to chassis, engine chassis earthing cable. Maybe too much resistance in connection. Causing no problems at light load (no headlights etc) and discharge at more load.

Maybe you should check loading battery first at light and heavy load.

Ronald

[NCE 61]

Have you checked the 100 amp fuse between the alternator & battery? This is located under the rear of the air box and is a strip type fuse that can fracture, best to replace with a 125 amp midi type fuse.

[Walford]

pena said:

Basically a brand new battery has only lasted a day.

[Basil Brush]

NCE 61 said:

Have you checked the 100 amp fuse between the alternator & battery? This is located under the rear of the air box and is a strip type fuse that can fracture, best to replace with a 125 amp midi type fuse.

+1 Especially as you say the voltage is fluctuating on the pod. It should be constant up around 14 volts and a cracked or loose fuse can cause the fluctuations.

[pena]

Thanks, I'll check the 100 amp fuse, and post my findings.

[ratboiler]

I had the same problem on an MGB fitted a new battery and next day not enough power to turn it over. A mechanic friend came over and said he thought it was an earth problem. He connected a jump lead to the battery and then clipped it onto the engine, car started straight away, when I checked it out the earthing strap from the gearbox to the chassis was broken.

[Hot Tuscan]

Had a similar, but not so extreme problem.

Checked all the usual suspects, 100amp fuse had no sign of cracks, but the ends looked 'dull'.
Cleaned them and the ring contacts on the end of the connecting cables with some 800grit emery to a bright metallic shine.
Now have a consistent 13.8 to 14.2v, lights or no lights.

Edited by Hot Tuscan on Monday 1st October 13:39

[Curdster]

Pena. Did you figure out the problem as I have developed the same issue and havea brand new 100 fuse in situ. I know that there is an earth in the passenger footwell, but where are the others and how many are there?

[ratboiler]

If you have battery corrosion on the terminals, the instant way to clean it off without emery paper is boil the kettle have a cup of tea and pour the rest of the hot water onto the corroded terminal.........comes up like new

[pena]

Yes..Problem is fixed.
It turned out to be a loose connection on the starter motor which was arcing.
Cleaned up all connectors & fitted a 125 Amp fuse.