Dropping voltage? Charing issues?

[Wildfire]

Due to not using the Griff pretty much ever the batteries then to die. Recently I couldn't get a battery before MOT and I was given one by a mechanic friend of my father. It was a tad smaller than the normal one but seemed to work fine. The car passed the MOT and went back in the garage.

Recently I have noticed that the volts on the volt meter aren't the same. Usually it sat around 14.5V and then dropped to about 13.5 when the fans came on. Now it sits around the 14V mark and drops to 13V when the fans kick in. If I load up the lights and the fans it does seem to bounce around 12V.

Usually when a batter is about to die it stops charging properly.

In the absence of a multi-meter (and knowledge of where to test, do I just test across the battery?) could it be:

1). The battery is too small and just can't cope?

2). The battery is on it's way out.

3). My alternator/charging circuit is failing

4). The connections to my fans need renewing (I think I will do this anyway).

I have had a failed alternator in the past, although this manifested itself half way to the Griff Growl one year and I had to drive above 3000rpm to keep charge.

[Hoover.]

Chris no expert but having suffered with loads of electrical probe in the last few years I would say battery aunt man enough for the job....... I've actually managed to stall cars that have been try to hump Graff due to drain required to start them

[Wildfire]

Cheers Hoov. I thought as much. It ran fine last night on an emergency airport run, but I think I'll have to change it out at some point.

The Griff is due some serious TLC, when I get time.

[PeteGriff]

Hi Chris, though it could well be the battery, the erratic voltage swings to me would also indicate a failing voltage regulator within the alternator! Regards, Pete

[Loubaruch]

When driving normally with the revs well above idling the alternator should be able to power everything and trickle charge the battery. The smaller battery gives you less capacity to start, it is quite a hefty lump to turn over. The battery also fills the gap to power things when the engine is idling. Although a larger battery is advisable I dont think it is your problem yet.

I would suggest first cleaning the connections to the alternator, they frequently work loose and make a poor connection.

[Wildfire]

Ah, I will have a potter around in the engine bay this weekend with some sand paper and files. Hopefully will improve things.