Alternator voltage regulator: symptoms

More voltage data. Ignore this message if you are easily bored :) The Haynes manual for the Micra gives the following voltages for battery charge condition:

12.5 V poor 12.6 V normal 12.7 V good 12.2 V to 12.4 V partially discharged less than 12.2 V discharged

I took my battery out of the Micra. The voltage was 12.52 V, according to my multimeter. I connected the battery to an entry-level Halfords battery charger. The charger lit up green, indicating that the battery was charged. Anyway, I left it charging for 20 mins or so and it was soon up to

13.2 V. I then stopped charging the battery.

I'll try it back in the car tomorrow. Hopefully I can get the engine fired up. Then I can take some measurements on the alternator.

Bruce

That's the price range I was looking for! Do you recommend I try some of the firms that advertise in the back of AutoTrader? Will they have alternators removed already, or does the customer have to do it? I've bought panels before from a scrappy and they have removed 'em for me. Bruce

If you haven't left it charging overnight on one of those then there's no way it's going to start the car.

Open circuit voltages are a pretty poor guide to the condition of a battery.

More test data:

• I topped up the battery cells and recharged overnight.

• Car started first time. Battery was over 14 V. Good

• Lights on full beam. Battery was still over 14 V. Good

• Increased revs. Battery was over 14 V. Good

Which made me think that the alternator was OK and pumping out plenty of juice.

• Left the car overnight. Next morning, car started but dashboard lights were faint.

So I now know that the battery won't hold a charge. I definitely need a new battery.

Thanks Bruce