On 03-Mar-17 8:01 PM, Roger Mills wrote:
On 03/03/2017 18:59, D.M. Procida wrote:
Here are the facts:

1. The car is used once or twice a week, mostly for short trips.

2. Nearly every time we use it, the battery is too dead to turn the
engine over and it needs to be charged. In fact it's so dead that even
trying will produce nothing but a click and drop the voltage across the
electrical system so low that it resets the clock.

3. After 20 minutes or so of charging, it'll start without difficulty
(it's only a 1.2l engine).

4. Alternatively, a quick push will do the trick.

5. If it has just recently been on a long drive (in the previous day or
so), or has been used once that day already, it will start without
problems, though.

6. More than once recently though I've stopped the car for a few moments
after driving several miles, and will find that it doesn't start and
needs a push to get going again.

7. It's getting worse.

8. The battery is fairly new.

I'm assuming that the problem is the alternator failing to charge the
battery properly, but no. 6 is a puzzle to me.

Thanks,

Daniele

Something is discharging the battery. Either the battery is duff and is
discharging itself or there is an electrical fault which is drawing
current from the battery when the car is parked.

To find out which, leave the car overnight and then measure the battery
voltage. Chances are that it will have gone down a lot. Then charge it
and run the car and then disconnect the battery before leaving it
overnight. If it has still gone down, the battery is duff. If it hasn't,
you need to investigate the 'leak'.

That wouldn't explain number 6.