Car battery question

Magic_x_uk · 26 Jun 2019 at 17:59

hi. One of our family cars is a Citroen C1

Lately I have come to the car and it won’t turn over. Normal lights on dashboard etc. But turn it over and it just clicks.
Chuck a jump lead and spare battery on and it starts immediately.

Now sometimes it is fine and works as normal and sometimes won’t start.

Was fine this morning after being left all night (16 hours). But would not start today after a 8 hour work shift.

Do you think this would be a battery problem or perhaps something else?

Thank you

Phemo · 26 Jun 2019 at 18:27

Certainly sounds like a flat battery, but you need to find out whether the problem is the battery itself or the alternator not charging the battery. For that you'll need a multimeter to see what the battery voltage is across the terminals with the engine off and with it running. Should be around 12.6v ideally for a fully charged battery, and around 14.5v with the engine running.

Magic_x_uk · 26 Jun 2019 at 18:28

Phemo said:
Certainly sounds like a flat battery, but you need to find out whether the problem is the battery itself or the alternator not charging the battery. For that you'll need a multimeter to see what the battery voltage is across the terminals with the engine off and with it running. Should be around 12.6v ideally for a fully charged battery, and around 14.5v with the engine running.

I can do that as have a multimeter. Will go and do that now.

Magic_x_uk · 26 Jun 2019 at 18:33

Just checked. About 12.5 engine off.
14.5 give or take with engine running

Armageus · 26 Jun 2019 at 18:46

Faulty Batteries can sometimes hold a "surface" charge for a little while (e.g. show ok on a multimeter for an hour or so after being charged) but still be faulty.

Check the battery again in a hour or so not running and if the battery voltage has dropped then it will need replacing.

Alternator sounds fine.

Magic_x_uk · 26 Jun 2019 at 18:55

Thank you Armageus

BUDFORCE · 27 Jun 2019 at 12:58

Armageus said:
Faulty Batteries can sometimes hold a "surface" charge for a little while (e.g. show ok on a multimeter for an hour or so after being charged) but still be faulty.

Check the battery again in a hour or so not running and if the battery voltage has dropped then it will need replacing.

Alternator sounds fine.

Yea I have had a battery on a motorcycle mind you, but doing this exact thing.

To the OP do you know how old the battery is?

Building Candy · 27 Jun 2019 at 13:05

My missus had a Toyota Aygo, basically the same as your C1, it developed an odd fault, the alternator would only start charging once the engine got to about 3500 rpm, then it'd be fine, charge for the rest of the journey. She'd often just poodle to work and not rev it much, after a 2-3 days it'd be flat. So try starting it and putting the multimeter on, then give it a quick rev and re check. Also I dont mean it only charged at 3500rpm and over, I mean once it had hit 3500 it was charging regardless of rpm.

GeX · 27 Jun 2019 at 19:07

I had a similar issue caused by, of all things, replacing the battery light bulb with an LED. It upsets the charging circuit and it won't work below around 3000rpm, until it had passed it once.