Battery or alternator?

flashg67

If it's little used, and parked near plug socket access, I can recommend a trickle charger. I use the 'AA Car Essentials Battery Charger and Maintainer' for a little used second car. After going through 2 batteries within months, this has been plugged in for a year and the car starts first time.

sevenhills

consumers_revenge wrote: »

car off - battery is 12.7v
cranking drops to 9.6v ( suspect that's the answer there! )
running no load - 13.61v
running under load - 13.57

deffo thinking new battery!?

Fully charged automotive batteries should measure at 12.6 volts or above. When the engine is running, this measurement should be 13.7 to 14.7 volts. If you don't have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights.

First voltage seems ok; but not charging enough, but only just.

Maybe something simple like leaving an interior light on?

System

I'm with the alternator. IME when idling most cars are >14V. I'd certainly not be happy at 13.6V.

A faulty alternator can drain a battery if there is a fault in the rectifier or voltage regulator.

The other side of the coin is that once a car battery's voltage drops below 11V you've knackered it. Whilst in many cases it'll just be minor damage not really noticeable on a car in regular use, for one that spends days stood you'll get issues.

thescouselander

consumers_revenge wrote: »

OK just test with multimeter


car off - battery is 12.7v
cranking drops to 9.6v ( suspect that's the answer there! )
running no load - 13.61v
running under load - 13.57


deffo thinking new battery!?

Yes, that cranking voltage looks too low to me. I suspect the infrequent use has led to sulfation of the cells. Since you've already tried to bring it back by charging it might be new battery time

Rolandtheroadie

I'd say both, unless, like my car, there's a bodge you can get to get the charging voltage up.
I've had two Chryslers, both charged around 13.6v, and constant under charging destroyed batteries. Starting issues wouldn't normally rear their head until winter though.
Had the first one 5 years, went through around 3 batteries. Done the mod on that one just before scrapping.
Second one I checked and modified first day it didn't start. It did also have a current drain, which has also been bodged.
Been ok since, on the battery that was in it when I bought it.

Join a Ford forum and check for under charging issues. Have you checked for a drain on the battery yet?

consumers_revenge

it gets used for 3 x 10 mile round journeys weekly then a bit of to-ing and fro-ing to the shops a couple of times a week so not idle idle.


however that means that with a low charge rate it probably doesn't get more charge than whats been used to start it most journeys.


only drain should be clock and alarm.


think will go for new battery first then hit alternator if no improvement. if it wasn't for the flicker she mentioned I would have gone straight for a battery swap with the symptoms.

Nobbie1967

I assume those load/no load values are at idle? Does it go up to 14-14.4 when you rev it? If not, then I'd suspect a fault on the charging circuit.

Rolandtheroadie

consumers_revenge wrote: »

only drain should be clock and alarm.

Should be, doesn't mean it is.