2WD technical question
 

Hi folks,

Went to pick up a friend from the airport last night. It was quite cold (5c) and my Mazda 323 really struggled to start. It did eventually, but was very reluctant. It was about a week ago that I last drove it. Once running it was fine and when I started it again at the airport to come back to the flat it started no worries.
I'm thinking it seems like a crook battery (it is pretty old I think, and I drained it completely flat once by leaving an interior light on).
When I tested the battery this morning it was reading 12.57 Volts across the terminals with engine off and no load on. Does this seem low? Of course, it got a charge on the drive to the airport last night, so I'll test it again tomorrow to see if the charge has dropped further.

What Voltage would you expect across the terminals in a healthy car battery?

Cheers,

Matt :)

Just over 13 normally. If it's reading 12.57 I would expect it to be still serviceable. A test really is how quickly it will go flat from fully charged when trying to start the car or with the lights left on.

Just wondering if it's a sealed battery, or whether you can check the levels and cells yourself. Also, connections can be a bit off and on.

I'm no mechanic - it's just something I had to do myself.

If it's got fill plugs, pull the caps off and have a look. Sometimes you can see grey "fungus" which is plate sulphation. This causes the voltage from that cell to be lower at rest and it will also drop a lot more as soon as load goes on it.

Sound like a battery problem to me, but that's easy to check. Have another battery and a set of jumpers ready for the next time it causes problems.

Kind regards

Nigel in NZ

These are good, though obviously useless on a sealed battery - battery fluid tester

They vary in price, but mostly around a fiver. I think I paid £4.50 for one very similar.

Thanks guys,

It's a sealed battery so looks like I'll have to get a new one. Probably best to replace now rather than have it let me down after a days hill-walking or something...

Matt :)

Batteries
 

Drive to any local garage and ask them to test the battery, every garage has a simple battery testing tool .... inview of the change in the weather, its a good starting point. Still problems afterwards book it in for a decent service ...

Salut Matt

12.6 would be normal for a battery that has been charged and allowed to rest for a few hours .
To check that the capacity is up to snuff you can have it load tested at a garage as suggested above .
But also check the battery terminals are clean AND the battery is clean ,an accumulation of muck and gunge on the outside of the battery in cold damp conditions can lead to a slow discharge as electricity can track across the battery between the terminals using the gunk as a conductor .