Is my battery knackered?

[sideymun]

Hi all, ive had a hunt thru the forum and found loads of tips on checking if my battery is indeed knackered, and im pretty sure it is but before i go out and replace it i just wanted to confirm my suspicions.

Basically over the last month or so my S2 cab (1989) has decided to not start most days. Often i only get to drive it once a week so there may be a gap of a week between drives - usually, in the summer at least, this doesnt seem to be a problem. However, since things have got cold i now often return to car that wont start without me taking the battery out and putting it on a charger over night. However, even after a night on the charger the battery only shows 12.8v (ish). So today, i went out with a fully charged battery and measured the battery volts at different times of the journey. I checked the battery before i started the engine and it showed 12.86v on a multimeter. After starting the engine, it was 14.07v - i think this means the alternator is working, is that true. Upon reaching my destination (about 50 miles away) i left the engine running and checked th volts, it was now 13.7v. Switched the engine off and left the car for about an hour. Upon returning i check the battery and the reading was back to 12.86v. Did the return journey home and its a similar story. Going to wait a bit and check again to see what it has settled to.

Now i think the battery is gone and needs replaced becasue i was expecting its no load voltage to be closer to 14v. Does the 12.8v i am getting mean a cell is damaged or something? Is it really completely knackered or can it saved? and if so how?

Also, if i do need a new battery what calibre is best to get? How many CCA do i need/want etc?

Cheers
Sid

 

[944cabby]

Mine's the same - if i use it 2 or 3 times a week it's ok, any longer though it seems to drain - it didn't like the recent cold spell at all and refused to start.
The battery is a numax? 72ah i think, just over 2 years old.

 

[John Sims]

Battery technology is very refined. As the battery is used it creates a sludge in the bottom which will ultimately short the cells. Manufactures are so good at predicting this that many batteries will fail within weeks of exceeding their warranty.

You can get around this by decanting the electrolyte, flushing out the battery to clean out the sludge and refilling but, to be honest, who can be bothered?

If your battery is out of warranty you can be reasonably happy that, if it isn't dead, it soon will be.

 

[944 man]

Id expect that anything over 12.6 volts was healthy?

 

[dodgydal]

Ive just been having a similar problem and ended up buying a new battery from a friend that works for dws autos , he looked up the spec from porsche I payed about £70 the voltage reads reads the same but it seems to have more grunt to get the car started for some reason even after 3 or 4 days of not starting . I will have a look in the morning and put the spec of the battery on here .

 

[Hilux]

However, even after a night on the charger the battery only shows 12.8v (ish). So today, i went out with a fully charged battery and measured the battery volts at different times of the journey. I checked the battery before i started the engine and it showed 12.86v on a multimeter.

Thats fine

After starting the engine, it was 14.07v - i think this means the alternator is working, is that true.

True

Upon reaching my destination (about 50 miles away) i left the engine running and checked th volts, it was now 13.7v.

It will be as the battery is fully charged and its only trickling in whats going out to overcome the natural battery resistance

Switched the engine off and left the car for about an hour. Upon returning i check the battery and the reading was back to 12.86v.

Thats fine

Now i think the battery is gone and needs replaced becasue i was expecting its no load voltage to be closer to 14v. Does the 12.8v i am getting mean a cell is damaged or something? Is it really completely knackered or can it saved? and if so how?

Nope, its not necessarily knackered - it should be about 12.9 to 13 volts with no load.

Also, if i do need a new battery what calibre is best to get? How many CCA do i need/want etc?

Cant see what the issue is (unless the battery is knackered) apart from the amp hour rating of the battery or poor earths. IIRC you should have a 65 amph as a minimum for the 944. Anything less will still start the car but you will not get many attempts.

If you cannot get more than a couple of starts then the battery is sludged/desulphated and tired. Do you use a trickle charger (bad) or a proper battery conditioner that recycles it and can (to a certain extent) desulphate the cells.

I would highly recommend testing your earths for resistance and continuity (also the +ve terminal lead) and certainly cleaning the earths especilly on the starter for it `could` also be your starter thats the issue in the cold weather due to failing windings?

Is (was) the battery/starting issue ok in the warm weather?

********************************

Edited to ask if you have an alarm fitted, most will start to take a toll on the battery after a couple of weeks and quicker if poor connections exist.

You could also test the battery with everything off and see if there is a voltage loss

 

[sideymun]

Cheers for the all the replies guys. Hilux, top reply, confirmed all my suspicions. After you said, 65AH is the min, i went out and rechecked my battery. It indicates 550A and only 63Ah so as you said, it is enough to start it but wont give me many goes.

I havent got a very fancy charger and i think it is only a trickle charger - definitley isnt a battery conditioner.

I didnt notice the non starting in the summer, but that was likely to be because the car got a drive most days - difficult to tell really. However, i did have a new (reconditioned) starter installed in june so i shouldnt think that is the proble,

It sounds like my battery is a little underpowered for the job so perhaps i should consider a new one.

 

[Hilux]

Glad to have been of help.

Take the battery to a proper battery seller/stockist (not Halfrauds) who will test it properly and tell you if a cell has gone down.

63 amph is not a lot less eg: its only 2 amps down, I was talking more like a 10 amph difference.

I`d still recommend getting it tested and check your earths. Cold weather and cold damp joints make a battery work really hard due to voltage drops.