what's duff about this battery?

grumpycrab

Our 3 year old battery hasn't been holding charge for more than a couple of days. (car has been little used over the last 6 months; keep having to charge it up).  Took it to Halfords for a free battery test - test receipt below - said its duff - can anybody explain what's wrong with it?  cheers.

AdrianC

Nothing on that receipt gives any "how long does it hold charge" figure, because they simply can't test that in two minutes flat, only by charging it then watching how the charge holds.

I suspect the figures they're looking at there are the first two. The battery is specified to be able to deliver 720A ("cold cranking" - to a starter motor). It's been tested and found to only be able to deliver 472A. 

I would presume the "life" is some nominal point on a scale between delivering the specified current and delivering some figure that's been designated "0%". Assuming it's roughly linear, that would suggest 280A is their 0%.

Grey_Critic

And your battery is how old? I ask because if this was a battery purchases 3 years ago it could have been several years old when you got it. Some stockists have them sat on the shelf for a long time before they are sold - I recall one being 10 years old that had sat at the back of the shelf.

forgotmyname

Battery left flat at any time? That reduces its life quite quickly.    I have a device that measures the battery like that and unsure
how accurate the results really are.  To get the 472CCA   (EN1) it uses the battery resistance and voltages but it doesnt put the
battery under a heavy load so real world figures may show different results.

I have one of the 400Amp load testers also. Checked with the electronic one and it said the battery had lost 30% of its life but the
400Amp load ran for quite a while before the voltage started to drop. I ran into the units time limit before the battery dropped into
the red warning/replace section.

Down to 44% though its probably due a replacement, if your parking up for a while in future get an external charger to keep the
battery topped up.

greyteam1959

If the battery is only 3 years old you should check to see what warranty it had when you bought it.
Many batteries have a 5 year warranty.

sk2402005

If its having to be charged every few days, every time that cycle repeats its damaging the battery, where lead acid batteries do not like to be drained, and even going below 80% of its charge starts to cause this damage.

If it really is draining in a few days, something may be loading the battery whilst its parked up, so a new battery wont sort that, so you would need to remove one of the terminals and see how many amps are being drawn with the ignition off, often the alternator is the cause, but it could be anything, and pulling fuses to narrow it down is the next step, if your not technically minded i suggest you call in a mechanic.

Flight3287462

Batteries have taken a hammering over the last 18 months.  My car which is OK just now was not happy in the cold weather and I suspect the battery will be replaced next winter. 

Had to replace the two 12v lorry batteries just after new year just because the lorry was sitting around not being used and it had a kill switch so no power leakage.  I guess 6-7 years isn't two bad.