My battery is confusing me

[Ian771]

Hi

 

First post and question.  Any help will be much appreciated. 

 

I have an Octavia (Petrol/estate/1.4l) is 10 years old with 51,000 miles has got its second battery (when I bought the car 4 years ago)

 

The current battery: VARTA 5K0 915 105 D (60Ah / 480 EN).  Acid level indicator is BLACK (level ok)

 

Not used the car for a week. Wife got ready to do the weekly shop and car was dead.

 

So disconnected battery and connected to a charger, fast charge 8A for 30 mins.  Got it up to 40% in 30 minutes and she did the shop and home ok.

 

Then overnight, placed on slow charge 1.5A.  Next morning 100%.  Happy.

 

24 hours later, checked level – down to 40%?

 

Placed back on slow charge 1.5A and within an hour 100%?

 

Next day, back to 40% (no car use). 

 

Placed on the repair mode, a 18 hour cycle.  Within an hour the charging unit had turned off (I assumed all the tests had run) It was showing 100%

 

Next day, back to 40%.

 

If battery cannot hold the charge, it is weird a slow charge at 1.5A can get it to 100% in 1 hour?

 

Two things I have not tried yet.  Disconnect battery and do a fast charge to 100% and disconnect battery and do a repair mode 18 hour cycle.  But is there any point?

 

Sorry so long!

 

Thanks!

[Liger1956]

Have you tried disconnecting the battery from the car, charging it fully, do not reconnect it and then test it 24 hours later? That would tell you whether the battery was holding its charge. When you say 40% charge do you measure the voltage? After the battery has been charged it should be left for at least an hour, in my opinion, before you measure the fully charged voltage. Also do you have anything like a dashcam that is drawing power from the battery all of the time?

[PetrolDave]

2 hours ago, Liger1956 said:

Have you tried disconnecting the battery from the car, charging it fully, do not reconnect it and then test it 24 hours later? That would tell you whether the battery was holding its charge.

+1

 

Leaving the battery connected to the car leaves two possibilities: either the battery is self discharging, or something in the car is staying on and draining the battery.

[Ian771]

19 hours ago, Liger1956 said:

Have you tried disconnecting the battery from the car, charging it fully, do not reconnect it and then test it 24 hours later? That would tell you whether the battery was holding its charge. When you say 40% charge do you measure the voltage? After the battery has been charged it should be left for at least an hour, in my opinion, before you measure the fully charged voltage. Also do you have anything like a dashcam that is drawing power from the battery all of the time?

 

Hi.  Thanks for your reply.  I will try your idea.  40% is the voltage reading on the charger.  Got no dashcam.  Just the factory alarm / immobiliser.  

[Ian771]

17 hours ago, PetrolDave said:

+1

 

Leaving the battery connected to the car leaves two possibilities: either the battery is self discharging, or something in the car is staying on and draining the battery.

 

Thanks.  So if the battery is self discharging - would the repair mode fix that?  Or is it just time for a new battery?  

[PetrolDave]

27 minutes ago, Ian771 said:

 

Thanks.  So if the battery is self discharging - would the repair mode fix that?  Or is it just time for a new battery?  

First, check the battery off the car - if it's discharging then the battery is the problem, but if not something in the car is staying on.

 

IF the battery is self discharging then there's no harm trying the repair mode - BUT that would at best be a temporary workaround as the battery is internally damaged.

[Ian771]

3 minutes ago, PetrolDave said:

First, check the battery off the car - if it's discharging then the battery is the problem, but if not something in the car is staying on.

 

IF the battery is self discharging then there's no harm trying the repair mode - BUT that would at best be a temporary workaround as the battery is internally damaged.

OK thanks again for your help and advise!