Is this voltage drop excessive?

[harrylime]

Is this voltage drop excessive, i.e. is my Battery rogered?

Further to my last post about bad Battery luck, I fully charged the Battery with my CTEK charger and disconnected the Battery to eliminate any parasitic drain from the car, I then took a voltage reading (almost ) daily, as follows

Friday after charging      12.8 V

Saturday                          12.58 V

Sunday                            missed

Monday                          12.53 V

Tuesday                          12.5 V                  

Wednesday                     12.49 V

Thursday                          12.47 V

I know there's a lot of wisdom and experience on this forum, and would appreciate any opinions/advice

[Herbie]

Here's a couple of Google results for you:

Self Discharge rates 1

Self Discharge rates 2

[BachelorDays]

The initial drop is misleading since there is a surface charge after charging which will drop. It doesn't look bad to me just on the voltage readings.

Battery condition, however, depends upon many things including age, acid level etc. Best way to check the state of a Battery which is used to crank start an engine is to put the crank load on it, preferably using a Battery tester.

Always test on a fully charged Battery.

An easier (rough) way to test is to check voltage whilst cranking a cold engine. If it doesn't drop below 11 the Battery is in great shape. If it's above 10 the Battery still has good life. If it drops below 9 then it's on its last legs.

Weather,  how easily the engine starts and how often the car is used also have a say. For instance, I'd change a Battery dropping under 10v during cranking if winter had not yet set in. Equally, I'd change a Battery dropping just under 10v in winter if I wasn't using the car every second or third day.

[Cotswold Pete]

The voltage drops you have are withing what might be a typical spec of a car Battery, though a Battery that is not in best condition.

The issue would be what the voltage was under load, such as cranking an engine, and that can only be known with a load test.

Is your Battery 'rogered', I would say not, could be better.

I guess that any sulfation in the Battery will degrading ability to actually charge, and hold a charge, but not being a total geek expert, not sure if this is my talking BS.

My experience is the Battery stops working when you are in the greatest hurry, but both my LS have suffered from alarm triggers caused by Battery nearly failing.  So when I get a regular run of alarms for no reason each and every day, I will be suspecting my Battery is about to go 'properly' west.

I always have a spared charged Battery in the cellar, which though no use long term in the LS (does not fit so well in the Battery tray), gives me the chance to get going, if ever I leave an internal light on by accident. That spare was fine last time and it had been sitting for over 5 months. 

[harrylime]

Thanks for the comments so far, I tried not to be lazy and did Google information on discharge rates. The Battery is suspect because it discharged a couple of weeks ago quicker than I would have expected (about a week) after not using the car. I usually charge the Battery periodically with my Ctek charger but it's not convenient where the car is currently located. I am guilty of having let the Battery run flat at least a couple of times in the 2.5years I've had it, so it may be self inflicted, as sulphation may have occurred. There's nothing worse than not being able to trust the Battery in an otherwise reliable car, so I may just buy another one and keep this one for a spare, assuming the main dealer batteries are not on an exchange basis

[Herbie]

25 minutes ago, harrylime said:

assuming the main dealer batteries are not on an exchange basis

I don't think anyone does exchanges on batteries anymore do they? Alternators and starter motors, but not batteries.

[Tinonline]

I’d go and get it tested.

It’s the cold test/recover rate whatever they call it that counts. Test will find a failed cell too.