How long should a car battery last?

forgotmyname

derrick wrote: »

It was regularly charged up with a charger as was the previous one that lasted well over 5 years!
Read the posts!

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Silly boy. Your alternator is now 5 years older and the figure you have posted suggest otherwise.

Maybe you should try an electrical course on how an alternator works and how they can DRAIN a battery when they start to fail. DIODES leaking current. A couple of clues there to google.

A faulty alternator can drain your battery overnight easily with no visual sign unless you have an infrared camera where you will detect a hotspot around the diodes.

Your alternator maybe putting out 13.6 volts, but is it putting out any current to go with it?

I have a car bulb here 12v 5W. I connect it to a 13v power source and it barely glows. WHY?
Because i have limited it to 0.05A instead of the required 0.41 amps. I turned the voltage upto 24V but it still didnt glow as brightly as a 5W bulb should.

Volts is not everything.

Joe_Horner

derrick wrote: »

On Wednesday I disconnected the battery and charged it for 24 hours, it was showing fully charged at 13.6v, 24 hours later, today, battery is down to 12.9v.


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For a starting point, that is a perfectly normal charging result.

A fully charged lead acid cell will have a quiescent (off load) voltage of 2.1v (at 20 deg C) which is 12.6v for a 6 cell battery. Immediately after charging the voltage will be higher, but will settle yto that level over a day or so. Allowing for meter accuracy etc, 12.9v is about right for the "settled" voltage off load.

13.5v is too low for the charging voltage on the car though. You should be seeing between 13.7 and about 14.4v with no extra loads switched on at a fast idel speed.

To avoid sulphation you should be charging at about 13.7v or more (up to about 14.4). Below 13.7v (2.28v per cell) sulphation is increasingly likely and there's virtually zero safety margin for weak cells.

At that level, if one cell has slightly high internal resistance then it will "see" more than its share of the charge voltage and other cells will be starved, leading to low charge and sulphation on those other cells, which will kill the battery over time.

The problem with that is, if you replace the battery without sorting it, it'll kill the new one in a year or two as well.

Incidentally, I have a Proline battery on one of mine which has been going strong for over 4 years now despite being abused a few times and being left dead flat for a month or so a couple of times so don't automatically assume it's down to it being a "cheap make".

Joe_Horner

derrick wrote: »

But still an average 4-5 weeks charge via a battery charger! So no change there then!

Bottom line a 2 year old battery should not fail.

If nothing constructive to offer don't reply!

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Constructive thing to offer:

Even the best battery will fail within 2 years if it's being consistently under-charged in service. It's almost as bad for them as over-charging.

Strider590

Just to make a point on voltage versus capacity, as batteries age they suffer sulphation (as mentioned above).

The best way to explain this is to imagine a 5 litre bucket of water, the level of the water is voltage, the amount of water is the capacity, dropping rocks into the bucket is sulphation.

The point is that you can have 12.8v (the generally agreed settled voltage of a fully charged car battery), but if the battery has suffered sulphation, the capacity could be barely enough to open the central locking.

AdrianC

derrick wrote: »

The fact that the same alternator was OK for the previous 5-7 years goes to suggest there is nothing wrong with it and I got a bad battery!

Riiight.

So much more than a river in Egypt.

derrick

AdrianC wrote: »

Discharges that are going on while the vehicle's parked - and you definitely will have. The question is whether they're acceptable or not.

They include remote locking, alarm, stereo memory, other ECUs. Disconnect the battery -ve terminal, and connect a multimeter on a current setting between the terminal and clamp. You'll have an initial spike, but once the alarm's been reset and everything's finished any self-testing, you'll drop down to a figure that should be small fractions of an amp.

If they're higher than that, then something's consuming current - that might include an interior light that's not going out, or it might include an ECU that's not being properly powered-down.

Done the above, reading 0.04


From OP:-

derrick wrote: »

On Wednesday I disconnected the battery and charged it for 24 hours, it was showing fully charged at 13.6v, 24 hours later, today, battery is down to 12.9v.

Today, Saturday, battery still at 12.9v with it still disconnected, I am going to leave this another few days so will not be able to retest the charging voltage until then and will also check the CCA



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AdrianC

derrick wrote: »

Done the above, reading 0.04

40mA. Not excessive.

Today, Saturday, battery still at 12.9v with it still disconnected, I am going to leave this another few days

So the battery doesn't seem to be just losing charge.

so will not be able to retest the charging voltage until then

OK.

and will also check the CCA

...and how will you be doing that?

derrick

AdrianC wrote: »

40mA. Not excessive.

So the battery doesn't seem to be just losing charge.

OK.


...and how will you be doing that?

As per Youtube video 4th down on this Google page, (it won't allow me to link the actual video).

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derrick

AdrianC wrote: »

So the battery doesn't seem to be just losing charge.

But as per my OP it "just lost charge" between 7 & 14 days.

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AdrianC

derrick wrote: »

As per Youtube video 4th down on this Google page, (it won't allow me to link the actual video).

The fourth link down for me isn't a YouTube video.

There is a YouTube video reasonably high in the list, though - https://www.youtube.com/watch?v=COJr7!!!3Hw

If that's the one you mean, then that's not checking the CCA - Cold Cranking Amps. The big clue there is that the meter is on a voltage setting, and is in parallel to the load. It's checking the voltage of the battery, not the current being delivered. You'll note the engine-running voltage at the end. Even if it was in series with a battery lead - and capable of handling that current - it still wouldn't tell you the maximum possible current the battery is capable of delivering, any more than your test of static consumption did - all it would tell you is how much your starter motor is consuming.

To test CCA, the maximum current the battery can possibly deliver, you would need test equipment capable of managing and measuring nearly 500A for your battery. Even that wouldn't tell you anything about the capacity of your battery to store current - which is what you're complaining about.

The fact that you need to keep charging your battery while the car is in the garage merely confirms that your usage is insufficient to properly charge it - if it was, there would be no need to use a charger, nor benefit in doing so. Your current alternator problems are merely exacerbating that, and are almost certainly what's causing your battery problems, not a manufacturing failure in the battery itself.