Weird Battery Drain

[JetspeedCamry]

Hey guys, haven't posted in a while, hope all are well and had a good new years.

My question relates to acceptable battery drain that can be observed in a vehicle in say, 1-1.5 weeks of having not been started. I've let my car sit for this long, with the alarm armed and in this period of time, the battery has failed to start the car.
If i start the car every day, then there seems to be no issues.
I've noted also that sometimes, when driving, the battery voltage can be 12-12.5V one time, and 13-13.5V another, during the day (with no lights on).
Is this a sign that the alternator regulator is poor and not doing it's job, and perhaps the battery is on the way out? The battery is a maintenance free AC Delco 550CCA and is approx. 5 years old.

My second question, which i'll put into this thread too, is i'm going to get a new battery anyways and was looking at the yellow top Optima range. Is the 650CCA model ok? Or would the larger, 750CCA be better. Also, the alternator is about 4 years old (reco'd RACV one), so would it be prudent to get this replaced/rebuilt?

Thanks for any info!

[Hiro]

5 years is pretty good for battery life, normally they'd have dropped a cell by now (which would result in the battery not holding it's charge, and dropping voltage under load). I had a Yuasa in the 102 that was a good 5 years old before it got to the point where it couldn't hold enough charge overnight to start it again in the morning.

[oldcorollas]

if your alternator is working properly, batteries can last a long time...

check fluid level in the battery first.. maybe 1 cell is dry? maybe all? top up and try again.
if battery is ok, then check alternator (brushes etc).. not hard to do.

if that all checks out, then need to start using multimeter to find the current drain.

[allencr]

What's weird is expecting a 5 YO battery to be OK and/or a 4 YO alt.(rebuilt or not) to need to be replaced without cause.
There is nothing weird at all about a 7+ days resulting in a battery being flat if the battery is old.
What kind of running/driving happens on the days that it is being used?

Testing the alt. output while driving may be the cause of the poor reading.
What is its output - battery terminals bridged by the voltmeter with GOOD connections - when you are not driving?

[JetspeedCamry]

Hiro - Yeah that's what i was thinking. Somewhere i was told that around 5 years is the general service life for batteries. (And why the Optima ones are so popular as they last double that).

OC - Battery is a maintainance free type, so can't crack it open i don't think? Can you tell me what to check in the alternator to see if it needs a rebuild/replacement? Probing with a multimeter is no issue, and i did that a few weeks back. Removing the EFI fuse gave me the largest drop in idle current. Typically though with everything normal,but no alarm armed it was sitting around the 60mA area.

Allencr - Well yeah i assume it's getting near the end of it's service life...this battery has done nearly 60k km's with me, so it's had a good life. Same with the alternator...nearing the 60k mark. On the days it is used it's usually driven for 2 hours, let to sit for a weekend and then driven back again for 2 hours. The last time i started it, i moved the car out of the garage and repositioned it, so wasn't really running for more than 10min's really.
Why is testing the output while driving a bad thing? I thought readings were supposed to be around the 13.8-14.4V range when driving, indicating a good alternator charge?
While sitting there with the engine off, after a drive, the battery shows about 12.5v. After a night, it's about 12-12.1V and after the 3 or so days, it's 10.5-11V.

Thanks so far for the help! Much appreciated.

[river]

Hi,

Just rev the engien to about 1200rpm and the alternator should pump out the approx 14v, so you don't need to actually drive it to measure its output.

The battery could have some internal short, from age, that slowly leaks the battery away over a few days.

The last ten years I have gone through about 6 batteries, but that's because the car is a garage queen and the battery gets so run down it becomes unrecoverable. Before that I was getting 7-8 years from a battery. Just a normal battery, and top it up with tap water. So, personally, I'd just go with the normal battery as I don't think there is any cost benefit, over 5 years, in going for an expensive one.

There is a Silicon Chip battery refresh kit which can bring some life back into batteries, but again, after 5 or so years of life, I am not sure if you are going to get much longer life out of it, even if it is refreshed.

If your alternator was bad then it would not fully charge your battery, and the lights would be dim and go bright when you rev the engine etc. So, I assume that having the battery fine to start the car (within a couple of days) means the alternator is probably okay.

So, I'd be looking at your battery. Maybe swap over with another car if possible, and if the other car has the same problem then its the battery.

seeyuzz
river

[cambelt]

And ive also seen a few yellow top optima,s fail , better to buy a normal battery and replace it every 3 to 4 years if you need 100% reliability. Century seem to last the 5 or 6 year mark . I use century in all my customer cars and most get 5 to 6 years out of them .
Personally in my own cars i change them at 5 Years .
Dave

[JetspeedCamry]

Ok sweet. I'll hunt around for a decent quality battery then and i'll also try another battery for the moment and see if it has the same symptoms.

Thanks for the replies!