Battery Problem

Hi Guys, having a bit of a problem with batteries at the moment.

Last weekend I drained my 3yr old battery while camping by listening to the stereo for about 8hrs straight. Not sure if that should do it so quick but anyway...

Chucked a mates spare in yesterday but it's a 3yr old 520CCA deep cycle. Started ok twice to work and home (15min trip). Woke up this morning, tried to hit it over and she's dead!

Is it an unlucky battery fault or is something up with the alternator?

Thanks for the help,
Guido

Without seeing any results of tests I'd say unlucky. Listening to the radio for 8 hours could easily drain a battery (I suppose you could do the maths and work it out exactly but it can depend on a lot of things so the simple answer is yes 8 hours could drain a battery).

Have you tried to charge either battery with a decent charger before putting them back in?

You could try a load test (meter on and turn the ignition on) or you could try a cell test (meter in each cell) and it may give you an answer to the state of the battery. But only after doing that much would I start looking at alternators

Whats the alternator charging at ?

First, deep cycle batteries shouldn't have a CCA rating, because they aren't cranking batteries - heavy current drain generally causes deep cycles some damage.

It's possible that your alternator is on the fritz, or your belt is just loose. Try taking the battery out, putting a charger on it and see what it does. How much fluid is in the battery? The water should be covering the plates. What is the voltage of the battery BEFORE you charge it?

Ok guys, sorry for the delay.

Put on a good charger last night and it started this morning and got me to work.

Multimeter reads:
13.82 at idle,
13.90 with the 'heat' switch on (up's the revs by about 250?)
13.40 sitting fully switched off.

EDIT:
13.8 at idle, a/c on drops to 13.6 and steadies, + lights on drops to 13.0 and steadies. Back on idle it rises back to 13.8.

Is that switched off voltage normal? From what I've read it should be about 12.6 at 100%

Cheers fellas
Guido

Switched off voltage shouldn't be read straight after the engine has been running or the battery has been on charge, in those circumstances a good battery will hold more than 2v per cell for a period of time but it wont hold it for ever.

There is many different factors to consider but at idle with 13.8 it means the alternator is atleast working, it may not be working at it's best but it is working, (you'd have to check the output specs to know what the max output voltage is and what RPM to get a better idea of exactly what is normal) and pulling it up to 13.9 with higher revs indicates a working model too.

If you've still got your meter with you do the same check before you leave work. Check the battery before you start, check it when you turn the key (if you can) and check it whilst idling (once at normal operating temps) then check with things like the A/C on and see how your reading compare. The battery might just have need a good kick in the guts by a decent charger.

If it were me I'd be cell testing the battery and checking the terminals before I bothered with checking the alternator much more, it might still have a problem in the alternator but the battery is a heap easier to check and rule out.

As Krafty said. The battery takes a while to settle after being charged - give it a good 6 hours or so to get a better idea.

You could watch the voltage after it comes off the charger. It should drop from "being charged" at 13.8V (or higher) to around the 13.0-13.2V and then it should SLOWLY fall over several hours to 12.6-12.8V. If the fall is more rapid, there's something in the battery doing it - most likely sulphation in the bottom - crystallised sulphur that falls between the plates in the battery and shorts out the cell. It's usually caused by over-discharging the battery and is unfortunately quite common in automotive batteries that are 2yrs old or more.

just a thought, could the CCA rating of the battery be too small? if he's diesel, don't they crank some where in the 520A range?

Joshman, nicely observed. The CR 2.5 engines do indeed crank around the 500A mark, so a 520CCA battery is going to be borderline - it should manage it, but it's not going to like it.

Being a 2002 STR it's possibly a 3.0L engine, which may even need more amps to turn it over.

Overdrawing current from the battery will warp the plates inside it. It's physical, non-repairable damage. Unlike mild sulphation where a couple of cycles with a C-Tek charger in "Repair" mode will recover the battery, any physical damage basically spells the end of the battery. It could short cells, it could lower its deliverable current - there are a number of different issues it could have.

Turned out to be the alternator. Battery lasted another few months then went flat. So I took it in and apparently it was putting out charge but just not enough. 400 bucks and a new 90amp alternator let's hope this is the end of this thread!

Guido