New battery
 

Sorry guys if this has been asked before, I have searched the forum for an answer, but with no success.
Can I fit a 110 size battery to our cars, or has someone done it?
I've noticed the dimensions of a Bosch S5 (with a whopping 85Ah and 800 CCA rating) to be 315mm long, 175mm wide & 175mm high. At first glance it looks like it will fit, but the securing strap wont (I don't think) as it's slightly longer and the bolt/hole would not line up.
The reason I'm looking for a 'big' battery is my diesel seems very prone to running it's battery down. I've had the alternator checked, and I've had a good look around for loose connections. The sat nav shuts down ok and once started with a booster pack will happily restart for days, or weeks later. Then one morning - dead. The battery I've got is probably about 4-5 years old, is a 096 standard fit which I think is a bit small on the Ah and CCA side as the same engine fitted to a 3 series BMW of the same age has a higher recommended battery rating. Any thoughts?

I'd say that you are correct Scott; it's too long. My research some years ago revealed that the largest battery to fit the box comfortably with the lid secured is a "100" (278 (l) x 175 (w) x 175 (h)).

I don't think that your problems are due to the battery. You probably have a constant drain. Have you measured what it is with a multimeter? Have you checked the glow plug module (flooded plenums cause damage)? Another possibility might be frequent use of the car for very short journeys (this will run any battery down).

Simon

Fitting a slightly higher capacity battery is treating the symptoms not addressing the cause. An 096 is a meaty battery so if it is flat there is definitely a drain on it from something. Measure the current drain which should be around 12mA after 20 mins when all systems have gone to sleep.

Ok thanks guys, will check the battery this week end. It's very strange as it will run ok for weeks, then, will just click next morning with no obvious reasons and won't start! Even left it at airport car park couple of years ago in mid winter, came back to find about an inch of ice/snow all over it, took some time to get in and then it fired up first time! Have had problems like this for some years, then the alternator was pronounced dead, changed that and new battery but the 'I'm going to catch you out one morning for no reasons and not start' problem has never really gone away. Plenums are checked and clear. No moisture in ECU nor the relay. Left car at station the other morning (7am) came back at 6pm to find it totally dead, the doors would not even unlock and when got door opened not even enough juice to power the interior lights nor the red flashing light on the IPK!! Breakdown service jump started it, and has ran ok for past two mornings ( didn't take battery off to charge....should I have?)

That's how the 75/ZT behaves. I suspect that within all the computerised jiggery pokery there's a voltage sensor which disables the starter motor when the battery reaches a certain level. That would explain why it's OK one day and apparently dead the next.
Yes. If you needed a jump start, you should really remove the battery and place it on a mains powered smart charger for at least 24 hours, preferably more. Do it now!

Simon

Often the case, when these problems are presented, the garage immediately assumes "new alternator or new battery" without checking what is really going on.

It is likely to have been something draining the battery, when the car is switched off, from the beginning.

As previously advised, check the current drain after the car has been parked up for ten minutes, then remove fuses one at a time, to find the culprit.