Was curious to know how long I could expect to leave a Verada 3.5 parked, without starting it or driving it, before the battery goes completely flat. I charged up the battery about 2-3 weeks ago, put it in the car and as of today it's completely flat, as in the car won't even crank. I've had multiple batteries in there and the result has been the same every time.

Does that amount of time sound about right or is it perhaps a bit too short? Personally think it should be lasting longer but with the added electrical equipment depending on a constant charge, I wasn't so sure. I'll have to grab out the test light and start searching otherwise, but thought i'd check first.

Cheers

2 weeks to a few months really depending on any draw while the car is parked. Just disconnect the +ve when you arent using it if you dont want it to go flat, then of course you will have the problem of having your ecu relearn every time you do drive it.

I would expect 2 - 4 weeks to be about right to be honest. It really also depends on how "new" the battery is. I wouldn't expect a slightly older battery to perform as well as a "newer one". I've seen up to 4 weeks but that was in my sisters Hyundai Getz. As for my own, never lasts more than 2.5 weeks untouched.

Grab a multimeter and check current draw at the battery with key out of ignition.

Way too short, a fresh battery should stay good for many months. I've got a non-used car too, but I start it twice a week and run it for 5 minutes to charge the battery but more so to keep the valve stem seals oiled up to stop them from going hard. Still starts well after 3 months but it was a new 430 cca battery to start with. Older batteries I've owned in other cars have been known to go flat after a few days of non use. But check for current draw just to be sure.

Just to give another experience to compare with - I bought a "heavy duty" 550CCA battery from BigW and squeezed it into our little Toyota a few years ago. Original battery was less than 400CCA.

I've accidentally left the HID head lights (35W) on too many times. Initially the battery was fine to run them for 9+hours and then start up like nothing had happened, but after 18 months had passed, I managed to flatten the battery.
In fact the battery has been flattened 3 separate times to the point where the starter motor won't even click when trying to start the car. It was then jumper started and ran fine.

This same battery and car sat in the garage from the week before Christmas until last night and it started just fine. Only things supposed to be using the battery during that time is an aftermarket alarm and headunit.

So although it's not a new battery, it's significantly larger than the factory item and I'm really happy with it's performance and longevity through abuse. :)

My experience has been that it all depends on what static load you have on the battery - all head units will consume power when off as will the immobiliser....some more and some less.
A few years ago we were overseas for 6 weeks and our VS Commodore with a 1 y.o. battery and a VW New Beetle with a 3 y.o. battery - both started immediately on our return.

Ive found that a slightly over rated battery will last for ages and ages and ages, untill that one time you accidentally leave something on or the keys in the ignition overnight after working on it and the battery is never the same after. Once the KH is ready to become a daily ill likely get a new battery but since all it does is sit for now it can wait.