Hi Guys

I have a simple question regarding how long I can expect a fully charged new 12 volt car battery to last sitting in the car that is not being driven?

Also, if the car is not going to be driven for a few weeks, should the battery be disconnected or can it be left in and connected to a charger?

Thanks

Regards
Greg

Hi Greg

it will discharge no matter what you do, the only thing that you can do is use a very good battery charger like a CTEK to keep it topped up.

Steve

Hi Steve

I'm curious as to how many weeks I can expect it to last.

Regards
Greg

several weeks generally. the old lead acid batteries were even better.

I used to only run my SB back in tafe days once a year due to study and living away from home. Started fine even after 1 year of not even touching it. That has the old school Bond lead acid just before calcium/silver became the norm.

Thanks mate.

IF left connected to the terminals of the car, you always have a current draw due to memory 12v etc to stereo head units.

But if a terminal left disconnected, its no different to a car battery at a store, left sittin on the shelf for 12 months. You don't see people at supercheap / autobarn running around recharging them after a couple of weeks. Well.. not while i was employed there lol.

Thanks Chris

Looks like my battery is stuffed.

Regards
Greg

I know that if I don't start mine every couple of days it's low enough not to start with in 4 days but the alarm is the cause in mine. Don't get a brant alarm.

A good strong healthy battery will be fine for weeks this time of year but a weaker one can discharge quick with the parasitic drain in car electric systems.

We've got a various cars and machinery that sit for months at a time without problems usually.
I try to disconnect them if I know its gonna be while but its easy to forget.

Telecom Research did a study on how long Lead-Acid batteries would last in normal but STATIC use (don't have the paper now), and gave up after about 12 years... So the lead-acid type should last indefinitely if kept fully charged, topped-up, and not vibrated -- so might last 3 to 6 years in a car, if looked after. It all depends on usage and care. We never get more than 5-6 years at best, regardless. A complete discharge (eg. leaving lights on overnight) may destroy even a new battery -- depending on how long it is left 'flat'.

They should typically be re-charged (topped up) at least monthly in cold weather, and every second month in warm weather. If you don't use car often, disconnect the EARTHED terminal (caution!), to prevent slow drain. They don't seem to hold charge as well in cold weather -- supposedly being only partially charged and it being cold is a bad combination. The easiest way to check for slow battery drain, while ign. is off, is to check for a tiny spark when touching the earth connection to the terminal (best seen in the dark), though you could possibly check with an milli-ammeter too. With a beetle, there should be no drain, except from the electric clock if working (unless have alarm etc.)

There seem to be two main types of charger. A.) The modern "smart" (electronically controlled) chargers can supposedly be used while the battery is still connected in the car, and is handy for top-ups, but won't charge a fully flat battery (it is TOO smart, so it detects an open circuit!). It supposedly can be left connected safely for longer periods too.
B.) The old style "trickle" charger MUST be used with one terminal of the battery connected. This sort will revive a flat battery - if possible (even if temporarily). Don't leave it charging too long, as it 'boils away' the electrolyte (generating H2 and O2 -- caution!! Can be explosion hazard).
So Greg, if your battery seems stuffed it may still be retrievable with an old-style trickle charger.
[Above applies to L-A batteries... if you have one of these new-fangled Ca-Ag batteries, refer to Vlad! Have not got one, yet.]

Thanks guys for all of the info.

Very much appreciated.

Regards
Greg