I Have a 2008 clubman S. I have been having dead battery issues, periodically, and inconsistently. I sometimes won't drive it for a few days, and it starts right up. Then there will be times where I'll drive it around all day, leave it for an hour or two, and it's dead. Usually a dead battery is more obvious.

It seems as though something is always running in my mini, even when it's just sitting.

Anyone know anything along this topic?
Thank you

 

That's how a bad cell behaves in a lead–acid battery, the same thing you are describing has happened to me before.

 

If you can put a meter on the battery terminals and take a reading when it's not starting for you, esp. if it's been driven that day, let us know what you find. If you ARE losing 1 cell inside the battery intermittently, you'll drop about 2.1 volts from a normal reading , key off, of around 12.1 to 12.8volts depending on state of battery charge, battery condition etc to something around a 10 volt range when that 1 cell is acting up on you.
A full on battery drain of something staying on in the car after you shut it off can either slowly or quickly drain the battery depending on the level of current that's being drawn from the battery.
If you DO find you're losing what appears to be a single cell, then gently shake the battery or car while your meter is hooked up, you may find the reading suddenly jumps above 12.0 volts since the vibrations of shaking the battery put that failing cell back into the circuit for a bit. You would still need a new battery no matter what, but at least you diagnosed your problem, and how cool is that....

 

Simplest test to see if it is the battery or the car, is to yank the battery...
Put it on an modern automatic charger...
If it sees that after it is "full" the voltage suddenly drops...like from a bad cell, an error code will appear...
If the battery is fine...
Time to do some detective work with the car, fuse by fuse with a meter, and figure out what is staying on...

 

Respectfully, no. If the loss of 1 cell is intermittent, no battery tester may catch or fail that battery if all cells are working correctly when checked. Esp. with Capacitance type or AC Conductance battery testers that are all the rage among car manufs. who insist that only that special tester from say, Midtronics, is approved for their warranty battery work because it generates a code for warranty purposes/paperwork, doesn't heat up like the old Carbon Pile testers, and is small and portable.

 

That's why I said CHARGER...not tester...let it sit for a day or so...so no load test...
If the voltage stays stable, it will enter float mode...
But a sudden drop in voltage, more than is typical self discharge, will trigger a battery fault code, for a bad cell/sulfated battery, etc....
Funny thing is it is just a cheaper electronically controled charger/matainer....
Works great...not a shop tester...but does a great job for about a $60 pep boys special from 5 years ago....
Sure...not a load test to determine amps, but if the volts suddenly drops and the battery accepts a charge for no reason, it is bad....

 

How old is the battery? If more than 3 yrs, I'd go ahead and replace it.

 

Thanks for input everyone.

This current battery was replace November 2012, which seems pretty new still in terms of car batteries.

 

The battery I had with a bad cell was only 14 months old. I think the likelihood of having an "intermittent" power drain from the car is really slim to none if you have not added something new to the electrical system recently.

 

I hear you, Charger, not tester.

 

Fairly new, but not certain to be good or not acting up. Let us know what you find either way.

 

Les Schwab said it has a bad cell. It's only at 37%. I'm on borrowed time with this battery. I won't be having Les Schwab install the battery. They kind of rummaged through my mini trying to find the battery, they thought it was in the rear where the storage compartment is. Idiots.

My car was in disarray when I got it back, which pisses me off because I'm pretty particular about it.

 

Ding, ding, ding. Sounds like the collective nailed it..

 

there are a number of electrical items that keep running even if the car is off like the cooling fan and the turbo cooling pump. then when you open the door, the windows drop further draining the battery. if you have the security system and keep the key fob too close to the car, the car does not completely turn off, it is "ready" to go on an adventure. one thing to check is if you have to reset your windows or the sunroof after the you experience a fault, if not, it may not be the battery as these two probelms are typical after a drained battery. I finally had to get a trickle charger for my mini due to the battery drain problems. there is also the chance that the battery was not reset in the computer when it was replaced. if the battery is not close to the origanal spec the charging system will not work properly.

 

Thanks for the update.

 

Apparently whoever previously installed the battery I just replaced did not register the battery, which in turn shortened the battery life. Discovered a great local shop here in southern Oregon that specializes in minis. $135 for a new battery installed.

 

That is a great price including installation

 

I have a 2012 R55 and they just had to replace the battery under warranty. It gave some warning sings, hard start when it was 30* out, went straight to Mini after work, 1 dead/going dead, intermittent cell. 1 hr. later, new battery, car was washed and vac., what service.

 

I have had my battery replaced in my 2011 Cabrio S 4 times over 4 years. Each time with no warning. I have never had any car even in AZ go through thismany batteries. The dealer tells me if it sits for more than 3-4 days the battery will start to degrade. Anyone have any advice? The car is a third car, so it sits from time to time. The other thing the dealer stated was to lock the car even in the garage to tell it to "stand down". Three were replaced under warranty, this last one was not.