Battery Charge

[u751920]

Hi All,

  I am considering an X5 diesel 3lt.  As it will be primarily for short school run journeys I assume the battery will degrade pretty quickly.
  What sort of a weekly run would be required to maintain the battery?  If I did an hour run on the weekend will  that compensate for the weekly pootle?

  I appreciate that there may be a discussion as to whether this is the right type of car for those types of journeys & I am aware that the DPF might have problems.  But if we could just be battery specific I would appreciate it.

Thanks

[535dboy]

Define short

[u751920]

  It will be like this:

  Weekly miles - 46
  Time driven - 3hrs 30mins
  Number of Starts - 41

  This is pretty accurate for the regular chores.

[535dboy]

[quote="u751920"]
  It will be like this:

  Weekly miles - 46
  Time driven - 3hrs 30mins
  Number of Starts - 41

  This is pretty accurate for the regular chores.
[/quote]

Mine did 7 miles a day sometimes.

As you have said just take it for a good blast at weekends

[X5Sport]

On average it takes approx 20 mins to put each start charge back into the battery.  You may find that you need to out the car on charge say once a month just to top it up.

Both our X6 and Mini Countryman start nagging about excess battery discharge via the iDrive approx monthly and we're not doing much mileage either.

I use a CTEK charger to top them up and both cars have CTEK comfort warning devices fitted to the jump start points under the bonnet.  These have Red/Amber/Green LEDs which give a clue to the battery state.  If low (flashing red) then the charger plugs straight into them.  It uses very little power so will not flatten the battery.

These are the ones I use.  All new CTEK chargers have matching plugs and you can get 2.5m extension leads between the car and charger with everything being water-resistant to high level.  No messing with croc clips, and you can keep the bonnet shut.

Richard

[u751920]

  Thanks for the replies very informative.

  [quote="X5Sport"]
On average it takes approx 20 mins to put each start charge back into the battery.
[/quote]

  Does this mean that my 41 starts per week would require 20 mins each of driving to regain the lost power?  Sorry if that's a silly question I've never had a big diesel engine before so am unaware of this.

  I'm sure as the summer roles on we will be doing more weekend jaunts so we will balance up the shortfall we hope.

[X5Sport]

The formula we used for battery loading was 20mins per start, so yes that's 20 mins of engine running above fast idle to put the charge back.....it's the same with most cars.  Because the car is running it is using some of the alternator output all the time hence it takes longer to put the 'starting charge' back.

The X6 I have draws almost 60AH doing nothing in 'Radio Ready' mode, even more when running.  The alternator has to overcome that AND charge the battery too, and that's why it takes as long as it does.  Cold weather takes more out because the battery is not as efficient at low temps so needs longer to charge.

Starting a big engine like ours can pull more than 600AH - for a few moments, then add preheaters on diesels and you can see the problems.  On a cold day add screen heaters, blowers, bum warmers, heated steering wheel, lights etc and the load on the battery goes up so the alternator has even less 'headroom' to put a charge back in, and that's with 110AH units - or bigger.

Richard

[kenniff]

This charging stuff is all very interesting. I'm just slightly confused why my previous E70 (had it from new for 4 years), which did the same sort of very short journeys and otherwise sat around (depreciating ) and going nowhere, except for long runs maybe 4 times a year.... never had any battery problems?

Also, what is the impact of the start / stop mechanism (in my new F15) on battery life? Even on short journeys it seems to stop and start quite frequently off its own bat. I'm assuming there's some kind of setting that means it wont "auto stop" until it is sure it can start again, but surely the impact on battery of all these starts will have some effect ojn the battery life per your earlier example?

[X5Sport]

We've got Stop/Start on the Mini and there are a number of circumstances when it will not operate such as low battery, AC running, engine temp, outside air temp, lights on in certain circumstances..

[scratchpole]

The problem with my X5 is similar in that the battery goes completely flat within three weeks. As I have other means of transport it does not get used very often but because the battery is usually flat when I want to use it I have no confidence in taking it somewhere in case the battery has not charged enough when I am miles from home.

It is booked into a garage next week for them to look at but I was told that it is not unusual for an X5's battery to go flat within four weeks of just standing! As I have to park in the road I cannot keep a charger connected so I do a battery swap every three weeks - I have become quite proficient at this now although it is not something that I want to keep doing.

What is other peoples' experience of leaving an X5 unused? How long before the battery is completely flat and the central locking will not operate?

[X5Sport]

Around a month for mine too.  Sometimes less.  I've come back from a couple of weeks holiday before to find the car would not start without help.  Dealers recharge their showroom vehicles at least monthly too.

Richard

[martin33100]

We have only had our E70 for about 4 months but the wife at the moment works only two miles away and so far we have had no problems. We had the same engine in our old E91 3 series and that was fine also.

[X5Sport]

Perhaps battery age may also affect how well they do......now my X6 is over three years old it happens more frequently than when it was new.  Just thinking out loud......

R

[martin33100]

[quote="X5Sport"]
Perhaps battery age may also affect how well they do......now my X6 is over three years old it happens more frequently than when it was new.  Just thinking out loud......

R
[/quote]I haven' even looked to see if we are on our original battery.

[scratchpole]

[quote="X5Sport"]
Around a month for mine too.  Sometimes less.  I've come back from a couple of weeks holiday before to find the car would not start without help.  Dealers recharge their showroom vehicles at least monthly too.

Richard
[/quote]

Thanks for the info. That's what worries me. Getting back to the Airport after a two week holiday and not being able to start the car - an extra day's parking charge at least plus taxi fare home and probably having to pay to get back into the car park. Perhaps I should carry a spare battery?