drained Battery within 7days

[dark_stranger]

All, I last used my car about 1 week ago, but went to start it last night and there was enough power to unlock the doors, etc, but not turn the engine over.  I had a similar issue a few months ago, where I left the lights on for a few hours and the battery was drained.  When I got the car the seller brought a new battery (http://www.tayna.co.uk/096-AGM-Banner-R ... P8260.html) and had to call the AA to give me a boost.  The battery doesnt fully fill the battery well and therefore could it be under powered?  if so, what battery would you guys recommend?
Cheers

[X5Sport]

What engine have you got?  If a diesel then the battery should be filling most of the space. 

The battery your link shows is way too small for a 30d, which should be fitted with something like this beast.

[dark_stranger]

sorry, have a 3.0 Petrol (04 plate).

[X5Sport]

In which case it needs to be something like this 85Ah 800A CCA rated brick.  The one you have is not for that version of the X5.  70Ah will be getting kicked very hard by the on board systems.

I have noticed that a number of battery sellers assumed that the standard battery for say a 3-series E46 330 Petrol is therefore the battery used across all BMW Models with the same engine.  The X5 electronics pull a much bigger load off the battery so the smaller battery will be worked very hard to keep up, even with the alternator running.

To give you a clue as to how much power is drawn, the X6 with the ignition on but no engine, draws 60A (or more than half the battery's hourly rating) off the battery!!  If you leave lights on, or sit using the TV for an hour then it won't start!

[dark_stranger]

Thanks, was looking on EuroCarParts and can get that battery for just under £80 with promo code.  Looks like I will have to get the credit card out.

Cheers

[X5Sport]

Before you do, it will be worth just checking if you have a 'parasitic draw' on the car.  If you have a multimeter then you need to disconnect the -ve terminal and connect the meter between the car and battery.  Use a high current range!!

Also check what the battery volts reading is on the jump starter points under the bonnet.  It should be more than 12.4 on a good and charged battery.  Anything below 12.2V is either flat or knackered!!

It isn't unknown for a bad starter to be the issue rather than the battery itself.  The battery is the usual culprit though.. >:(

Richard

To do a parasitic draw check safely (without frying the meter) loosen the -ve battery connector at the battery end, but do not remove it.  Leave the boot open so that you can get at things and then lock the car.  Leave it until the orange tell-tale LED on the gearshift goes out.  The car is now 'asleep'. 

Carefully and without breaking the electrical connections anywhere put the -ve lead of the meter under the battery -ve lead and directly on the battery -ve terminal.  Put the +ve meter lead on the -ve battery cable terminal end.  Lift the battery cable away from the battery and you know have the meter in circuit.  You can now reduce the meter reading scale down and you should end up with a reading of around 120mA if all is well.  If you have a tracking device which is charging itself you might see about 220mA for thirty minutes or less, but it should then drop off.

If the reading you are getting is higher then there might be a circuit drawing too much, which will kill your battery.

If you break the connections at the time you lift the cable off then the car will 'wake up' as soon as the connection is remade so you have to start over again - a 16 minute wait.  I wonder where the 16 came from?

[rjkc600]

I lift my ignition on by mistake for 30 mins.  When i realised, the whole car was dead.  No power at all.  Had to get it jumped and go for a drive to recharge.