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Topic Closed8 series batteries

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david 840 View Drop Down
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Direct Link To This Post Topic: 8 series batteries
    Posted: 13-November-2005 at 10:49

Hi, wondered if anyone had experience utilising a battery conditioner such as an optimate etc over the winter months on an 840 (1996 4.4 Ci). 

My 8 wont be used daily and I want to try and keep the batteries topped up with charge.  I understand that the maintainance chargers are good for the job but i'm not sure of how to go about connecting one up on a car with twin batteries like the 8 series. 

I have bought one from Halfords and it says its good for maintaining a 70 Ah battery at maximum.  I've saved the receipt so I can always take it back if not suitable!!

Which is the best way to connect up to the car without damaging the ECU or other electrics.  One battery has about four red leads connected into the positive side!

Is it OK to connect via the positive and earth points in the engine bay or is it better hooked up to the battery terminals in the boot.  How are the batteries wired??

Help please!

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aussie840 View Drop Down
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Direct Link To This Post Posted: 14-November-2005 at 06:27

Hi David

I don't use one as mine is a daily driver, but I know other 8 oweners  in the states often use them (like this one)

The two batteries in the boot are wired in parallel so you could connect to either one, however most connect to the battery terminal under the bonnet. Connect pos to batt. terminal and neg to the lug mounted on top of suspension strut.

You won't damage the ECU, that is more likely to happen if you were jumping starting the car from another car - the conditioners/tenders only put out a trickle charge and most new ones stay open circuit unti it detects its been connected to a battery, so no sudden discharge or spark will happen.

I've also heard BMW sell a rebadged version of this one

http://www.batterytender.com/

Cheers Skip

 

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david 840 View Drop Down
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Direct Link To This Post Posted: 14-November-2005 at 13:33

Hi Skip,

Thanks for you advice on that one.  I'm gonna hook up my Halfords maintainence charger tonight and hopefully no flat battery problems. 

Incidentally, when I removed the carpet panels in the boot I noticed the batteries were both a different make to each other and both non BMW brand - is this a problem and if I do need new batteries as and when, can anyone reccomend a make and rating etc e.g. Bosch , Lucas etc?

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Direct Link To This Post Posted: 15-November-2005 at 02:03

Hi,

Next time you replace the batteries I would use the same make, the reason is the 18 or so onboard computers...

 

...can do weird things if they don't to get fed the right loading and the factory nearly always says replace both batteries before attempting to troubleshoot OBC issues...both batteries need to be supplying the same current loads.

I would use 2 of the heavy duty batteries that UK 7 series owners use. Perhaps worth asking the same Q on that board too.

Found these specs saved on my PC...

With the luggage compartment lights off:
1.) Driver's door open: 4.8 - 5.0 Amps
2.) Driver's door closed: 4.1 Amps for 20 seconds, then reduced to approx. 450-470mA for next 16 mins., then reduced to approx. 50mA

With the luggage compartment lights on:
1.) Driver's door open approx. 6.1-6.4 Amps
2.) Driver's door closed--approx. 5.9-6.1 Amps for 20 seconds, then reduced to approx. 2.5 Amps for the next 16 mins., then reduced to approx. 50mA

Think its roughly 1.5% of batteries per day if left untended.

Skip

 

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Direct Link To This Post Posted: 19-November-2005 at 13:27

Hi, thanks for all the info Skip, its helpful on a car like the 8 with little data readily available!

Hooked up the Halfords maintainence charger to the points under the bonnet.  Started trickle charging (indicator on red) then when I checked the following day it had changed to a green indicating light, which shows the charger is in "maintainence" mode.

When I lifted the boot lid, activating the courtesy lights on the boot lid, I noted that the charger kicked back on (light to red) obviously sensing the drain from the lamps. 

The car seems to run fine but when I replace the batteries I think a pair of heavy duty Bosch will be in order !!

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