battery tender, prolonged storage

[TOPEC]

So i have the X5 in storage right now since i dont drive it much. Its been sitting for a little over a month and since the day it was parked, a battery tender was put onto the positive terminal in the engine bay. Started the car for the first time today and got the increased discharge warning which i thought was weird since i have a tender on. I then measured the 2 batteries in the trunk with a multimeter and found the main battery to be at around 13V(normal) but the auxiliary battery to be at 11V(low) only. This leads me to believe that the positive terminals in the engine bay cannot charge the aux battery at the same time as the main battery. Now I am stuck with a dilemma on maintaining both batteries. In order to charge the aux battery, i will need to directly connect a tender to it, which means

a) i will need to leave a gap in my trunk so the tender can be plugged in, which leaves the potential of bugs/dirt/dust/moisture getting into the interior
and
b) i will need to get 2 tenders plugged in at the same time, or move the tender between the 2 batteries every other week, or find a tender with 2 outputs at the same time

Anyone have any suggestions?

[alphaod]

That's the first time I've heard of that problem. I always just leave the tender up the front and I've never gotten increase discharge problem. Granted I've only left max three weeks.

[CatalinP]

I have the battery tender hooked up to the car using the connections under the bonnet for 3 months at a time, no issues at all, however I don't have the 2nd battery.

[Maverik259]

Originally Posted by TOPEC

So i have the X5 in storage right now since i dont drive it much. Its been sitting for a little over a month and since the day it was parked, a battery tender was put onto the positive terminal in the engine bay. Started the car for the first time today and got the increased discharge warning which i thought was weird since i have a tender on. I then measured the 2 batteries in the trunk with a multimeter and found the main battery to be at around 13V(normal) but the auxiliary battery to be at 11V(low) only. This leads me to believe that the positive terminals in the engine bay cannot charge the aux battery at the same time as the main battery. Now I am stuck with a dilemma on maintaining both batteries. In order to charge the aux battery, i will need to directly connect a tender to it, which means

a) i will need to leave a gap in my trunk so the tender can be plugged in, which leaves the potential of bugs/dirt/dust/moisture getting into the interior
and
b) i will need to get 2 tenders plugged in at the same time, or move the tender between the 2 batteries every other week, or find a tender with 2 outputs at the same time

Anyone have any suggestions?

Thought the batteries were in series and thus charge congruently. Maybe this is not the case.

[redline9001]

Originally Posted by Maverik259

Thought the batteries were in series and thus charge congruently. Maybe this is not the case.

They have to be or the car would be 24v ....

More then likely a bad battery...

[CatalinP]

Series would mean 24V....

[Maverik259]

Originally Posted by CatalinP

Series would mean 24V....

Correct meant parallel lol. Damn my EE prof would be upset.

[TOPEC]

Originally Posted by Maverik259

Thought the batteries were in series and thus charge congruently. Maybe this is not the case.

well im sure the batteries are wired up in parallel as its being charged by 1 alternator, but its the under hood positive terminal that is isolated(seems to be the case here) to the main battery as it is meant for boosting the car, which makes sense logically.

[CatalinP]

AFAIK, the 2nd battery is related to the Active Steering.
What battery and when it shall be charged is controlled by the electronic module on top of the main battery. As per BMW instructions for dealers having cars parked for a long time, the tender needs to be connected under the hood, nowhere alse.

[TOPEC]

so i looked into the service manuals for anything related to charging the auxiliary battery. turns out u guys r partly correct. the aux battery is wired up in series to the main battery and its main function is to provide 24V of power solely (it seems like) for the purpose of "EPS/Electronic Power Steering". the manual also states to put a charger only on the positive terminal inside the engine bay, nth regarding the aux battery. makes me wonder how the aux battery gets charged.

[Maverik259]

Originally Posted by TOPEC

so i looked into the service manuals for anything related to charging the auxiliary battery. turns out u guys r partly correct. the aux battery is wired up in series to the main battery and its main function is to provide 24V of power solely (it seems like) for the purpose of "EPS/Electronic Power Steering". the manual also states to put a charger only on the positive terminal inside the engine bay, nth regarding the aux battery. makes me wonder how the aux battery gets charged.

I knew it!!!! Hahaha

[CatalinP]

Well, is used in series so 24V to supply the EPS, but it is charged in parallel at 12V (more like 14.4V).

[Rotzy]

Originally Posted by TOPEC

...a battery tender was put onto the positive terminal in the engine bay...

Just to cover all the bases: Did you also ground the battery tender to the grounding post in the engine bay? Obviously, it won’t charge unless you did.

[MrTookies]

Originally Posted by Kzang

Here is a pic of the 50i battery compartment.. I'm certain the 35d is the same.. not sure if it is different with 3rd row or not though.

(https://f15.bimmerpost.com/forums/sh....php?t=1349802)

Originally Posted by CatalinP

Well, is used in series so 24V to supply the EPS, but it is charged in parallel at 12V (more like 14.4V).

I know it was said that there is a second battery for active steering, now I'm confused... I have active steering and, I'm pretty sure there is no second Battery at least not next to the main one? Am I missing something here?

[TOPEC]

in the service manual it states for vehicles that see higher axle load only, not totally sure on what that means. do u have any suspension options or just regular springs all around?

[Silververtu]

Originally Posted by PlayTookies

(https://f15.bimmerpost.com/forums/sh....php?t=1349802)

I know it was said that there is a second battery for active steering, now I'm confused... I have active steering and, I'm pretty sure there is no second Battery at least not next to the main one? Am I missing something here?

I see 2 batteries there too. A larger one on left and regular size one on right

[MrTookies]

Originally Posted by PlayTookies

(https://f15.bimmerpost.com/forums/sh....php?t=1349802)

I know it was said that there is a second battery for active steering, now I'm confused... I have active steering and, I'm pretty sure there is no second Battery at least not next to the main one? Am I missing something here?

Yes, you are missing the part that the picture is not my car, rather the car form the guy I quoted.

[MrTookies]

Originally Posted by Silververtu

I see 2 batteries there too. A larger one on left and regular size one on right

That's the Point, he has a second one... with active steering and I'm pretty sure even though I have active steering I don't have one there unless it's hidden somewhere else...

[MrTookies]

Originally Posted by TOPEC

in the service manual it states for vehicles that see higher axle load only, not totally sure on what that means. do u have any suspension options or just regular springs all around?

Interesting.. well... no I decided not to get the air suspension... but if it goes by axle load shouldn't that be given for a diesel and towing etc?

Just trying to make sure they didn't squeeze a battery somewhere I don't know of, or wouldn't look at.

The SCR ECU/Control Unit is for example located under the passenger side headlight, would have never know to search there since that unit is in the trunk in the 3 and 5 Series...

[TOPEC]

heres what it says

Auxiliary battery
On some types of vehicle with certain combinations of engine and gearbox (weight on the front axle), a more powerful electromechanical power steering system is fitted for the option (SA2VH) "Integral Active Steering". The electromechanical power steering can be operated with 24 Volts.

An auxiliary battery is fitted for the power supply (24 Volts) of this power steering. By means of a cut-off relay, this auxiliary battery is switched into series with the vehicle battery.

The EPS control unit transmits the request signal as a bus signal to the charging controller for the auxiliary battery via the engine control (EPS stands for "Electronic Power Steering"). The charging unit activates the cut-off relay.

Functional description
A higher front axle load occurs due to the higher weight of different motorisations. This, in turn, leads to an increase in the power required for the steering assistance. In combination with Integral Active Steering, an even greater effort, and therefore an even higher current, is demanded from the steering assistance. Because of these high currents, it was necessary to increase the EPS voltage supply to 24 volts.

During operation at 24 volts, the auxiliary battery can be loaded with the aid of the charging controller for auxiliary battery. For this purpose, the charging controller draws power from the vehicle electrical system via the rear right power distribution box and uses it to load the auxiliary battery.

https://www.newtis.info/tisv2/a/en/f...ery/1VnXzY6x4V

the more i look into this the weirder it gets

Integral Active Steering
Active steering (AL) and rear axle slip angle control (HSR)
The combination of active steering (AL) and rear axle slip angle control (HSR) is referred to as Integral Active Steering: optional equipment 2VH.

Integral Active Steering can influence the steering angle set by the driver without affecting the steering wheel angle. This means that for the first time the steering angle is specified at the front and rear axle independently of the driver.

This leads to the following advantages:

The variable steering gear ratio optimised for every driving speed means that on the whole the vehicle can be driven with a more sport-oriented style and more accurately. The amount of effort required by the driver is reduced, thus making an additional contribution to active safety.
At lower driving speed, very agile driving characteristics set in. The turning circle of the vehicle is reduced.
At higher driving speed, effortless, comfortable driving characteristics set in. The vehicle seems to be directly ”linked”.
This document describes the function of the Integral Active Steering with rear axle slip angle control. The active steering function on the front axle is described in detail in the vehicle engineering diagnosis 320103001.

https://www.newtis.info/tisv2/a/en/f...ntrol/2ckumbID

and if u search for "integral Active Steering", everything points to rear wheel steering, which to my knowledge, i "shouldnt" have, unless it was included inside some package that i wasnt aware of. infact, is this even an option for the F15 X5? never seen it mentioned anywhere

[MrTookies]

Originally Posted by TOPEC

heres what it says

https://www.newtis.info/tisv2/a/en/f...ery/1VnXzY6x4V

the more i look into this the weirder it gets

https://www.newtis.info/tisv2/a/en/f...ntrol/2ckumbID

and if u search for "integral Active Steering", everything points to rear wheel steering, which to my knowledge, i "shouldnt" have, unless it was included inside some package that i wasnt aware of. infact, is this even an option for the F15 X5? never seen it mentioned anywhere

Couldn't find that under the Diesel section...

[TheUltimateDrivingManiac]

Originally Posted by CatalinP

AFAIK, the 2nd battery is related to the Active Steering.

I don't have an Active Steering and have a second battery.


And according to ETK you get 2nd battery if you've got any of these options: S496A (heated rear seats), S536A (parking heater), S601A (TV), S6FHA (rear seat entertainment), S791A (fridge).

I've got heated rear seats out of these.