Charging up the batteries on the X5. Info and Pictures.

[scotty339]

I used to have a 2006 Toyota Tundra DC. I'd consider my self pretty well versed in 12VDC systems. I turned it into a bit of an off-road exploration rig. One of the things I did was install two Odyssey PC 1200 batterys under the hood so I could isolate my fridge, winch, starter, house electrical ect. It had a relay, that I could flip or would auto depending on voltage. Very handy.

Since buying my 2015 X5, I have been looking at the battery system and learning more and more about the Effecient Dynamics and when the alternator outputs voltage. I first took my multi meter to the posts under the hood for jump starting when I got the vehicle, curious on the status of my almost 5 year old batteries..... and saw a low voltage, IIRC in the 11's. I found it odd tho that I was getting jumps and spikes, getting some low readings in the 10's.

After some more reading and poking around and education, learning about effecient dynamics (keeping charging to only during braking applications or coasting to increase fuel economy by reducing load on the engine) the one question I could not find was how do the two batteries handle the separation of the voltage from the alternator.

Sitting here in my garage, I decided to hook the batteries up to the charger again and measure the outputs in the rear. The charger in question is an Odyssey OBC-20A.

Numbers Before -
Jump Terminals Under Hood - 12.41V
92AH Battery - 12.42 (Mfg Date 31/15)
50AH Battery - 12.54 (Mfg Date 17/14)

Numbers During Charging -
Jump Terminals Under Hood - 14.60V (will vary depending on your charger and when in the charging "cycle/pattern" you take a reading)
92AH Battery - 14.61 (Mfg Date 31/15)
50AH Battery - 12.54 (Mfg Date 17/14)

As somewhat expected, the terminals under the hood designed for jump starting only send voltage to the 92Ah starting battery.

My charger told me my "battery life before charging was around 40%" Take that FWIW. I am curious what BimmerLink says.

I am sure there is a relay that links the batteries to provide charging voltage while driving and keeps the 50Ah topped up, but I dont plan on put my wife behind the wheel while I ride in the back and test the voltage of the battery.

Just some random info for a Sunday morning that may help some people. With the OEM 50Ah BMW battery being around $400+ CAD and being proprietary BMW, I'd love to push its life as long as I can. Currently it sits around 6 years since MFG.


BMW NEWTIS states

Attention!
Lead-acid battery, AGM battery:
To prevent the intelligent battery sensor from malfunctioning,
 use the charging points in the engine compartment.

(https://www.newtis.info/tisv2/a/en/f...older/1Lil7vLT)

Any thoughts on hooking up to the 50Ah in the back?
Does anyone know what the BMW procedure is?


Cheers.

[ajob]

Great post, thanks!
I was wondering too and now I (sadly) know that the small battery can't be charged from outside

[Qsilver7]

Originally Posted by scotty339

As somewhat expected, the terminals under the hood designed for jump starting only send voltage to the 92Ah starting battery.

My charger told me my "battery life before charging was around 40%" Take that FWIW. I am curious what BimmerLink says.

I am sure there is a relay that links the batteries to provide charging voltage while driving and keeps the 50Ah topped up, but I dont plan on put my wife behind the wheel while I ride in the back and test the voltage of the battery.

Just some random info for a Sunday morning that may help some people. With the OEM 50Ah BMW battery being around $400+ CAD and being proprietary BMW, I'd love to push its life as long as I can. Currently it sits around 6 years since MFG.


BMW NEWTIS states

Attention!
Lead-acid battery, AGM battery:
To prevent the intelligent battery sensor from malfunctioning,
 use the charging points in the engine compartment.

(https://www.newtis.info/tisv2/a/en/f...older/1Lil7vLT)

Any thoughts on hooking up to the 50Ah in the back?
Does anyone know what the BMW procedure is?

Since the warning about charging the vehicle’s battery to the terminals in the engine bay are due to the engineering design of the IBS...I think we can presume that this doesn’t apply to the auxiliary battery since it’s not hooked up directly to the IBS. There are components between the vehicle’s regular battery and the aux battery (relays and a charging controller to name a few). So if one wanted to check the aux battery or even charge it (if the charging controller for some reason is failing to keep it charged)...it probably can be directly hooked up without causing any issues with the IBS.

Here’s a direct link to info about the auxiliary battery charging controller on how it works and what its fundamental operation is for:

https://www.newtis.info/tisv2/a/en/f...ttery/GH1wlj6L

[Sophisticated Redneck]

Sounds like they didn't change a thing on the F15, my E70 does the same thing, dips down into low 11', high 10's sometimes, with spikes past 14 during braking/coasting. I think their algorithm is crap.

BMW did program it so certain high-drain accessories will disable the "intelligent" charging system. You can override it by turning on your foglights, puts out a consistent 12.6. This will make a difference on tuned vehicles running higher boost, 2 volts is about 6000 volts at the sparkplugs. IMHO many drivetrain malfunctions are caused by the low voltage fluctuations.