2000 750il Battery issues...draining.

[Magus528]

Battery drain:
I unlocked the ODB and ran a diagnostic from the dash.

Start Car up: Test 9
UB: 11.5v

Turn Car on:
at idle 13.3-13.5

Jumped on Highway with heater at full blast 70mph
13.3-13.5

It never goes over 13.6 when driving
If it is at 13.5 does this mean that the alternator is O.K or is the alternator on it way out?

I drive around town 30-45mph. RPMs never really go past 1500 driving through town
It seems like I am hooking the charger up to the battery every couple of days.

[XAlt]

One of two batteries are probably bad.

You've been experiencing drain for a while now, but the car was going to sleep last time we checked.

[Magus528]

One of two batteries are probably bad.

You've been experiencing drain for a while now, but the car was going to sleep last time we checked.

Yes, the car does go to sleep. I have two batteries...the AMG battery at the bottom and one regular battery at the top.
The AMG battery will go down to 44% and it is hard starting. The battery at the top will get to about 60%..so..Im thinking the battery at the bottom is bad?

[XAlt]

Yes, the car does go to sleep. I have two batteries...the AMG battery at the bottom and one regular battery at the top.
The AMG battery will go down to 44% and it is hard starting. The battery at the top will get to about 60%..so..Im thinking the battery at the bottom is bad?

Replace both and call it a day.

[Magus528]

Replace both and call it a day.

So with those readings, its probably not the alternator correct?

[XAlt]

So with those readings, its probably not the alternator correct?

Judging from the engine on reading and consistent drain, probably not. By the way, did you ever replace the expansion tank?

[Magus528]

Judging from the engine on reading and consistent drain, probably not. By the way, did you ever replace the expansion tank?

O.K...I will get two batteries. No, I am ordering the expansion tank today. The floater is stuck at the bottom

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where would be a good place to order the expansion tank?

[XAlt]

O.K...I will get two batteries. No, I am ordering the expansion tank today. The floater is stuck at the bottom

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where would be a good place to order the expansion tank?

ECS Tuning\Pelican parts. Same as the M62\TU tank.

[Magus528]

Also the expansion tank...FPCeruo has some ...OEM, Meyle and Behr...will the Meyle and Behr be fine?

[XAlt]

Also the expansion tank...FPCeruo has some ...OEM, Meyle and Behr...will the Meyle and Behr be fine?

Behr

[psjr]

The Behr is "Behr Service" which is made in China and people often have issues with them cracking within a year or two.
Genuine BMW is best but will be cheaper from a dealer than from FCP.

[XAlt]

The Behr is "Behr Service" which is made in China and people often have issues with them cracking within a year or two.
Genuine BMW is best but will be cheaper from a dealer than from FCP.

Some have great luck, some have bad luck.

The design just sucks as a whole.

[RIboater]

if the float is stuck at the bottom, banging on the tank with a screwdriver handle has made it pop up for me.

[XAlt]

if the float is stuck at the bottom, banging on the tank with a screwdriver handle has made it pop up for me.

Willing to bet it's the original tank though, still a grenade.

[aharbaugh9]

How's the car doing?