Scotty, I have a 2013 BMW E88, Manual, 68k miles, and I'm having issues with the electical power in my car.
My start stop system still works which suggests the alternator is keeping the battery charged. I can leave my car for multiple days and the battery holds a charge however if the car is awake in any way, such as by opening a door, the battery drains insanely quickly. With engine off it can take about 20 minutes to drain the battery very low (to the point that modules start shutting down such as ABS, TPMS, roof control etc) just having the door open and no key in the ignition and it can drain in as quickly as 30 seconds to 5 minutes if the blower, stereo and headlights are on with accessory power and engine off.
Running the engine for a few minutes restores the modules back to normal.
Any ideas?
Long time watcher on YouTube, thank you for everything you do!
the battery does look new.
there should be a date on it.
l it holds that charge at 12.6-12.8v (no dead cell),
batteries need to be properly load-tested to ascertain their health
I unlocked the car with the remote. Voltage dropped to 9.6 volts immediately
even cranking with the starter which uses hundreds of amps, it should not dip that low. The battery is either bad, or there's a unfused dead short somewhere.
witched on accessory power and my headlights and it dropped to 10v immediately and then quickly fell to 9.6v and stayed there.
that's sounding more and more like a failed battery
I'll pull the battery in the morning and have a look for a date, can't really see much in its location.
And yeah, after what I saw, I'm pretty much of the mind that the battery is toast. If it is indeed new, then I want to know why it died so quickly.
I think, before I buy a new battery, I'm still going to use the charger/maintainer on it and see what it says. If the charger runs it's anti sulphation cycles and charging cycles etc and says it's fully charged and it still reads 10.5v after running the headlights for a few minutes then I can be 100% sure it's a dead cell and I'll get the battery swapped out. I'll do a parasitic draw tests etc no matter what. Especially if I get a new battery. Don't want it killing a new one, they ain't cheap.
I'll keep the thread updated with the outcome.
Is there a way to see how much power is being demanded from the battery as I switch things on individually like headlights, stereo, blower/ac, dashcam etc?
There is.
method 1
Some vehicles actually track power usage. This live data would be available with a diagnostic tool.
method 2
most cars will have a main fuse.
Find the datasheet for your fuse.
Here is the data for the fuse in the example photo below: Littelfuse MEG100BP
Find the resistance. e.g. 0.56 mΩ
Switch your meter to the most sensitive voltage range (mV), and put the probes across the fuse. It helps to have a meter with interchangeable tips for this so you can use crocodile clips. Otherwise you might be able to squeeze your probes underneath the terminal. Do not use jumper wires. This will affect your reading.
Now monitor the voltage and use Ohm's law:
Let's say the voltage reads 1.1 mV. Using Ohm's law we get 1.1 / 0.56 = approx 2 amps of current
Method 3
If you don't have a main fuse, or your meter isn't sensitive enough, you can use Scotty's method with a resistor.
But if your drain is really high as you say, then the resistor is going to get hot so be careful.
Incredibly useful! Thanks for this!
Sorry, forgot to update.
I pulled the battery, forgot to check for the date mainly because when I removed it I could see physical damage to the battery. It looked like it had been dropped on its bottom corner and it was clearly buckled. So I'm certain a cell was toast.
Bought a new Bosch S5A13.
Fitted it, coded it, registered it and now everything is perfect. Load tested it for quite a long time and it didn't even stutter.
Problem solved thanks for all the help from everyone!
In other news, since changinging the battery I'm now getting an intermittent misfire on Cylinder 4 so on to the next job of changing sparks, yey!
A battery and alternator load test will alert you to either needing replacement. Fixing either one might eliminate a future issue but that doesn't mean you don't have a parasitic drain on your system. So yeah, get a new battery, but continue on - troubleshoot just as you've planned.
I think, before I buy a new battery, I'm still going to use the charger/maintainer on it and see what it says. If the charger says it's fully charged and it still reads 10.5v after running the headlights for a few minutes then I can be 100% sure it's a dead cell and I'll get the battery swapped out. I'll do a parasitic draw tests etc no matter what. Especially if I get a new battery. Don't want it killing a new one, they ain't cheap.
Have you changed the battery recently? All batteries degrade over time. It may be time to change it. I had a 1994 BMW 540i 10 years ago, and that battery was last changed in 2006. I noticed it when the car was slow to start after a cold snap. It may start up fine, but it's only 3 or 4 seconds before the alternator kicks in. Sustained power is another story.
I've only had the car 4 months and according to the paperwork the battery was replaced before delivery. They did a full service, oil change, filter change, battery replacement etc before handing the keys over.
Obviously I'm not able to confirm if ANY of this work was actually done but the battery does look new.
I have general dealer/mechanic trust issues though which is why I intend to do as much as I can myself.
For instance, I took the car to a local garage last week and they told me the alternator and battery were reading ok but I know something is going on that's way outside normal so I've ordered myself a multimeter and I'll have a look myself when it arrives today.
Further to my initial question, my multimeter is about to arrive any second now.
Part of my testing will be an initial parasitic draw test by putting the meter in series with the negative battery cable while the car is 'sleeping'.
This got me thinking... I also have a battery charger/maintener coming tomorrow (Ctek MXS 5.0). If I don't have a parasitic draw while the car is sleeping and, after charging the battery to full it holds that charge at 12.6-12.8v (no dead cell), something must be drawing large amounts of power while the car is simply awake with no key in the ignition and then even more power with just accessory power on and engine off.
I know I can't have the meter in series and test this because it'll exceed the 10A of the meter.
Is there a way to see how much power is being demanded from the battery as I switch things on individually like headlights, stereo, blower/ac, dashcam etc?
it can take about 20 minutes to drain the battery
That's a significant amount of power and the energy has to go somewhere. so, whatever it is probably gets pretty warm.
That's what I was thinking. It's an insane amount of power and I'm sincerely hoping I find a fault with the battery that the car THINKS it's fully charged and therefore still using the start stop system but in reality it's nowhere near full.
Not to mention its incredibly annoying.
When I take my mother to the store, for instance, I'll usually wait in the car and have some music playing while I browse my phone.
Can't do that anymore!
Have to really baby it and switch everything off, remove the key and lock the car so it goes to sleep with me inside.
Can't live like this.
Is it possible that if/when the battery was changed at the dealership they didn't register/code the new battery? Would that cause these symptoms?
Is it possible that if/when the battery was changed at the dealership they didn't register/code the new battery? Would that cause these symptoms?
On a BMW, it wouldn't surprise me if there were some special procedure for battery installation.
But I don't think it would be the cause of a severe drain.
I know if you're installing a new battery that the new battery needs to be registered with the cars computer. Apparently the car tracks the battery age, charge etc and adjusts what it does accordingly and if you install a new battery, without informing the computer it will treat the new battery like it's old.
Furthermore, if you install a new battery with different specs, like a higher CCA or higher Ah rating, not only does it need to be registered with the computer but it needs to be actually coded in to tell it what the battery is capable of.
But hey, check this out... It's nearly 2am here and I got bored.
I was going to wait till the battery charger/maintainer came tomorrow before I started messing around but I figured I would do a couple prelim tests in the dead of night. The car has not been touched in any way, shape or form in 19 hours.
Went out, unlocked the car, popped the trunk and spoofed the latch so the car thinks it's closed. Locked the car again and waited a few minutes.
Popped the meter on the battery posts and got 12.68 volts.
With the meter still on the battery posts I unlocked the car with the remote. Voltage dropped to 9.6 volts immediately and then slowly rose to about 12.2v and stayed there. I switched on accessory power and my headlights and it dropped to 10v immediately and then quickly fell to 9.6v and stayed there.
By this time the car is having a temper tantrum and shutting down modules.
I started the engine. Now getting 14.66v at the battery terminals. Alternator is good.
After a few seconds the headlights brighten up, the modules power up and all the lights on the dash go back to normal operation. Switch off the engine. Getting 12.4v at the posts.
Lock the car and voltage drops to 9.6 volts for a moment and then goes back to about 12.6v
Unlock the car and switch on accessory power and my headlights. Leave it like that for about 30 seconds. 9.6v at the posts.
Turn off the car and lock it. 10v at the posts and I wait maybe 60 seconds. Car goes to sleep and the voltage at the posts rises to 10.5v and stays there.
Think this confirms a dead cell? Am I wrong?
Has my car really been 'running and operating', including operating the start stop system purely on surface charge?!?