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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 12-04-2013, 04:08 AM
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[SOLVED] E93 Short Commute Battery Issues

So I've had my new battery (Autozone 94R-DLG) for a year now it's ran 100% ok.

. This is a third car which lives on my storage life for up to three weeks at a time
. My commute is 3.2 miles each way
. Car has done under 5K miles in the last year (16.5K on it now)

Since the new battery I have not followed the myths of locking car when leaving in garage etc. The only thing I do differently is (generally) ensure the engine is running while opening/ closing the roof.

If anyone has the low battery light I suggest swapping out the battery. At under ~10K miles my car was virtually always showing the low battery light if the engine off for more than a couple of minutes + radio turned on. After three or four dealer visits I gave up on them and DIY installed an Autozone 94R-DLG + self registered. With hindsight this is a no-brainier. I wasted lots of time performing battery analysis, messing with battery tenders, following vodoo advice like 'lock cars even if parked at in garage at home'. Swapping the battery made the car act like all my other cars, it seems to be a myth that BMWs cannot handle short commutes..

Quite likely there is an issue with OEM batteries and/or the extra drain from convertibles shortens battery life. Either way.. this car barely ever sees trips much more than three miles and has worked fine since the new battery.
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Last edited by MP3_E46; 12-04-2013 at 04:09 AM.
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  #2  
Old 12-04-2013, 04:41 AM
roadkillrob roadkillrob is offline
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Nice - thinking of putting a new one in mine in the spring - it lives like yours, it is 6 years old (on original battery), 3rd car, 18k miles in 6 years, my commute is about 5 miles, car sometimes sits for a week or more at a time, I never lock it, I typically even use the roof when the car is not running. To make it even worse, I installed a dashcam this year that is on all the time unless the voltage drops under 11.8v and still even sitting a week it won't have an issue. I do put it on a tender if it sits for more than a week and of course when it is stored in the winter.

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Old 12-04-2013, 04:45 AM
fdriller9 fdriller9 is offline
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This doesn't really tell us anything. We don't know your original specs for your battery nor the specs for the new one.

The engine only charges above 2k rpm or something like that so basically highway driving.

If you upgraded to a larger capacity battery with a higher Ah rating, then the car needs to be programmed for that capacity and then registered.

If you're leaving the car for 3 weeks at a time, a battery tender is your only solution. They make maintainers that come with o-ring terminal harnesses so you can permanently install the harness under your hood. So all you need to do is pop the hood and plug the car in.

Your battery will surely show the same symptoms again, however if you bought a larger capacity battery, it will obviously take longer to show decreased discharge wanings in the car.
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Old 12-04-2013, 05:04 AM
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Quote:
Originally Posted by roadkillrob View Post
Nice - thinking of putting a new one in mine in the spring - it lives like yours, it is 6 years old (on original battery), 3rd car, 18k miles in 6 years, my commute is about 5 miles, car sometimes sits for a week or more at a time, I never lock it, I typically even use the roof when the car is not running.
Once the battery light start appearing I'd just swap it out. Researching how to register took a little effort but the physically swap is easy.

My new one is a 90Ah lead acid. People can say "it proves nothing" but it's gone ~twelve months already with zero hassle.

If the new battery started going wrong tomorrow I'd just swap it again rather than faff around with trickle charging etc. Likely it'll go many years.. my MX-5 is over three years old on the original battery. Zero issues and it sits on the storage lift for up to three months at a time. My lawn tractor's tiny battery lasted over seven years and it sat in storage for eighteen months while we were overseas.
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  #5  
Old 12-04-2013, 06:58 AM
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A good report .... how did you self register the battery if I may ask?
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Old 12-04-2013, 07:01 AM
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[SOLVED] E93 Short Commute Battery Issues

I have my car for 2 years now and have a bmw battery tender, no issues so far. Car has 6k miles and drive it only in the summer for short commutes.


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Old 12-04-2013, 07:18 AM
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CALWATERBOY CALWATERBOY is offline
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Well MP3, it is good to change a battery, but is it the real issue?

Often not. One solution is to turn the car on and off 7 times, but not starting the engine, activating the LEFT turn signal on the 7th ON cycle. While the turn signal is ON, depress the brake pedal fully 16 times and press the RADIO ON button. Now, press the START button while depressing the BRAKE pedal to start the car.

So far, so good. Press the START button to turn the engine OFF, but do not press it long enough to turn OFF the dash display. Then, if you are in an E93, activate the TOP DOWN sequence to move the forward and aft top sections fully midway. STOP! Move all key fobs out of vehicle range - more than 20' in every direction, and wait 15 min for the ECU to go to sleep.

CAUTION! Your top must have been fully UP at the beginning of your reprogramming sequence!

If not E93, press the START button to turn the ignition OFF, but do not press it long enough to turn OFF the dash display. Then, open all vehicle doors. STOP! Move all key fobs out of vehicle range - more than 20' in every direction, and wait 15 min for the ECU to go to sleep.

After the ECU has gone to sleep, move a key fob to the interior of the vehicle and press the START button while depressing the BRAKE pedal to start the car. If E93, press the top operating button to return your top to the CLOSED position. If not E93, close all doors.

Congratulations! Your ECU is reset and battery issues may well disappear. Battery code so refreshed frequently extends battery life 2-3 years.

_________________________________


Now, a bone to pick. I do not believe the blue car in your SIG is an E46. I am sorry if wrong, but it looks nothing like that. Should you change your handle?


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Last edited by CALWATERBOY; 12-04-2013 at 07:28 AM.
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Old 12-04-2013, 07:27 AM
R1200 R1200 is offline
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There is a post describing how our cars are designed to never fully charge the battery to allow room for regenerative charging with the alternator kicking in during deceleration. This explains a lot for me about why an older battery cannot run accessories without the low battery error displaying. It is always under charged.

I recently replaced my 7 year old battery to mitigate any risk during cold winter starts. I was getting the low battery indicator if I didn't immediately start the engine. Being frugal I can always use a spare battery for other applications so I decided to recharge the old BMW battery. The 'magic eye' indicator was black (under charged) when I started and after 24 hours at 15 amps it was green again and subsequent voltage tests show that it is resting normally and above 12.5 VDC. There is still life in the seven year old battery.

I'll keep this battery as a 12 VDC source for testing and as a booster battery for other vehicles. For longterm charging I am using a small computer UPS that was discarded because the internal battery cost more than a new unit. It does the job very well.

Just sharing some thoughts.
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Old 12-04-2013, 07:46 AM
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Quote:
Originally Posted by laser View Post
A good report .... how did you self register the battery if I may ask?
D-CAN cable and some simple software. Tools32.exe or similar IIRC. In the end it was just a case of editing/checking a text file to ensure the battery spec is correct and finding the menu option for 'reset battery'. Very easy but it took a while to find a post with this procedure.


Quote:
Originally Posted by CALWATERBOY View Post
Now, a bone to pick. I do not believe the blue car in your SIG is an E46. I am sorry if wrong, but it looks nothing like that. Should you change your handle?
The blue car is BMW number seven for me. Forum name is from attempting to find a solution to play MP3s in the E46 I owned back then. This pre-dates iPods and other MP3 players.. the main solution back then was to have a PC in the trunk. How fast things change

Think I'll stick with MP3_E46.

Aside: I just googled this. The original iPod was launched in late 2001 at $399 for 5GB. Until about 2004 it was a Mac only device.
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Old 12-04-2013, 07:48 AM
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Quote:
Originally Posted by fdriller9 View Post
This doesn't really tell us anything. We don't know your original specs for your battery nor the specs for the new one.

The engine only charges above 2k rpm or something like that so basically highway driving.

If you upgraded to a larger capacity battery with a higher Ah rating, then the car needs to be programmed for that capacity and then registered.

If you're leaving the car for 3 weeks at a time, a battery tender is your only solution. They make maintainers that come with o-ring terminal harnesses so you can permanently install the harness under your hood. So all you need to do is pop the hood and plug the car in.

Your battery will surely show the same symptoms again, however if you bought a larger capacity battery, it will obviously take longer to show decreased discharge wanings in the car.
Don't know if it is the only solution, but it will make life much easier. N4S
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Old 12-04-2013, 08:58 AM
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CALWATERBOY CALWATERBOY is offline
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Quote:
Originally Posted by R1200 View Post
There is a post describing how our cars are designed to never fully charge the battery to allow room for regenerative charging with the alternator kicking in during deceleration. This explains a lot for me about why an older battery cannot run accessories without the low battery error displaying. It is always under charged.

Well, the alternator charges any time, on demand, its sole purpose. How's charging during deceleration impact?
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Old 12-04-2013, 11:05 AM
fdriller9 fdriller9 is offline
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Quote:
Originally Posted by MP3_E46 View Post
Once the battery light start appearing I'd just swap it out. Researching how to register took a little effort but the physically swap is easy.

My new one is a 90Ah lead acid. People can say "it proves nothing" but it's gone ~twelve months already with zero hassle.

If the new battery started going wrong tomorrow I'd just swap it again rather than faff around with trickle charging etc. Likely it'll go many years.. my MX-5 is over three years old on the original battery. Zero issues and it sits on the storage lift for up to three months at a time. My lawn tractor's tiny battery lasted over seven years and it sat in storage for eighteen months while we were overseas.
Your MX-5 has a lot less going on in "sleep" mode than your E9x.

Newer BMWs will wake periodically to check status of systems and will cause excess drain, especially if they hang.
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Old 12-04-2013, 11:32 AM
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I don't think locking the car in your garage is voodoo. That shuts down electronics that are otherwise a drain on the battery. After my original battery died after just a few years, I just following that voodoo, and slap a battery tender on it once a month. The new battery is still strong and I have zero issues with it. Maybe with a stronger battery you may not need to go through all that, but this will make an OEM battery last.
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Old 12-04-2013, 11:48 AM
fdriller9 fdriller9 is offline
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Locking the car will allow the car to fall into sleep mode faster, which reduces electrical draw when the car if off. It will just take a bit longer for the car to fall asleep when you don't lock it.
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Old 12-04-2013, 12:41 PM
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Quote:
Originally Posted by MP3_E46 View Post
Forum name is from attempting to find a solution to play MP3s in the E46 I owned back then. This pre-dates iPods and other MP3 players.. the main solution back then was to have a PC in the trunk. How fast things change
Great to hear from a fellow E46er!!! My E46 MP3 solution involves a BlitzSafe adapter and an Alpine MP3-capable 6CD changer, all in the trunk. So I can play MP3 burned CDs with the changer selected on the head unit, or connect an iPod or any other mini-plug headphone-out equipped device to the aux input of the Blitz adapter, and select it on the head unit using the track up/down buttons.

EDIT: I also just noticed our forum join dates are the same month and year, Oct 2003.
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Old 12-04-2013, 01:52 PM
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Quote:
Originally Posted by CALWATERBOY View Post
Well, the alternator charges any time, on demand, its sole purpose. How's charging during deceleration impact?

As I understood it, the battery is never fully charged leaving some capacity to be made up during deceleration. The explanation was that the overly complex charging system tries to use the load of the car to provide free energy to charge the battery. During acceleration the alternator can then be disconnected for better fuel economy. We have 'Hybrid electric' cars, sort of.

This explained for me why the battery coding is so important and why there are current sensors on the battery cables.

It really is overly complex for the small savings that must be generated not to mention batteries being trashed too early because they are never fully re-charged for their entire life.

I'll defer now to the expect who originally posted this finding.
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Old 12-04-2013, 03:08 PM
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MP3_E46 MP3_E46 is offline
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Originally Posted by bmwrocks View Post
Great to hear from a fellow E46er!!!

I also just noticed our forum join dates are the same month and year, Oct 2003.
Ten year anniversary, wohoo! The iPod mini came out in 2004 and late 2005 I used one with a DIY aux input: http://dotnetworkaholic.com/2005/06/...-listening-to/ - scroll to bottom of post for pic.. looks like that old post was messed up by a blog migration over the years


There was similar guessing way back then... one of the popular assertions was that E46s will all have dead engines by 100K miles because of the 17K+ mile, two year oil change interval.

Fast forward to today: people who changed their oil every 3->5K miles are saying how it's helped their car last... but there are loads of people who bought used at over 100K + have over 200K today following recommended oil changes.


Similar thing with this battery issue. We can argue voodoo all we like and indeed those that use battery tenders, lock their doors overnight etc may have the battery last 6+ years. Mine might die in four years time and I'll spend twenty minutes swapping it out. More than likely the effect of all the voodoo will be next to nothing like the 3K mile oil changes.

Is it worth the hassle of popping the hood, plugging in battery tender and all the other faffing just to (best case) get another couple of years out of the battery?


Somewhere I wrote up results of testing locking/ not locking the doors + resulting current draw using an amp meter in series with the battery. Even not locked the car enters low power mode within ~15->20 mins IIRC.

Not charging until 2K rpm? I know it's survived the 3.2 mile commute and low miles for a year so it must be charging sometime..
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Old 12-04-2013, 06:09 PM
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Nordic_Kat Nordic_Kat is offline
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Guilty of buying into lock the car voodoo and battery tender black magic. My concern was that the original to the car battery never even made it 4 years, much less 5 or 6 and the official line given me was that there were too many cycles logged by the car's computer where the car door was opened but not driven.

For the first three years I never had one iota of trouble, and I never did get a "low battery" indicator. Maybe the battery just had a bad cell that finally cratered, but without warning at the three year point, the battery imploded little rhyme or reason.

The one thing I've immediately noticed with the 'lock the car' practice is that there is no more random whirring 30 or 45 minutes after shutting the car off.

Plugging it into the battery tender once a month really isn't inconvenient, it has just become part of the weekend car washing routine. It never takes more than 4 hours for the battery tender to indicate all is back to a happy and healthy charge. Plus, doing this affords me the luxury of not worrying about dropping the top without the engine running.

That, in and of itself, is more than worth the 5 minutes it takes me to hook up/disconnect from the battery tender.

To OP:
You and I have very similar car usage and climate. As you and I both replaced our batteries in the fall of 2012, what would be very interesting is to compare notes in about 4 years and see where things fall out.
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Old 12-04-2013, 06:56 PM
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Quote:
Originally Posted by R1200 View Post
As I understood it, the battery is never fully charged leaving some capacity to be made up during deceleration. The explanation was that the overly complex charging system tries to use the load of the car to provide free energy to charge the battery. During acceleration the alternator can then be disconnected for better fuel economy. We have 'Hybrid electric' cars, sort of.

This explained for me why the battery coding is so important and why there are current sensors on the battery cables.

It really is overly complex for the small savings that must be generated not to mention batteries being trashed too early because they are never fully re-charged for their entire life.

I'll defer now to the expect who originally posted this finding.

Battery cable sensor is, best I can tell, a conventional battery charging chip to prevent destructive overcharging, undercharging, etc. For lead acid batts, a 3 stage charge is typical. Battery registration optimizes behavior/parameters.

Now, that wouldn't have much to do with when the alternator charges, likely controlled elsewhere based on engine state, as battery charging takes much longer than alternator cycles. Come the day we have air supercapcitive storage, maybe diff.

Complicated? You betcha! Keeps kids off the street, programming....
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Old 12-04-2013, 07:23 PM
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[SOLVED] E93 Short Commute Battery Issues

Most of what y'all are saying is true. BMW wants to maintain the battery at approx 80%. The newer vehicles will over charge on long decel to make up for small under charging while the vehicle is driving to save fuel. Bmw's really don't like to be short tripped. Most cars don't but bmw's are worse with all the electronics that rely heavily on the battery. I've install battery tenders permanently in vehicles so all a customer has to do it run an extension cord to the vehicle. I can do that for anyone interested and register battery as long as your near the middle tn area. Pm if interested.


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Old 12-05-2013, 06:26 AM
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MP3_E46 MP3_E46 is offline
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It's worth noting that when swapped out the BMW's 'dead' battery had 43Ah capacity remaining according to my hillbilly testing (see pic). I keep it in our garage charging with a CTEK every six months just in case any car needs jump starting + if we have a power-cut it will give a little power via an inverter for charging cell phones etc.

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Old 12-05-2013, 07:01 AM
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One thing I do not doubt is that having a lead acid battery to go entirely flat radically shortens its life. This seems to be case with most battery types; Li-ion in our laptops/phones is particularly sensitive to being too low which is why they tend to turn off at ~10% remaining. The best battery life I've had is in a lawn tractor which was an end-of-season discounted buy.. its battery would not hold charge from 'new' and the store provided brand new one. That 12V motorcycle battery lasted at least seven years (probably more as after swapping I learned the tractor's ignition switch was faulty and left the lights on).

Further to that theory I'll wager many vehicles battery goes entirely flat while waiting to be sold. Once in owners hands they rarely go entirely flat which is why my lawn tractor's second battery lasted seven years (despite being stored for ~1.5 years which we overseas!).

Why do batteries go flat on dealers lots? Likely as they are often moved just a few yards and the battery never has change to charge. Also continually locked/unlocked which depletes charge bit by bit. My lawn tractor sat for 1.5 years inside with likely zero idle current draw which likely never fully discharged the battery - it started right up on our return.


Quote:
Originally Posted by Nordic_Kat View Post
My concern was that the original to the car battery never even made it 4 years, much less 5 or 6 and the official line given me was that there were too many cycles logged by the car's computer where the car door was opened but not driven.

For the first three years I never had one iota of trouble, and I never did get a "low battery" indicator. Maybe the battery just had a bad cell that finally cratered

The one thing I've immediately noticed with the 'lock the car' practice is that there is no more random whirring 30 or 45 minutes after shutting the car off.

To OP:
what would be very interesting is to compare notes in about 4 years and see where things fall out.
Until lately virtually all my vehicles were new and sold within two years max (moved countries often). Since 2008 we've staying in the USA and have had:

. Honda CR-V : battery died a month before we'd owned it five years
. MX-5 : battery is fine at three years old (long stints of zero use)
. Lawn Tractor : its motorcycle battery may have died at seven years (turned out its ignition switch was faulty would leave the lights on)


Quote:
Originally Posted by CALWATERBOY View Post
Battery cable sensor is, best I can tell, a conventional battery charging chip to prevent destructive overcharging, undercharging, etc. For lead acid batts, a 3 stage charge is typical. Battery registration optimizes behavior/parameters.

Now, that wouldn't have much to do with when the alternator charges, likely controlled elsewhere based on engine state, as battery charging takes much longer than alternator cycles. Come the day we have air supercapcitive storage, maybe diff.

Complicated? You betcha! Keeps kids off the street, programming....
Soon I'll post a video in new thread about unnecessary over-complicated German engineering. Very simply circuitry can keep a battery slightly undercharged + prevent overcharge (my first degree majored in Microelectronics). If a low-end lawn tractor battery can last seven years expensive circuity is obviously not required - the entire machine on cost ~$1,800 including twin cylinder 750cc motor and hydrostatic transaxle!



Quote:
Originally Posted by bimmertech113 View Post
Most of what y'all are saying is true. BMW wants to maintain the battery at approx 80%. The newer vehicles will over charge on long decel to make up for small under charging while the vehicle is driving to save fuel.
As above: I am sure the complex battery circuitry in our BMWs is not really necessary. Look how many BMW owners on here are having battery issues.. likely it's counterproductive complexity.

Personally I have analogy in my own field of software engineering. While assisting a Fortune 10 company one of their mission critical systems kept going offline with terrible performance problems (CPU pegged for days and zero work done before timeout). My fix was effectively three lines of code... replacing an uber-complex cache that colleagues said the original coders had taken a patent out on! Sometimes internal politics make it impossible to stop such insanity.. probably that this happens inside BMW and Mercedes.
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Last edited by MP3_E46; 12-05-2013 at 07:09 AM.
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  #23  
Old 12-05-2013, 10:44 AM
fdriller9 fdriller9 is offline
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Originally Posted by MP3_E46 View Post
It's worth noting that when swapped out the BMW's battery had 43Ah according to my hillbilly testing (see pic). I keep in our garage charging with a CTEK every six months just in case any car needs jump starting + if we have a power-cut it will give a little power via an inverter for charging cell phones etc.
46Ah is the lowest capacity E9x models are equipped with from the factory. Highest is 110Ah.

I'm surprised your car was equipped with such a low capacity battery to begin with.

I had a 90Ah battery in my E90. Swapped it out for a 100Ah AGM, programmed, then registered.

Referring back to my comment about the vehcile only charging above 2k rpms....It is more of a guideline to follow. Charging varies based on engine load. The alternator will charge the battery when there is a light load on the engine which is normally above 2k rpms. This is normally highway driving. Stop and go traffic and short commutes put a higher load on the engine and thus the battery barely charges.
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Last edited by fdriller9; 12-05-2013 at 10:50 AM.
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  #24  
Old 12-05-2013, 11:41 AM
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MP3_E46 MP3_E46 is offline
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Quote:
Originally Posted by fdriller9 View Post
I'm surprised your car was equipped with such a low capacity battery to begin with.
That was the 'dead' battery. It provided 46 Ah driving an inverter that kept that light build lit until the inverter saw 'too low voltage' and shut itself down.

Presumably with only 46Ah remaining its voltage was not enough for the BMW. IIRC the original was 90Ah and so is what I replaced it with.

Desulphication cycle was ran a few times on it via my CTEK which probably boosted the Ah a little.
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  #25  
Old 12-05-2013, 11:50 AM
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need4speed need4speed is online now
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Originally Posted by fdriller9 View Post
Locking the car will allow the car to fall into sleep mode faster, which reduces electrical draw when the car if off. It will just take a bit longer for the car to fall asleep when you don't lock it.
+1. Also, why not lock it? If it doesn't help a lot, it surely does not hurt. N4S
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