Pictorial discussion of charging, testing, removing, & replacing the BMW E39 battery by bluebee

By diyauto
( 2 )

34 minute read

Pictorial discussion of charging, testing, removing, & replacing the BMW E39 battery

Compliments of bluebee @ bimmerfest.com


This is intended to be a pictorial thread, showing the steps to remove, test, charge, and replace the BMW E39 battery.

[WARNING] This may be too detailed for some for such a simple task! [ / WARNING ]

Note: For how to actually perform an exhaustive battery test, see detailed procedures here:

DIY how to test a BMW E39 battery & alternator

For one reason WHY you'd want to test your battery, see details here: 

Warning: I charged my battery today & apparently killed my instrument cluster & MID

Even the MID lost it's clock:

So, today, after Autozone tested the battery, in situ, and found the following:

1. The charging system was good

2. The starting system was good

3. The battery was bad

I decided to remove the battery and charge it OUTSIDE the vehicle (far far far away from the vehicle!) ...  and then to test out the procedures listed in the how-to-test-a-battery thread, one by one, in exhaustive detail (for the team).

The first step is to loosen the 10mm nut on the negative battery cable & pull the cable loose; then do the same for the positive cable:

Next step is to remove the 13mm bolt that holds the cross brace to the fender well, and the 13mm bolt that holds it to the floor of the trunk.

Notice I used the brace to short the 'cables' and 'almost' shorted the terminals! That would be a very bad thing!

Then remove the 10mm hold-down clamp bolt from the tail end of the battery.

HINDSIGHT WARNING: At this point, I had completely forgotten about the vent!

So, what I did was try to lift up on the battery handles:

Yeah, right! That thing is HEAVY! 

I could not, for the life of me, lift the battery directly upward! So I tilted it to the rear and tried to nudge it up, ever so slowly one end at a time.

Eventually, I had tipped the entire thing on its end! 

I don't think this is the proper way to remove it, but, it was the only way I could!

Note: I didn't realize it at the time, but the vent, still attached, must have had something to do with the problems I was having!

Eventually, I muscled the thing out of the vehicle!

Note: Reading "1 Stuck Piece" on the BMW label gave me a laugh!

With the battery out of the vehicle, for the first time, I could 'see' the green hydrometer in cell #2, and I could see there was no date stamp on the negative terminal (after brushing off the oxidation with a wire brush).

Looking below, I happened to notice the washer that was under the hold-down clamp bolt ...

So as not to forget it, I placed the washer back on the hold-down clamp bolt:

And, I replaced the hold-down clamp in its original position (as I lose bolts if I don't put 'em back right away).

I looked for the six cell caps, but didn't see any on the top:

The side view told me the manufacturer was "DBMC, Winston - Salem, North Carolina", which turns out to be Douglas' consumer line, which was (apparently) purchased by East Penn Batteries (details here).

Looking all over, I couldn't find a date stamp. Maybe this engraving is the date, hidden in battery code?

  • DB0412160806

Getting to the hidden caps was as simple as peeling up the sticker ... 

Even with a green hydrometer, the battery tested at around 10.5 volts, so I put the battery charger on. Guess what. It pegged (again) at something higher than 6 amps.

Yet, the DC voltage was only 11.40 volts, with the charger running (I expected higher).

Suddenly I had the bright idea of checking amperage (maybe the gauge was wrong on the 25-year old charger) ... so I pulled out my Radio Shack ammeter ... 

But, I soon realized that ammeter probe was only for AC current, so, after about a half hour, the amperage on the charger meter lowered somewhat and I felt I could risk the Fluke 75 on the 10amp setting. 

By now, the charger was reading about 6 amps, which jived with the Fluke DC amperage reading.

At some point, the VOLTAGE on the fluke wouldn't read; it just showed as overloaded. I wasn't sure what that meant (and I didn't snap a picture because I didn't believe the reading)... but ... maybe ... just maybe ... the charger has an intermittent high-voltage spike???

Anyway ... this picture shows why a sharp awl was a 'bad idea'. Do not use a sharp awl to twist the caps out!

For one, the caps don't twist out. For another, you'll puncture the super-thin plastic of the head of the cap, and, well, I'm sure that would allow electrolyte to evaporate out in the wrong way.

Giving up on spinning the caps out (they don't spin out), and on the sharp awl (I punctured the cap head), I used an 1/8th inch screwdriver. I really needed something thinner, but that was all I had. 

No matter how careful I tried to be, the cap chipped at the edges.

With all six caps off, I checked the fluid levels and noticed some were below the plastic L-shaped level indicators:

So I got the bright idea of using a 1ml eyedropper to fill but after fifteen of those, I gave up and moved on to a 10ml graduated cylinder to measure how much water was being poured in.

The amount of fluid added was:

  • Cell #1 = 15ml

  • Cell #2 = 15ml

  • Cell #3 = 15ml

  • Cell #4 = 60ml

  • Cell #5 = 20ml

  • Cell #6 = 30ml

I wonder if tipping the battery on one end had anything to do with the top end needing more water than the bottom?

I decided to run out to the store to buy a hydrometer, but, by the time I got the bright idea, it was dark and the stores had all closed.

So, on my trusty computer, I googled to search for decent battery replacements.

What I did wrong was I didn't realize a seach for a "2002 BMW 525i battery" would NOT get the cheapest batteries!

Almost all the batteries were in the 150 dollar range!

What I 'should' have googled for was any decent battery of the following specifications:

  • Group 49 (aka DIN H8)

  • or Group 95 (aka DIN H9)

Not knowing that, at the time, here's what I put into Pleiades' thread 'before' I realized my whole car-specific approach was wrong:

E39 (1997 - 2003) > Good Replacement Batteries for the e39?


Originally Posted by bluebee 
Following your advice, and doing additional research (so others benefit from the results), I find these batteries are listed as fitting my 2002 BMWS 525i sedan:

Pep Boys:
  • PB/Johnson Controls PJB

    1. $105+ 9% tax, Bosch 49-850B, 850CCA, 140 RESERVE MIN

    2. $155 + 9% tax, Bosch 94R730B, 730CCA, 140 RESERVE MIN

    3. $200 + 9% tax, PS Platinum 95R850PP, 950CCA, 110 RESERVE MIN

Napa Auto Parts
  • $256 + 9% tax, Napa Legend International, BAT 7595R, 850 CCA, 190 min reserve

  • $144 + 9% tax, Napa Legend International, BAT 7549, 900 CCA, 185 min reserve

  • $235 + 9% tax, Napa Legend International, BAT 9849, 850 CCA, 170 min reserve

  • $169+ 9% tax, Napa BAT 8449, 900 CCA, 185 min reserve

O'Reilly (Kragen)
  • $157 + 9% tax, Super Start 94REXTJ, 765 CCA, 140 AH reserve capacity

  • $165 + 9% tax, Super Start 95R72J, 110 AH reserve capacity

  • $155 + 9% tax, Duralast Gold 94R-DLG, 730 CCA, 140 min reserve capacity

  • $167 + 9% tax, Duralast Gold 95R-DLG, 850 CCA, 110 min reserve capacity

  • $125 + 9% tax, Duralast Gold H8-DLG, 760 CCA, 100 min reserve capacity

  • (prices not available on the Firestone web site), Interstate Mega-Tron II (specs not available on the Firestone web site)

  • (prices not available on the Firestone web site), Interstate Mega-Tron Plus (specs not available on the Firestone web site

  • (no price on the web site) Rayovac Maximum SLI94RH7M, 790 CCA, no reserve listed [Replaces: 694RMF, MTPH7, SLI94R-LI, SLI94RH7-MERGE06252011]

  • (no price on the web site) Rayovac Maximum SLI49H8M, 900 CCA, no reserve listed [Replaces: 649MF, MTP93, MTPH9, SLI49-LI, SLI49H8-MERGE06252011, TY25224]

Sites that failed to bring up any batteries for a 2002 BMW 525i:
  • Walmart (the Walmart California sites brought up ZERO batteries!)

  • Sears (they didn't have the right size)

  • Target (nothing came up)

  • Costco (they don't have the right size but that's not listed on their web site; it's listed here)

    • Costco California, Kirkland Auto Batteries

Who'd have thought a car-specific search would be the wrong way to do it, but, I only realized that after the only two decently priced batteries that came of the search were:

  • $105 + 9% tax, Bosch 49-850B, 850 CCA, 140 reserve minutes (Pep Boys)

  • $105 + 9% tax, Duralast 49-DL, 850 CCA, 150 minutes reserve capacity (Autozone)

And, even then, the Duralast never showed up in that search (because, technically, it's the 'wrong' battery for the E39).

Originally Posted by Fudman 
So, was the battery the cause of your cluster problem?

I don't know yet.

The first thing I did was check the battery because charging the battery was the precipitating event to the cluster blowing out.

Since I like to learn about what I'm doing, I'm still on the topic of the battery.

I did digress a bit to start to check the fuses. The only fuses I've checked so far are those next to the battery in the trunk.

I put the (confusing) trunkbox fusebox information in this existing thread:

- Need help with location of the fuse boxs and overview of fuse positions for 528i?

For fun, I painstakingly annotated this picture of my fusebox, showing exactly which fuses I had in place, so that others may benefit:

I can't easily check the glovebox fuses at night, and my garage is so stuffed I can't open the passenger door; so I will wait until a good battery is in to see what the glovebox and ebox and under-seat fuses have in store for me!

BTW, one question I asked in that thread was:

Q: What is the "onboard monitor" (and could it possibly affect the instrument cluster display?)

Originally Posted by JimLev 
too long for me to sit thru

Hi Jimlev,

This thread is a pictorial thread, just about the battery, as I like to take things one at a time and have some fun (and learning and teaching) with it.

The 'real' problem-solving thread is this one, as you alluded to:

Warning: I charged my battery today & apparently killed my instrument cluster & MID

But, for here, this is the response:


Originally Posted by JimLev 
was the charger voltage ever read?

Many years ago, I had placed it on an oscilloscope and engraved on the back what I found (which was a 17-volt wave, peak to trough, above ground), at 12 volts RMS at 120 Hz being the output. Clearly there is a simple wheatstone-bridge like diode arrangement that flips every other oscillation of the 60 Hz input. There was a 25 Hz +/- 1.175 volt AC component superimposed on the DC (i.e., 41.5 msec in period); so it's not a "clean" waveform, by any means ... but it is sufficient to charge batteries for vehicles in the 'olden days'.

I no longer have access to an oscilloscope, but the RMS readings from my decades-old Fluke 75 bear out that the charger is apparently still working to spec.

Without the battery in the loop, the 25-year-old half-wave charger reads 12.52 volts RMS, open circuit. 

I bounced the unit around and it still read the same (I shook it and tugged at all the wires).

The battery, after charging since about 6pm (almost 12 hours), still reads only 11.39 volts (so it's obviously not taking a charge).

When I hook the charger to the battery, the battery climbs from 13 volts to about 13.3 volts (give or take as it bounces a bit & climbs slowly).

And, the current on the meter seems to be accurate based on the Fluke DMM doublecheck:


Originally Posted by JimLev 
Turning the key on seems like it might have been what killed things.

I don't remember if I left the key on when I was charging it. I don't think I did. 

I had left the key on after I checked the mileage on the odometer; and that's what (I thought) killed the battery.

But now, I simply think leaving the ignition on just clued me into the fact that I had a suddenly-bad battery.


Originally Posted by JimLev 
I always charge the battery while it is connected, never had a problem.

In the past, so did I. Now that I may be facing a very expensive (and tedious) repair, I'm not so sure I would recommend that moving forward. 

What I need now to do, when it gets light, is to check the rest of the fuses - but that's for a whole 'nuther thread! 

Originally Posted by dvsgene 
If history is any indication, I don't think the BB exhaustive investigation is complete yet until an autopsy has been performed

You know me well! 

I WANTED to do an autopsy. I really did! 

But, they insisted they wouldn't give me back my core charge if I didn't (and, worse yet), they said I'd end up polluting the environment.

So I gave them back my old battery, in trade for the Duralast 49-DL! 

Here they are, on the showroom floor, side by side, for a size comparison.

The goal is to learn as much as possible & to teach (with photos) as many as possible

Originally Posted by dvsgene 
So did you ask them why the silly website says "Does Not Fit'?

Again, you know me well.

Of course I asked them WHY.

The counter guy wasn't sure, but, he surmised it was because it 'was' smaller in height and length (if only slightly); and, more importantly, it has the vent hose in entirely the wrong position. 

In fact, when you install the vent hose adapter that comes with the battery, and then when you put the battery in the vehicle, there is a VERY GOOD CHANCE that the vent hose will collapse unbeknownst to the owner (unless he's aware of this) ... 

This is due to the geometry of the battery compartment, where a plastic piece juts out exactly where the collapsible vent hose lies. 

So, it 'is' a bit dangerous if you're not aware of this misfit.


Originally Posted by AnotherGeezer 
I just had AAA come out and replace it

Just to be clear, the goal, in this case, isn't just to fix the problem and move on. 

I'm not saying there's anything wrong with single-minded goal of just fixing it ... but I was trying to both re-write the battery-testing DIY (which I did rewrite based on this experience) and learn from the endeavor. (EDIT: I have plenty of time & the weather out here is phenomenal, day or night, so it's a tropical paradise compared to what some of you have to deal with when testing YOUR batteries!).

Here is a picture, of the problem fixed, for example:


Originally Posted by dalekressin 
the Duralast battery replacement took me ~20 min

It's worth repeating that the goal here isn't to just fix the problem. That's what mechanics do. Day in and day out. Nothing wrong with that. But that's no fun. 

If I thought 'that' were fun, I'd be a mechanic!

I'd bet they don't take pictures of every step, analyze all their options, experiment, research, ask questions, autopsy, and report back and discuss every minute detail. Do they?

I'm trying to learn as many things as I can, and to show others as much as I can. Yes, even the mistakes are instructive.

Here, for example, is the vent hose highlighted that I overlooked when I had removed the original battery:

Since the Duralast vent opening is in the center of the battery, far from the end of the vent hose from the BMW, it wasn't obvious to me, before I did this, HOW that, rather rigid, vent hose was going to reach the middle of the Duralast battery. (Is it obvious to you?)


Originally Posted by Fudman 
looks like your battery is dead

Absolutely no doubt the battery is dead. Actually, I knew that already because I had stopped by Autozone (sans camera, unfortunately), the day before to have them test it in situ. I wrote up all the steps they performed in the how-to-test-a-battery DIY, so others would benefit.

Knowing the battery is bad shouldn't stop us from having fun learning as much as we can. Especially since our DIY for testing the battery was so lousy before I updated it, based on all the steps performed here (so others benefit, as always).

BTW, here's the Autozone hand-held unit that showed the battery was bad in vitro. I watched the guy input the temperature (he simply guessed), append the CCA (for the load), and add few other variables before running his tests.


Originally Posted by dvsgene 
until an autopsy has been performed.

You know me well! 

I wanted to do an autopsy. It would be fun. But the counter guy talked me out of splashing H2SO4 all over myself! 

He told me it's illegal to cut open the battery and not dispose of it properly. And that I'd lose my core charge (although it was only 12 bucks). I hesitated, but, then I just let him have it. Afterward, I felt badly, giving up my redox reaction science experiment so easily ... without a fight.

At least I got a chance to watch and ask questions while he tested it. Here he puts it in a covered 'bomb-proof' door, just in case it explodes under test. Rest assured I made him test the new one too! 


Originally Posted by AnotherGeezer 
Exhaustive being the key word in that statement.

This thread is intended to show a newbie all the steps. 

I'm always amazed how much must be 'obvious' to you guys that isn't at all obvious to me (like how to make the BMW vent hose, that only reaches to the side of the battery, reach to the MIDDLE of the new battery).

Like this:


Originally Posted by piperguy 
I would've been at the battery shop, back, had a new one in and on to another project "days ago"

I ask these rhetorical questions nicely ... to prove a point:

  • Q1: How many DIYs have you written for the team?

  • Q2: How much research have you summarized, for the team?

  • Q3: How many parts autopsies have you reported on for the team?

  • Q4: How many tough BMW problems have you helped solve & report on for the team?

  • Q5: How many relatively easy BMW problems have you made even easier for others to solve by documenting what to do, and more importantly, what not to do?

  • etc.

Point is, the goal isn't to just solve the problem and run. That's what mechanics are for. 

The goal is to have fun; LEARN as much as we possibly can; and to TEACH as many as we can.

If all we wanted to do was solve the problem, then I wouldn't be snapping pictures inside an Autozone to give the users an idea of what it's like testing the battery there. 

I'd just pay my $115 to Autozone at the counter, and be done with the entire job! 

Like this! 

Originally Posted by dvsgene 
So has the coroner determined how long the battery lived before dying of sudden electrocution?

That was the third battery for this vehicle. Two BMW batteries, and now, the Duralast.

The dead BMW battery was put in about six years ago, by the dealer, as far as I can remember.

This time I wrote on the battery the date, and I even included a copy of the receipt, taped to the side, for future reference.

For the record, these next pictures show why, I think, Autozone shows the Duralast 49-DL as NOT fitting the BMW E39:


Originally Posted by AnotherGeezer 
In this situation I think you're confusing "simple-minded" with "single-minded".

I agree. I'm sorry for the connotation my words may have conferred. My fault. I changed it in the prior post from simple-minded to single-minded & I added that the weather out here is tropical, day or night, and that I have a LOT of time (not having worked for almost two years). That's how I can spend the time (it took hours) to fix the battery-test DIY so others can just follow the procedure.


Originally Posted by AnotherGeezer 
Ever change a battery in sub-freezing weather, at 6am, right before work?

I lived in the east coast for decades. I 'know' what reasonably cold weather is like. It's miserable! Aluminum door handles break off in your hands; keys won't go in the ignition; you drive your first few miles peering through the blinds of ice & snow melting off the windshield; the days are short and the nights are freezing; you can't use proper gloves so the tools stick to your hands. The ferocious wind & freezing temperatures make everything, even simple things like debugging a battery, a disconsoling task. It's so much more fun here in California for doing work outside, any time, day or night, winter, or summer. About the worst that happens here is that drizzly rain for weeks on end accompanied by a warmish wind from the ocean. People out here call 'that' a 'storm'. 


Originally Posted by AnotherGeezer 
Why buy a membership to AAA if you don't use it?

I've used AAA many times!


For the record, we're still not done, because there is a very real danger that the Duralast 49-DL battery vent tube 'can' get pinched between the very heavy battery and the hard plastic protrusions on the side of the battery compartment. 

That would be a very bad idea (see this thread if you don't know why).

So, by way of being excessively clear in a DIY, if you're going to put the 'wrong' battery (technically) into your E39, at least make sure the venting tube extension elbow isn't pinched.

See details starting from post #96 here:

E39 (1997 - 2003) > Good Replacement Batteries for the e39?


Originally Posted by pleiades  
The positive terminal plastic cover on the original BMW batteries will fit into the Duralast battery because the "feet" have the same spacing

Here is a picture of the 'feet'. The spacing is very similar although the more substantial BMW positive terminal cover is better built all around. 

I found it only slightly difficult to press fit the little feet into the holes in the Duralast 49-DL battery - but overall - it's a much nicer component than the flimsy Johnson Controls piece.

Originally Posted by pleiades  
but the original BMW version has a gap that I found useful to channel the Duralast vent hose across the terminal and through and into the car-side hose.

Hmmmm... I don't see what you're talking about - but - I do see that the BMW positive terminal cover is muuuch more undulate than the cheaper flatter Johnson Controls cover.

Would you kindly snake a drawn arrow where you're suggesting we route the flimsy battery vent tube (this will help me, and also everyone to follow in our footsteps - so it should be worth the effort):

Originally Posted by QSilver7  
shortens the distance from the battery's vent hole to the side of the car...and allows the tube to amble over to the car's vent tube.

That idea should work!

Notice in the picture above and in the picture below, the elbow of the Johnson Controls battery vent tube extension is pinched by the plastic sides of the BMW E39 battery compartment.

I understand what you say and will see if I can shorten the battery side of that flexible elbow, in the hopes that it prevents it from being pinched (for others, please look here for what happens if the vent tube isn't venting).

Originally Posted by QSilver7 
Here's a pic of the OE cap that covers the positive battery cover...installed on a Duralast 49 DL.

And, here's a QSilver7 picture of a similar (maybe even the same?) battery showing that the Duralast 49-DL vent elbow isn't pinched in all cases; at least this QSilver7 picture seems to show slightly more room for the elbow than I seem to have in my battery compartment.
E39 (1997 - 2003) > Battery Weak found Replacement

Originally Posted by QSilver7  
Nice find. Just go back and make sure...positively make sure...that they INSTALLED THE VENT tube to the battery. You do NOT want to be driving around with the battery NOT vented. If it's an EXCIDE mfg'd battery, then the battery's vent hole should be on the side of the battery like the original BMW battery that was installed. So you won't be able to see it because it's on the side of the battery by the positive battery post. If it is a Johnson Control mfg'd battery...then the battery vents from the top center (like the Duralast pictured below).

While we're on the topic of what not to do when replacing the BMW battery with the Duralast 49-DL, see this warning from cn90:

E39 (1997 - 2003) > 2003 530i battery dead today...


Originally Posted by cn90 
Couple things:
1. Charge your battery then go to local Autozone and get a new Duralast 49DL for $80.
There are a few Autozone in Omaha NE where you live.

2. The DIY is here, all you need is 10-m wrench. Pay attention to the hold-down rod and retaining bar (on top). Watch the existing setup and copy it:

3. Last but not least, do NOT overtorque the 10-mm nut. If people ever break that particular battery T-bolt (shown below), then read this thread and buy VW part:
Positive battery cable T-bolt:
PN: 6X0-915-138


Originally Posted by dvsgene 
although it may be common sense, press down on the clamp until fully seated before tightening the nut.

Since this is intended for newbies (I can't write any other DIY), that advice is apropos.

BTW, for closure on modifying the vent tube setup of the Duralast 49-DL so that it fits in the E39, pleiades & QSilver7 kindly showed me, over here in post #100, how best to route the Duralast 49-DL vent hose and/or to cut the last ¼ inch off the battery vent tube extension elbow so that the vent tube isn't squished between the heavy battery & the rigid vent grid on the side of the vehicle.

Here, for example, is Pleiades' method of routing the vent hose (notice the re-use of the original BMW positive terminal cover as this won't work with the flimsy Duralast terminal cover):

And, here is QSilver7's method of snipping off the last ¼ inch or so of the elbow so that it isn't kinked:

See also:

This post #20, from today, shows yet another way to route the vent tube when retrofitting the Duralast 49-DL into the BMW E39:

E39 (1997 - 2003) > Battery Voltage

  • Pleiades' way (up over the top & then under the positive battery cover)

  • QSilver7's way (cut 1/4" off the vent tube extension elbow)

  • Monkeyking's way (up over the top and into the cell-cap groove)


It may be sophomoric to note I read, with a certain weak satisfaction, that I wasn't the only one here who had a difficult time getting the battery out of the trunk! 

E39 (1997 - 2003) > Question about alternator, 02 530