[ferocity02]

I need to replace the battery in my 2007 335i. The stealership wants around $240 for the new battery. People have had success with the cheaper Walmart or Autozone batteries so I was going to give one a try. They also have good warranties, up to 5 years.

However, most of these batteries do not specify the capacity (Ah) which I would need to know for coding the battery. They do specify reserve capacity but I have not found a clear way to convert reserve capacity to capacity. It would appear to be more complicated than an equation.

I've seen a few methods... divide by 2, divide by 2 and add 16, multiply by 0.4167, etc. These all give different results, some may be simplifications of the others.

Anyways, here is the battery I'm looking at specificially: http://www.autozone.com/1/products/4...ld-h8-dlg.html

I would go with the Walmart H8 battery but they are out of stock, and the Duralast battery has a $20 rebate so it ends up being around the same price.

[ferocity02]

Bump!

[Tom K.]

If the dealer includes installation and registration in that $240, that's a very good price.

Tom

[Maranello455]

I would go with a genuine BMW factory one or Bosch OEM battery. Nothing else.

[El Cheapo Loco]

Originally Posted by Tom K.

If the dealer includes installation and registration in that $240, that's a very good price.

Absolutely no way that price includes installation and registration. I'm also a bit surprised you can get an OEM battery for "only" $240. Last I heard BMW had switched battery vendor and their batteries now cost over $350.

[ferocity02]

Originally Posted by Tom K.

If the dealer includes installation and registration in that $240, that's a very good price.

Tom

Originally Posted by El Cheapo Loco

Absolutely no way that price includes installation and registration. I'm also a bit surprised you can get an OEM battery for "only" $240. Last I heard BMW had switched battery vendor and their batteries now cost over $350.

$240 was the battery alone and includes a generous employee discount. Install and coding was another $200. I can install and code myself.

[ferocity02]

Originally Posted by Maranello455

I would go with a genuine BMW factory one or Bosch OEM battery. Nothing else.

That is usually my thought, but the Autozone and Walmart batteries have a 5 year warranty. Pretty sure you don't get any warranty on the factory battery. Maybe you do if they install it but even then it couldn't be more than a year or two.

These cars seem to eat through batteries so the warranty is a very nice perk.

[GATORB8]

I cannot vouch for the vendor but:
http://www.oemautopartsandaccessorie...60e6a1b2de4c5/

Matches:
http://www.realoem.com/bmw/enUS/show...diagId=61_1999

Also, although not all of them will do it, I've had Autozone match Walmart's pricing on batteries before, just showing the manager the walmart.com page on my phone.

[Wolfgang Schneiderhan]

Originally Posted by ferocity02

I have not found a clear way to convert reserve capacity to capacity. It would appear to be more complicated than an equation.

It is. There's no formula to precisely convert RC to AH, but you can calculate a rough estimate.

The Auto Zone battery had a Reserve Capacity of 185 (25 Amps for 185 minutes), so 25 X (185 / 60) is 77 Amp Hours.

[fazman]

Originally Posted by ferocity02

I need to replace the battery in my 2007 335i. The stealership wants around $240 for the new battery. People have had success with the cheaper Walmart or Autozone batteries so I was going to give one a try. They also have good warranties, up to 5 years.

However, most of these batteries do not specify the capacity (Ah) which I would need to know for coding the battery. They do specify reserve capacity but I have not found a clear way to convert reserve capacity to capacity. It would appear to be more complicated than an equation.

I've seen a few methods... divide by 2, divide by 2 and add 16, multiply by 0.4167, etc. These all give different results, some may be simplifications of the others.

Anyways, here is the battery I'm looking at specificially: http://www.autozone.com/1/products/4...ld-h8-dlg.html

I would go with the Walmart H8 battery but they are out of stock, and the Duralast battery has a $20 rebate so it ends up being around the same price.

* Where in the USA are you located?

* What is the RC and AH rating stamped on the top of your existing BMW battery?

* Is the oem battery you have now, does it have a black (AGM) or white (Non-AGM) color shell?

* Do you have access to a coding laptop or a coding cable?



Here is the nutshell of what your choices are:
1) If you get a replacement battery of the same type (AGM/non-AGM) and the same RC/AH value as your existing battery, then you don't need to code the car and battery registration is a nice to do (but not required) item.
2) If you get a replacement battery that changes either the battery type or the RC/AH value... then you MUST code the car for the new battery profile AND register the new battery.

[robthewrench]

Originally Posted by fazman

*
1) If you get a replacement battery of the same type (AGM/non-AGM) and the same RC/AH value as your existing battery, then you don't need to code the car and battery registration is a nice to do (but not required) item.

Any 'good' brand H8 or group 49 conventional battery will work assuming you are replacing a conventional lead acid battery. The CCA's will be very similar across all brands as it is mostly determined by the size of the battery.

Please don't give the dealer hundreds of dollars to replace your battery.

[fazman]

Originally Posted by robthewrench

Any 'good' brand H8 or group 49 conventional battery will work assuming you are replacing a conventional lead acid battery. The CCA's will be very similar across all brands as it is mostly determined by the size of the battery.

Please don't give the dealer hundreds of dollars to replace your battery.

that's not how you replace a battery in a modern BMW, that works for japanese or american cars... BMW's need either a like-for-like or recode for a different battery profile.

ferocity02 The formula you need to figure out is the battery AH rating:

AH = (RC /2) + 16
Round the AH number to the nearest 10's and that is what you should have your car coded to.

The possible profiles you can code your car to are the following:
60AH non-AGM
70AH non-AGM
80AH non-AGM
90AH non-AGM
110AH non-AGM

60AH AGM
70AH AGM
80AH AGM
90AH AGM
110AH AGM


My oem battery was a white shelled (non AGM) 90 AH / 160 RC battery if you use the formula above you will get:

AH = (160 /2) + 16
AH = (80) + 16
AH = 96

Wait Faz, didn't you just say your BMW battery said it was a 90 AH, your formula is wrong? No... 90 AH was stamped on my battery meaning that is what BMW wants me to CODE the car as a 90AH battery. No 100 AH battery profile exists, if you use rounding of the number 96 and have to choose a number that is closer to 96 between the choices of 90 vs 110... your answer is 90 AH.

That means my car came coded as a non-AGM 90AH battery profile.

I ended up buying a replacement battery from AAP using coupon code "HUGE50" to get $50 off $175. I got an H8-agm battery and then my friend PichaDis11 was kind enough to code it for me as a 90AH AGM. You can find a lot of remote coders who can help you setup your laptop and code you over the internet if you have a laptop and coding cable on your own. I then used smooth1 's free BMWLogger software to register my battery which took all of 2 clicks and .5 seconds to do.


note: coding the battery profile is one thing. But the better choice is to update the VO to use the correct battery profile. Because if you code the car only... and do not update the VO... if anyone ever resets the coding back to the VO or a blank MAN file... your battery profile will revert back to the setting that was in your VO.

[beto17]

No registration is needed i replaced my battery 2 years ago without a registration and no problems at all....

[fazman]

Originally Posted by beto17

No registration is needed i replaced my battery 2 years ago without a registration and no problems at all....

Were you option 1 or option 2 from my statement above?

[ferocity02]

Originally Posted by fazman

The formula you need to figure out is the battery AH rating:

AH = (RC /2) + 16
Round the AH number to the nearest 10's and that is what you should have your car coded to.

That equation does not work, or it's for a very specific battery.

Using the H8-AGM Duralast battery as an example, its RC is 170 mins and capacity is 92 Ah. But that equation gives a capacity of 101 Ah. Or if my reserve capacity is only 10 min, the equation would suggest the battery has 21 Ah...

If BMW is sourcing these batteries from vendors I don't know why they wouldn't put the exact capacity as an option for coding.

Might seem like I'm making a big deal about a few Ah, however people have reported their batteries exploded due to improper coding and/or not registering it. The correct values also help the battery management system optimize battery use and increase life span, or so I've read.

[mlifxs]

my walmart everstart max battery is now 4 years old, no hiccups. registered but not recoded. Johnson Controls would not give me a definitive ah but estimated around 75 to 80 iirc. Again, no issues without recoding for ah. perhaps recoding would maximize it's life.

only sites I've seen where ah are shown are Exide and possibly interstate.

[GATORB8]

So, looking a little harder.

Chatted AZ on the H8-DLG and he had no idea of the AH.
Chatted Pepboys on the Bosch H8-900B and she had no idea (said to talk to tech at store) - Bosch's website doesn't have the stat either


Walmart's H8 Everstart Maxx has a product expert Q&A response of 76 Amp Hours http://www.walmart.com/ip/EverStart-...ttery/16782659

Advance's AutoCraft Gold Part No. 49H8 has a product expert (named Panda) Q&A response of 90 AH
http://shop.advanceautoparts.com/p/a...597#fragment-1

[blackhawkk22]

Had my battery replaced a couple of weeks ago for $304 total. BMW 'approved' battery (whatever that means) with registration and coding. I forgot the brand but my bmw indy uses it because its good and comes with a 5 year warranty as long as you drive at least a thousand miles a month.

Dealer quoted me $700 for it.

[ferocity02]

Ok I'll probably just go with the Duralast H8-DLG and code it for 80 Ah.

[fazman]

Originally Posted by ferocity02

That equation does not work, or it's for a very specific battery.

Using the H8-AGM Duralast battery as an example, its RC is 170 mins and capacity is 92 Ah. But that equation gives a capacity of 101 Ah. Or if my reserve capacity is only 10 min, the equation would suggest the battery has 21 Ah...

If BMW is sourcing these batteries from vendors I don't know why they wouldn't put the exact capacity as an option for coding.

Might seem like I'm making a big deal about a few Ah, however people have reported their batteries exploded due to improper coding and/or not registering it. The correct values also help the battery management system optimize battery use and increase life span, or so I've read.

I don't think you understand what I am saying, let me show you with the battery you are describing.

Linky: http://www.autozone.com/1/products/1...um-h8-agm.html

Battery specs:
Part Number: H8-AGM
Amp-hour: 92
Application: Automobile
BCI Cold Cranking Amps (CCA): 850
BCI Cold Cranking Amps Value: Tested to BCI Standard
BCI Designation: 49
Cranking Amps (CA): 975
Reserve Capacity (min): 170


AH = (RC / 2) + 16
AH = (170 / 2) + 16
AH = 85 + 16
AH = 101 AH

This is what I would expect since my RC 160 battery was a 96 AH (10 RC / 2) = 5 AH difference

You could code that battery as a 110 AH AGM or 90 AH AGM (You will need to make sure if the 110 AGM settings is a valid profile, i think 110AH was only for non-AGM... but you can get all those details in the coding section of e90post).

[ferocity02]

Originally Posted by fazman

I don't think you understand what I am saying, let me show you with the battery you are describing.

What I'm saying is that specific battery (H8-AGM) is advertised as 92 Ah, but your equation says it should be 101 Ah. So either the manufacturer is wrong about their own battery, or your equation is not correct (or it does not apply in this situation). The difference of 9 Ah is not insignificant.

The argument for rounding up or down to the nearest code-able option is separate. I do not think any of us knows whether or not this was the intention when BMW was generating the coding options for battery Ah. Considering all BMW OEM batteries match the coding option exactly, seems to suggest this was not the intention.

[fazman]

Originally Posted by ferocity02

What I'm saying is that specific battery (H8-AGM) is advertised as 92 Ah, but your equation says it should be 101 Ah. So either the manufacturer is wrong about their own battery, or your equation is not correct (or it does not apply in this situation). The difference of 9 Ah is not insignificant.

The argument for rounding up or down to the nearest code-able option is separate. I do not think any of us knows whether or not this was the intention when BMW was generating the coding options for battery Ah. Considering all BMW OEM batteries match the coding option exactly, seems to suggest this was not the intention.

As for coding purposes, the solution is the same... you can code it as a 90AH AGM and call it a day and be happy that nothing will go wrong (I don't believe there is a 110AH AGM profile for our car... so 90+AH rating will always fall into the 90AH AGM profile coding).

Just like if you were to go buy a racing bike AGM battery like a braile 31 AH AGM... you can install it in your car and it will power your car. since the smallest profile available to code your car is 60 AH AGM... that is what you will code it as. It's a totally different story if you come complaining to me asking me why on a bitter cold night of 32*F your car won't start because it doesn't have enough CCA's to crank the motor