[fazman]

Originally Posted by ferocity02

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

Unless the battery you are pulling out of your car was an 80AH AGM battery... you do know you are going to have to recode the car. If you need to recode, you might as well find the biggest AH rated battery for your car that will fit in that space. (H8 size is the largest that will fit).

Now the question is... is an AGM better or a non-AGM battery better of the same AH? I have no answer for you on that one. I am experimenting with that myself. All I can say is my OEM 90AH nonAGM battery lasted me 95k miles and exactly 7 years before my first high discharge battery warning came on. The following week I replaced the battery with an AAP 90 AH AGM and in another 7 years or 95k miles I'll have my answer of which is truely better.

[ferocity02]

I have no problem coding and registering the battery. It's currently coded for a 90 Ah AGM, but the battery in it is 90 Ah non-AGM. So whoever installed the battery last time dropped the ball.

The Duralast AGM and non-AGM batteries have more or less comparable specs but AGM weigh more, cost more, and have a shorter warranty period.

No brainer to go with the non-AGM version IMO.

[robthewrench]

You probably won't have any issues if you are coded for the wrong amp hour profile. Remember the battery loses capacity over time anyway, so the charging cycle attempts to adapt to the new profile. This is why registering the battery can affect longevity. It tell the system to reset the profile and learn the new battery from the initialization point.

I would bet even the dealer will swap from an H6 to an H8 or vice versa and only register the battery, not recode it.

[drawz]

Originally Posted by ferocity02

I have no problem coding and registering the battery. It's currently coded for a 90 Ah AGM, but the battery in it is 90 Ah non-AGM. So whoever installed the battery last time dropped the ball.

The Duralast AGM and non-AGM batteries have more or less comparable specs but AGM weigh more, cost more, and have a shorter warranty period.

No brainer to go with the non-AGM version IMO.

Supposedly AGM is better for vehicles with lots of short trips, deep cycling, and rapid charging. They're also supposed to weigh less, but I can't say I've compared. When my battery is due for replacement, I plan to switch from FLA to AGM. Given the changes in how AGM should be charged, it does seem coding the car is important if switching battery types.

Here's are a couple articles for those interested in learning more:

http://batteryuniversity.com/learn/a..._glass_mat_agm
https://www.pepboys.com/car_care_cor...ntages_of_agm/

[drawz]

Originally Posted by Maranello455

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

There's only a small number of battery manufacturers - Exide, Johnson Controls, and Douglas, I believe - so there's really nothing special about BMW or Bosch branded ones. You won't get a "factory" one even from the dealer.

[fazman]

Originally Posted by drawz

Supposedly AGM is better for vehicles with lots of short trips, deep cycling, and rapid charging. They're also supposed to weigh less, but I can't say I've compared. When my battery is due for replacement, I plan to switch from FLA to AGM. Given the changes in how AGM should be charged, it does seem coding the car is important if switching battery types.

Here's are a couple articles for those interested in learning more:

http://batteryuniversity.com/learn/a..._glass_mat_agm
https://www.pepboys.com/car_care_cor...ntages_of_agm/

drawz you should dig in a little more about how AGM batteries work and if they like being charged at voltages above 15v?

You also need to research if non-agm batteries are commonly charged at over 15v?

hence the entire reason bmw put in "Charging profiles"

Also, non-AGM batteries don't like being below 11v... where as AGM batteries can be deep cycled (see charging profiles).

[fazman]

Originally Posted by drawz

There's only a small number of battery manufacturers - Exide, Johnson Controls, and Douglas, I believe - so there's really nothing special about BMW or Bosch branded ones. You won't get a "factory" one even from the dealer.

true, but they are all made to different specs and levels of quality. even if you buy a battery from one specific vendor and 6 months later go to buy the same battery again... it could be made by someone else and with varying warranty and specs.

[fazman]

Originally Posted by robthewrench

You probably won't have any issues if you are coded for the wrong amp hour profile. Remember the battery loses capacity over time anyway, so the charging cycle attempts to adapt to the new profile. This is why registering the battery can affect longevity. It tell the system to reset the profile and learn the new battery from the initialization point.

I would bet even the dealer will swap from an H6 to an H8 or vice versa and only register the battery, not recode it.

the dealer will update the VO and recode the car, then register the new battery. They will then extract money from you for doing it too.

[drawz]

Originally Posted by fazman

true, but they are all made to different specs and levels of quality. even if you buy a battery from one specific vendor and 6 months later go to buy the same battery again... it could be made by someone else and with varying warranty and specs.

It's much easier for the manufacturer to have one line for a given size. I highly doubt they are significantly different inside. The primary difference is in the warranties and pricing. Usually you pay more for the better warranty, but they all have sales.

[patents]

Originally Posted by fazman

the dealer will update the VO and recode the car, then register the new battery. They will then extract money from you for doing it too.

I bought a BMW battery from the dealer, installed it myself, and took the car back to have it coded and registered. I left the parts receipt on the seat so they would know exactly which battery I bought. I specifically asked for coding and registration. The new battery was different than the original (non-AGM vs. AGM)

Not long after I was having someone code some features into my car, and I had them check the battery coding. Sure enough, the dealer didn't code the battery, they only registered it. It was still coded as an AGM battery.

Regarding battery specs, the reason I got a BMW battery was because I couldn't find any other battery that published their Ah specs.

[fazman]

Originally Posted by patents

I bought a BMW battery from the dealer, installed it myself, and took the car back to have it coded and registered. I left the parts receipt on the seat so they would know exactly which battery I bought. I specifically asked for coding and registration. The new battery was different than the original (non-AGM vs. AGM)

Not long after I was having someone code some features into my car, and I had them check the battery coding. Sure enough, the dealer didn't code the battery, they only registered it. It was still coded as an AGM battery.

Regarding battery specs, the reason I got a BMW battery was because I couldn't find any other battery that published their Ah specs.

Go back to the dealership and ask them for your money back. They are professionally trained people who are suppose to known your BMW the best. but it seems like they failed you. They were suppose to update the VO, so even if your coder blows away your settings with a blank man file or resets it back to the VO... you will still be fine. But now you are in problems. A battery registration does nothing for you other than clear history data and records the mileage at when you registered the battery (its all for audit/logging purposes... has no performance impact).

[MrSmileyDC]

I used this one http://www.tristatebattery.com/9agm4...ry-p-1321.html

[VXEric]

I'll throw my $0.02 in here to clear up some confusion/offer some knowledge.

Reserve capacity is the runtime minutes at a constant 25A discharge to a voltage of 10.5V. The formula used to calculate Ah from RC is: RC (minutes) x 25 (amps) / 60 (minutes/hour). So if you had an RC of 180 Minutes, you would calculate 75Ah.

BUT

The Ah rating of a battery is completely dependent on the discharge time. So a battery could have an Ah capacity of 75Ah over 3 hours, 100Ah over 8 hours and 110 Ah over 12 hours. In the case of coding the car or rating a battery for the label, the Ah capacity is based on "nominal" rating which is either based on a discharge of 8 hours to 10.5V @ 77F (USA) or 10 hours to 10.80V @ 20C (Europe, also called IEC rating)

There is no way to convert your RC to the nominal Ah rating accurately. That relationship is a function of the plate size, shape, thickness, specific gravity and construction of the battery. No two battery sizes, manufacturers etc will share the exact same relationship between RC and Nominal Ah capacity. The equation used earlier in this thread is an approximation that may work in some cases, but I have no idea what the thinking behind it was.

If you are bored, look up Peukert's law, it explains why the Ah capacity of the battery changes based on discharge rate/duration.

As far as construction goes, most of what was said is fairly accurate. AGM type batteries for the most part will cycle better than a standard (flooded) type. AGM tends to be heavier than flooded and also has higher capacity than its flooded counterpart. The main reason behind that is because AGM batteries have more plates in the same space. The cells within the battery are under 20-30% compression to force contact between the AGM separator and the plates, so you have more plates in the same space. That means more weight and more capacity.

When it comes to charging, the recommended charging voltage is based on the specific gravity of the battery acid. Standard automotive batteries are around 1.265 specific gravity, typical AGM batteries are higher (1.300+). AGM batteries would normally get charged at a higher voltage because of the higher specific gravity. 14.4V is pretty common for AGM batteries

That said, AGM batteries are generally more prone to damage from overcharge and over-discharge conditions because the separators are actually quite fragile and can be damaged by plate growths that occur during over discharging or dry out from continuous overcharge.

It's also true that there are only a few battery manufacturers (though more than three). Many "private label" batteries have their own unique design elements, but the manufacturing process/quality control procedures remain largely unchanged between different models made within the same factory. What could change are the materials, specifically the grid alloy and plate paste formulation which plays into longevity and performance, hence the differences in warranties and performance.

In case you're wondering, I am the technical training manager and product manager for a very large lead acid battery manufacturer. (no, we don't make batteries for BMW, and no I can't get you a discount)

[ferocity02]

I went into Autozone today to grab the H8-DLG battery and on the label is lists Reserve Capacity at 150 minutes, not 185 like it shows online. This is much less than OEM...

Their H8-AGM shows 95 Ah on the label, and 92 Ah online.

They need to get their shit together.

Needless to say I did not get a battery today. Will continue looking around.

[ferocity02]

Decided to go ahead with the Autozone H8-DLG battery and coded the CAS module for 80Ah. It fit perfectly. Comes with a plug for the unused vent hole, or use the plug from the stock battery.

So far so good! It starts a lot easier than before, and now my comfort access doesn't disable itself after sitting for a few minutes.

I was also getting IBS codes and "clamp 15", whatever that means, but I search suggested it was due to a bad battery. Hopefully they don't come back.

[Kaz26]

I recently went with the biggest Ah H8 battery I could find for a reasonable price and it happened to be the Bosch H8-900b since it was on sale. It lists its Amp hour rating at 107Ah. I registered the battery with the 110Ah option, but now I'm concerned that it might get overcharged. I read of someone else doing this and they didn't post back that there was any explosion or short life and it was posted 5 years ago, so I'm probably ok, but I'd like to get some more input.

I didn't really want to use the 90Ah option since it's nearly 16% undercharged at that rate and that seemed worse to me than overcharging it by 2.8%.

Thoughts?

[401FlaGATOR]

Originally Posted by Maranello455

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

I'm on my 2nd H8 from Walmart. The first one lasted 5 years.

[401FlaGATOR]

I never input the AH into the system, just registered the battery with my Bavarian Technic tool. The Walmart battery lasted 5 years. Just bought the same model H8 from Walmart again 2 weeks ago.

[401FlaGATOR]

Originally Posted by Kaz26

I recently went with the biggest Ah H8 battery I could find for a reasonable price and it happened to be the Bosch H8-900b since it was on sale. It lists its Amp hour rating at 107Ah. I registered the battery with the 110Ah option, but now I'm concerned that it might get overcharged. I read of someone else doing this and they didn't post back that there was any explosion or short life and it was posted 5 years ago, so I'm probably ok, but I'd like to get some more input.

I didn't really want to use the 90Ah option since it's nearly 16% undercharged at that rate and that seemed worse to me than overcharging it by 2.8%.

Thoughts?

I doubt you will have trouble, lead acid batteries charge is detected by measuring the voltage of the cell at a certain temp. So regardless of the amp hour capacity of the battery once the voltage rises high enough, the charge circuit will determine that the battery is fully charged. The amp hour variable may be utilized to adjust maximum charge current and may be utilized to determine charging efficacy and calculate watt hours remaining during discharge. A difference of 10 to 15 AH will probably not matter much. Of course this is purely speculation.

[bufasion]

Originally Posted by Kaz26

I recently went with the biggest Ah H8 battery I could find for a reasonable price and it happened to be the Bosch H8-900b since it was on sale. It lists its Amp hour rating at 107Ah. I registered the battery with the 110Ah option, but now I'm concerned that it might get overcharged. I read of someone else doing this and they didn't post back that there was any explosion or short life and it was posted 5 years ago, so I'm probably ok, but I'd like to get some more input.

I didn't really want to use the 90Ah option since it's nearly 16% undercharged at that rate and that seemed worse to me than overcharging it by 2.8%.

Thoughts?

6 years ago I replaced the factory battery with a Walmart Maxx-H8 and purposely did NOT register the new battery. Now I'm back to tell you what happened to the battery:

Absolutely nothing.

In fact, the Walmart battery has outlasted the factory one by a year now.

I've observed the charging voltage on long trips. The battery receives a higher voltage at the beginning of a trip. As the trip progresses the charging voltage gradually drops to barely charging at all. This is not limited to BMW only. I suspect all modern cars with ECU-controlled alternators do this to increase fuel efficiency, but never heard any other brand needs to "register" a battery.

[Efthreeoh]

I replaced my original factory battery at 5 years and 5 months and 158,800 miles. I replaced it with the same OE BMW battery. The original battery wasn't bad per se, but I did have one instance of a low battery warning and I could get the new battery free of charge at the time, so I replaced it. I registered it using the Bav Tech tool.

I'm still on that second battery 6 years 3 months and 183,000 miles later. The current battery cranked over my ancient well used engine those last few weeks ago when the temp was 1 deg. F here in good ole' Virginia (on the original starter too).

As for the original battery, I've kept it on a battery maintainer for the past 6 years, and it'll jump start my diesel tractor when asked. In December 2016 when my alternator went tits up and I barely got home on battery, I had to swap in the old original battery to get my car over to the garage when I did the DIY to replace the alternator.

When these cars lose an alternator, they don't go very far on just the battery supplying juice. My car went only about 23 miles. It was cold so the heat was on and raining so the wipers and lights were on. By the time I got home I had to shut the heat down, turn off all the lights, and the wipers were in slow motion and stopped in the middle of a swipe as I was pulling into the compound.

[LilBari]

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