Battery sizes

[BAK613]

Most of the major auto parts websites specify a H5 or size 47 battery for my M Roadster. My last battery, from Autozone an H5, was too small.

On the posted spreadsheet, I see sizes from H5 to an H7 (wow!).

I'm specifically interested in the NAPA battery https://www.napaonline.com/p/NBE9848 (size 48) but does not come up as M Z4 compatible on their website. Albeit they don't allow you to distinguish between a Z4 and an M Roadster.

What are the correct sizes for the M Roadster.

Thanks
Bruce Kaplan

[garz747]

H6 is a euro equivalent to group 48. I would recommend you go with AGM type for our cars.

[StickMon]

^WHS.
Yes, I've also found that all of the auto parts chains have it wrong.
H5 is too small for an ///M.
H6 is stock.
I hear H7 fits, if you want to go big.
The Battery Options Summary Listing may be a worthwhile, albeit long, read.

[chickdr]

Originally Posted by garz747

H6 is a euro equivalent to group 48. I would recommend you go with AGM type for our cars.

IMHO no difference at all in standard vs AGM. My original AGM battery lasted 5yrs(06-11), my second battery was LA and lasted 5yrs too(11-16). Now on my third which is an LA again. No need to spend the extra $$$ to me.

[XMetal]

Originally Posted by chickdr

IMHO no difference at all in standard vs AGM. My original AGM battery lasted 5yrs(06-11), my second battery was LA and lasted 5yrs too(11-16). Now on my third which is an LA again. No need to spend the extra $$$ to me.

It's not a matter of how long it last. As you've found out that both AGM and LA usually have the same lifespan. It's about packing more reserve charge. For example, you should compare what your voltage readings are between AGM and LA when left sitting the same amount of time. I can let the car sit longer without needing to put a tender on the battery with an AGM.

Of course, if you daily drive it, then it makes no difference. That's why there is no one generic answer to this question - it all depends on the application (how you use the car - daily driven vs weekend vs special occasions vs track, etc., etc.)

[antennahead]

Originally Posted by XMetal

It's not a matter of how long it last. As you've found out that both AGM and LA usually have the same lifespan. It's about packing more reserve charge. For example, you should compare what your voltage readings are between AGM and LA when left sitting the same amount of time. I can let the car sit longer without needing to put a tender on the battery with an AGM.

Of course, if you daily drive it, then it makes no difference. That's why there is no one generic answer to this question - it all depends on the application (how you use the car - daily driven vs weekend vs special occasions vs track, etc., etc.)

^ My experience as well. When I drove it daily, I had no issues. Early retired and the car might sit for a day or two or three, and the driving distances are much shorter on average now. LA would not hold the charge long. I got tired of low battery warnings from my Escort and worrying that it might leave me stranded. Switched to an AGM and no more issues.

[mr_z4mc1m_oz]

BMW have quoted me for a 70 AGM battery for my z4mc.

[Finnegan]

Originally Posted by StickMon

^WHS.
Yes, I've also found that all of the auto parts chains have it wrong.
H5 is too small for an ///M.
H6 is stock.
I hear H7 fits, if you want to go big.
The Battery Options Summary Listing may be a worthwhile, albeit long, read.

^This

I sorted the spreadsheet so the most recent records are at the top. Some part #s from 2012 are likely superseded.

[chickdr]

Originally Posted by XMetal

It's not a matter of how long it last. As you've found out that both AGM and LA usually have the same lifespan. It's about packing more reserve charge. For example, you should compare what your voltage readings are between AGM and LA when left sitting the same amount of time. I can let the car sit longer without needing to put a tender on the battery with an AGM.

Of course, if you daily drive it, then it makes no difference. That's why there is no one generic answer to this question - it all depends on the application (how you use the car - daily driven vs weekend vs special occasions vs track, etc., etc.)

I experience no difference in holding a charge either. My car often sits for a month between drives. I have used a charger once every 1-2 mths since owning the car.

[RGlenn]

Originally Posted by BAK613

Most of the major auto parts websites specify a H5 or size 47 battery for my M Roadster. My last battery, from Autozone an H5, was too small.

On the posted spreadsheet, I see sizes from H5 to an H7 (wow!).

I'm specifically interested in the NAPA battery https://www.napaonline.com/p/NBE9848 (size 48) but does not come up as M Z4 compatible on their website. Albeit they don't allow you to distinguish between a Z4 and an M Roadster.

What are the correct sizes for the M Roadster.

Thanks
Bruce Kaplan

Just picked up a NAPA AGM Group 48 over the weekend & fits perfectly. Identical casing to the BMW battery that came out of the car & fits the same as well. I had the same issue most places were showing H5, but the battery that came out of my car was a H6/group 48 size.

[RobMCoupe]

I go with AGM because LA might spill acid inside the car. I read somewhere LA batteries are for engine compartment while AGM is for inside the car.

Local auto part stores like NAPA, O'Reilly carries H6 but you have to tell them what you want instead of going by car model.

[Twixboy]

I was looking for that battery spreadsheet, but couldn't find it before I replaced my battery about 2 months ago. Anyways, I just added my new battery to the list.

My car sat untouched in my garage for 14 months. When I opened my trunk there was a large area of mold growth on the carpeting right above the battery. I wonder if this had anything to do with the battery being lead acid. I ended up buying a Duralast lead acid H6 battery from Autozone. If I knew the AGM version was only $15 more I woulda gotten that instead.