[Yangorang]

From threads it looks like most E90s come with an H8 90Ah battery OE. Have any of you guys replaced the battery with a smaller H7 or H6 battery? It seems like BMW gives you the option both physically with threaded holes for the hold down clamp and the coding also gives you various smaller options. It's rather a bit of a pain to get a 60lb H8 battery in and out of that compartment in the corner, and without auto start/stop in this generation I wouldn't think 90Ah would really be needed?

[gbalthrop]

Originally Posted by Yangorang

From threads it looks like most E90s come with an H8 90Ah battery OE. Have any of you guys replaced the battery with a smaller H7 or H6 battery? It seems like BMW gives you the option both physically with threaded holes for the hold down clamp and the coding also gives you various smaller options. It's rather a bit of a pain to get a 60lb H8 battery in and out of that compartment in the corner, and without auto start/stop in this generation I wouldn't think 90Ah would really be needed?

My 2007 328xi had an Interstate H7 in it when I bought it ~ 3 years ago, and it just flunked Starter Load Test dropping from 12.5V to ~ 10V when failing to crank engine. It was installed 5 years ago based upon the Battery Registration km & service records. INPA showed same as your ProTool: 90Ah FLA, but I doubt H7 is more than 80Ah. In fact, the Interstate battery was labeled 80 Ah; 130 RC. Any conversions of RC to Ah I have seen, would say a 130 RC battery = MUCH LESS than 80 Ah. So much for labels.

I replaced the Interstate with a Walmart Maxx H8, Group 49 ($120):
https://www.walmart.com/ip/EverStart...up-H8/49988398

The Maxx H8 has NO RC or Ah rating on it, but simply based upon size, I left CAS setting at 90 Ah.

As for weight, I didn't weigh either the Interstate or Maxx, but I doubt either one weighed more than 40 lb. Both have handles on them, and at average size, I had no difficulty removing, installing either with one hand. You want to make sure you disassemble the Rear Power Distribution Panel, and set it aside. Also tie back the Battery Terminals, (+) & (-), so you don't damage the BST connector or ISB, and you have room to lift old Battery out, and drop new IN, without getting tangled up in wires. H8/Group 49 takes up ALL available space, but with wires out of way, you do NOT need a shoehorn.

George

[ewicky]

I couldn't agree more.

I currently have an oversized battery (>H8) in my car; I had just installed it in my 7 series, so I stole it back when I sold the car. That is a heavy mofo. When I eventually replace it, I'm going to install the smallest battery that will fit and be secured.

I think it depends on equipment level, but for the most part these cars don't use much power when they are off. I think passive entry, if equipped, might be the biggest consumer when the car is sleeping. My car doesn't have passive entry, and I've deleted the "TCU" modem because it was an old 1G model. The only thing left that draws significantly when the car hasn't yet gone to sleep is my CCC iDrive. But I think an H6 or even smaller could handle that for a few minutes, no biggy.

I also understand that the sleep time-out can be adjusted in coding. So, worst case, I could shorten it from 15 minutes to, say, 5. And I don't think there would be any real-world difference, besides reduced energy consumption.

[gbalthrop]

Alternate View:

Keep the H8 Battery. If concerned about lifting it, or Gross Vehicle Weight as driven (by you ;-): GO TO GYM.

[bluesy_cube]

I dropped it down to H7 80ah battery cuz my local shops do not sell H8 90ah batteries. Ended up using Costco H7 battery and coded to 80ah.
No problem at all!

I saw some people dropped it down on to smaller sized 60ah AGM batteries and got away with it too.

[ctuna]

My Interstate H8/49 is 8 years old .
I top off with a ctek 4.3 once or twice a month.

[smallseafishie]

Sure no issues. Just make sure you code the car to reflect the new battery rating / type.

[gjm120]

Originally Posted by gbalthrop

My 2007 328xi had an Interstate H7 in it when I bought it ~ 3 years ago, and it just flunked Starter Load Test dropping from 12.5V to ~ 10V when failing to crank engine. It was installed 5 years ago based upon the Battery Registration km & service records. INPA showed same as your ProTool: 90Ah FLA, but I doubt H7 is more than 80Ah. In fact, the Interstate battery was labeled 80 Ah; 130 RC. Any conversions of RC to Ah I have seen, would say a 130 RC battery = MUCH LESS than 80 Ah. So much for labels.

I replaced the Interstate with a Walmart Maxx H8, Group 49 ($120):
https://www.walmart.com/ip/EverStart...up-H8/49988398

The Maxx H8 has NO RC or Ah rating on it, but simply based upon size, I left CAS setting at 90 Ah.

As for weight, I didn't weigh either the Interstate or Maxx, but I doubt either one weighed more than 40 lb. Both have handles on them, and at average size, I had no difficulty removing, installing either with one hand. You want to make sure you disassemble the Rear Power Distribution Panel, and set it aside. Also tie back the Battery Terminals, (+) & (-), so you don't damage the BST connector or ISB, and you have room to lift old Battery out, and drop new IN, without getting tangled up in wires. H8/Group 49 takes up ALL available space, but with wires out of way, you do NOT need a shoehorn.

George

I've read somewhere that people were finding out this battery is 80Ah. I have the same battery and it had a RC listed (this was Jun 2018). Based on a correlation I did the Ah comes out to 81 so I coded it to 80.

I don't expect you'll blow anything up having it coded to 90.

[tlow98]

Originally Posted by gjm120

I've read somewhere that people were finding out this battery is 80Ah. I have the same battery and it had a RC listed (this was Jun 2018). Based on a correlation I did the Ah comes out to 81 so I coded it to 80.

I don't expect you'll blow anything up having it coded to 90.

I did the same - coded at 80Ah. A couple reasons:
1 - batteries wear at the extremes. 100% full and 0% full are when the chemicals degrade the fastest. Leaving the battery some small amount from full charge may actually lead to a longer life, my research showed.
2 - The incremental charge from 80-81Ah is insignificant to me. Battery life is more important.

[tlow98]

Originally Posted by gbalthrop

I replaced the Interstate with a Walmart Maxx H8, Group 49 ($120):
https://www.walmart.com/ip/EverStart...up-H8/49988398

The Maxx H8 has NO RC or Ah rating on it, but simply based upon size, I left CAS setting at 90 Ah.


George

FYI, the RC is rated as 140minutes for the current battery they sell.

https://www.walmart.com/ip/EverStart...0aAgoTEALw_wcB

[gjm120]

Originally Posted by tlow98

FYI, the RC is rated as 140minutes for the current battery they sell.

https://www.walmart.com/ip/EverStart...0aAgoTEALw_wcB

Pretty sure that's what mine was rated at when I purchased it.