Battery as a tuned mass dampner, huh.

glhs837

Power with Control
So, boys 99 BMW convertible is going to be needing a battery. Prices seems a bit steep, and here's why. AS you might expect, if you know anything about structure, a convertible is a more vibration prone structure than a coupe, lacking the rigidity a roof brings. Stiffer A-pillars and underbody braces can only do so much. So, how does BMW soak up some of that vibration? Since the heavy battery is already in the trunk for longevity and weight and balance (mounted in the rear passenger fender to partially offset driver weight, 40lbs outside rear axle and close to fender does a lot for weight closer to CG), why not use that heavy weight to soak up some vibration? So the battery tray on the verts, unlike the coupes and sedans, is actually allowed some movement, suspended sort of.

This is why the batteries cost a lot, because BMW specified a special vibration resistant sort of battery. I know most folks will "Meh, who cares", but I thought I would share it with my fellow gear heads. I heard that GM did a similar thing, just using extra parts, not the battery. Seems the PT Cruiser and Sebring verts used the drivetrain as a tuned mass dampner
 

b23hqb

Well-Known Member
PREMO Member
So, is the battery gonna do you in, or will you continue your love affair with the old beemer?
 
So, is the battery gonna do you in, or will you continue your love affair with the old beemer?

No reason why it should. Those battery specs were designed around a high performance vehicle and worst case speed and vibration conditions. I'm sure a standard battery will be fine for local driving.
 

black dog

Free America
So, boys 99 BMW convertible is going to be needing a battery. Prices seems a bit steep, and here's why. AS you might expect, if you know anything about structure, a convertible is a more vibration prone structure than a coupe, lacking the rigidity a roof brings. Stiffer A-pillars and underbody braces can only do so much. So, how does BMW soak up some of that vibration? Since the heavy battery is already in the trunk for longevity and weight and balance (mounted in the rear passenger fender to partially offset driver weight, 40lbs outside rear axle and close to fender does a lot for weight closer to CG), why not use that heavy weight to soak up some vibration? So the battery tray on the verts, unlike the coupes and sedans, is actually allowed some movement, suspended sort of.

This is why the batteries cost a lot, because BMW specified a special vibration resistant sort of battery. I know most folks will "Meh, who cares", but I thought I would share it with my fellow gear heads. I heard that GM did a similar thing, just using extra parts, not the battery. Seems the PT Cruiser and Sebring verts used the drivetrain as a tuned mass dampner

What model BMW is this ?
 

glhs837

Power with Control
BD, my son has a 99 3 series, and I have a 98 also.

And no B23 it wont do me in. I'll most likely get an AGM (absorbent glass mat), which is by it's nature more vibration resistant than a lead plate battery. GW, some folks use the lead batteries and they do last a while, just not as long. Were I expecting to sell these in a year or two, I would most likely go that way.

Larry, the takeaway is that sometimes "elegant" engineering has a cost. In this case, a tougher battery. Driving dynamics takes a lot of thought. At least if you also want some modicum of comfort.
 

black dog

Free America
View attachment 116541

I replaced the battery in my 24+ yr old Lexus a few months ago and I forgot to reinstall the battery gyro ion release limiter, is that why the check engine light is on and it sounds like a Cessna Airplane ?
Maybe it was a mistake, but I installed a battery from Walmart that was $49.99
 
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glhs837

Power with Control
View attachment 116541

I replaced the battery in my 24+ yr old Lexus a few months ago and I forgot to reinstall the battery gyro ion release limiter, is that why the check engine light is on and it sounds like a Cessna Airplane ?
Maybe it was a mistake, but I installed a battery from Walmart that was $49.99

Might be you disconnected the blinker fluid level sensor.
 

GURPS

INGSOC
PREMO Member
This is why the batteries cost a lot, because BMW specified a special vibration resistant sort of battery.


at one time, there was a Sears Platinum Diehard just for 4 Wheel Drives .... that was supposed to be 'vibration resistant'
 
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