Where is my battery

[MrElussive]

I'm curious as to why everybody referes to it as a "safety" issue. How is a battery harmful in any way, even in an accident?

bmwrocks, I checked the hood of my car, just a little while ago. It is a weird setup...the battery is located far up in the left corner of "engine contents", right in front of where the front passenger seat is. It is completely separated and enclosed and to access positive and negative connectors, you have to pop open this flap and even then you cannot pull the battery out. Weird stuff.

 

[xLibelle]

hmm, which reminds me, Audi puts them (or at least used to) underneath the back seat.
...no, i dont think they go that any more.

 

[Average Jae]

compartmentalizing the whole thing, esp the battery maybe for the corrosion/ acids that do come out of the battery during the life of it. maybe it gets to the other parts? or they just want it to look good?i had to replace my battery on the talon and it wasn't horrible, but it wasn't pretty either. isloation from the elements may help battery from spewing the acids? who knows..

as for the g35, i think most car manufacs, well those that care about weight balance would locate their engine deep in the engine compartments now, (ie nissan midship engine plat w/ the g35, z, altima/maxima) rather than just above the front axle, (which also shows why the front wheels are really close to the bumper now) battery isn't a light thing either, so they'd push it as far back as possible.

and if you saw the trunk in the g35, you know why they can't put that guy in the back it's almost an engineer feat to be able to stick 2 golfbags in that trunk.

 

[MrElussive]

Hahaha, actually I was gonna make a joke about that. I was thinking that if my battery was in the trunk maybe my weight distribution would go from 53/47 to 52/48, but the trunk is just too small to handle it.
What's funny is that there is actually a diagram on the inside of the trunk lid that explains how to squeeze the two golf bags into the trunk. And now when I see the trunks of other people's cars I always freak out, I'm like, "HOLY SH*T THAT IS A HUGE TRUNK !!" lol.

 

[Average Jae]

yea i remember the "how to fit two golfbags" i had a good laugh about it. [rolf][rolf](it's still filed under, yea, i'll believe it when i see it catagory)
i wish they'd do a split fold, rather then the whole thing collapsing, but then again, the peanut shaped passthrough isn't all that big to begin with...

 

[MrElussive]

Jae, the collapsing rear seat is an advantage and disadvantage on its own. It's not 50/50 split-folding, but folding it down is so easy...just pull the latch, and move the seat-back forward just a bit and it falls down flat. You're right, the pass-through is oddly-shaped and may not be practical for some. But for me, the cargo capacity of the vehicle is as much as I need and not all that bad. I moved into my college dorm with my car and I had my computer and my 19" monitor and all.

 

[Krafty04]

Since there seems to be a poll starting,,,, the factory rep explained to me the battery was in the back for weight dist.... the added safety benefits are just a "bonus"...

 

[mikev]

Since there seems to be a poll starting,,,, the factory rep explained to me the battery was in the back for weight dist.... the added safety benefits are just a "bonus"...

If its for 50:50 weight distribution then why is it the same on my E30? (not 50:50 as far as i know correct me if im wrong) the only reason for my battery in the boot rather than engine bay is size. it physically wont fit under there with the engine and still be able to turn it over!

 

[330i and like it]

Battery - thanks

So that is where it is. Thanks for you help!

 

[Bryan330i]

yeah, someone needs to better explain the safety issue. and i mean a different explination than relating weight balance and lower center of gravity to safety.

what did those guys say about it Bryan? ...or was that to point you made, that they just said it was for safety and not giving a reason.

(bmw has always put the battery in the back)

I remember the basics of what he said. He said that due to the extensive drop-down feature of the engine in the event of a crash, combined with the front crumple zones, created a potential hazard from the battery and it was found that it could become disconnected and travel past the engine.

This was a 2-3 minute, unsolicited explanation by someone that I thought knew the car well and had a lot of BMW sales experience (he said 20 years). It is where I got my information and why my first post said “safety.” Otherwise I would have had no idea.

 

[Bryan330i]

If its for 50:50 weight distribution then why is it the same on my E30? (not 50:50 as far as i know correct me if im wrong) the only reason for my battery in the boot rather than engine bay is size. it physically wont fit under there with the engine and still be able to turn it over!

After looking into the issue a bit more my final opinion is that there is more to it than weight. BMW had done this in ALL vehicles, even those that are NOT 50:50, and in all new designs where they had to plan for weight issues from the ground up. Essentially, the rear placement has been designed into all new products and they are all not 40#'s off. And think about it, to change a weight distribution by only 40#'s from front to back involve such a small shift relative to the weight of the car. It may only involve some component movement by a very small fraction of an inch, or fraction of a millimeter depending on what is shifted.

I guess after looking further I am not willing to completely write off the sales guys. But I am sure BMW would not want them to tell customers what they told me. And why cram it in the front, that may indeed cause issues past weight.

 

[jrt67ss350]

It is a well known fact throughout racing that placing the battery in the trunk helps with weight distribution and balance. All serious drag racers have their batteries in the trunk and it has absolutely nothing to do with safety. In fact, placing the battery in the trunk requires more work to make it safe than if it was in the engine compartment - It must be a sealed battery or in a sealed container that is rigidly mounted and vented to the outside. It cannot vent to the trunk air as a charging/discharging battery gives off flammable gases. The weight transfer involved is not insignificant - remember you aren't just adding weight to the back of the car, you are removing weight from the front axle and adding that removed weight to the rear axle.

Putting the battery in the trunk does help with the longevity of the battery as well - heat kills batteries.

And mikev, the battery can fit in the engine compartment in an E30 - there is a flat spot right in front of the firewall and behind the strut tower on the passenger side for it. This is where the battery is located in convertible e30s.

 

[Bryan330i]

A simple answer to a complex question, its for weight. But 40# is so insignificant relative to so many other factors. Different engine sizes, different transmissions, yet they engineer around all of this...but man....that damn battery is just too much to work around...with all the math skills, computers, and years of design, just can make that adjustment and balance weight for that battery. [fake] [joke]

Just think about it, the engineers would prorobably laugh their ^@*#@ off to read this thread. There is probably a list of considerations none of us have even thought of.

 

[Kirby]

The weight transfer involved is not insignificant - remember you aren't just adding weight to the back of the car, you are removing weight from the front axle and adding that removed weight to the rear axle.

Well said.

And there is an additional weight transfer effect due to leverage. The front position of the battery is behind the front axle, whereas the rear position is 18" or so BEHIND the rear axle. This adds leverage about the rear axle. In effect it's like removing 40# from the front of the car and adding 50# to the rear. The weight distribution DIFFERENCE might be approaching 100#. On a 3300# car that is 100/3300 = 3% of the vehicle weight - not insignificant is certainly a true statement.

 

[Bryan330i]

Well said.

And there is an additional weight transfer effect due to leverage. The front position of the battery is behind the front axle, whereas the rear position is 18" or so BEHIND the rear axle. This adds leverage about the rear axle. In effect it's like removing 40# from the front of the car and adding 50# to the rear. The weight distribution DIFFERENCE might be approaching 100#. On a 3300# car that is 100/3300 = 3% of the vehicle weight - not insignificant is certainly a true statement.

Hey Kirby, I think this is in your field, but don't you think it is more of a desire for weight in the back (and/or other factors) than an inability to balance 50:50 with the battery in the front? And without question the overall effect is much greater than 40#, but I bet even a few of us here could give it 50:50 with the battery in front, with a very minor adjustment or two, provided we have all the numbers.

 

[tyler]

I'd like to believe more that it is primarily for proper weight distribution and then maybe for safety reasons. But isn't it close to the gas tank than when in front ? hmmmmmm...

 

[flashinthepan]

The one thing that confuses me more is WHY they put it there. There is a large open space under the hood (upper-left) where it can go with no problem.

I wrote Cris Bangle -

Here is what he said:

"Our design team felt it necesarry to leave adequate space and ample clearance for any & all Forced induction components."

Sincerely Chris.

(P.S., if I lose my job, I have a great retirement account.)