WHY DO BMW PUT THE BATTERY IN THE BOOT OF MY 325ISE.

[e30geezer]

I JUST DONT KNOW IS IT TO DO WITH THE HEAT/ OR TO MAKE ROOM FOR THE 325I ENGINE ANY 1 KNOW THE REAL REASON, OR JUST GERMAN TUV SAFETY.

[dazleeds]

ecu isnt in the boot??

well never has been on any ive had??
should be above ya knees mate Daz

as for batt in boot i like it much easier to get to plus gives you some space under the bonnet

[e30geezer]

ecu isnt in the boot??

well never has been on any ive had??
should be above ya knees mate Daz

as for batt in boot i like it much easier to get to plus gives you some space under the bonnet

THERE IS A BIG SILVER BOX IN THE BOOT LOOKS LIKE THE BRAIN, FOR THE CAR.

[jonb]

switchable auto box ecu.

[e30geezer]

switchable auto box ecu.

AHHH, NOW I KNOW WHAT IT IS CHEERS MATE.

[dazleeds]

well i learn something new everyday mate glad you sorted it Daz

u had me baffled for a bit there

[A1BMW325iSport]

i prefer having the battery in the boot, its way better

[JazzMan]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

[e30_Turbo]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

Battery is in the boot on 325 models to aid weight distribution

[Richy325iTouring]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

Battery is in the boot on 325 models to aid weight distribution

yep cos they have the oil cooler in the front

[gcorky]

325 tourings are in engine bay.

[Richy325iTouring]

325 tourings are in engine bay.

so is the convertable but they are heavyer cars as well

the tourng has a bigger back end to balance the weight about

[e30geezer]

i prefer having the battery in the boot, its way better

me too mate it's much better , also more room in engine bay, and its quite practical too.

[e30geezer]

325 tourings are in engine bay.

so is the convertable but they are heavyer cars as well

the tourng has a bigger back end to balance the weight about

intresting i thought they were in the boot too, do the sports have them in the boot.

[e30geezer]

325 tourings are in engine bay.

i also know that this is the case as i had a e30 touring once great car.

[e30geezer]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

Battery is in the boot on 325 models to aid weight distribution

yep cos they have the oil cooler in the front

this is all making sense now, i was very curious to find out.

[e30geezer]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

Battery is in the boot on 325 models to aid weight distribution

it does make sense, and very good idea from bmw.

[e30geezer]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

thanks for the tip mate will bare this in mind, cheers.

[e30geezer]

well i learn something new everyday mate glad you sorted it Daz

u had me baffled for a bit there

me too.

[rickk]

The story I heard is that the 325i battery is bigger/heavier than 320i etc. b/c they figured people would order them with more electrical gizmos - and so indeed, they moved it to the rear for better weight distribution.

I still need to move mine for the same reasons (and the fact that I fooked up the bolt that's holding it up front ), altough I don't like to loose that convenient stowing space in the boot :/

It's also safer (that's why it's in the boot on a lot (all?) of new cars) when you crash.

- Rick

[zaust]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

???????????????????????

[JazzMan]

I thought it was for weight distribution with the heavier 6 pot in the front they move it to the back as its an easy to move heavy object.

The only problem with batt in the boot is if your runing more heavy duty amps in the back. The cable becomes a bottle neck and needs to be upgraded.

???????????????????????

Which bit? If you mean the cable:

If your running an amp that pulls say 150amps and another say 60amps at full load then a single 4AWG cable is not sufficient to keep the voltage from dropping over a 5 meter run. So you need to replace it with a 2AWG of 0/1 AWG cable. I run two amps in the back of my E46 and the stock cable is not enough. Its only a 4AWG run. The amps output a maxium of 540RMS to the front end and the sub amp 1.2Kw RMS. I use a second battery to help buffer for the moment but its not an ideal situation. As soon as I get the chance I will put a second run of 4AWG in - which is equivelant to a single run of 0 with the stock cable as well. This will stop the cable getting hot and possible causing a fire as well reduce and stop headlight dim. It also prevents amps without a regulated power supply or protection going pop with voltage dropping too low.

Combined with replacing a few other cables under the bonent this is known as TB3 "The Big Three" power cables between the battery, alternator and chassis. In a car with a 5 meter run between the alternator and the battery is makes even more sense.

In a small audio system, say a single 4 chanel amp runing 50RMS per side or 150RMS bridged a battery in the boot can be ideal as there is no need to pull up the carpets and run a chuncky power cable into the boot.

[Nostrils]

The batter is also in the 4pot! M3. I much prefer it in the boot myself because it gives to points of access should I have the need for a jump start!!

[e30geezer]

The batter is also in the 4pot! M3. I much prefer it in the boot myself because it gives to points of access should I have the need for a jump start!!

i agree very handy .

[japcarkiller]

some one asked me how mine started as there was no battery.lol.
i told them it was magic.
shhhhh. don't tell them its in the boot.
have to agree its very handy. When ever i had a flat battery it was parked either in the garage or parked front end on to a wall. so it being in the boot has been a massive plus point.
hurray for german enginering.

[e30geezer]

some one asked me how mine started as there was no battery.lol.
i told them it was magic.
shhhhh. don't tell them its in the boot.
have to agree its very handy. When ever i had a flat battery it was parked either in the garage or parked front end on to a wall. so it being in the boot has been a massive plus point.
hurray for german enginering.

lol!! do u think anyone will find out our secret, i wont tell if u don't

[rowemeister]

re JAZZMAN

If the battery is in the boot then surely the 4awg cable to each amp will be short!! so there should be little loss of current down the cable. A battery at the front would cause the problems your talking about.
Also two 2 micra farad capacitors sat next to the batt in the boot helps.

[sabrje]

Maybe they just copied the layout of the old mini.....

Apart from RWD of course

[JazzMan]

re JAZZMAN

If the battery is in the boot then surely the 4awg cable to each amp will be short!! so there should be little loss of current down the cable. A battery at the front would cause the problems your talking about.
Also two 2 micra farad capacitors sat next to the batt in the boot helps.

Yes your right there, the run from the battery to the amps is short - however the source of all the power is the alternator so the idea is to maintain a constant supply from there without getting additional voltage drops from a long cable, in theory it aught to be enough but I get serious voltage drop in my car which has prompted the need to upgrade I've added a bapcap which keeps things a little more stable for the moment.

The upgrade of the big three is highly recommend in cars with a battery in the front as well. Most OE cables tend to be very small. Lots of positive results from doing this - mostly relating to headlight dim.



Sorry gonna go a bit off topic here:

First off let me say I dont claim to be an expert on this stuff, I just have interest in car audio and consider all this to be my opinion on the subject :

CAPs are almost completely useless in most instances due to the lack of capacity. 1 Farad is not very much so halfway through a bass note it runs out and becomes a burden on the system pulling the voltage down further as the charge system trys to cope with supplying the amps and charging the caps. They can have their uses in SQ system. However all well built amps will have enough internal capacitors to maintain a good supply internally.

There is an alternate product know as a batcap - this essentially does the job a capacitor is widely advertised as doing but doesnt really. Its a very fast charging battery with a much higher capactity than a cap.

http://www.batcap.net/

There's been pages and pages of argument about caps on places like talkaudio but the usual (and proven) answer usually is that they dont help.

In the case of the batcaps I've done some testing myself. Here's a video with sample voltages showing the difference between running without anyting, beefing up the calbles and running with a batcap:

System:

DLS A6 running at 1 ohm (1.2Kw RMS)
Helix HXA500 Mk2 (2x 250RMS)
Genesis Profile 2 (4x 50RMS)

Initially with single 4AWG cable into the boot (battery up front system) - upgrades done due to adding the A6 previously a Genesis Profile Sub ran in the system which didnt need as much power. The A6 is class A/B and therefore requires a lot of power.

Video shows all tests
Video:- Standard Wire & Upgrade Wire - Batcap V No Batcap
(divx5 - 2.28mb)


http://www.rshort.co.uk/talkaudio/compact/powertest.avi

Lowest voltage drop

Original System - 10.17v
Original System with batcap - 10.70v
New System - 13.20v
New System with batcap - 13.20v

Overall adding a second run of 4AWG made the most significant difference to reducing the voltage drops.



The batcap seems to help keep the voltage up a little however after the bass has hits it needs to recharge so the voltage stay down a bit longer than without the batcap.

So again the results show the buffer causes extra strain on the charging system, but then tended to drop down while the bass idled so the charge system was not stressed by having to run the amps as well.

Unfortunatly I only had a multimeter and not scope with data logger for the tests so the very small higher and lower peaks couldn't be registered.

[rowemeister]

I agree with you mate. I thought you were refering to the drop from battery to amp. Of course there are voltage drops from altenator to batt.

Also 1 Farad is not enough as you say. Ideally a 1 Farad cap per amp should be used and it really should be as close to the amp as possible so the current/voltage drop is minimal. If you have enough capacitance for each amps load there should be minimal current/volt drop from the batt etc.

Any storage drop in the cap will surly charge up when the current sapping bass stops, remember the charge is constant but the power drag from the amps is not.

The point about more cables is also correct mate, its all about resistance, the lower the resistance the higher the current hence less voltage drop.
A poor contact or earth creates high resistance and this causes current/voltage drop too.

[JazzMan]

Yep spot on, bad earths will also cause alternator wine through the speakers - this is the most common cause in my experiance.

Only I would not recommend the use of cap for anything other than "looks pretty." Batcaps on the other hand have more like 500 times the capacity of a 1 farad cap and will charge up just as quickly which is why they work