How to install seconday battery?

[///Sniper535]

I have a spare battery and I was curious how to go about doing this. Anyone have any write ups?

[BMWDriver]

Gosh, I'm learning new things here. I think some big rigs like 7 series and other bigger vehicles would need some, especially with all the electronics you can shove in there : screens for all passengers, satellite navigation, cel, Bluetooth items, what-not.

I wonder that this would also warrant a more powerful alternator. I'll let the experts speak, and perhaps you could be more specific about the needs and potential use, or perhaps is it you just want backup.

My 2 cents ($0.016 US 'cause I'm Canadian).

[BennyM]

Interesting...
I know the gauge cluster has status lights for battery #1 and battery #2, but the bulb for #2 is not installed. I wonder what factory configuration warranted a second battery. It just seems like unnecessary extra weight and more charging resistance for the engine.

[tim eh?]

I have a spare battery and I was curious how to go about doing this. Anyone have any write ups?

i want to do this too, just a tiny one. i would like to install it so that it is only connected with the ignition on, mayybe with a switch to bypass this and connect directly.

few reasons for this.

1- my manual unlock doesn't work (really, it doesn't - must be busted) and i don't want to ever rig into the license plate lights ever again just to open the doors.

2- would be really handy for a boost if i kill my primary battery somehow.

3- mini fridge going in this summer i hope and i would like it to be powered after i shut the engine off but not from the primary battery.

[BMWDriver]

The e34 shares many items with the 7 series siblings, like the cluster. So it's likely that the lights are there for that super luxurious 7. Unless it's for the unusual fridge-in-the-armrest option... seriously !

[shogun]

The E32 7 series had as optional extra a 2nd battery, or it was standard when certain options were ordered such a phone preparation. 1 battery is the main battery under rear seat, the 2nd battery is in the trunk right side behind the cover. There is a separating relay to separate the 2 batteries, the main battery has priority to start the engine. Use the E32 7 series wiring diagrams, then you can see it.
Needs quite some wiring.
My 750 Highline even has 2 alternators + 2 batteries. See online ETK E32, select a E32 750iL in ECU specification from 1992 for example, U.S. never got Highline E32 cars.

[632 Regal]

find a spot as showgun mentions behind pass side in trunk. Wire it up in parallel and go on with it. The alternator will be good enough as long as both are not dead. and last of all I dont think you need 2 batteries... I mean there are a couple of us on here getting away with one battery.

I have a spare battery and I was curious how to go about doing this. Anyone have any write ups?

[shogun]

2nd battery retrofit, the detailed instructions here, various languages, 21 pages
http://www.e32-schrauber.de/bmw/date...terie-1961.pdf



and if you need parked heating retrofit, here
http://www.e32-schrauber.de/bmw/date...eizung_eba.pdf

[Paul in NZ]

my 535 had a second (auxilary)battery when i got it.It is a 25 AH (i think) and it was installed as shogun said behind the boot lining on the lh side,with a metal tray and clamp,probably a specific boot liner too.As far as i know i didnt have a phone,but i know i have the 10 spker stereo and "boosted power output',which i always thought applied to the second battery...The battery was as dead as a dodo when i got it so i have since removed it.It did have some sort of relay or switching associated and a 6mm or so cable went round the boot to the main battery terminal.I have posted a link to the parts before too

[shogun]

original installation, (battery removed in the pic)
http://img165.imageshack.us/img165/3...ttarie2rr6.jpg
My replacement battery is from a mini truck. As it did not have a hose for the drain of the gases, I made it DIY with parts from the pet shop, connections and hoses from a fish tank, the original BMW battery is pretty expensive, this I could buy in the local battery shop