2nd battery - what models had it? and can it be retrofitted?

[A1BMW535iSport]

Hi,
in the E34 handbook BMW say there was a 2nd smallish battery like 25ah
fitted to some models, anyone know what models had them? and what for?
also can it be retrofitted to 535i which doesn`t have it?

Cheers, Matt

[Tiger]

For alarm... located in rear driver side just above wheel reached from trunk

[netmgr]

Im sure it had nothing to do with the alarm but was for the cellular telephone.

and in any case its not designed for starting the car or anything like that it just powers certain circuits.

not sure if u want it for power but personally ive fitted a full size battery in the boot on the right side and linked it direct to the cars major power connectors via a high rating relay - it charges while the car is running - but at the flick of a switch i can run the car from it incase of a flat battery. Not a bmw addon but my own version.

this is the etk image showing the aux battery and the cellular phone
http://www.carsoft.ru/avtorepair/bmw_e34/6561.0/00.png

[A1BMW535iSport]

here is the battery install set as shown on parts cd....

http://img109.exs.cx/img109/6026/e34012.jpg

looks like it can be fitted as an upgade.