Master Switch v disconnecting the battery

[MarkD]

I have my 7 in a garage away from the house so no ability to attach a battery charger / conditioner and so far I have been disconnecting the battery (Banner in a1.8  K series) when I don't use the car for more that a week, I am now considering having a Master Switch fitted and wonder whether this will be better.

I know it will be easier to use and I will have it fitted professionally but how do they interact with the immobiliser? will this still operate and is there any chance of the battery still being drained too much if the car isn't used within a certain period?

Any advice welcome, thanks

[revilla]

If wired in properly the master switch will cut power to everything and the battery should hold its charge well. If you have the standard 5AS immobiliser, cutting the power "stops the clock", so if it's a later (97MY+) immobiliser that "passively arms" (i.e. immobilises the vehicle after a period of time with the ignition off without you having to set it on the key fob) that functionality won't work - the immobiliser will stay in the state it was in when the power was cut. Not a big problem though, you can just arm it on the key before cutting the power (a lot of them are programmed to need this anyway). Otherwise it shouldn't cause issues for the immobiliser or ECU.

[garybee]

That's how I have mine.  During the winter I put a charger on the battery a couple of times but it always switches to 'charged' after a couple of minutes.  That is with a (£30, lawnmower spec.) gel battery though which has a lower rate of discharge than wet lead acid.  I think that battery's been in about 7 or 8 years now.  

I never bother arming the immobiliser.  The only downside to this is that as it never gets armed/disarmed you may get caught out by a flat fob battery at some point but I suppose this could happen anyway.  I need to get round to learning how revilla's (very kindly shared) ECU programming tool works and just disable it.  I have always had a suspicion that you could leave the keys for a 7 on the bonnet and nobody would be able to drive it away anyway.  Particularly so with a cut-off fitted. 

[SLR No.77]

Mine (1999 K-Series):

• arm immobiliser
• remove FIA key to disconnect the battery

When returning to the car:

• refit FIA cutout key
• press unlock on immobiliser fob 4 times - this reconnects everything and sets it to disarmed
• drive car!

Stu.

[MarkD]

That's great thanks both, I will get one fitted.