Rover 75 battery issue
 

Hi all,
New here so please take it easy on me.
My grandad has a 55 plate 2.0 diesel 75 auto. It doesn’t get driven much, once every 2 weeks or so. We think something is draining the battery, even when we put a new battery on, when we go to start it a week later, it’s flat so we’ve always disconnected the battery after use which is a pain. Anyway, fast forward a couple of years and we decided To get a new battery and keep in the boot to jump off if needed. Battery light is on permanently even with the new battery installed and the brake lights stay on when everything is turned off and the key out of the ignition. When I turn the ignition on, the brake lights go out.
Any advice?
Thanks in advance

Sounds like you have water ingress somewhere that is upsetting the electrics, does the car have a sunroof or the highline sat nav fitted?

No, neither. Any help is much appreciated

If the brake lights stay on with the ignition off, I doubt whether even a brand new fully charged battery would last more than 48 hours. That's a major electrical fault. You need to fault find the brake light circuit. Has anyone worked on the car that might have inadvertently cross connected a lead somewhere?
Are the brake lights permanently on with the ignition off and when was this first noticed? The resting current drain on the car should be in the 30-50 ma range.
Two brake lights would be a drain of roughly 4000 ma. My 2004 Astra G will go over three months without being used and still start. My 2004 ZT V8, after only three weeks, the battery is flat, so I keep it connected to a CTEK MXS 5.0 as advised by others more knowledgeable than myself on this forum. Many modern cars with aftermarket 'goodies' only last two weeks due to the plethora of computers all monitoring all of the systems. There are many good videos on YouTube under 'finding parasitic drain' which will be of enormous help to you. Meanwhile I'd definitely isolate the battery

I find this much quicker than undoing a bolt.

Ii can whole heartedly agree Miss Moppet, excellent gadget.

Hi Sam,

This is a fault without precedent. I think your best course of action is to see if T4 can give you a clue. There's a club member based in Leamington Spa who might be able to help. He is mobile and his user name is GAVIN (in capitals).

Simon