Happy to say goodbye to my battery drain woes. I don't drive my car much in the city here so it is not uncommon for it to sit for 1-2 weeks at a time. Also I like to tinker with the car and it is nice to be able to quickly and easily disconnect the battery for safety reasons.
I have a simple battery cutoff wheel for my 300ZX which works great - especially for when I put it away for the winter. As we all know the X5 battery, as on most German vehicles is located in the rear and unfortunately it is buried under the spare tire and you have to unbolt and remove the compressor once you remove the cargo board. In other words it is a PITA to reach. Even tho I have a really nice smart charger with engine start, it's a hassle to to go through all that and the battery seems to be dead at the most inconvenient of times.
Enter the wonderful gadget called the
Battery Brain. This glorious device sits between the positive battery post and your positive battery connection. It can be turned on and off via the provided remote control transmitters or manually via a waterproof capped push button. Just what the doctor ordered right?
Unfortunately installation is not as easy as you would think. First off I figured I could just mount it directly to the battery terminal as shown in the provided directions. No matter how hard I tried I could not get the compressor to clear the BB unit or the positive battery cables.
So as you can see from the following picture where I relocated the unit to. I shoved it down on the right side of the battery, zip tying it to the battery mount screw. I hacked off a length of my amp's power cable and clamped another brass ring terminal on the extend the (+) connection from the post. The positive battery cable easily attaches to the other side of the BB unit and will clear the compressor and everything else. You will have to either mod your plastic BMW holder to fit it back in, or (as I did) just trace it out on some cardboard or plastic to make a new cover. I suggest you put something there to protect the electronica.
So on to the next problem. When I press the button on the remote everything turns on like I expect it to but then to my dismay it turns off about 30 seconds later. It responds perfectly fine when I turn it back on but will repeat this behaviour. I'm not sure if something funky is happening with the ECU or if the BB just thinks that the car is off or what. Once I put the key in the ingition and turn to ACC or start the car everything stays on (since I installed the supplied ignition/remote 12V wire to the BB unit). So I emailed their product support to ask them if this is normal and what is going on and their response was that they think my battery might be below 11.8V and in need of charge or worse the battery might be starting to die and that is why it is turning off. This concerns me since the BB itself has a nominal charge and may inevitably run the battery down below 11.8V itself.
Well I haven't had a chance to do a voltmeter test yet and/or charge the battery but just in case I have run a 12V lead from the battery (small red wire in the picture) over by my remote lead (tapped off my amp terminal). This way I can simply install a SPDT toggle switch to go between BB bypass (12V constant from battery) and staying on with ignition. Either way it now will achieve what I want. Highly suggest.