As Riddler mentioned, don't bother with the carbon fiber batteries. I've had two of them and both failed to hold a charge for more than a day. I since switched to the non-carbon fibre Braille battery and it has worked great. I do leave it on a trickle charger when the car is going to be sitting in the garage for more than 4 days.
It will definitley run down quickly, for example -you need to be careful not to leave the lights on for any period of time without starting the car. I leave a set of jumper cables in the trunk just in case.
| Z4MC | KW Clubsport | BBS-RGR 19 + Bridgestone RE11 | BBS-RGR 18 + Hoosier R6 | Sparco DTM RS | Vorshlag mounts | Braille battery | Euro Headers | Supersprint exhaust | Stoptech lines | Stongstrut | TCK camber arms | UUC SSK | APR GT-200 wing & splitter | ESS Tune | Speedware Motorsports custom roll cage | Schroth harness |