BMW e30's have a factory trunk battery setup with 0 gauge cables, so you can go junkyard shopping from 80's BMWs and get a nice battery cable for a trunk block heater setup.

http://jalopnik.com/5107178/junked-bmw-e30s-provide-cheap-easy-way-to-trunk+mount-your-battery

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1980 240d
1999 SL500