i believe Porsche uses LiFePo only in their 12V batteries ( in regular gas cars ) as a replacement for lead acid batteries, because in this application ruggedness trumps weight and capacity. I heard only good things about these 12V LiFePo batteries in Porsches. They are far lighter than Lead Acid and they are bombproof. A replacement battery is about $600 but this isn't because LiFePo is expensive ( actually LiFePo is cheaper to make than common Lithium chemistries, which is why it is popular in China ), rather it's $600 simply because Porsche.