My choice for battery three years ago was the Bioenno BLF-1250AS, LiFePO4 (Lithium-Iron). Yeah expensive, but: - Inherent thermal and chemical stablility, so no runaway like LiIon - 50AH vs C&D's 30AH (yeah it's an inch deeper - had to make a new strap) - Provides 2500 - 7000 cycles & a 10 year lifetime compared to 200 - 500 cycles & a 3 year lifetime for C&D. - Holds above 12V for up to 90% of its capacity usage providing huge boosts in run-time compared to only 50% in lead acid. - Use of phosphates avoids cobalt's awful environmental concerns. - Bioenno's customer service can't be beat. Had a problem with my battery after a year and they replaced it, no pro-rate, no fuss.