[modmonster]

for the same energy storage, lithium batteries are 3 times lighter than lead batteries and some cells (like A123) are supposed to be 30C compared to 9C with lead. therefore your lithium battery would also be 9 times lighter. so you could shed about 15-20kg curb weight. if 100lb = 2% FE reduction, then you could save 1% of your fuel bill. the pay back time would be about 5 years on this basis.