I spoke to a BRAILLE rep at Summernats...they are not cheap but they are lightweight and claim very high cold cranking amps....
Braille Battery Australia      Lighter • Stronger • Faster. At their display I picked up a motorcycle battery and stated that it must be a 'demo prop' It weighed like it was just the empty case. The Rep. said no that was an actual battery. It weighed about 500 gms.