Originally Posted by Antigravity
I have the same results Anorak, and have a 12-cell under the truck seat just for emergencies... But there is factor here that allows that great performance in cars and it is usually the great starter reduction gearing in cars with that super large ring gear on the flywheel/torque converter area, and also the efficiency of the system in general with the nice grounding and fat cable usually a miniumum of 4 awg and the starters also seem very efficient. Some bikes also have great starter reduction gear though it varies alot and the efficiency of the starter plays a part too... for example our 4-cell starts the GSXR 750 fine... yet it is slower to turn over the CBR 600.... it turns out the CBR has not as good starter reduction gearing and also a starter that isn't as efficient.
I heard on the new super killer Ducati Superbike they did some engine efficiency work to allow for easier turn over so they could use a much smaller battery than normal... so the bike is able to use a smaller battery to achieve the good starting results by making the engine easier to turn over on the start attemp,t where-as normally twins are a harder turn-over than inline 4 cylinders....
I guess the point is just that it not just the battery but the vehicle also that can make for a harder start...
And speaking of Ducati's, my 998R is a BEAST to turn over
but my 999R & Aprilia spin over without breaking a sweat!