Interesting Comparison: Lithium Ion vs. Standard Battery--Ah vs. Weight

I was curious about how lithium ion batteries compared with standard batteries regarding weight.  I found an interesting lithium ion battery that is rated for 12 v 7 Ah that weighs only 1.87 lbs.  And their larger battery is rated at 12 v and 18.4 Ah and weighs only three lbs. 

Two of these would weigh just 6 lbs and supply 36.8 Ah compared with a standard lead acid car battery that is 38 Ah and weighs 44 lbs; a sealed absorbant glass mat battery with 35 Ah would weigh about 25 lbs and a comparable nickle metal hydride battery pack might weigh about 32 lbs.

That's a pretty remarkable weight differential...only bad part wiht lithium is you pay about $100 for each of those pounds!