Battery technology does not increase at Moore's Law speed. If it did, we'd have pennies with the power of cars. But it IS increasing at a steady rate, and we now have small hand-size batteries that can get you up a hill. This photo shows my e-bike battery and charger. I did not get to weigh either before I left, but I estimate the battery to be about 3 pounds (or 1+ kilos)., and the charger at 2 pounds. The battery is Lithium-ion and takes about 3 hours to recharge. The lights on the side indicate capacity, here shown as 100%. Fully charged the battery will give me enough assistance for one day. The caveat is that I am only using the electric assist on steep uphills. But there are plenty of these along the Oregon coast. Some of the long hills require that I run the motor for 20 minutes or longer since I am pedaling in low gear and going up slowly. (The motor turns the crankshaft at a steady "normal" rotation.) This is an electric assist bike which means it is assisting me as I pedal (and believe me I am still working hard). On days with a lot of hills, I will recharge the battery at lunch in a restuarant. I carry a smaller spare charged battery but have not used it yet.
While the battery is charging next to me while I recharge my own bodily battery with food, I have been struck by how powerful this technology is. Little electrons are pushed into the small cylinders, and with that stored energy, it is able to move all of me and my gear uphill for several hours! But so will a plate of pancakes!
I am using this cool e-bike from Gruber in Austria called the Vivax because while pancakes will get me up the hill, my old legs don't go fast enough to keep up with my 15-year-old son and 16-year-old nephew. The battery is my fountain of youth, giving me back the legs I had when I rode my bicycle along the same route 35 years ago on pancakes alone.