I once bought an electric bike, the vendor claimed up to 50km range. I found that even with pedal assistance 15km was the limit. The vendor didn't lie, after all 15km is up to 50km, his claim was just exaggerated.
The original C5 gave a range of 15 to 20 miles (38ah IIRC), so I find the same figure for a 20ah battery, even though lighter, to be suspect. But, there again I'm not an expert on new battery technology.
If your pockets are not deep, and you don't have short arms, then I would recommend the larger battery. A battery life is often measured by the number of times it can be recharged. Now for an extreme example, to cover a total distance of 1000 miles a small battery will need to be recharged more often than a large battery, thereby having to be replaced more often.
On the other hand, if a 20ah battery is exactly half the price of a 40ah, then I'd go for two batteries. I bought two identical batteries at the same time, one gave up the ghost after a short time, the other is still going strong.
And with sod's law, the battery always gives out just at the point it shouldn't.
If you are not in a hurry wait for the Graphene supercapacitors, they can be charged in seconds, weigh next to nothing, and are super light. Capacity can be brought up to that of a battery. They are in use at the present time, but price is not known to me at the moment. It's claimed they will be a lot cheaper than batteries, and may well be the end of conventional batteries.
posted on: 29/01/2015 08:30:28