250W vs 350W? Watts & Volts...

[Mo Sizlak]

Hi,
I'm a noob. I've gone thru some of the FAQ. Some good info there, but I'm not good with things like watts & volts & amps... I just need some help.
I know Amp is battery capacity but how do Volt & Watt work??
There are 2 e-bikes I'm looking at that are somewhat similar (although one is a co-axial motor), but the price is very different ($1,200 vs $2,200).
The first bike is 250W, the 2nd is 350W (and co-axial motor). They're both 36V.
http://www.costco.ca/Yukon-Trail-Xplorer-XF26-7-speed-Step-through-Lithium-Electric-Bicycle.product.100022783.html
http://www.eprodigybikes.com/banff.aspx
I'm an urban commuter who doesn't need a super powerful bike, just some pedal assist. The most distance I would ever bike in one day is 25-30km.
Is the 250W enough for that? I test drove the 350W Eprodigy Banff and it had lots of juice, enough for me.
I'm leaning towards the Costco 250W bike, as it's a lot less expensive.
I'm guessing, after a couple of years, if I find the battery isn't strong enough or lasting long enough, I can upgrade the battery, yeah?
Or should I get the Copenhagen wheel (48V/350W) and attach that to my current bike? That would be even less expensive ($1,000).
I know Copenhagen has had some issues with release date, but they say Spring 2015.
Anyway, please let me know your thoughts.
Cheers!

 

[spinningmagnets]

The Yukon is a rear geared hub, and the rest of the bike will be of a very low quality. Hence the price.

The eProdigy is a Bofeili mid-drive, so the motor has the use of the bikes gears. This is very useful if you have hilly terrain on your commute. However, even if your commute is relatively flat, the fact you are limiting yourself to 250W/350W...I would definitely recommend the eProdigy (which I have test-ridden at Interbike 2014).

As far as the power ratings, they cannot be trusted. They are often found to be listed as too low or too high (sounds odd, but it's true)

 

[Drunkskunk]

A watt is a unit of power. the more watts you have, the more power you have. 750 watts, for example, is commonly called 1 horse power in the same way 12 eggs is commonly called a dozen. So from that you can tell that the 350 watt motor is more powerful.

If you want the math, Volts times amps is Watts. (V x A = W) Think of a water barrel. The volts are how tall the barrel is. the Amp hours are how big around the barrel is, and the watt hours are the actual capacity of the barrel.

In this case, the 350 watt motor in the Banff is also mounted in the crank, allowing the motor to use the gears of the rear 3 speed, so it's even better, in theory. However, for what you want the bike to do, the Yukon may be all the bike you need. it has the benefit of a slightly larger capacity battery.

The Copenhagen wheel doesn't actually exist yet. They have been promising that thing since 2009 I think, always promising it was coming soon. The release day they give is always just a season away, and they just keep moving it. Pure Vaporware.

As for the batteries, take their claims of range with a grain of salt. When they say "Up to 49km" they really mean 49km when riding on a flat oval track with no wind and a 35kg rider in a Lycra bodysuit, or something like that. You might get half that on a good day.