nominal vs. peak - is it just marketing fluff?

So I've noticed a pattern amongst commercial ebikes where the motor power listed is often something like "nominal power" or "rated power" expressed in watts, and the battery capacity is often expressed in "max capacity" in watt-hours. I've also seen a few cases where "experts" on ebikes have stated that a well-balanced ebike is one where the battery Wh and the motor W are close to the same value. I think I've heard that referenced most in YouTube videos of either shop owners or people at expos repeating that saying.

I'm digging for a specific example still, but a generalized example would be something like a bike with a 10s4p battery being called a 42V, 504Wh pack, and with a 500W motor. That then makes the bike both sound more powerful (42V vs 36V), and more balanced. By contrast, if we use our more typical (read realistic) ratings, we'd call this a 36V, 12Ah pack. And as for the power of the motor, we know that it depends on what the controller will send into the motor. So if we assumed the common commercial controller default of 15A, that would make peak power as much as 630W on a full charge (or 432W at nominal capacity).

So I'd like to know if you guys think that this is an attempt by the industry to come up with figures that are digestible by the general public, or do you think it's more deceptive and the manufacturers are just trying to skirt under regulations or meet that imaginary capacity/power balance?

Well, yes, the better you understand it the easier choices will be. But consumers will never get it. Peak=Exaggerated, right? Nominal is more like normal use. Deceptive, I don't think that's too strong, but I would say you're showing that it's easy to get around it.

Marketing fluff for sure, but its up to the consumer to have knowledge. For example: EPA mileage on new vehicles is never right.

Add in ebay sellers or crowd-funders or Sondors or anyone for that matter, of course they are going to either fudge the numbers a tad or outright lie. That is why Justin has available to you a bunch of tools on his website, http://www.ebikes.ca/tools.html - The key is to pick the most appropriate motor that suits whatever you are buying which can be hard to do, but you can always come here and ask.

To clarify, I personally completely understand the real numbers and how to compute pack power/capacity, versus peak or nominal or minimal motor power. I was just commenting on what I've observed in the commercial arena.

I'm not even gong to go near the range numbers they quote... :wink:

zro-1 said:

So I'd like to know if you guys think that this is an attempt by the industry to come up with figures that are digestible by the general public, or do you think it's more deceptive and the manufacturers are just trying to skirt under regulations or meet that imaginary capacity/power balance?

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It's marketing. Better companies tell you what the battery is (i.e. a 10s 12ah battery) which is a lot more accurate and easy to compare with. Current limit is the best way to figure out max motor electrical power; nominal isn't very meaningful unless there are two power levels or something.

zro-1 said:

I'm not even gong to go near the range numbers they quote... :wink:

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:wink:

You'd be lucky if they even mention what type of cells they are using inside their battery, let alone the discharge or watt-hour, or stated conditions of said mileage numbers - down hill for miles and miles and miles, with tail wind

https://www.quora.com/Where-is-the-longest-downhill-stretch-of-road-I-could-ride-my-bike-without-ever-having-to-pedal?share=1

A short google search allowed me to find that the longest uninterrupted road descent in the world is is 117 km (72 miles) long and it is in Peru between Concocha and Paramonga. The starting point is at 4095 m (13440 ft) of altitude, the end at 16 m (52 ft).

Incidentally, if you do it in the opposite direction, this is also the longest uninterrupted road climb in the world.

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it is pure marketing wank. you can have a massive motor with a tiny battery and still not exeed ratings.