How to choose between 1000w and 1500w

[Nealh]

In that case, a 1000w motor going full speed, would drain the 48v/17Ah in about an hour? (and will achieve a lesser top speed than the 1500w motor?)

No not necessarily, if the 1kw is wound faster then it would go faster then a lesser wound 1.5kw.

A lesser example :
I have a 250w hub that tops 24mph coupled to 36v battery and 15a controller.
Also I have a 350w and a 500w hub coupled to a 36v battery and 20a controllers they top 19.8 mph.
The difference is in the hub motor windings the 250w is 270rpm whilst the other two are 201rpm, they are a bit slower but have a bit more low down torque, so can climb a bit better at low speeds.

 

[minime]

OK, building a custom bike seems too complicated so I'll go with one off the shelf.

Thanks for all your input.

 

[danielrlee]

OK, building a custom bike seems too complicated so I'll go with one off the shelf.

Thanks for all your input.

Motor theory is not too complicated, but can be totally perplexing to a novice. The amount of misinformation you have been given over your multiple threads on this forum is immense. Combined with your own misunderstandings, it is no surprise that you're confused.

 

[minime]

Motor theory is not too complicated, but can be totally perplexing to a novice. The amount of misinformation you have been given over your multiple threads on this forum is immense. Combined with your own misunderstandings, it is no surprise that you're confused.

Could you suggest a credible online resource to clear things up?

 

[Woosh]

it takes time to digest all the info you get given. First, the physics. Air resistance increases very quickly with speed. Almost all ebikes can do 20mph with pedaling when unrestricted, but above that, the increase in air resistance is so fast that for 25mph, you already need heavy artillery (BBS02 or 1000W DD motor) to beat the air resistance. 30mph is among the specialist bikes, beyond even 1500W DD motors. There is a tool:
http://www.ebikes.ca/tools/simulator.html
You can look up about 200 popular combinations of powerful motors (including 1500W ones and more) and battery. Even so, most of them cannot sustain 30mph indefinitely.

 

[minime]

it takes time to digest all the info you get given. First, the physics. Air resistance increases very quickly with speed. Almost all ebikes can do 20mph with pedaling when unrestricted, but above that, the increase in air resistance is so fast that for 25mph, you already need heavy artillery (BBS02 or 1000W DD motor) to beat the air resistance. 30mph is among the specialist bikes, beyond even 1500W DD motors. There is a tool:
http://www.ebikes.ca/tools/simulator.html
You can look up about 200 popular combinations of powerful motors (including 1500W ones and more) and battery. Even so, most of them cannot sustain 30mph indefinitely.

Great resource. So the claims at https://www.thesmallgreenroom.com/high-performance-electric-bikes are exaggerated?

 

[Woosh]

Great resource. So the claims at https://www.thesmallgreenroom.com/high-performance-electric-bikes are exaggerated?

they did not use the word 'continuously'. In the same way that you can get a road racer and hit 30mph easily and keep it up for 3 minutes.
I used to sell this e-bike, powered by a DD motor, for £299, complete with basket.
It has a throttle, apparently nobody ever bothered to pedal it.

 

[minime]

they did not use the word 'continuously'. In the same way that you can get a road racer and hit 30mph easily and keep it up for 3 minutes.

I'll ask them about "continuous speed" and report back. Any other things I should ask/look out for?

 

[Woosh]

If you use the tool at ebikes.ca, select the Crystalyte 404, with a 35A 48V controller and 48V 20AH battery. This is a typical build for a 30mph bike.
The tool will show maximum speed is 31.5mph for this base configuration.
Look at the black load (A) curve, it shows the mechanical power needed versus speed. You see how steeply it goes up when speed exceeds 20mph.



At maximum speed, your battery goes flat in about 25 minutes. Your effective range is about 15 miles.

 

[minime]

If you use the tool at ebikes.ca, select the Crystalyte 404, with a 35A 48V controller and 48V 20AH battery. This is a typical build for a 30mph bike.
The tool will show maximum speed is 31.5mph for this base configuration.
Look at the black load (A) curve, it shows the mechanical power needed versus speed. You see how steeply it goes up when speed exceeds 20mph.

View attachment 18133

At maximum speed, your battery goes flat in about 25 minutes. Your effective range is about 15 miles.

Very informative post.

So 15mph requires about 10N/m whereas 25mph requires about 30N/m? (assuming full throttle, no PAS)

How did you deduce from the diagram the time at which the battery goes flat?

Also, could it be that this particular bike is atypical, as far as 30mph bikes go, and the 50mph claim on the website is not an exaggeration? Otherwise, we are talking false advertisement, plain and simple.

 

[Woosh]

How did you deduce from the diagram the time at which the battery goes flat?

In the right bottom table (labelled Performance), you see consumption: 49.7WH/m.
Your battery has a capacity of 48V 17AH, it is likely built with 13S5P using NCR18650B cells. You get at most 800WH usable before the low voltage cutout kicks in. That's about 16 miles at most. Hence the effective range of 15 miles. You ride at 31.5 miles an hour, that works out about 25 minutes of enjoyment before the battery runs too low to ride anywhere over 10-12mph.

So 15mph requires about 10N/m whereas 25mph requires about 30N/m? (assuming full throttle, no PAS)

I don't know where you get those figures from. BTW, torque unit is NM, not N/M.
From the chart, looking up at the load (A) plot, 15mph requires 150W RPM=201 for 26" tyres, 25mph requires 620W, RPM=335. The torque as measured at the rear wheel, can be deduced from the power and RPM: 7.13NM at 15mph, 17.67NM at 25mph.

NB: the chart assumes user input power of 100W

 

[minime]

In the right bottom table (labelled Performance), you see consumption: 49.7WH/m.
Your battery has a capacity of 48V 17AH, it is likely built with 13S5P using NCR18650B cells. You get at most 800WH usable before the low voltage cutout kicks in. That's about 16 miles at most. Hence the effective range of 15 miles. You ride at 31.5 miles an hour, that works out about 25 minutes of enjoyment before the battery runs too low to ride anywhere over 10-12mph.



I don't know where you get those figures from. BTW, torque unit is NM, not N/M.
From the chart, looking up at the load (A) plot, 15mph requires 150W RPM=201 for 26" tyres, 25mph requires 620W, RPM=335. The torque as measured at the rear wheel, can be deduced from the power and RPM: 7.13NM at 15mph, 17.67NM at 25mph.

NB: the chart assumes user input power of 100W

Why aren't you offering non-legal e-bikes for "off-road" usage? You seem knowledgeable and willing to help the uninitiated; why let the competitors take a chunk of your customer base. Some of your competitors, whom I've contacted via e-mail about buying a new e-bike, didn't even bother to reply.

 

[Woosh]

I am pro personal choice, but company's policy is to stay on the straight and narrow...

 

[minime]

I am pro personal choice, but company's policy is to stay on the straight and narrow...

Oh ok, I thought you were the owner of the business. Still, it doesn't make sense not to offer high-powered bikes since it is perfectly legal to do so but I guess they have their reasons.

 

[Woosh]

yes, it is legal to offer high power bikes for sale but if you consider the whole business cycle, provision, marketing, sale, support, on-going spares, the technology moves too fast to make any sensible return on investment. We need to sell at least 500-1,000 units of any model to make the whole cycle viable. With fast moving technology, the product is unlikely to stay topical for 4 years. There is no hope to sell anything like 100 high power bikes a year unless we go through normal distribution channels. Then the price shoots up, and so does expectations.

 

[flecc]

it doesn't make sense not to offer high-powered bikes since it is perfectly legal to do so

Just like the power question, the e-bike law isn't quite so cut and dried.

Firstly, "private land" in this context hardly exists. Anywhere where the public have access to is subject to the pedelec regulations so, since the right to roam legislation was put in place, we're largely only left with riding illegal bikes around our gardens. Even the few large private estates often have public footpaths running through them.

Secondly, even though it's not illegal to sell bikes that are not legal for road use, a company can still incur liabilities. In an accident case where an insurance company is facing a multi-million pound liability, they might well pursue at law the supplier of a bike involved in the accident on the grounds of their negligent behaviour. Then the supplier would need to show that they had taken every precaution to inform the buyer of the true status of the bike and the legal restrictions on its use.

All very messy and not the sort of tangle that a supplier would want to get mixed up in. A few major suppliers have posted as such in this site.
.

 

[minime]

yes, it is legal to offer high power bike for sale but if you consider the whole business cycle, provision, marketing, sale, support, on-going spares, the technology moves too fast to make any sensible return on investment. We need to sell at least 500-1,000 units of any model to make the whole cycle viable. With fast moving technology, the product is unlikely to stay topical for 4 years. There is no hope to sell anything like 100 high power bikes a year unless we go through normal distribution channels. Then the price shoots up, and so does expectations.

Just like the power question, the e-bike law isn't quite so cut and dried.

Firstly, "private land" in this context hardly exists. Anywhere where the public have access to is subject to the pedelec regulations so, since the right to roam legislation was put in place, we're largely only left with riding illegal bikes around our gardens. Even the few large private estates often have public footpaths running through them.

Secondly, even though it's not illegal to sell bikes that are not legal for road use, a company can still incur liabilities. In an accident case where an insurance company is facing a multi-million pound liability, they might well pursue at law the supplier of a bike involved in the accident on the grounds of their negligent behaviour. Then the supplier would need to show that they had taken every precaution to inform the buyer of the true status of the bike and the legal restrictions on its use.

All very messy and not the sort of tangle that a supplier would want to get mixed up in. A few major suppliers have posted as such in this site.
.

That's what I suspected. One retailer will offer the "derestriction codes" only if you sign a disclaimer. But I suppose an insurance company wouldn't take on a small bike shop; they'd be interested in bigger fish with deeper pockets.

 

[flecc]

But I suppose an insurance company wouldn't take on a small bike shop; they'd be interested in bigger fish with deeper pockets.

I wouldn't be too confident about that, insurers are notorious for attempting to dodge liabilities. Even a small bike shop can have some liability insurance which might be underwritten by a large insurer capable of big payouts.
.