Setting up a GMAC for "250W nominal power" ?

Jil

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This subject can sound weird. Why would you want a GMAC to limit it to 250 watts ? :?:

Actually, I'm thinking about building an hardtail eMTB (or eFAT, I've not decide yet) with steel frame and rear motor. Not for me, but for sale in small serie. For the moment, it's just an idea, not a concrete project.

Then the idea is to keep it "street legal" as per UE criteria, i.e. 25 kph and 250 watts nominal power.
For a mountain bike, the 25 kph is not really an issue, as you need the motor mainly on hills.

The GMAC seems to me a good choice to have strong torque, durability (especially when limited to 25 km/h), limited weight and size, and regen.

Concerning the power limit, it's tricky, because all manufacturers of central motors (Bosch, Brose, Shimano...) sell their motor as "250 watts nominal power", but everybody knows that the maximum power can be much higher (and sustainable for a long time), up to 700 watts or more.

The question is the definition of "nominal". A GMAC motor would be difficult to brand as "250 watts", but is there a specific setup that could be implemented in the controller to make it as "250 watts nominal" ? i.e. able to maintain higher power but just for limited duration (let's say 800 watts for 15 minutes) ? Could this be made with a Phaserunner ?
Setting the temperature limit at a low level (like 80°C) could be a way to limit the ability of the motor to handle strong power for a long time.

Or any other idea ?
 
> UE criteria

What is that?

Are you needing to actually submit your finished design for some sort of certification?

If not, is there a pattern to how this regulation gets enforced? Do the cops impound the bike then test it somewhere?
 
john61ct said:
Are you needing to actually submit your finished design for some sort of certification?
Yes, preferably.
 
It is very simple and cheap to limit performance. It is the opposite that requires lots of work and expanses. :twisted:
 
Might as well buy a stick a couple 250W holographic stickers on a 1000 watt motor and controller setup 36V 30A, if the french person is that scared. And don't forget to buy a half dozen spares for when the old stickers fade or are not there.

Might as well hide the rear hub motor behind a rear rack with pannier bags where the battery lives if french person is scared. A visible black generic controller blends in very nice on the top of the rear rack with a black frame, black pannier bags, black rear rack, black tires, black rims.
With pedal assist hooked up, and speed limited to a roadie wearing lycra casually pedaling speed, say 35kph then as long as you arent doing wheelies and being a general goof then everything will be alright.
 
That BS line even scares you :lol:
I just laugh at those kinds of statements, literally just laugh, not at you, I laugh at the penalty.... but you are right, it is France so who knows. I know that it is very very highly unlikely anything will happen when you use common sense, have pedal assist and hide the motor and slap on some holographic 250W stickers, and if you want to go further, use an engraver but make it look professional and neat.

So going "500W" Small geared hub with 36V 20A or "1000W" 9C 20-30H hub motor with 36V 35A is reasonable. Going to a big 45H mxus "3kw" hub motor is not reasonable if you want to stay within the common sense riding parameters mentioned. Aside from the weight, efficiency issues of 45H vs 9C vs small geared hub.


https://ebikes.ca/learn/power-ratings.html
there is no standard or even consistent way to provde a numeric 'watts rating' for a motor system. You can see the exact same motor listed as 250 watts, 500 watts, and 1000 watts by different vendors, and there is a valid justification for all those number. That makes a vendor or manufactuer's watts rating in isolation a fairly pointless figure for choosing or comparing setups, and we're not keen to particiate in that kind of arbitrary numbers game.

There is NO SUCH THING as a "rated watt" or any standarized method for rating ebike motor power. That's the truth, regardless of what other companies imply.

With electric motors, they do not produce a fixed amount of power when you turn them on.



RunForTheHills said:
markz said:
if the french person is that scared.

I don't know what enforcement is like, but France has pretty harsh ebike laws. They will fine you 30,000 euros and sentence you to up to a year in prison if you break them.

https://www.bike-eu.com/laws-regula...anned-in-france-with-30000-euro-fine-10137459
 
markz said:
That BS line even scares you :lol:
I just laugh at those kinds of statements, literally just laugh, not at you, I laugh at the penalty.... but you are right, it is France so who knows. I know that it is very very highly unlikely anything will happen when you use common sense, have pedal assist and hide the motor and slap on some holographic 250W stickers, and if you want to go further, use an engraver but make it look professional and neat.

Except that he is planning to build and sell these bikes to other people. As an ebike manufacturer, his chances of getting a fine are much higher than an individual riding a non-compliant bike.
 
RunForTheHills, you’re right.
My own ebike has also a GMAC which is unlimited. I know its capabilities !
But when it comes to creating and selling an ebike in small serie, it’s another matter. « 250 watts » stickers will not be enough :wink:

And you want a very durable motor also, a GMAC with low temperature limit (80-90 degrees C) and a power limitation around 800 watts for peak use will probably be a good choice. The 25 kph limit will do the rest.

Thanks for the links and quotations to all, I’m going to have a look at them.

If ES members have other insights about this matter, please share ! 🙂
 
RunForTheHills said:
Yes indeed. The 25 kph/250 watts limit is an European norm.

RunForTheHills said:
Are you planning to use a CAv3 and either a Phaserunner or Baserunner controller? If so, you can find information on the settings here:

https://www.ebikes.ca/downloads/documents/CA3-0_settings.html#PLimTag
Probably Phaserunner for its high quality (I have one) and small size. And CA3, unless there are other good displays/analysers compatible with the Phaserunner (if you know some of them, I will be glad to have your advice).
 
john61ct said:
> UE criteria

What is that?

Are you needing to actually submit your finished design for some sort of certification?
I dont’t know yet if submitting the finished design is needed, or if it will be enough to sign a certificate like this one : https://moustachebikes.com/wp-content/uploads/2019/12/moustachebikes-s9-certificat-conformite-vtt-2020-uk-tlv.pdf
 
john61ct said:
If not, is there a pattern to how this regulation gets enforced? Do the cops impound the bike then test it somewhere?

To my knowledge, there is no actual check by law enforcement of the application of this rule, except the speed limit that can be verified in some crowded areas. You can be controlled if you are driving at 50 kph with your ebike. But it has never happened to me 😉
I think it’s mainly in case of accident that this matter will be brought to the table.
 
Last I looked at phase runners, they were expensive (excellent but still costly).

You could do a small arduino project with a 50 Amp shut in one of the power conductors from the battery. Use one of the arduino outputs to trigger NC relay to cut the power at 250 watts or whatever power/time limits you choose.Alternately one could open NC relays for the throttle and PAS then restore them when the power level has dropped for a given interval. On some controllers all you need to do is drive the "Brake Signal" high or low. The possibilities are almost endless.
 
With a self imposed 250-500w limitation managed by the CA3 I just don't see the extra capabilities of the GMAC being a benefit. So unless there was some very specific hardware requirement for the GMAC (locked clutch, external torque arm, 10mm round axles, higher power potential, L10 connector, etc.) I might not spend the extra money (+$200 CAD) on it.

Instead you could look at something like the SX2 hub motor (from Grin with it's internal temp sensor) combined with the BaseRunner controller. This way you don't have to carry around that extra Kg or so of weight and you get a more efficient setup. You get the same temperature management/protection when used with the CA3 so you're not going to burn it up.

There are some tradeoffs with the smaller Shengyi motor - the smaller case means less heat dissipation so you will bump into the temperature driven power rollback/protection a bit sooner in hilly areas, and the smaller gears could mean a bit shorter lifespan (but again, with the lower power used this likely won't be an issue). The clutch also means no regen potential on the downhills but much more comfortable pedaling without power.

With the smaller Z9 connector on the SX motor you won't have to rewire it (as compared to the larger L10 connector on the GMAC) to use an un modified cassette lockring tool or if changing the nuts and washers. The 12mm axle with it's flats (and torque washers) means that with the lower wattage setup you might even get away without external torque arms if you have good solid dropouts.

Just something to think about.
 
Mclewis1 said:
With a self imposed 250-500w limitation managed by the CA3 I just don't see the extra capabilities of the GMAC being a benefit.

It would be 250 watts on average, with a max power set at ~7-800 watts.
As far as I know, the GMAC has no « official » power rating. And this rating means nothing anyways, it is well known that the « 250 watts » MTB sold in Europe can have peak power of 6-700 watts or even more.
https://www.emtbforums.com/community/threads/torque-curves-shimano-bosch-brose-yamaha.595/

The interest of the GMAC is the possibility of regen, and its capabilities for climbing. A small motor like the SX2 or the Bafang G310 will quickly overheat in hilly terrains.

In principe, these 250 watts "nominal" is the power that the motor is able to handle continously (let's say for 1 hour or more). For the GMAC, it is obviously more than this on flat terrain, but not on hilly terrain.
The GMAC, on a 10% hill, will overheat in 1 hour when used at 250 watts. At 12%, it's 30mn. I think it's sufficient to "prove" that this motor can be considered as "250 watts nominal", i.e. is not able to maintain a sustainable power above 250 watts without overheating in any conditions.
https://ebikes.ca/tools/simulator.html?motor=GMAC10T&batt=B4814_EZ&wheel=27.5i&cont=PR&grade=12&autothrot=true&throt=30.732051911026502


Mclewis1 said:
Instead you could look at something like the SX2 hub motor (from Grin with it's internal temp sensor) combined with the BaseRunner controller. This way you don't have to carry around that extra Kg or so of weight and you get a more efficient setup. You get the same temperature management/protection when used with the CA3 so you're not going to burn it up.
My problem here is that for an offroad use, I don't want a motor susceptible to overheat too quickly... But I'm open to other good geared rear motors, if you have advices :) (regen is a plus, but not mandatory).
 
According to the simulator, you can get well over a kilometer out of a G310, at 730W pulling 120kg up an 8% grade, before it overheats, at the lowest standard controller setting - 20A.

If I lower the current limit from there, the performance improves - I mean, you get farther, though of course you go slower. At 20A you're making 18kph up that hill, at 12A it's a little over 9 kph, but you can keep it up for well over 2 km, at 300W.

That 12A setting will still get up to 36 kph on the flat - running 450W until the battery runs dry, so is the G310 a 450W motor?

GMAC is clearly overkill. Expensive, heavy, not fun to ride unpowered. The BaseRunner is probably overkill too. As MadRhino points out, this is an easy feat that has been accomplished by everyone who makes electric bicycles.

You just need to find out exactly what's required. Any real enforcement on the street is going to depend on the label, and there's presumably some process through which the manufacturer certifies the bicycle's acceptable performance and is allowed to put the bicycle in the European market. What is that process? It appears that no one here knows, and we get no closer to knowing by speculating on it.
 
donn said:
GMAC is clearly overkill. Expensive, heavy, not fun to ride unpowered. The BaseRunner is probably overkill too. As MadRhino points out, this is an easy feat that has been accomplished by everyone who makes electric bicycles.
At 3.8 kg, I wouldn't classify the GMAC as "heavy". As far as I know it's the lightest hub motor in this power/torque class. Or do you know an equivalent (or better) ?
I have thought about the Heinzmann Cargo also, but it's too heavy (5 kg) and bulky.

The GMAC is expensive indeed, but it's not a major point. If I decide to build in small serie this steel electric MTB (with central gearbox), I don't plan to try competing on the prices, but to make the best possible one. In the price range of high-end eMTB. Is there a market, even small, for this kind of product ? That's another point that I need to check :wink:

The alternative that I see to this eMTB with central gearbox (Pinion...) and rear motor, is a central motor with rear gearbox (like Rohloff).
My problem is that I don't want to depend on global system motor+battery like Bosch or Shimano. I think that it's still possible to use a third-party battery with Brose, but for how long ? And I don't know if Mr. Brose is going to pick up his phone if I want to order, let' say, a dozen motors :lol:
 
Jil said:
At 3.8 kg, I wouldn't classify the GMAC as "heavy". As far as I know it's the lightest hub motor in this power/torque class. Or do you know an equivalent (or better) ?

No, that's just the point - that motor is out of your power/torque class. Maybe I misunderstand what you're up to, but you've been talking about a "250W" motor. A G310 is that, and it's lighter and doesn't get in your way if you want to pedal on a dead battery.

If you're looking for a "250W" system with a difference - ADEN Powerkit
 
People are being a bit vague here about EU regulations. Here are some relevant ones:

- EU No 168/2013 states "maximum continuous rated power means the maximum thirty minutes power at the output shaft of an electric engine as set out in UNECE regulation No 85"
(copy here: https://lexparency.org/eu/32013R0168/ART_3/ )
- UNECE 85 has a full definition of how a peak and continuous power test is to be conducted
(copy here: https://op.europa.eu/en/publication-detail/-/publication/44471446-bc46-44f0-bc97-0de997b18106/language-en)

My reading of these is that only a manufacturer of a motor would be able to conduct a certifiable test for drive train power. I think they also explain how most geared hub motor manufacturers can claim to be "250W maximum continuous" (yes, really) since all the tests are conducted "at a speed specified by the manufacturer".

If you are planning to produce something that is not street legal, such as a mountain bike not intended for road use, then none of this applies of course. In the UK, there are very restrictive regulations about what is permissible on a public right of way, such as a bridleway for example. Non street legal machines cannot be legally used, although enforcement is unheard of.

I have no idea what regulation apply to off road trails in France, but would not be surprised if something similar existed.
 
I had to look up what a Pinion Gearbox was. While it is interesting, I don't see how a mountain ebike would benefit from it. A hub motor still can't use the bikes gears, so would still have the issue of overheating on long hills or slow speeds on hilly terrain. You would be better off building a commuter bike if you want to use those components. At least with a hardtail you could offer a belt drive with the system. I like and own a GMAC. However, the CAv3's dated looking display won't give your bike much bling. It might be a difficult sell to people buying a high end ebike that are not DIY enthusiasts.

I think you have the right idea to do some market research first. Instead of building a small series of the same bike, you might consider a bespoke ebike business customizing each bike for what the customer wants.
 
Is the point of using the GMAC so that you can sell the ebike as legal, and allow easy modification by the buyer to unlock the potential? If so, then limiting via a programmable controller seems like the best route.
 
RunForTheHills said:
I think you have the right idea to do some market research first. Instead of building a small series of the same bike, you might consider a bespoke ebike business customizing each bike for what the customer wants.
That's an idea to consider indeed :wink:
 
donn said:
No, that's just the point - that motor is out of your power/torque class. Maybe I misunderstand what you're up to, but you've been talking about a "250W" motor. A G310 is that, and it's lighter and doesn't get in your way if you want to pedal on a dead battery.

I have been thinking about this. Fazua has set its high-end mid-drive motor for 250 watts maximum power, unlike all its competitors Bosch, Shimano, etc..., even on the US market. They explain here why : https://fazua.com/en/support/help-center/toolbox-software/maximum-vs-minimal-assist/

As the idea is to propose an ebike with light assistance, limiting to 250 watts maximum (and not nominal) power is a path to explore. In such case, a G310 would be perfect for any terrain without risks of overheating, even long hills.
 
E-HP said:
Is the point of using the GMAC so that you can sell the ebike as legal, and allow easy modification by the buyer to unlock the potential? If so, then limiting via a programmable controller seems like the best route.
No, the idea is to sell a legal bike, not (easily) possible to unlock.
 
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