Wireless Throttle, Ebike Trailer

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JED1990   1 mW

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Wireless Throttle, Ebike Trailer

Post by JED1990 » Mar 13 2021 8:03pm

Hi, I'm creating a powered trailor that can be quickly attached / detached to any bike.
My prototype will have a 36v 500w motor. I'm aware most standard, variable speed throttles send a voltage between 0-5v to the controller which effects the speed.

Is there a way to create a variable speed thumb type throttle than can send signals to the controller? I was looking at Arduino boards and a little bit lost on where to begin. The reason I'm looking for wireless is I'd like to be able to remove the throttle quickly without messing with wires.

Any help / guidance will be appreciated :)

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Re: Wireless Throttle, Ebike Trailer

Post by LeftieBiker » Mar 13 2021 8:18pm

I think that we aren't seeing wireless throttles for sale because of the risk of RF interference causing runaway motors. It should be possible to protect against that, but the issue does stand in the way of the usual cheap Chinese manufactured parts we generally see.

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Re: Wireless Throttle, Ebike Trailer

Post by LewTwo » Mar 13 2021 11:45pm

JED1990 wrote:
Mar 13 2021 8:03pm
Hi, I'm creating a powered trailor that can be quickly attached / detached to any bike.
My prototype will have a 36v 500w motor. I'm aware most standard, variable speed throttles send a voltage between 0-5v to the controller which effects the speed.

Is there a way to create a variable speed thumb type throttle than can send signals to the controller? I was looking at Arduino boards and a little bit lost on where to begin. The reason I'm looking for wireless is I'd like to be able to remove the throttle quickly without messing with wires.

Any help / guidance will be appreciated :)
Check out ESCs designed for use with skateboards. I know at least some of those have wireless remotes.
The 'pusher trailer' concept has come up before. I do not recall it getting much enthusiasm.
The more I learn the more obvious the immensity of my ignorance becomes.
Weight Wennie E-Bike https://endless-sphere.com/forums/viewt ... 3#p1173723
Shaft Drive Grocery Getter https://endless-sphere.com/forums/viewt ... =6&t=90718
...and thanks to Justin!

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Re: Wireless Throttle, Ebike Trailer

Post by amberwolf » Mar 14 2021 12:46am

As noted above, esk8 stuff often uses wireless throttles.

However...if there is interference in the signal, the controller needs to handle this by shutting down, because you don't want to lose control of it and have it "stuck" on the last input. ;)

One way to do that with a regular ebike/etc controller, is to use a receiver at the controller end that simply outputs zero volts when it isnt' receiving a valid strong signal from the throttle. Typically, ebike controllers expect about 1v to about 4v (for hall throttle types), and any signal below or above that should trigger a fault and cause the controller to shutdown power to the motor. That's something you'd need to test with the specific controller you end up using, and if you ever change which one is used, you'll need to retest this. Some controllers *don't* fault on these conditions, so things like a broken throttle ground can raise it's output to basically supply voltage, and the controller just goes full blast instead. :(

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Re: Wireless Throttle, Ebike Trailer

Post by amberwolf » Mar 14 2021 12:56am

Some thoughts, which you may have already considered:

Regarding pusher trailers in general...if the push is in the wrong place on the bike, or happens under the wrong conditions, it can do a great job of pushing the bike over and crashing.

If the trailer is not heavy enough, right over it's wheel(s), it wont' have enough traction to push the bike and rider.
can be quickly attached / detached to any bike.
that might be a stretch to be able to do. There are quite a lot of radically different designs, and unless it comes with a number of different ways of connecting it to a bike, it is not likely to fit all of them.

There are a number of pusher trailer designs out there that might give you help working yours out, and some of them are in threads listed here (not everything in the list is relevant, but you can tell what is pretty easily):
search.php?keywords=push*+trailer*&term ... mit=Search

and a more general trailer list that has stuff not listed above, most of which is not relevant but some of which will be:
search.php?keywords=trailer*&terms=all& ... mit=Search

There are also some about the ridekick:
search.php?keywords=ridekick&terms=all& ... mit=Search

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Re: Wireless Throttle, Ebike Trailer

Post by JED1990 » Mar 14 2021 1:24pm

amberwolf wrote:
Mar 14 2021 12:56am
Some thoughts, which you may have already considered:

Regarding pusher trailers in general...if the push is in the wrong place on the bike, or happens under the wrong conditions, it can do a great job of pushing the bike over and crashing.

If the trailer is not heavy enough, right over it's wheel(s), it wont' have enough traction to push the bike and rider.
can be quickly attached / detached to any bike.
that might be a stretch to be able to do. There are quite a lot of radically different designs, and unless it comes with a number of different ways of connecting it to a bike, it is not likely to fit all of them.

There are a number of pusher trailer designs out there that might give you help working yours out, and some of them are in threads listed here (not everything in the list is relevant, but you can tell what is pretty easily):
search.php?keywords=push*+trailer*&term ... mit=Search

and a more general trailer list that has stuff not listed above, most of which is not relevant but some of which will be:
search.php?keywords=trailer*&terms=all& ... mit=Search

There are also some about the ridekick:
search.php?keywords=ridekick&terms=all& ... mit=Search

Hi AmberWolf

Thanks alot for the advice and the links ! I'll have a look through them all. :D
Totally get what you mean with the interference and the potential risks what come with it. Not the end of the world to wire it up, but just appeals to me to be able to swap it from bike to bike.
I won't be relying on the trailor to do any work for the bike / rider. I'm hoping to 'offset' the load it carries through electric power. Design wise I'd make a simple alloy frame with mesh insert for the base (possibly make some sides) and have a box attached underneath containing battery / controller. I'd try and keep this all central, between the wheels, to try and balance the weight. I'm hoping to use the motor I've bought to feed a chain to a cog on the axle that would provide power to the wheels ..(almost like a mid drive motor) rather than have one or two motorised wheels. I've found a simple speed controller from Amazon

And a motor https://www.ebay.co.uk/itm/114626824158

[urlhttps://www.amazon.co.uk/Controller-Adjustable- ... B078TC3DTX[/url]

Battery I've made using 18560 cells to run at 36v

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Re: Wireless Throttle, Ebike Trailer

Post by JED1990 » Mar 14 2021 1:28pm

LewTwo wrote:
Mar 13 2021 11:45pm
JED1990 wrote:
Mar 13 2021 8:03pm
Hi, I'm creating a powered trailor that can be quickly attached / detached to any bike.
My prototype will have a 36v 500w motor. I'm aware most standard, variable speed throttles send a voltage between 0-5v to the controller which effects the speed.

Is there a way to create a variable speed thumb type throttle than can send signals to the controller? I was looking at Arduino boards and a little bit lost on where to begin. The reason I'm looking for wireless is I'd like to be able to remove the throttle quickly without messing with wires.

Any help / guidance will be appreciated :)
Check out ESCs designed for use with skateboards. I know at least some of those have wireless remotes.
The 'pusher trailer' concept has come up before. I do not recall it getting much enthusiasm.
Thanks! I'll take a look at ESCs ! Not heard of them before so useful :)

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Re: Wireless Throttle, Ebike Trailer

Post by amberwolf » Mar 14 2021 10:56pm

JED1990 wrote:
Mar 14 2021 1:28pm
LewTwo wrote:
Mar 13 2021 11:45pm

Check out ESCs designed for use with skateboards. I know at least some of those have wireless remotes.
The 'pusher trailer' concept has come up before. I do not recall it getting much enthusiasm.
Thanks! I'll take a look at ESCs ! Not heard of them before so useful :)
This subforum has a number of remote-controlled esk8s:
viewforum.php?f=35

Some of these threads may be relevant (haven't read them):
search.php?keywords=remote*&terms=all&a ... mit=Search

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Re: Wireless Throttle, Ebike Trailer

Post by TDB » Mar 15 2021 7:29pm

JED1990 wrote:
Mar 14 2021 1:24pm
Hi AmberWolf

Thanks alot for the advice and the links ! I'll have a look through them all. :D
Totally get what you mean with the interference and the potential risks what come with it. Not the end of the world to wire it up, but just appeals to me to be able to swap it from bike to bike.
I won't be relying on the trailor to do any work for the bike / rider. I'm hoping to 'offset' the load it carries through electric power. Design wise I'd make a simple alloy frame with mesh insert for the base (possibly make some sides) and have a box attached underneath containing battery / controller. I'd try and keep this all central, between the wheels, to try and balance the weight. I'm hoping to use the motor I've bought to feed a chain to a cog on the axle that would provide power to the wheels ..(almost like a mid drive motor) rather than have one or two motorised wheels. I've found a simple speed controller from Amazon

And a motor https://www.ebay.co.uk/itm/114626824158

[urlhttps://www.amazon.co.uk/Controller-Adjustable- ... B078TC3DTX[/url]

Battery I've made using 18560 cells to run at 36v
I can't help with wireless... that is something I'd do if it were easy. Maybe if mine was throttle only... it uses a PAS ring (no PAS) for pedal first and brake sensors. It is otherwise a throttle setup. The trailer is permanently fixed to my bike because of the wiring.

Just a thought regarding power requirements... 500W is waaaay more than offsetting drag and weight.

A modestly trained cyclist needs less than 160W (200W electrical) for that. Mine runs 200W maximum and that is for punching through headwinds on my commute and guaranteeing my arrival time. My bike has a Powertap hub power meter and I climb at about 4W/kg, decently fit... a "lycra"... 4W/kg multiplied by the 35kg maximum weight of my trailer is 140W mechanical power. That is a simplistic calculation, but it holds up well in real life for climbing. Any more and the trailer is pushing me. The goal is zero net thrust / drag. 100-120W is about the minimum power for reasonably efficient battery use (motor efficiency drops quickly at very low power) and that is my range for flat ground. It is a slight push at my endurance pace of 180-200W. Slower riders will need less assist if the only goal is offsetting weight and drag.
At these power levels the trailer doesn't have any really nasty habits. I am aware of its presence though.

I'll say it again in case you were distracted... 500W is waaaay more than offsetting drag and weight.

Not preaching, just saying.

This my second build on this trailer. At the moment I am riding about 1000km and climbing more than 14,000m per week. 200W (mechanical) is the legal limit for this class of motorised bicycle here and I am good with that.
IMG_0091-2.jpg
IMG_0091-2.jpg (540.61 KiB) Viewed 383 times
BTW, push trailer isn't my first choice. IF I didn't have a hub power meter and IF I could have found a rear hub motor compatible with 11s road cassettes or IF I could have had a mid-drive with a 145-150mm Q-Factor without taking out a second mortgage the motor would have been on the bike. Trailer is still a requirement for all the crap I haul around and I'd happily keep the battery back there, but it wouldn't have been powered.
Last edited by TDB on Mar 17 2021 11:03pm, edited 2 times in total.

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Re: Wireless Throttle, Ebike Trailer

Post by JED1990 » Mar 17 2021 5:07pm

Really neat tailor you have there !
thanks for the advice over wattages... I've got a cheap 300w motor from eBay. Probably still abit overkill but it was a good price. I agree, any higher than that is pretty pointless, as it's not really about speed. I'll post a few pics up here once I make some headway with it !

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Motor set up, help !

Post by JED1990 » Mar 27 2021 2:57pm

Hi Guys - hope this question is roughly in the right section.

I'd just like someone to check over my power set up for a Motor / PWM / Battery / BMS

I've built a battery 10s 5p 36v 15a capacity and fitted with a BMS rated: Applicable voltage: 36V, Applicable power: <1000w, Max. working current: 30A, Continuous max current: 20A

So assuming this is okay, next comes the PWM and motor... I'm assuming the PWM is the gatekeeper to the current released to the motor... My motor is 36v and rated 11a. Do I need to buy a PMW rated 10a max ? My current PWM is rated 30a max so assuming this will allow the full 15a capicity of the battery to be thrown at the motor, which will be bad, surely? :shock:

Any help would be appreciated!

I also have a Low Voltage Cutoff circuit to install as couldn't see the BMS listing this feature.

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Re: Motor set up, help !

Post by amberwolf » Mar 28 2021 12:46am

JED1990 wrote:
Mar 27 2021 2:57pm
I've built a battery 10s 5p 36v 15a capacity and fitted with a BMS rated: Applicable voltage: 36V, Applicable power: <1000w, Max. working current: 30A, Continuous max current: 20A
Is the battery 15A, or 15Ah? The difference is very important; A is how many amps the banks (groups) of cells can output, and Ah is their capacity.

What specific cells is the battery made from? (that will help us help you figure out what it is *really* capable of, not what the specs the seller might have given say it can do).

For the BMS, how long can it sustain the "Max. working current" of 30A? If it doesn't say, you should assume a few seconds at most, and so call it a 20A BMS (since that is it's max continuous rating).

So assuming this is okay, next comes the PWM and motor... I'm assuming the PWM is the gatekeeper to the current released to the motor...
If by "PWM" you mean the controller (sometimes called an ESC or Electronic Speed Controller), then yes, it is. But it is more important that the controller not draw more than what the *battery* can output, as the motor will draw whatever it needs from the controller, up to the limit of the controller to supply it.

If the motor is capable of handling the loads you will be placing on it, then that isn't a problem--if it isn't big enough to do what you want, *then* it will overheat when overloaded hard enough and long enough.


What specific conditions will the system be used in? Meaning, terrain, winds, road/path conditions, hills (and how steep and how long), complete system and rider weight, continuous riding or stop/start traffic, etc. More info is better, as it will help us help you figure out if the parts you have will do the job you want to do.


To see how complete systems work, so you have a better idea of what parts are needed to do the job you want to do, I recommend going to the Grin Tech motor simulator, where you can setup different kinds of systems to see how they react under the various conditions you will be using your system in. It doesn't matter if they are exactly the same as yours, just that they are similar enough for you to learn from. :)

I also have a Low Voltage Cutoff circuit to install as couldn't see the BMS listing this feature.
Generally, a BMS that has wires that go to the individual cells (or groups) should have a cell-level LVC. It may not be adjustable, but it would normally be preset to a level safe for the cells it is sold to be used with.

The controller itself should also have an LVC, usually printed on it's label. This LVC is usually set for the typical pack voltage it is intended for. If it has a wide voltage range then the LVC may only be suitable for the lowest voltage range pack.



If you can provide links to each the exact products you have purchased from the same sites you bought from, it will help us help you by giving us direct access to whatever information those sites have about them.



Lastly, I would recommend using one thread for your whole project, so that everything about the project is contained in one place, and anyone helping will have access to all the info about it if they need it to help you, so you don't have to keep answering questions about things already discussed. ;)

If you like, this thread could be merged with your original one, and the title changed to whatever your project name is.

Or you can continue with separate threads, but you may end up answering the same things repeatedly. :)

Or you can make a project thread where the main stuff is, and then link back to it in each new thread you make, and link to each of the new threads from that thread, so it's still all tied together and those helping don't have to search around for other info (which people don't usually do ;) ).

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Re: Motor set up, help !

Post by Chalo » Mar 28 2021 12:55am

You're using a brushed DC motor, with two wires?

Amberwolf is correct that amp-hour battery capacity and battery amp limit are not directly related. If your battery is 5P of 18650 cells, it's probably got an amp rating of 25A or more (possibly much more).
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Re: Motor set up, help !

Post by JED1990 » Mar 28 2021 3:33am

Hi there AmberWolf,

Thanks for your reply. Yes if this thread could be merged with my previous this would be helpful for everyone - Sorry, quite new to forums. Is this something I can do? My original thread was about an electric assisted bike trailer.


Thanks for picking this apart, I can see I've been quite unclear so to clarify further ....
Is the battery 15A, or 15Ah? The difference is very important; A is how many amps the banks (groups) of cells can output, and Ah is their capacity.
It's 75a max continuous discharge , 15Ah capacity
It's 10s 5p Samsung 30q with this BMS:

https://www.amazon.co.uk/gp/aw/d/B07T55 ... asin_image


The controller itself should also have an LVC, usually printed on it's label. This LVC is usually set for the typical pack voltage it is intended for. If it has a wide voltage range then the LVC may only be suitable for the lowest voltage range pack.
Checking the listing again, it mentions a 'low discharge protection at 2.6v' (I assume this will be 26v for a group of 10 in series) ... so the seperate Low Voltage protection circuit I mentioned...

https://www.amazon.co.uk/gp/aw/d/B08BCM ... asin_title

.... may not be required? I quite like the idea of setting your own cut off, as this allows you to do.



Thanks for clarification on 'PWM', I now understand a 'Controller' is the correct term and the PWM simply refering to the type of control signal. The one I've initially bought is...

https://www.amazon.co.uk/gp/aw/d/B078TC ... asin_title



And finally the motor... Slight reservations, as I feel it may be too 'weak' for the job (my theory is to start lower and cheaper and work my way up) here is is:

https://www.ebay.co.uk/itm/36v-300w-Mot ... 6c493b7895

Can you load too much current into the motor? Or does the motor draw as much current as it needs?

My plan B motor option: Ideally looking for a 500w brush less.. I'm only looking for the ones with one stub axle (go-kart type) I've seen one, but no hall sensors and a little worried as I've heard they can go a bit haywire without them? I guess I could install hall sensors into the motor?

The motor / battery and controller will be fitted into a 'box' with a chain feeding a sprocket on an axle (similar to a go kart set up). I'm not looking for the trailor to 'push' its contents and the bike and the rider. It's mostly to offset the weight of the trailor and it's contents. Modest hills occasionally, (perhaps 5% gradients (feet) at most) but majority of time on flats or gradual inclines.
Last edited by JED1990 on Mar 28 2021 5:34pm, edited 2 times in total.

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Re: Motor set up, help !

Post by JED1990 » Mar 28 2021 3:43am

Chalo wrote:
Mar 28 2021 12:55am
You're using a brushed DC motor, with two wires?

Amberwolf is correct that amp-hour battery capacity and battery amp limit are not directly related. If your battery is 5P of 18650 cells, it's probably got an amp rating of 25A or more (possibly much more).
Hi Chalo, thanks for your reply.. I've provided some more information above which will hopefully make things a little clearer ..

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Re: Motor set up, help !

Post by amberwolf » Mar 28 2021 10:47pm

JED1990 wrote:
Mar 28 2021 3:33am
Yes if this thread could be merged with my previous this would be helpful for everyone - Sorry, quite new to forums. Is this something I can do? My original thread was about an electric assisted bike trailer.
If this is also about that trailer, I can merge the threads for you, and retitle it to whatever you would like.

It's 75a max continuous discharge , 15Ah capacity
It's 10s 5p Samsung 30q
Then the battery itself can probably handle whatever your motor needs, to do whatever it is your project has to do for you.
Ok, the specs from that page show
Features:
1.The protection board is for 10 series cell Li-ion batteries, it can be used for 3.7V ternary batteries, manganese acid batteries and cobalt acid batteries.
2.It has balance function which would ensure each battery cell being fully charged at same time.
3.Support overcharge protection, over-discharge protection and short circuit protection.
4.It is suitable for electric car, electric power assistant car, skateboard car, inverter, etc
5.With temperature control protection function, safe and reliable

Specifications:
Applicable voltage: 36V
Applicable power: <1000w
Max. working current: 30A
Continuous maximum current: 20A
Overdischarge protection voltage: 2.6v
Overcharge protection voltage: 4.25v
Charging current: max. 10A
Balance voltage: 4.2v
High temperature discharge: 75 ℃
Low temperature charge: - 7 ℃
Weight: 46g
which means that as long as your charger outputs at least 42v, the BMS will keep your cells balanced, and it will also shut off the battery output when any cell drops down to 2.6v, which is pretty low but that would also be under load, so they'll likely bounce back a few tenths when the BMS shuts off and the load is disconnected.

It also has an HVC of 4.25v / cell, meaning if any cell goes over that it will turn off the input port, so the charger cant' overcharge the cells. THen the balancers will drain each one down to 4.2v to balance them.

It doesn't specify the Max current time, so I would go with 5 to 10 seconds, as that is a typical enough peak specification time. It might take it for longer, it might not. So don't depend on that BMS being able to handle more than the 20A continuous, just in case. ;)

It mentions a temperature cutoff, and one of the pictures shows this is a little block sensor you can install between the center cells in the pack, so that if the pack heats up too much it will shut off the output (and probably the input). Same if it gets too cold.

, I now understand a 'Controller' is the correct term and the PWM simply refering to the type of control signal. The one I've initially bought is...

https://www.amazon.co.uk/gp/aw/d/B078TC ... asin_title
Since this is designed to work down to 6v, it doesnt' have an LVC useful to your battery. So you will be either dependent on your BMS to shut off when cells are low, or you'll want to use that separate LVC.

However, the LVC unit says
【SPECIFICATION】- Power supply voltage: 12-36V battery; Power: < 1.5W;
so if that <1.5W means how much power it can handle, rather than how much it uses, it cannot be used for your system without modification to use an external contactor (relay) that *can* handle the power your system will use. I think the 1.5w refers to how much power it uses, though, because:

The relay on it says it is 20A for up to 14VDC, which means that it could handle up to 20A thru it and presumably be able to switch on or off at that current without damge. However, it's only good for up to 14VDC which means that when the relay tries to open with 30V+ across it, it may continue arcing across the contacts and be unable to open the circuit, and may either weld the relay shut or cause a tiny fire inside the relay from the arcing (which is basically like a tiny welder). It might work perfectly fine...but it might not.

You may be able to use it a different way than directly in series with the battery (which appears to be how it's meant to be used) to the load. You'd run battery positive and negative to it, still, but you'd use the relay to switch a signal on the BMS on or off to enable or disable it, and let the BMS itself do the switching. Or, use the relay to control the On/Off switch on the controller. Both of those would require a bit of rewiring of the relay on the LVC board, so ti isn't connecting battery voltage to it's output, but rather just directly exposes the relay switching contacts.

And finally the motor... Slight reservations, as I feel it may be too 'weak' for the job (my theory is to start lower and cheaper and work my way up) here is is:

https://www.ebay.co.uk/itm/36v-300w-Mot ... 6c493b7895
Is a typical MY1016 brushed motor. Used in lots of things. They have no ventilation so when overloaded they can get pretty toasty inside. ;) But they work fine when not overloaded. Plenty of threads/posts about them (and similar Unite motors), if your'e interested:

search.php?keywords=MY1016&terms=all&au ... mit=Search

search.php?keywords=unite+motor*&terms= ... mit=Search
Can you load too much current into the motor? Or does the motor draw as much current as it needs?
IT draws whatever is needed to do the work asked of it. So if you are doing something that physically takes more power than the motor is made for, it may eventually overheat. THe more the overload, the faster that will happen. If the work asked of it is less than what it's made to do, then it won't have any problem with it.

My plan B motor option: Ideally looking for a 500w brush less.. I'm only looking for the ones with one stub axle (go-kart type) I've seen one, but no hall sensors and a little worried as I've heard they can go a bit haywire without them? I guess I could install hall sensors into the motor?
You're actually not looking for "stub axle" motors, as those would bolt the axle to the frame, and drive the wheel (or whatever) with the body of the motor (outrunner).

You're looking for an inrunner, which spins the shaft, rather than the body of the motor (like a hubmotor does). Most chaindrive motors (and beltdrive) do what you want, and they are available up to several kW though you don't need anything that large. ;)


The motor / battery and controller will be fitted into a 'box' with a chain feeding a sprocket on an axle (similar to a go kart set up). I'm not looking for the trailor to 'push' its contents and the bike and the rider. It's mostly to offset the weight of the trailor and it's contents. Modest hills occasionally, (perhaps 5% gradients (feet) at most) but majority of time on flats or gradual inclines.


If the motor doesn't have to do a lot of work, then it will probably be fine. If the offset weight is high enough and the slope is steep enough, it may have too much work to do but if if it only has to do it for a short enough time it may still be ok.

A controller with a current limiting circuit (which this controller implies it has, but might not work the way is needed) will protect itself against any overloads by reducing output to stay within it's limits. Some cheaper brushed controller designs don't properly current limit, and get fried by motor stalls or overloads fairly easily. Easy to tell when it's fried, as the motor won't shut off and goes full speed (the most typical failure mode), or stops and wont' spin anymore.


So....generally the "best" way to setup specifications for a system are to first determine the power necessary to do the work to handle the worst-case situations you'd encounter. Then find a motor that can easily handle that. Then find a controller to run that motor and be able to provide that much power, but that will limit power to what the motor can handle, so if it *is* overloaded, it won't melt the motor down as easily. Then find a battery that can provide at least that much power, at the voltage needed to run the motor at the speed you want it to go. (and the controlelr has to handle that voltage, too). There are other things, but those are the primary first things, in order.

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Re: Motor set up, help !

Post by JED1990 » Apr 09 2021 4:32pm

amberwolf wrote:
Mar 28 2021 10:47pm
JED1990 wrote:
Mar 28 2021 3:33am
Yes if this thread could be merged with my previous this would be helpful for everyone - Sorry, quite new to forums. Is this something I can do? My original thread was about an electric assisted bike trailer.
If this is also about that trailer, I can merge the threads for you, and retitle it to whatever you would like.

It's 75a max continuous discharge , 15Ah capacity
It's 10s 5p Samsung 30q
Then the battery itself can probably handle whatever your motor needs, to do whatever it is your project has to do for you.
Ok, the specs from that page show
Features:
1.The protection board is for 10 series cell Li-ion batteries, it can be used for 3.7V ternary batteries, manganese acid batteries and cobalt acid batteries.
2.It has balance function which would ensure each battery cell being fully charged at same time.
3.Support overcharge protection, over-discharge protection and short circuit protection.
4.It is suitable for electric car, electric power assistant car, skateboard car, inverter, etc
5.With temperature control protection function, safe and reliable

Specifications:
Applicable voltage: 36V
Applicable power: <1000w
Max. working current: 30A
Continuous maximum current: 20A
Overdischarge protection voltage: 2.6v
Overcharge protection voltage: 4.25v
Charging current: max. 10A
Balance voltage: 4.2v
High temperature discharge: 75 ℃
Low temperature charge: - 7 ℃
Weight: 46g
which means that as long as your charger outputs at least 42v, the BMS will keep your cells balanced, and it will also shut off the battery output when any cell drops down to 2.6v, which is pretty low but that would also be under load, so they'll likely bounce back a few tenths when the BMS shuts off and the load is disconnected.

It also has an HVC of 4.25v / cell, meaning if any cell goes over that it will turn off the input port, so the charger cant' overcharge the cells. THen the balancers will drain each one down to 4.2v to balance them.

It doesn't specify the Max current time, so I would go with 5 to 10 seconds, as that is a typical enough peak specification time. It might take it for longer, it might not. So don't depend on that BMS being able to handle more than the 20A continuous, just in case. ;)

It mentions a temperature cutoff, and one of the pictures shows this is a little block sensor you can install between the center cells in the pack, so that if the pack heats up too much it will shut off the output (and probably the input). Same if it gets too cold.

, I now understand a 'Controller' is the correct term and the PWM simply refering to the type of control signal. The one I've initially bought is...

https://www.amazon.co.uk/gp/aw/d/B078TC ... asin_title
Since this is designed to work down to 6v, it doesnt' have an LVC useful to your battery. So you will be either dependent on your BMS to shut off when cells are low, or you'll want to use that separate LVC.

However, the LVC unit says
【SPECIFICATION】- Power supply voltage: 12-36V battery; Power: < 1.5W;
so if that <1.5W means how much power it can handle, rather than how much it uses, it cannot be used for your system without modification to use an external contactor (relay) that *can* handle the power your system will use. I think the 1.5w refers to how much power it uses, though, because:

The relay on it says it is 20A for up to 14VDC, which means that it could handle up to 20A thru it and presumably be able to switch on or off at that current without damge. However, it's only good for up to 14VDC which means that when the relay tries to open with 30V+ across it, it may continue arcing across the contacts and be unable to open the circuit, and may either weld the relay shut or cause a tiny fire inside the relay from the arcing (which is basically like a tiny welder). It might work perfectly fine...but it might not.

You may be able to use it a different way than directly in series with the battery (which appears to be how it's meant to be used) to the load. You'd run battery positive and negative to it, still, but you'd use the relay to switch a signal on the BMS on or off to enable or disable it, and let the BMS itself do the switching. Or, use the relay to control the On/Off switch on the controller. Both of those would require a bit of rewiring of the relay on the LVC board, so ti isn't connecting battery voltage to it's output, but rather just directly exposes the relay switching contacts.

And finally the motor... Slight reservations, as I feel it may be too 'weak' for the job (my theory is to start lower and cheaper and work my way up) here is is:

https://www.ebay.co.uk/itm/36v-300w-Mot ... 6c493b7895
Is a typical MY1016 brushed motor. Used in lots of things. They have no ventilation so when overloaded they can get pretty toasty inside. ;) But they work fine when not overloaded. Plenty of threads/posts about them (and similar Unite motors), if your'e interested:

search.php?keywords=MY1016&terms=all&au ... mit=Search

search.php?keywords=unite+motor*&terms= ... mit=Search
Can you load too much current into the motor? Or does the motor draw as much current as it needs?
IT draws whatever is needed to do the work asked of it. So if you are doing something that physically takes more power than the motor is made for, it may eventually overheat. THe more the overload, the faster that will happen. If the work asked of it is less than what it's made to do, then it won't have any problem with it.

My plan B motor option: Ideally looking for a 500w brush less.. I'm only looking for the ones with one stub axle (go-kart type) I've seen one, but no hall sensors and a little worried as I've heard they can go a bit haywire without them? I guess I could install hall sensors into the motor?
You're actually not looking for "stub axle" motors, as those would bolt the axle to the frame, and drive the wheel (or whatever) with the body of the motor (outrunner).

You're looking for an inrunner, which spins the shaft, rather than the body of the motor (like a hubmotor does). Most chaindrive motors (and beltdrive) do what you want, and they are available up to several kW though you don't need anything that large. ;)


The motor / battery and controller will be fitted into a 'box' with a chain feeding a sprocket on an axle (similar to a go kart set up). I'm not looking for the trailor to 'push' its contents and the bike and the rider. It's mostly to offset the weight of the trailor and it's contents. Modest hills occasionally, (perhaps 5% gradients (feet) at most) but majority of time on flats or gradual inclines.


If the motor doesn't have to do a lot of work, then it will probably be fine. If the offset weight is high enough and the slope is steep enough, it may have too much work to do but if if it only has to do it for a short enough time it may still be ok.

A controller with a current limiting circuit (which this controller implies it has, but might not work the way is needed) will protect itself against any overloads by reducing output to stay within it's limits. Some cheaper brushed controller designs don't properly current limit, and get fried by motor stalls or overloads fairly easily. Easy to tell when it's fried, as the motor won't shut off and goes full speed (the most typical failure mode), or stops and wont' spin anymore.


So....generally the "best" way to setup specifications for a system are to first determine the power necessary to do the work to handle the worst-case situations you'd encounter. Then find a motor that can easily handle that. Then find a controller to run that motor and be able to provide that much power, but that will limit power to what the motor can handle, so if it *is* overloaded, it won't melt the motor down as easily. Then find a battery that can provide at least that much power, at the voltage needed to run the motor at the speed you want it to go. (and the controlelr has to handle that voltage, too). There are other things, but those are the primary first things, in order.

Hi AmberWolf

Just a belated thanks for your answers. Very useful to know and us helping loads. My project is completing slowly... I'll update this thread with images once done.

If you'd like to merge the thread to 'electric assist bike trailer' that will be great.

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