Motor Question for a Newbie

[borqueoneal]

Hi guys

I am kind of new to e-bike and i was making my search about the motors .

Now i want to build my e-bike and i have the following questions;

1- Motor .

Due to budget i will either buy Bafang or Dapu. I have heard that Dapu is a better motor. Do any of you have idea about it ?

What things shall i consider while buying a motor?

Most of you will think that maybe i am stupid. But does rated power mean everything ? For instance a 350w bafang and dapu have similar efficiency rate on websites which are >80%. So does it mean they have the same performance.

I am sure there must be certain differences. What are they ?

Do i need to check the torque curve to make a better judgement ?


2- Pump the motor.

i hear that some guys overclock the dapu 350 w motor to 750w motor. How can it be done ? What are the risks about it ? ANd while doing it what things shall i pay attention?


3- I don't think i will use my e-bike over 30 km/h often. But i will be needing some nice acceleration and also hill climbing . IN this case a higher amp battery will be a better choice for me rather than investing for voltage.

So with equal amp batteries a 36V and 48V will create same torque ? I know 48V will give a better high speed.

And with same voltage battery a higher amp battery will give a better torque ? is it correct


4- Hall sensor .

I know hall sensors can sometimes create problems in motor. But do they give a better performance ? If not a better performance why do we need them. Just for not a shaky start?

thanks for all your help and answers.

 

[borqueoneal]

I am thinking to make my own battery pack. And i am at early stage of research.

I am confused between buying a Samsung or a Chinese Brand Battery cells. Ofcourse Samsung should be a more reliable cell but comes with extra cost.

1- Do they really differ in performance ? What are the differences. Or are the differences more on variation of values of each production lot. I think samsung must have a smaller margin of variation of values.


2- Do i really need Lifepo rather than Lithiom IOn.
I see lifepo have a much better charge cycles and a smaller charge time.

3- For a pack what is difference for "Discharge rate for rated life " and "Discharge rate continous".
Also difference between "rated capacity" and "usable capacity"

Thanks for my extremely newbie questions.

 

[mvly]

Not sure why you even ask. Always and I say Always go with anything other than chinese batteries if possible. You'll save more money in the long run. If you are looking for lowest cost, get Lead Acid.

 

[999zip999]

I try to go for cheapest chinesse no name or rewrapped cell.
Look you have to pay shipping. So get a good cell from a vendor somebody here has had luck with.

 

[borqueoneal]

I think i will give a try to a chinese cell but i am 99% sure i will end up with a samsung cell in the end.

I also have another question. I am not so much into high speed but i want some good acceleration so torque is more important for me.

So in this case i think i won't need 48V rather 36 V battery will be enough for my 500 W motor i guess.

But i am planning to build my battery around 14A - 16A. So how much max current i can get from such battery? Does it all depend on C factor ?

And for such battery what amp controller will i need for high torque but without blowing my motor or controller? Will 30A controller be enough?

 

[borqueoneal]

I want to ask a simple question.

I know it isn't suggested but what if i use a 48V battery in a 36V motor ? What are the possible risks other than overheating the motor ? Can it work in this way ?

Do any of you guys tried it ?

 

[borqueoneal]

I need a high torque so i am going for a Dapu 350W (M155RD) motor and i want to use either 36V or 48V battery but in any case i want to deliver high amps .

My questions are followings;

- If i use a battery with 15A capacity. I think i can easily give 30A peak current right ? What is your idea and suggestion for my battery .

- If i want to give such high amps what shall the controller be ? I think 30A controller will be enough for me. What other things i need to pay attention in controller.

Why is controller crucial for higher torques ? So it can provide higher current to motor without letting itself burn out ?

Also will 30A cause any damage in motor ?
I don't want to use holes to cool the motor . i want controller the shut the motor down when it is overheated. Is there anyother way other than using temperature sensor?


I really don't care about top speed so much but i want a smooth climb and nice acceleration feeling.

thanks in advance

 

[Ykick]

Less concern about the motor (particularly BLDC) than the controller.

Whaddya got? Pics? Specs?

 

[borqueoneal]

Thanks for reply.

1- Motor is Dapu M155RD

2- Controller : Generic Chinese COntroller. Current limit 15A. ( i think i need a higher amp right ? )

What kind of controller do i need? I like the lyen's controllers but they are expensive for me.

 

[spinningmagnets]

I Googled "Dapu M155RD", does this look right?
http://dapumotor.manufacturer.globa.../pdtl/DC-motor/1084040708/M155-Rear-Motor.htm

The 36V motor (whether it is brushed or brushless) should be fine using 48V. However, it will spin about 30% faster. You would likely need to use a 48V controller (make sure the controller is brushed or brushless, to match the motor). This one looks brushless.

There will not likely be much extra heat. Maybe some, but the majority of the motor heat comes from how many amps you are using.

 

[LockH]

Ding Ding Ding!

(On Alt. Reality planet ES search found only 33 matches: +Dapu)

 

[borqueoneal]

Thanks for the answer. I think i will go with using 36V motor and i am intending to use 15A battery. Can i get 30A from such battery without a major problem?

I think i also need to upgrade my controller to be able to handle 30a. Is it correct ?

I Googled "Dapu M155RD", does this look right?
http://dapumotor.manufacturer.globa.../pdtl/DC-motor/1084040708/M155-Rear-Motor.htm

The 36V motor (whether it is brushed or brushless) should be fine using 48V. However, it will spin about 30% faster. You would likely need to use a 48V controller (make sure the controller is brushed or brushless, to match the motor). This one looks brushless.

There will not likely be much extra heat. Maybe some, but the majority of the motor heat comes from how many amps you are using.

 

[NeilP]

Just so you understand correctly..

there is no such thing (in general terms with regard to these motors) ..as a '36 volt motor'

It is the controller that is voltage limited...by the components inside. You could run the motor with a 150 volt controller no problem.

The motor will have wattage limits brought on my how much heat it can dissipate, and how much current it can handle.

( OK, yes there are voltage limits..not that you will hit them, unless you maybe want to start running it at thousands of volts and the insulation starts breaking down.)


So it is the controller you need to worry about first.

First try and find out from the seller if they know what components are inside the controller...what MOSFETS, capacitor voltage values etc...If they don't know, next bet search the forum and red those 33 posts mentioned earlier and see if any one else know..
lastly ..if you are competent with a screwdriver...open the controller...probably screws on the end, plus three or four on the side.

This is last thing to try if all else fails, as people do do dumb things , like not re assemble properly and short circuit things or cross thread screw etc.
If you open it up..take pictures of bits f it..post them here and then we will probably guide you better...probably which bits to take clearer pictures of to start with.


YOU need to know what the max voltage the controller can take...your motor will be fine

 

[spinningmagnets]

Some of the countries where these motors are sold have a speed limit. If a motor is labeled a 36V motor, it sometimes means that it is a faster Kv, so it will achieve a certain speed at 36V. If that is the case, then the same motor when it is labeled 48V is a slower Kv, so it will go the same speed at the higher voltage.

Sometimes the wholesalers who are selling direct to the public don't actually understand the product they are selling. Often, the advertisements have incorrect information in them, or vital information is missing. The link I supplied suggests that this model only has one Kv to choose from. It can be run at 36V or 48V...in which case it will run faster at 48V, and slower at 36V.

You mention a 15A battery, but I think you might mean that it is a 15-Amp hour (Ah) battery, which tells us the size of it. when you ask about this 15-Ah size of battery, you are wondering if it can provide 30-Amps of current (30A)?

I would recommend keeping the stock 15A controller, because it will only allow you to use a maximum of 15-amps of current, which is likely to be the maximum you can apply to this small motor without the motor getting too hot. A 15-Ah size of common Lithium-Ion batteries is a perfect match for this motor.

If you want to be able to use 36V X 30A = 1,080 watts of power, you will need a bigger motor, a high-current battery, and a bigger controller. This motor will get too hot at 30A, and the 15A controller can be forced to flow 30A, but it will also get too hot. If you try to draw 30A from a battery that is only able to safely supply 20A at the temporary maximum...it will die very quickly.

 

[bowlofsalad]

I need a high torque so i am going for a Dapu 350W (M155RD) motor and i want to use either 36V or 48V battery but in any case i want to deliver high amps .

My questions are followings;

- If i use a battery with 15A capacity. I think i can easily give 30A peak current right ? What is your idea and suggestion for my battery .

- If i want to give such high amps what shall the controller be ? I think 30A controller will be enough for me. What other things i need to pay attention in controller.

Why is controller crucial for higher torques ? So it can provide higher current to motor without letting itself burn out ?

Also will 30A cause any damage in motor ?
I don't want to use holes to cool the motor . i want controller the shut the motor down when it is overheated. Is there anyother way other than using temperature sensor?


I really don't care about top speed so much but i want a smooth climb and nice acceleration feeling.

thanks in advance

I wouldn't use a battery beyond it's rating.

The motor you mention has a rating of 350w, apparently. What that probably means is that it can suck down 350w all day and it'll be fine, exceeding this may cause some negative effects (heat). Volts times amps equals watts. 48v times 30a equals 1440w. 1440w will surely destroy that hub in a short amount of time, maybe a minute or less.

You should probably consider a mac instead of a dapu, you can check them out at em3ev.com.

I am not sure what else will shut down the motor beyond it over heating and breaking unless you want to involve a temperature sensor. The mac I mentioned has a temperature sensor, pair that with a cycleanalyst 3 and you'll have some thermal protection for the hub.

 

[dogman dan]

RE sensors in the motor. In general, planetary gear motors need to run sensored.

But when you over volt or over watt a motor, it can heat them up fast, and the hall sensors is often what cooks off first.

A 750w controller in a small gearmotor can last ok, 36v 20 amps.

If you are on a really tight budget, the battery is your problem. If you cannot afford a large lithium battery, you may not have enough range to fry a motor. In particular, lead sla batteries will run down before you get very hot.

 

[borqueoneal]

Hi

I was searching for this cell and i see the chart about the specifications. I want to make a 10S4P.

Specifications of the battery are as followings;
Nom. Voltage : 3.6V
Typical Capacity : 2150 mah
Max Discharge Current : 10A (THIS CONFUSE ME A LOT ).

With my design my pack shall be : 36V and 8.6 Ah.

But what does this 10A mean for one battery cell. Is it related with C value? Can someone explain it like explaining to a dummy? (Frankly i feel sometimes i am a dummy)

Does that mean my battery will last 8.6/10= 52 minutes ?

 

[wesnewell]

Divide 10 by 2.15 to get the C rate, so ~4.65C rate.
It's a 2.15ah cell, so you can draw 2.15A for 1 hour. 4.3A for 30 minutes, etc.
At 10A, roughly 10 minutes.

 

[borqueoneal]

Thanks a lot for the reply. Now it became clear.

As my pack will be 10S4P. i think i can get max 10x4= 40 A current . Is it correct?

 

[wesnewell]

Yes, That's what they are rated for. if they live up to their rating 40A is right.

 

[borqueoneal]

hi guys

I completed my e-bike and it works well. And now want to upgrade my gf's ebike. She have a battery which is older than me so sure needs a replacement.

her e-bike have a 350W motor *hub ofcourse* , And 18A controller.

As i use a ICR 18650-22P battery cells in my e-bike earlier, i was very satisfied due to their high discharge rate. with 10s4P i achieve (in theory) 10x4=40A.

My questions are as followings;

- If i just change the battery without replacing motor and controller, will i face any problem?
- Will the motor handle 40A? What is your idea ?
- This is more theoretical question. But in the following link there is specs of the battery cell. And it says max current = 10A. So is it a continuous current or just max current? And how long it generally can stay there ?
http://www.tme.eu/en/details/accu-18650-2.2p-hv/rechargeable-batteries/samsung/icr-18650-22p/
- If i need to change the controller, what is your suggestion? What parameters i need in the new controller ?

 

[spinningmagnets]

Try it at 25A and see if the motor gets hot before you try it at a higher current.

 

[borqueoneal]

So you ask me to buy a programmable controller and adjust it to max25A current ? Am i correct ?

As i think 25A will work pretty well with it but still i can't be sure about it.

And i don't have so much cash so don't want to waste it. (Even i have so much i think i will still not want to waste tough).

 

[Russell]

I'm confused by the specs for the Samsung 22P cells. I see in a number of places that the discharge is 10A, some say continuous and some say maximum. On this Samsung site http://www.samsungsdi.com/lithium-ion-battery/e-bike it says 3C continuous so I'm inclined to believe then it's 3C continuous and 10A (4.65C) maximum.

Of course that's not the whole story because just as important is how much the voltage sags under load. In that respect the 22P cells are pretty lousy. You can see from this plot that they immediately sag about 0.4V at a 5A discharge (2.3C).

http://www.dampfakkus.de/akkutest.php?id=73

For a 10S4P pack that would mean 8V at a 25A discharge.

In a test of a 13S4P downtube battery constructed of the 22P cells a Sphere member got similar results.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=58928&start=50#p887799

So yeah while the cells can discharge the current they sag like a mutha when ask to do so :?




-R

 

[wesnewell]

You don't need anything new. A 10s4p pack will provide 18A easy. Assuming there's nothing wrong with the controller or motor, just hook the battery pack to it and go.