Slow acceleration for 72v 2000w ebike.

[Paco007]

Hi all,

I recently picked up a new electric dirt bike for myself. The specs are as follows:

Battery: 72v 18ah lithium ion
Controller: 48/72v 40amp
Motor: 72v 2000w hub motor. (Unknown model or rpm)
Lcd: sw900



I have been able to ride up to about 35mph although the acceleration is a bit slow to reach those speeds. Is there any way to upgrade my setup and get more acceleration? I feel that the acceleration should be more than what it's at considering the specs. I already made sure to remove the speed limiter jumper wires on the controller.

 

[flat tire]

2kw is slow on a bicycle, on a heavy thing like that it will be slower.

To upgrade you want for sure a better controller, maybe a better battery, and then maybe a bigger motor.

 

[goatman]

I would open up the battery to see what batteries you have and what amp your bms is to see if you can just get a higher amp controller or you might need a new battery, bms and controller or maybe lace a smaller diameter rim to the motor.

kinda sounds like you might be better off getting a different bike. you have street tires and if you got knobbies it would suck under acceleration even more, now add mud to the equation.

im not trying to beat on your bike, if you like it you can upgrade it but lets see what battery you have.

 

[amberwolf]

I have been able to ride up to about 35mph although the acceleration is a bit slow to reach those speeds. Is there any way to upgrade my setup and get more acceleration? I feel that the acceleration should be more than what it's at considering the specs.

first step is to replace controller with higher current version. double the battery current limit (at least) would be a good start.

then your batteyr will be being hammered at least twice as hard as it was meant to be, so it's going to sag more and heat up more and wear out faster, and have less range. so your next step is a bigger better more capable battery (which won't be cheap...if it's cheap, it's probably not going to be what you need).

if the motor isn't getting hot, then you can keep the same motor, but if it starts getting hot then it's time to replace that, too.


to learn more about the relationships between the parts, and why you get better acceleration with some configurations than others, you should go to http://ebikes.ca/simulator and read the *entire page*, so you will know what everything is for and what it does and how to use it, then play with different systems to see what they do and what different changes do to the performance.

 

[Balmorhea]

I have been able to ride up to about 35mph although the acceleration is a bit slow to reach those speeds. Is there any way to upgrade my setup and get more acceleration?

Do you know what the free top speed of your motor is? It sounds like you might have too fast a motor for the electrical power you have to spend. Accounting for efficiency losses, your current system has at most 3 horsepower to propel the bike with. If you want affirmative acceleration from 3hp, it has to come available at pretty low speed.

 

[DogDipstick]

For me on my 85lb bike 40A is slow.. 80A begins to get fun.... 100A is the most fun certainly, and can be uncontrollable fast....

Of course the battery must be able to support that 100A should you upgrade the controller.

On simple thing tht may be an option is a "shunt mod", for more amperage.

 

[dogman dan]

Well, nobody yet has asked how much weight you are trying to accelerate. The bike is clearly not light. Does it have lead battery?

And er,, are you heavy?

Your bike may have a 2000w motor on it, but at 72v, you have potentially 3000w.

Battery sag could easily have your voltage low enough under load, to only have 2000w. and that will feel slow, even if you are not a big guy.

First, investigate battery sag. See what happens on take off, by putting a volts display on the bike. Chances are very good that a 40 amps controller, plus a battery type that sags a LOT less, will get you more motorcycle like performance.

Lastly, if the motor is a particularly fast wind, it will take off very sluggish if overloaded, but your top speed does not suggest that you have an extremely fast wind motor. I think its battery, and simply that 2000w is still kind of moped performance, vs motorcycle like power. Mopeds also take off kinda slow.

 

[Tommm]

Hate to put it this way, but it would of been much better if you asked our opinion before you bought it.

Anything to modify it will require quite some knowledge/time/money.

That said the last part you will need to replace is the motor, they can take 2-3x rated power from factory.

The bad news is, the motor isn't the most expensive part, but the battery.

 

[999zip999]

Can you give us a link to the motorcycle ? I wonder what mutter they're using is a 35 mm magnet ? And what battery ?

 

[goatman]

id be tempted to put those parts on a chinese stealth bomber frame or any full suspension MTB. atleast you would have pedals and be somewhat street legal, if only by appearance.

 

[Paco007]

Hi guys,

Thanks for the helpful input. I will do more research into the lithium battery specs and see if upgrading the controller amps will help. On the lcd it shows watts being pushed out is ~2600watts.

I may just take the bike back to the vendor. I have come to the conclusion that it's mainly just a heavy bike and needs more amps to increase torque. Running the bike with the wheel off the ground the speedometer goes up to 60mph.

I am pretty light at only about 130 lbs but last night I increased the tires psi since they were a bit low and it made a good difference.

 

[Paco007]

Okay so I requested a refund from the vendor. I can either return the bike to get my refund(I paid 2k for the bike). He can also refund 200 and I keep the bike. I am on the fence if i should return it or keep it and use the 200 to put towards controller or battery upgrades if needed.

My other options if i get a full return would be something like an oset MX10 or similar. I am just looking for a fun mx style ebike for under around $2500. Do you guys have any suggestions for a fun mx style ebike that can pop wheelies and take hills with a battery range of around 30miles top speed of around 30-40mph?

 

[amberwolf]

My other options if i get a full return would be something like an oset MX10 or similar.

a quick google shows that thing is even *less* power

It has a rechargeable 48-volt lithium pack that drives a 1400-watt, 48-volt Oset neodymium magnet DC motor.

my guess is you'll probably be even less happy with it. (but it depends on it's drivetrain and other stuff i didn't look up).


as for range, that depends on your riding style and speeds and terrain and winds and weight, tire style, tire pressure, road condition, etc.

if you want useful recommendations, you'll have to give us *complete* details, not leaving *anything* out, of *exactly* how you want to ride the bike (not just a general description, be very very very very specific), and *exactly* what the terrain is like, the roads, the weather/winds/etc, weight, specific acceleration required, how much range *at what speed*, etc.

all other details you can think of are probably useful too.


i also still recommend you go to the http://ebikes.ca/simulator and do as suggested before, so you can learn how this stuff all relates, so you will have a better idea of what you're actually looking for.

 

[dogman dan]

Hmm, Its not your weight then.

It could be something really simple, like one connector on the motor is connected, but not well. If that is the case, soon you will see that wire connector melting.

But my guess is that if its taking off too slow for you at 2600w going into that motor, then its just that you expected a motorcycle, which is more like 5000 to 10000 watts of power. You bought a moped, which has 3000w.

But still, at a stop light, you should be keeping up with cars as they take off. Not zooming ahead like a 15 hp 250cc, but keeping up like a moped, with 3 hp. If not, something is wrong.

Your top speed though, is spot on for 2600w. This makes me think nothing is wrong with it, except you thought it was a motorcycle, since it looks like one.

Improving it is not so hard. Simple to put a much stronger controller on it. But I betcha your battery struggles already, so a more powerful, higher c rate battery is costly, and a type that is not very safe.

It becomes a slippery slope, where go fast money ends up a lot more expensive than just buying a used 250cc motorcycle. Battery alone for what you describe would cost your entire $2500. Time to go back to gas bro, or get out the wallet.

 

[skeetab5780]

Ive been eyeing these bikes for some time on Ebay, I actually like the look of it and wish they sold the frame only. For $2400 its too much if it was $1200 id buy one for kicks, you know me

-a few things to point out, they say speed goes up to 50mph when you cut limit wire which requires way more than 2600w with that weight id imagine (even though you are light yourself)so im curious as to what controller is being used(maybe a cheap 12 fet)

-the bike comes with a 72v 18ah battery and claims it can get up to 50 mile range which is impossible with the weight of this bike, you will likely get about 18miles

-i would imagine the stator is atleast 40mm wide and likely a 9x7 wind motor? in a 19" wheel would be around 47mph i guess

-Your body weight is added to the unsprung weight of the rear swingarm because of how they made the bike? Not sure if this is a good thing or not. Depending on how stiff the rear shock is it could make the ride better or worse taking into account the weight of the hub motor already.

if you paid $2000 you already got a better deal than Ebay, they offer local CA pickup so this is probably how you got it

What did you end up doing with the return? Do you know the actual weight of the full bike?

Skeetab

 

[Paco007]

Quick update! I sold the bike and picked up a used Kuberg Freerider 48v 8kw. Dammn thing is like a bat outta hell! This thing is more to my liking it's lightweight and front wheel pops ups if your not careful. Now I just want to customize this freerider as far as height and suspension to make it more comfortable.

 

[torker]

Is that double the money. Isn't it over 4 grand?

 

[Paco007]

Is that double the money. Isn't it over 4 grand?

I got a deal $2500. Its a bit unkept I will need to look at adjusting the chain since it rubs on the frame a bit and the tires will need to be replaced soon. The battery looks to be in good condition I rode for several miles last night.

 

[Paco007]

The previous owner of the kuberg replaced the original shock 240mm to a 265mm shock and its causing the chain to rub on the rear arm. I am looking to get the original shock to fix the chain issue as well as lower the ride height as it sits the back is more raised than the front making the ride super uncomfortable.

 

[skeetab5780]

Pic or it didnt happen!

Nice upgrade and good deal on the Kuberg even if its beat up. I love mine all i did was put larger wheels on it

 

[Paco007]

Okay here it is. I installed new rear shock as well as front and rear tires. I freshened up the chain and applied chain oil.

 

[skeetab5780]

Thanks for pic! Looks like you got a killer deal, bike looks nice IMO

How do you like the lighter weight and more power?

Here is mine

 

[Balmorhea]

It looks like the gas and oil are going to leak out when you do that.

 

[skeetab5780]

It looks like the gas and oil are going to leak out when you do that.

Nope! Just my right hand grip fills up with dirt!

EDIT: I just bought one of these slow dirt bike looking objects...Why? I don't know, i guess i've been mid drive for a few years now and i miss the hub motors

 

[skeetab5780]

It looks like the gas and oil are going to leak out when you do that.

Nope! Just my right hand grip fills up with dirt!

EDIT: I just bought one of these slow dirt bike looking objects...Why? I don't know, i guess i've been mid drive for a few years now and i miss the hub motors

This bike is so bad its not even funny, I bought a used broken one from the Ebay vendor out of CA. I paid via Paypal like half price for it the vendor stated it had a controller issue...

I'm thinking swap the controller out and be ready to ride, but the second I start doing testing I find out the hub motor has shorted phase windings...I remove the heavy ass rear wheel and pull the motor apart and it smells like KFC Mmmmmm!!

The controller is a 72v 40a I think sine wave with a SW900 display which is pretty nice, at first I thought it has a blown Mosfet so I took it apart to inspect and it looked perfect with some pretty beefy copper trace lines on the PCB

The battery is a fairly weak 72v 18ah (it claims) I have not been able to actually test the capacity yet, but I did use this battery temporarily on my Denzel 4-spd Dirt bike. The battery worked OK but cut out fairly soon with the weight and current of the Denzel bike. I imagine it has a 30a BMS in it with 18650 generic cells

The charger looks fairly nice and seems to work fine, the vendor stated they do not know if the bike or charger works since the end of the charger cord was cutoff with just wires hanging out, I simply soldered on a DC connector and it works fine

The rear shock on the bike is a complete crap pogo stick, it says warning nitrogen filled blah blah but it does not do anything to a huge adult rider, this thing is sized similar to a 110cc pit bike and with a weak pogo shock its designed for a 10 to 15 year old rider. The shock is about 210-220mm long so I will be replacing it. I may try to one off my DB 17 Tao Tao since it is wicked stiff and I love the feel of it, but its only 180-190mm and I do not want to sacrifice the height loss

The plastics and the fake gas tank are all put on the bike makeshift and half assed, whole rear plastics/seat held on by two tek screws, plastic gas tank had one broken mount hole

The foot pegs are cheap plastic folding bike pedals and are pretty bad, one mount is slightly bend and they also do not even thread in all the way...

The kickstand is also pretty bad, its supposed to spring back automatically when you lift the bike up, but it barely functions properly

The rear swingarm i'm pretty sure has zero bushings or bearing in it, its likely metal on metal bolted together with a long thru bolt, it seems fairly stable while riding around but if you lift the ass end up to move the bike its sort of clunky and scary

The headlight assembly that I took off the bike and put on my Denzel dirt bike one of the blinkers does not blink or light up

The selector switch on the SW900 display had a broken plastic mount that needs repair

The SW900 has 5 different modes, and I doubt they all do something different

0 pedal assist mode draws like 3000w and cuts off the motor every few seconds if throttle is held pinned
1 mode says eco
2 mode says eco
3 mode says eco
4 mode says power draws like 4000w

after ripping the bike apart and seeing all these things wrong with the bike I reached out to the vendor and asked if he could refund me money for a new motor which I told him would be a very hard task to replace, they agreed and refunded me $200 back to my Paypal account

I then searched on Ebay and found the exact same motor that was on this bike, I took about a week before I clicked "Buy It Now" because I wanted to make sure it would be as easy as possible of a swap since it has moto hydraulic brakes and a moto wheel laced really tightly with not alot of room for error

The motor came in over the winter and I was putting off lacing the new motor into the moto rim for months. Just recently I googled a really easy website with like 5 pictures of a guy assembling/lacing old motorcycle wheels, I read the first few paragraphs and easily assembled the wheel going off his pictures as a guideline

Once that was done I put the laced motor back on the bike frame with the bike up side down so I could spend a few days spinning/ truing the wheel to my liking, I am no pro at this so I took my sweet time until I was happy with the results

The tires are also very heavy junk, the sidewalls below the bead of the tires had in excess of over an inch of rubber and I had to almost ruin the rim to get it off, I cut off all this excess rubber to help get the tire back on and to balance it out better. I had to replace the inner tube which was punctured trying to remove the tire that is how tight it was on, after lacing the new motor it took me two days to get the tire back on without hurting anything else or puncturing the new tube

Now just yesterday I finally was able to get the bike out for its first test ride, one thing I must say which I am not used to is that the bike is completely silent, it doesn't make any noise at all! I even drive my Vector Lite bike with a 9x7 Ebay stamped steel hub motor and even that bike wines and makes weird noises with the old Lyen controller especially during takeoffs, but no this bike is silent

The brakes are not too bad, look like single piston hydraulic pit bike brakes, pretty hefty and stop decent

The front forks are pit bike ish and are inverted with not a ton of travel, but they are stiff enough that I will continue to use them, the front end of this bike does seem pretty heavy since this bike will never wheelie on its own power even though it will likely get up to speeds of 35-40mph on flats

I am still not sure weather I want to sell this to some young rich kid on craigslist who will cherish it, or try to upgrade the pogo spring and add it to ever growing collection of ebikes

I can say one thing, all of the cheezy dirt bike plastics will not stay on the bike if I continue to ride it, I already have plans to put a Voloci seat on the bike since they are sleek and comfortable and a great design