Slow acceleration for 72v 2000w ebike.

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Paco007   100 µW

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Slow acceleration for 72v 2000w ebike.

Post by Paco007 » Mar 24 2020 12:40pm

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
20200324_104011.jpg
20200324_104011.jpg (266.78 KiB) Viewed 257 times
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.
Last edited by Paco007 on Mar 25 2020 1:37pm, edited 1 time in total.

flat tire   1 MW

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Re: Slow acceleration for 72v 2000w ebike.

Post by flat tire » Mar 24 2020 9:27pm

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   10 kW

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Re: Slow acceleration for 72v 2000w ebike.

Post by goatman » Mar 24 2020 11:14pm

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.

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amberwolf   100 GW

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Re: Slow acceleration for 72v 2000w ebike.

Post by amberwolf » Mar 24 2020 11:50pm

Paco007 wrote:
Mar 24 2020 12:40pm
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.

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Re: Slow acceleration for 72v 2000w ebike.

Post by Balmorhea » Mar 25 2020 12:31am

Paco007 wrote:
Mar 24 2020 12:40pm
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.

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DogDipstick   1 kW

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Re: Slow acceleration for 72v 2000w ebike.

Post by DogDipstick » Mar 25 2020 6:42am

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.
Allota Watts @ 83.1v of raw QS power takes me everywhere on my Ironhorse DW link XC... :) Powered by Chevy. :D Broke 10 horses the other day. ( BTW; ...don't get hurt... :? )... (Currently building a battery datalogger.). :roll: Playin with (24) IRFB4115s now. :wink:

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dogman dan   100 GW

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Re: Slow acceleration for 72v 2000w ebike.

Post by dogman dan » Mar 25 2020 6:56am

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   10 kW

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Re: Slow acceleration for 72v 2000w ebike.

Post by Tommm » Mar 25 2020 10:31am

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   100 GW

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Re: Slow acceleration for 72v 2000w ebike.

Post by 999zip999 » Mar 25 2020 11:16am

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   10 kW

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Re: Slow acceleration for 72v 2000w ebike.

Post by goatman » Mar 25 2020 11:22am

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   100 µW

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Re: Slow acceleration for 72v 2000w ebike.

Post by Paco007 » Mar 25 2020 1:32pm

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   100 µW

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Re: Slow acceleration for 72v 2000w ebike.

Post by Paco007 » Mar 25 2020 2:08pm

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?

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amberwolf   100 GW

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Re: Slow acceleration for 72v 2000w ebike.

Post by amberwolf » Mar 25 2020 5:55pm

Paco007 wrote:
Mar 25 2020 2:08pm

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.

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dogman dan   100 GW

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Re: Slow acceleration for 72v 2000w ebike.

Post by dogman dan » Mar 26 2020 6:15am

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.

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