72v 3000w motor locked at 18mph

Kyle6036

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Hello, I upgraded a razor dirt bike with a 72v 3000w Chinese motor kit with a 60v 3000w battery. It has torque but only tops out at 18mph.

I know a lot of y’all might say gearing, but I had a 48v 1800w motor kit before and it topped at 31mph with enough torque to bring the wheel up a bit.

I’d like if it could at-least get to 30mph with the torque it has now. Thank you
 
Kyle6036 said:
Hello, I upgraded a razor dirt bike with a 72v 3000w Chinese motor kit with a 60v 3000w battery. It has torque but only tops out at 18mph.

I know a lot of y’all might say gearing, but I had a 48v 1800w motor kit before and it topped at 31mph with enough torque to bring the wheel up a bit.

I’d like if it could at-least get to 30mph with the torque it has now. Thank you

You'll need to provide more information about your motor and controller, or a link to the kit or components, in order to receive anything more than general advice.
If the kit shows specs assuming 72V, then it will run at around 80% of the speed when run at 60V.
 
We'll need as complete a set of details as possible to really figure out the problem. Links to both of the kits you've used will help give us necessary details of those to compare them.

Hubmotor? frame mounted motor via chain/belt/etc to wheel? Any and all details you can provide, including pictures of the setup as it was and as it is now, could help us help you.

Kyle6036 said:
Hello, I upgraded a razor dirt bike with a 72v 3000w Chinese motor kit with a 60v 3000w battery. It has torque but only tops out at 18mph.

I know a lot of y’all might say gearing, but I had a 48v 1800w motor kit before and it topped at 31mph with enough torque to bring the wheel up a bit.

I’d like if it could at-least get to 30mph with the torque it has now. Thank you
 
Motor/Controller Kit: https://www.ebay.com/itm/353965671268?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=x3zx43cvqnc&sssrc=2349624&ssuid=iyhwj5coRzK&var=&widget_ver=artemis&media=COPY

Battery: https:
//www.ebay.com/itm/334270383099?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CpVwusCfTPa&sssrc=2349624&ssuid=iyhwj5coRzK&var=543268544739&widget_ver=artemis&media=COPY

I think I found the issue, the battery is 50amp Max while the controller pulls 60amps with a voltage drop regulator, every time I full throttle the voltage drops 20-30 volts setting off the “limp mode”
 
What is a "voltage drop regulator"?

FWIW, if the battery drops 20-30 volts, there's likely something wrong with it. Most likely it is the set of lies the seller posted as specifications. ;) They say it uses 3C cells, so if the pack is 20Ah, then 3C is 60A. But they also say peak current is only 50A, and continuous is 30A. So *at best* they are 1.5C cells, and my guess is they are not even 1C cells, given that voltage drop.

Even if they are actually the cells they claim, they could well be recycled garbage cells from scrapped batteries. It is unfortunately not uncommon for this to be the case, especially for "cheap" packs (whether or not they actually cost less than others). There's not really anything you can do to make this battery do what you want.

I think the only fix for the problem is going to be buying a good battery that is truly capable of more than the current required of the system. If the controller is actually limited to only 60A, then getting a battery capable of *at least* 60A continuous, preferably more (so it still works well as it ages over time).

Ebay and Aliexpress and Amazon, etc., are all full of garbage packs, so I recommend places like EM3EV, Grin Tech (ebikes.ca), etc, to get stuff that will actually do what it says it will do (and has customer service to help with problems if they do arise). If you have to buy from an unknown seller, I recommend posting a link to the item before buying, so we can help you determine if it will really do what you need it to.



Description Delivery Payment Return
60V 20ah 21700 16s4p Electric Bicycle Electric Scooter Lithium Battery Pack 1000W 2000W E-bike Batteries
Product Details:

Battery Model: 60V 20Ah
Nominal Capacity (AH) : 20ah
Nominal Voltage (V): 60V
Cell Source Resistance (mΩ) : < 40 mΩ
Cell Specification : 3.7V 5000MAH 21700 3C Powerful Cell
Cell Combination : 4-parallel 16-series
Cell Quantity (parallel*series) : 64 pcs
Discharge Cutoff Voltage (V) : 48+/- 1V
Charge Cutoff Voltage (V) : 67.2V
Maximum Continuous Discharge Current (A) : 30A
Instantaneous Maximum Discharge Current (A): 50A
Charge Mode : CC/CV
Standard Charge Current (A) : 2A
Charge Time under Standard Charge Current : 10 hours
Max Fast Charge Current (A) : 5A
Charge Time under Fast Charge Current: 4 hours
Charge Temperature Range : 0-45°C
Discharge Temperature Range: 20-65°C
Battery Size : 185*172*75mm
Battery Weight About: 4.5kg

This Battery can use for 60V 300W-1000W Electric Motor

Kyle6036 said:
Motor/Controller Kit: https://www.ebay.com/itm/353965671268?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=x3zx43cvqnc&sssrc=2349624&ssuid=iyhwj5coRzK&var=&widget_ver=artemis&media=COPY

Battery: https:
//www.ebay.com/itm/334270383099?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=CpVwusCfTPa&sssrc=2349624&ssuid=iyhwj5coRzK&var=543268544739&widget_ver=artemis&media=COPY

I think I found the issue, the battery is 50amp Max while the controller pulls 60amps with a voltage drop regulator, every time I full throttle the voltage drops 20-30 volts setting off the “limp mode”
 

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Kyle6036 said:
I think I found the issue, the battery is 50amp Max while the controller pulls 60amps with a voltage drop regulator, every time I full throttle the voltage drops 20-30 volts setting off the “limp mode”

Wishful thinking that the pack can deliver anywhere close to 50A. This listing doesn't specify the cells used, so you can safely assume generic Chinese cells. IF, for instance, it were made with brand name high energy cells (5Ah per cell would be high energy, not high current), like a Samsung 50E, then it would cost over $500 for the cells alone, without the BMS or build costs. High energy cells have lower discharge current, so the 50E is rated at 9.8A, so a 4P pack would be rated at 39A, and that's will brand name cells; much less with generic. If you're getting 30V of sag, you're basically killing the battery and it will only get worse. If you can limit the current to 20A, that may help.
 
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