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Question about Electric Motorcycle conversion parts

StultusEst

100 µW
Joined
Oct 5, 2022
Messages
8
Hi everyone. I'm currently trying to figure out what parts to buy for an electric motorcycle conversion. My goal is to make a commuter bike that is capable of highway speeds, as well as ideally getting around 70 miles of range on surface roads. I plan to build the bike off of a gas bike frame, right now I'm thinking of using the frame of a Honda Hawk. For reference: I do not have any experience with EV's, but I know people who are very experienced with them. I also have access to a machine shop, so I can do some fabrication. After lurking on these forums for a bit I've realized there is an incredible wealth of knowledge that I'd be dumb to not take advantage of. Could any of you tell me if the main components I have selected would be able to get the performance that I'm looking for, and if not could you point me in the right direction? I'd also appreciate any general advice for someone new to this. Thank you for your time!

For the motor I'm thinking of going with a hub motor from QS ([QS v3 273 8000w) that comes in a kit with a motor controller (72V 150A Sabvoton), some brake levers, throttle, a screen, and some other stuff. https://www.amazon.com/NBpower-Hydraulic-Motorcycle-Controller-Bluetooth/dp/B083KNQ51Z/ref=sr_1_2?crid=3258R3TIM56KY&keywords=qs%2Bmotor&qid=1661104399&sprefix=qs%2Bmoto%2Caps%2C95&sr=8-2&th=1

For the batteries I'm thinking of 3 72v 40ah 60aBMS lithium ion battery packs in parallel.
 
Last bit of info we might need is the actual weight of the bike you're converting, as least an estimate. One google result for honda hawk weight came up with 399 pounds, so let's start there. Assume you'll be able to stop 50 pounds off that weight by removing the ICE components.

The qs 8000w hub should be just fine for what you need, they're pretty tough and can usually run pretty well at a bit higher power. The rest of your components, on paper at least, are undersized by about 50 percent, based on your goals: highway speed and 70 mile range.

On an EV, especially on a hub motor, speed is going to mainly depend on battery pack voltage. At 72v nominal on your estimated motorcycle weight, you can expect to top out at 60-65mph. For highway speeds, you'll need 96-108v nominal.

You'll find that amperage requirements increase exponentially with speed, rather than linearly. At 70mph, you'll be seeing cruising amperage around 125-150 amps. And that's just cruising; if you need to quickly overcome a slow truck or want to pass, or go 80mph, you'll find your amps easly surpassing 200. Meaning your 150amp controller and your paralleled 180amps of BMS will be surpassed (fyi, if you do parallel more than one BMS, youll need each one fused at the bms's rating).This might be okay for 5-10 second bursts, but not sustained highway traveling. And as a generally rule, you don't want to run your components at their rated limits on a regular basis, that's asking for early failure.

Finally, 70 miles of range is a lot. And if you really want highway traveling, remember that EV range is much more suitable to slower, stop-and-go traffic. The faster you want to go, the less range your battery will be able to give you. I have a roughly 325 pound bike, and a 5.1kwh battery, at 72v. My range is 45-50 miles. Your proposed battery is about 8.6kwh, which is great, and it will get your very close to your goal of 70 miles of range, if you can fit it in the frame. It'll just be very close, maybe under, and sustained highway speeds will really eat into that range.

So you will very likely need a controller with a higher amp rating, more like 250-300a. If you can't fit more battery in kwh, and cant get higher than 72v, you'll definitely want to at least get a BMS with a higher amp rating. Or, you could compromise on your highway speed and range goals: if you stick to 50-60 mph, and keep the rest of your suggested components you mentioned, you should be good on that speed and range.
 
Thank you for your help! Where could I find a controller that has a 300a rating and can handle 96v?
 
My scooter has 180kg aproximatly 380pound
It is equipped with a Sabvoton SVMC72150 and an 8kW 13" Hub Motor.
Acceleration up to 30km/h is realy slow. Top speed is 100km/h 60mp/h.
Range with 21S100Ah battery is 80-160km.

I have ordered , recieved and tested a Fardriver ND96850 (96V 450A) but not installed yet.
Software is more complicated than sabvoton.
 
StultusEst said:
Thank you for your help! Where could I find a controller that has a 300a rating and can handle 96v?

you need to take in to account also the battery spec to reach such power. What kind of cell and layout you want to use ?
 
BigBlock said:
StultusEst said:
Thank you for your help! Where could I find a controller that has a 300a rating and can handle 96v?

you need to take in to account also the battery spec to reach such power. What kind of cell and layout you want to use ?

Originally I was planning to use 3 of these in parallel https://www.amazon.com/Battery-Protection-Waterproof-Electric-Mountain/dp/B07XRBLHR3/ref=sr_1_11?keywords=72v+battery&qid=1661693056&sr=8-11

For a 96v system I was thinking of using 48v lithium ion ebike batteries in series. I'm not sure if that's the best option budget-wise and space-wise though. Something like 10 of these batteries: https://www.amazon.com/Lithium-Battery-20000mAh-Electric-Bicycle/dp/B094ZCF4BL/ref=sr_1_4?crid=1RPJ1VEXNE85J&keywords=48v%2Bebike%2Bbattery&qid=1665109265&qu=eyJxc2MiOiI2LjYxIiwicXNhIjoiNi40MCIsInFzcCI6IjUuNTEifQ%3D%3D&s=sporting-goods&sprefix=48v%2Csporting%2C97&sr=1-4&th=1
 
A Honda Hawk has a single sided swingarm. So that will not work very well with a hub motor. Better choose a different motorcycle.
 
SlowCo said:
A Honda Hawk has a single sided swingarm. So that will not work very well with a hub motor. Better choose a different motorcycle.

Can't believe you beat me to it: I just was perusing my local classifieds, saw a beat up honda hawk for like $100, passed because its a shaft drive. I came to the thread to warn OP of the potential difficulties.

Presumably there's a standard swingarm out there that would fit into the same frame. No idea for sure, just thinking out loud.
 
harrisonpatm said:
Can't believe you beat me to it: I just was perusing my local classifieds, saw a beat up honda hawk for like $100, passed because its a shaft drive. I came to the thread to warn OP of the potential difficulties.

Presumably there's a standard swingarm out there that would fit into the same frame. No idea for sure, just thinking out loud.

That wasn't a Honda Hawk then. Because those have chain drive. Its touring brother the NTV Revere does have shaft drive.

Better look at something like a Suzuki GS500. That has a steel frame so is easier to weld to and modify.
 
harrisonpatm said:
SlowCo said:
A Honda Hawk has a single sided swingarm. So that will not work very well with a hub motor. Better choose a different motorcycle.

Can't believe you beat me to it: I just was perusing my local classifieds, saw a beat up honda hawk for like $100, passed because its a shaft drive. I came to the thread to warn OP of the potential difficulties.

Presumably there's a standard swingarm out there that would fit into the same frame. No idea for sure, just thinking out loud.

As it happens, the Honda hawk I'm looking at has a standard swingarm already attached to it.
 
SlowCo said:
That would be an non standard swing arm then :lol:

You got me there.

I've heard good things about Kelly Controllers, would this https://kellycontroller.com/shop/kls-8080n-nps/ controller work? It's fairly expensive but it seems to have the specifications that were recommended. Thank you all for your help!
 
StultusEst said:
BigBlock said:
StultusEst said:
Thank you for your help! Where could I find a controller that has a 300a rating and can handle 96v?

you need to take in to account also the battery spec to reach such power. What kind of cell and layout you want to use ?

Originally I was planning to use 3 of these in parallel https://www.amazon.com/Battery-Protection-Waterproof-Electric-Mountain/dp/B07XRBLHR3/ref=sr_1_11?keywords=72v+battery&qid=1661693056&sr=8-11

For a 96v system I was thinking of using 48v lithium ion ebike batteries in series. I'm not sure if that's the best option budget-wise and space-wise though. Something like 10 of these batteries: https://www.amazon.com/Lithium-Battery-20000mAh-Electric-Bicycle/dp/B094ZCF4BL/ref=sr_1_4?crid=1RPJ1VEXNE85J&keywords=48v%2Bebike%2Bbattery&qid=1665109265&qu=eyJxc2MiOiI2LjYxIiwicXNhIjoiNi40MCIsInFzcCI6IjUuNTEifQ%3D%3D&s=sporting-goods&sprefix=48v%2Csporting%2C97&sr=1-4&th=1

ebike packs comes with own internal BMS so if you connect more packs you will most likely end up to unbalance them unless you charge each one separatelly. For optimal security and optimization you need a single BMS that control all cells.

BTW the cells you linked are rated at 40-60A continous so way far from the potential of 300A controller you are looking for....
 
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