What is it going to take to do this?
- Thread starter marsrover
- Start date
Hillhater
100 TW
to be clear...
you want a 40 mile range between recharges ?
you want a 50 /45 mph average speed ??
..If correct you will need a very powerful motor and a very large battery pack !
This is E motorbike territory !
you want a 40 mile range between recharges ?
you want a 50 /45 mph average speed ??
..If correct you will need a very powerful motor and a very large battery pack !
This is E motorbike territory !
John in CR
100 TW
My ebike is much lower than a typical upright, so significantly lower wind resistance. Tucking down as best my 250lb self can I use 61wh/mile averaging 50mph on the highway. I didn't do any test runs at 45mph, but keeping it pegged at 40mph I averaged 46wh/mile on the identical 10 mile route. I did 3 runs of each with nearly identical results, and I'm at a loss for an explanation of why the lower speed run didn't yield an even bigger difference since the increase in wind resistance with speed is geometric, not linear.
That should give you a rough idea, but keep in mind that you really need to budget a significantly bigger battery in case of a headwind, and at the end multiply your battery requirement by at least 1.2 because you want to avoid more than 80% DOD for better battery life.
As far as cost, if you go basic in construction the bulk of your cost will be batteries, and those prices vary quite a bit. With a commitment to really learning about batteries up front, and still accepting a higher fire risk, you can get good RC lipo batteries up to the task for under $.30/wh. Their added benefit is they're small in size and weight, which will be important for the size pack you'll need. Safer but still high power batteries will run over double that price per unit of capacity. Motor and controller prices vary pretty widely too, but at a bare minimum for a sustained 50mph with an ebike weighing not much more than 100lbs you're probably looking at $1k in motor and controller. If you've got hills to contend with then that might need to double.
That should give you a rough idea, but keep in mind that you really need to budget a significantly bigger battery in case of a headwind, and at the end multiply your battery requirement by at least 1.2 because you want to avoid more than 80% DOD for better battery life.
As far as cost, if you go basic in construction the bulk of your cost will be batteries, and those prices vary quite a bit. With a commitment to really learning about batteries up front, and still accepting a higher fire risk, you can get good RC lipo batteries up to the task for under $.30/wh. Their added benefit is they're small in size and weight, which will be important for the size pack you'll need. Safer but still high power batteries will run over double that price per unit of capacity. Motor and controller prices vary pretty widely too, but at a bare minimum for a sustained 50mph with an ebike weighing not much more than 100lbs you're probably looking at $1k in motor and controller. If you've got hills to contend with then that might need to double.
No hills, this is Florida.
That high cost is really depressing though. Oh well, looks like i'll just have to wait till sidewalks come out this far.... (so I can go cheaper and slower)
I was thinking some sort of trike that could keep up with traffic.
That high cost is really depressing though. Oh well, looks like i'll just have to wait till sidewalks come out this far.... (so I can go cheaper and slower)
I was thinking some sort of trike that could keep up with traffic.
TylerDurden
100 GW
My math and logic is often faulty, so feel free to correct/revise/refute.
45mph: >2kW
50mph: >2.5kW
20mi @ 45mph = ~26.6min
26.6min * 2kW = .886kWh
20mi @ 50mph = ~24min
24min * 2.5kW = 1kWh
1.886kWh * 1.4 [60% eff] = 2.64kWh
2.64kWh * 1.2 [80% DoD] = 3.16kWh Pack Capacity
3.16kWh / 72V = 43.8Ah
45mph: >2kW
50mph: >2.5kW
20mi @ 45mph = ~26.6min
26.6min * 2kW = .886kWh
20mi @ 50mph = ~24min
24min * 2.5kW = 1kWh
1.886kWh * 1.4 [60% eff] = 2.64kWh
2.64kWh * 1.2 [80% DoD] = 3.16kWh Pack Capacity
3.16kWh / 72V = 43.8Ah
SamTexas
1 MW
The math looks good to me.
I would love to see someone try 50mph for 20miles on a bicycle in real life traffic.marsrover said:
AussieJester
1 TW
EDiT: dunno how i manged it but i posted a comment for another thread here 
:|
:|John in CR
100 TW
marsrover said:No hills, this is Florida.
That high cost is really depressing though. Oh well, looks like i'll just have to wait till sidewalks come out this far.... (so I can go cheaper and slower)
I was thinking some sort of trike that could keep up with traffic.
Sidewalks are one of the least safe places to ride, though that does depend on the sidewalk. Some in newer locales with no crossing driveways and few streets would be safe, but not a typical city or neighborhood sidewalk.
dogman dan
1 PW
It's a job for a 150cc or larger motorcycle or scooter really. Or similar frame electrified.
What you want is simply beyond the capabilities of anything "designed for a bike". Even the most robust motors are going to be over watted to reach that speed, and then you are walking a fine line with your controller choice. Every bit you cross that line to get to 50 mph, or near there, is going to be making heat. That's fine for about 10 miles, but by 15-20 miles many bike intended motors are going to be melting.
Then there is the battery size issue. Every 5 mph more speed is going to increase the wh needed a lot. Low and aerodynamic will help a lot, like a recumbent bike, but you are still going to be looking at a lot of weight to somehow carry on a bike designed to carry perhaps 20 pounds of cargo, or none at all. I also think TD's math is pretty close. Consider the weight of 72v 40 ah. It's about 50 pounds if you use lipo. 60-70 for lifepo4. That much weight on my bikes makes them handle a lot worse, even when carried in an ideal location. It's the poor lateral stiffness of a typical bike frame, compared to a motorcycle. High speed wobble is no fun. Got years of experience with motorcycles? You better, when you get the wobblies on an ebike going 50 mph.
Now, you shorten that ride length to 10 miles or so, and then the problems are much more solvable. You just cut the battery weight from 50 pounds to 10-12 pounds. Now the bike can be comfy enough at 50 mph. And the motor meltdown is likely to be after 10 miles riding.
Lastly, Aren't florida cops notorious for stomping on ebikes and scooters that don't comply with thier hugged up moped law? You'll be riding on a completely illegal, homemade, unregistered motorcycle. Perhaps with no drivers licence as a cherry on top?
The budget for nearly impossible is nearly infinite, especially if they take your bike. It can be done, but not cheap. Battery budget can easily be a couple thou including the charging and monitoring, wiring, connectors. Then you'd need to weld a frame able to accomodate a motorcycle hubmotor, or go with a very powerful motor through the chain. Not the bike chain, but a strong chain on the other side of the wheel, like the gas bikes do it. Rims and tires need to be moped stuff at least. Almost, if not definitely easier to just build the frame from scratch. I would think 3-5 thou would eventually be spent.
Propose to do the same thing for 20-25 mph, and then you are back into the comfortable envelope for "bike stuff". And on a budget not much over $2000.
What you want is simply beyond the capabilities of anything "designed for a bike". Even the most robust motors are going to be over watted to reach that speed, and then you are walking a fine line with your controller choice. Every bit you cross that line to get to 50 mph, or near there, is going to be making heat. That's fine for about 10 miles, but by 15-20 miles many bike intended motors are going to be melting.
Then there is the battery size issue. Every 5 mph more speed is going to increase the wh needed a lot. Low and aerodynamic will help a lot, like a recumbent bike, but you are still going to be looking at a lot of weight to somehow carry on a bike designed to carry perhaps 20 pounds of cargo, or none at all. I also think TD's math is pretty close. Consider the weight of 72v 40 ah. It's about 50 pounds if you use lipo. 60-70 for lifepo4. That much weight on my bikes makes them handle a lot worse, even when carried in an ideal location. It's the poor lateral stiffness of a typical bike frame, compared to a motorcycle. High speed wobble is no fun. Got years of experience with motorcycles? You better, when you get the wobblies on an ebike going 50 mph.
Now, you shorten that ride length to 10 miles or so, and then the problems are much more solvable. You just cut the battery weight from 50 pounds to 10-12 pounds. Now the bike can be comfy enough at 50 mph. And the motor meltdown is likely to be after 10 miles riding.
Lastly, Aren't florida cops notorious for stomping on ebikes and scooters that don't comply with thier hugged up moped law? You'll be riding on a completely illegal, homemade, unregistered motorcycle. Perhaps with no drivers licence as a cherry on top?
The budget for nearly impossible is nearly infinite, especially if they take your bike. It can be done, but not cheap. Battery budget can easily be a couple thou including the charging and monitoring, wiring, connectors. Then you'd need to weld a frame able to accomodate a motorcycle hubmotor, or go with a very powerful motor through the chain. Not the bike chain, but a strong chain on the other side of the wheel, like the gas bikes do it. Rims and tires need to be moped stuff at least. Almost, if not definitely easier to just build the frame from scratch. I would think 3-5 thou would eventually be spent.
Propose to do the same thing for 20-25 mph, and then you are back into the comfortable envelope for "bike stuff". And on a budget not much over $2000.
dogman dan
1 PW
No way to do the ride at 25-30 mph? A typical kit can do 27mph on 48v 20 amps. The battery would still be large, but the speeds would be more doable carrying it.
The sweet spot for commuter ebikes, is about 25-30 mph for about 15-25 miles. Only need about 15-20 pounds of battery for that.
Still an illegal motorcycle in some states, but much less obvious about it.
The sweet spot for commuter ebikes, is about 25-30 mph for about 15-25 miles. Only need about 15-20 pounds of battery for that.
Still an illegal motorcycle in some states, but much less obvious about it.
