Some Ideas on building a 5000w E-bike

[Warren]

Some recumbents handle like a chopper at low speed. Long bikes with a slack head angle, and too much trail will flop at low speed, just like a poorly designed chopper. A highracer, with the same front to rear weight distribution, and same front end geometry as a roadbike will handle pretty much like a road bike. That said, for very low speed maneuverability, nothing will match an upright, where you have complete freedom to move around the bike. At the extreme...trials riding...even a seat just gets in the way.

I really wish this guy's videos were still up. His recumbent motorcycle slaloming between the lines on the road was a great demonstration of a highracer's maneuverability.

http://www.evomoto.de/index-Dateien/page0078.htm

He is still riding it, and getting great mileage, after six years.

http://www.spritmonitor.de/de/detailansicht/446021.html

 

[hypertoric_amplituhedron]

I don't remember which recumbent was the twitchy one. Might have been a BikeE or something. They weren't all like that. Some handled really well, just like a road bike. I could see myself putting a motor on it, too.

Well, you guys would be proud of me. Today I agreed to take on a project to put an electric assist motor on a new customers' bike. She wants to get up the hill easier (Mount Dora area). Seeing that I would get experience from the build for my own project, I went ahead and said yes! Should be interesting. I've never put a motor on anything before, but I'm very particular about my work and safety. Plus, this might bring more business to the shop.

 

[hypertoric_amplituhedron]

After doing a lot of reading around, and going through all of the "I'm a noob and want to go 50" threads, I have decided that 70mph is too much for a first ebike. I'll keep it at 50, the original plan. Realistically, I'll be going 20~30 for 80% of the time, when I ride this thing. So far, I came up with this list of items to get:

? = undecided, looking for suggestions

- QS 205 H50 V3 with 30*4T winding
- 17 x 1.6 moped wheelset, 12mm front thru axle, 10 ga black spokes (21.5" tall)
- Hutchinson GP1 17 x 2.25 tires
- Thorn-resist 17 x 2.25 tubes
- 18 fet 4110 controller [some manufacturer?] 100V? 100A?
- Charger?
- Display?
- Battery: something similar to :http://em3ev.com/store/index.php?route=product/product&product_id=252
- Half-twist Throttle
- Shimano Saint 203mm brakes
- 12mm Thru axle front fork
- Short length crankset <165mm ?

After doing the math, and using a 0.9:1 ratio for loaded:unload rpm, it seems that using the 30*4T winding at 84V with a 21.5" tall tire should max out at 55mph.

And, some questions I have, to better understand how this works:

- How is the voltage to the motor determined? Is it entirely up to the battery? Does the controller change voltage?

- How is the max output amps of the battery determined? Something to do with the amp-hour of the battery, and the c-rate?

 

[Warren]

The controller basically switches the power on and off, very rapidly, to reduce the average voltage going to the motor. At 50% throttle, the power is on half the time. At 100% throttle it is on all the time. The maximum voltage is set by the number of cells, or paralleled cell groups, in series. The maximum output amps possible is determined by the load across a bare battery, up until it burns up. That said, the battery's BMS typically sets a limit, as does the controller. The cell manufacturer determines the recommended continuous, and burst C-rates. If you want to increase the the safe C-rate, you need to put more cells in parallel. You can do this when the pack is built, or by paralleling several finished packs.

 

[wesnewell]

After doing the math, and using a 0.9:1 ratio for loaded:unload rpm, it seems that using the 30*4T winding at 84V with a 21.5" tall tire should max out at 55mph.

In a 22" diameter wheel, you'll need 770rpm to reach 50mph. And that's unloaded speed. You'll probably need 900rpm unloaded to hit 50mph loaded. That means your 4T motor must have a KV rating of 10.71Kv at 84V. Is the 4T Kv rating that high? The best I can do with my 4t MXUS 3000 at 100V is 48.2 mph. And it's been tested at 9Kv. You may be better off with a 3T motor, or looking at a 24s battery pack.

 

[MadRhino]

A QS 205 H50 V3 in 30*4 winding is 11.39 kv

 

[hypertoric_amplituhedron]

I'm also trying to fit 5kWh on the bike. I guess that can be accomplished with two separate 84V 30Ah batteries. At least somewhere in that range. If there's anything I'd rather splurge on, it would be some ridiculous range. I think it would be a good idea to have such a vehicle, for many reasons.

 

[hypertoric_amplituhedron]

Another question I have:

How effective is the regen brake on a back hub motor? Depending on what frame I use, I may not be able to put a rear disc brake on it. Is the regen brake along with a 203mm hydraulic front going to be sufficient (at stopping from 50mph)? I'd rather hold out on a full disc bike, but maybe I don't need to. The front brake is really what stops the bike, while the rear just needs to be strong enough before locking up.

EDIT : Actually, nevermind. I will be able to put a rear disc brake on the bike after all.

 

[Warren]

Just stumbled on this.

https://www.youtube.com/watch?v=lTqkdGgRbPU

 

[hypertoric_amplituhedron]

Wow, that's very fast! On a nice runway of all places. I'll bet that fairing just a nice job with the wind. Has anyone built an ebike out of a Cannondale Bent 2? Those always rode very nicely. I could see myself putting a motor on one.

 

[Warren]

I won't consider a bike with a 16" front wheel for anything over 15 mph myself. But suit yourself.

 

[999zip999]

Get a great battery make sure it fits the frame that you want to do your build with the muxus 3000 V3 Turbo is just fine the other motors are even heavier .
. Get a sinewave controller and cycle analyst. What amp can your battery support. You can't run a battery at near it's limits. It will fail. Good headroom equals long lasting. You want or need it to last . Many 1- 3 month meltdowns here. If cheap wrong battery or no temp sensor hooked up to C.A. Cost money.
Plus two mega torque arms for regen braking. Get em3ev handlebar off/on switch and a 3speed half throttle and never hook up cruise control Never. Need ebrake motor cutoffs. Plus No jewelry on the handle bars ( lock ). I have more.

 

[hypertoric_amplituhedron]

So, I rode my friend's electric bike yesterday. It's a mountain bike with a 5T Leaf 1500 laced to a 26" rim, running a 52v battery. The max power setting was about 1500w, which is about 30 amps to the motor. Topped out at 45mph.

For only 2 hp, that thing pulled really strong. Holy shit, man. I had no idea it was going to be that powerful. It was very sobering. I was immediately impressed, and began to rethink my build goals.

Lately, I've been doing the math, getting these numbers, like 79v 70a, without having a clue what that feels like. Well, now I have some idea, and I don't need to go that crazy with it.

 

[MadRhino]

Now you have a reference to guess how 20kw does feel 8)

 

[amberwolf]

It's a mountain bike with a 5T Leaf 1500 laced to a 26" rim, running a 52v battery. The max power setting was about 1500w, which is about 30 amps to the motor.

That's actually 30amps *from the battery* into the system. To the motor could be a lot more; it's just how PWM controllers and motors work.

As for the power that bike actually had, unless you measure it with a wattmeter, you can only guess at it's power level based on "settings".

 

[Baron]

So, I rode my friend's electric bike yesterday. It's a mountain bike with a 5T Leaf 1500 laced to a 26" rim, running a 52v battery. The max power setting was about 1500w, which is about 30 amps to the motor. Topped out at 45mph.

For only 2 hp, that thing pulled really strong. Holy shit, man. I had no idea it was going to be that powerful. It was very sobering. I was immediately impressed, and began to rethink my build goals.

Lately, I've been doing the math, getting these numbers, like 79v 70a, without having a clue what that feels like. Well, now I have some idea, and I don't need to go that crazy with it.

In Neptronix's leafmotor tests he only hit those speeds with a 4T leaf in 26" rim, overspeed controller setting, and a lot more amps than 30. Something doesn't add up here.

 

[hypertoric_amplituhedron]

Don't take the numbers too seriously. The owner said it was around 1500 watt I was feeling, however the math adds up. I just did a quick calc of 50v x 30a = 1500w to get 30 amps. Is it derived some other way? If I have a 50 volt battery, and I measure 30 amps at the motor, is the motor making 1500 watts?

 

[amberwolf]

I just did a quick calc of 50v x 30a = 1500w to get 30 amps. Is it derived some other way? If I have a 50 volt battery, and I measure 30 amps at the motor, is the motor making 1500 watts?

You'd need to actually measure everything to find out what it is. A wattmeter between battery and controller will do it all for you.

To be able to calculate it, you have to measure voltage at the same time as you measure max *battery* current, (you can't measure motor current directly unless you have a brushed motor, or have at least two ammeters, one on each of two of the three phases of a typical brushless motor).

Then multiply that lowest battery voltage by the highest battery current (measured at the same time), to get the actual watts being pulled from the battery. Watts at the wheel will be lower by whatever the controller and motor efficiencies are, but for common usage most poeple just go by watts pulled out of the battery.


For instance, if I calculate watts for my SB Cruiser using the controller ratings, I have two 40A controllers running on a 58v fully charged pack. So that should give me over 4600w. But in reality, there is voltage sag, and the controllers dont' actually deliver rated current, so I really measure only about 3000-3500w, depending on pack's state of charge.


On my CrazyBike2, I actually get pretty close to the calculated 4600w, cuz the controllers provide better than rated current.

 

[wesnewell]

So, I rode my friend's electric bike yesterday. It's a mountain bike with a 5T Leaf 1500 laced to a 26" rim, running a 52v battery. The max power setting was about 1500w, which is about 30 amps to the motor. Topped out at 45mph.

For only 2 hp, that thing pulled really strong. Holy shit, man. I had no idea it was going to be that powerful. It was very sobering. I was immediately impressed, and began to rethink my build goals.

Lately, I've been doing the math, getting these numbers, like 79v 70a, without having a clue what that feels like. Well, now I have some idea, and I don't need to go that crazy with it.

In Neptronix's leafmotor tests he only hit those speeds with a 4T leaf in 26" rim, overspeed controller setting, and a lot more amps than 30. Something doesn't add up here.

The leaf 35mm 5T motor is on the simulator. According to it, it only does 32.4 mph using a 52V battery pack. With a 72V pack it tops out at 43 mph and ~3000W at 50A. No way it does 45 mph on 1500W unless you're going downhill.

 

[Wheazel]

Nothing looking like a regular upright bike does 45mph on 1500W unless you add more power from another source.
Be it more electrical power or power from position energy transformed to kinetic energy. 2500-3000W would be closer to the reality I think.

My bad aero, and heavy cargobike with a leaf 5t would top out around 60-65km/h (~40mph) at ~3000W.
That's with 18s 18650s. Even if your friend has field weakening settings in the controller, I doubt a 5t would reach that speed on that voltage.
Maybe it was a 3t or 4t? And more power overall?

 

[hypertoric_amplituhedron]

Huh, well, I have every reason to believe you guys, the ebike sim, and the owner as well. I wonder what the actual numbers really were, then. The only things for sure were running 14s with samsung 25r (~50v), a leaf 1500, 5T, square wave controller, 26" rim. He's had it up to 43mph.

But, that doesn't really matter. The important thing is that it was mighty impressive. Based on this reality check, a qs 205 h50 v3 can do far more than what I was thinking, lol

 

[hypertoric_amplituhedron]

Now you have a reference to guess how 20kw does feel 8)

Yeah, about that, how in the hell are you controlling that much power? This thing wasn't popping wheelies, but it pulled fairly strong (for me, I guess). Is your bike stable enough to punch it at low speeds? What kind of throttle do you use?

 

[amberwolf]

14s with samsung 25r (~50v),

Unless it's not being fully charged, that should be about 58v when full. 50V would either be pretty saggy if it was fully charged but under load, or getting closer to empty than full (if tha'ts 50v at rest).

 

[hypertoric_amplituhedron]

So, what's people's opinions on Adaptto products? Apparently, I should be looking into these, for the custom battery I want to build. It'll be a 22s8p of GA cells at first, then maybe a second one for a full 22s16p. The BMS, display, tunability, and size all seem to have good points. I've been looking at the midi-e.

 

[Voltron]

For some perspective on the 1500 watts.. thats what my cheap generic controller was labeled as also, but when I got around to measuring it in use is was putting out closer to 3300 watts peak. That 1500w rating is the continuous rating, not what it actually puts out when you punch it. Other controllers might go by the max output.