[EVDL] Electric Bike Advice

[Lock]

Thought I'd post this to ES... Dennis is definitely a bright light on the EVDL, but out of his depth w/power-assist...
Ya might post here then I/we can hand Dennis the link! (Hehe... where's Randy when you need him?)

From: "Bill Dennis" <wjdennis@qwest.net>
To: "Electric Vehicle Discussion List" <ev@lists.sjsu.edu>
All right all you Electric Bike guys out there, I need your advice. My wife has asked me if I can build her an electric bike to ride to and from work. Her commute home ends with a 4-mile uphill climb with an elevation gain of 1700 feet. During that climb, she would like to be pedaling as if she were on a flat road, or maybe just a little bit harder. I know there are commercial electric bikes that make this claim, but what kind of motor would I need to pull it off for a home-built EV? And do you have any estimates on a battery pack that would have enough kilowatt and kilowatt-hour capability to handle it?
Thanks.
Bill Dennis


Geeesus... I am only familiar w/401ft up over 15kms or so... Yah, Canuck but also mixed up between land and sea and air (hence Statute and Kms and Knots)... ES ppl... whadda you think Missus Dennis needs?
tks
Lock

 

[pwbset]

Her commute home ends with a 4-mile uphill climb with an elevation gain of 1700 feet. During that climb, she would like to be pedaling as if she were on a flat road, or maybe just a little bit harder.

I climb 1,600ft over about 3.5mi each morning so have a pretty good idea of what she'd need. I run a souped up rear 4011 @ 84v and between 20-40 amps. I'm averaging about 35-45wh/mi and I'm pedaling a ton. Like drenched in sweat when I get to the office and I'm in pretty good shape. Keep in mind half my commute is on pea gravel with grades up to 15-20% at spots so that's pretty taxing. If her commute is more consistently graded 8-10% and paved that's a lot easier.

I guess in a nutshell if she wants to pedal like flat road or a little bit harder she's absolutely going to have to get a Clyte 5 series like a 5304/5 with at least 48v and 40amps. That's just my opinion, but you'll notice around here that a lot of people tend to overestimate the power of their ebikes and will tell you she could do it @ 36v with a Golden or Wilderness. Sorry, but for a climb like that it just ain't gonna happen with less than a 5 series. You could try a geared motor, but if you over volt, which you'd want to, you run the risk of stripping the nylon gears (unless you've got mad cash for a heinzmann or something).

 

[wjdennis]

Hi, guys. Bill Dennis here. Lock pointed me to the forum from the EVDL. Thanks for taking up my cause. The climb is paved and fairly consistent, though it does end with a steeper 1.5 miles at the end. In fact, I'm still working on tweaking my recently completed electric car to make it up that portion without sagging the batteries too much. I have 10 leftover 90Ah lithium cells from ThunderSky at my disposal--though at their nominal 3.6V per cell, perhaps they're not an appropriate choice. Is there a good place on this web site to visit to get a beginner's overview of motors and controllers for electric bikes?

Thanks.

Bill

 

[Link]

Is there a good place on this web site to visit to get a beginner's overview of motors and controllers for electric bikes?

I dunno, but try going through some n00b posts. There's usually good info in there. You have experience with electric car parts, so you shouldn't have a problem. They're pretty much the same thing, but on a smaller scale.

I have 10 leftover 90Ah lithium cells from ThunderSky at my disposal--though at their nominal 3.6V per cell, perhaps they're not an appropriate choice.

Their voltage is fine, but, Jeebus, that's a HUGE amount of capacity for an ebike. You should only need like 20Ah worth.


Anyway, I'd recommend either a geared motor or an X5305 at 72V in a 20" wheel. I don't know too much about the geared motors, so someone else will have to chime in to say which could do it, but I know an X5305 on 40-50A in a 20" would climb ANYTHING.

 

[swbluto]

Anyway, I'd recommend either a geared motor or an X5305 at 72V in a 20" wheel. I don't know too much about the geared motors, so someone else will have to chime in to say which could do it, but I know an X5305 on 40-50A in a 20" would climb ANYTHING.

True dat. It also seems like it has a comfortable real-life top-speed of 28-30 mph(on flat land) which isn't bad.

 

[lazarus2405]

First off, welcome! Grab a pint and enjoy the ambiance.

Head over to ebikes.ca. They've got lots of information for beginners. When you need to get down to the math, there are two calculators you'll learn to love: ebikes.ca/simulator and kreuzotter.de/english/espeed.htm.

To pull a 160lb rider and a 60lb bike (no offense intended to the Missus) up an 8% grade at 20mph will require 1kw, and to do 25mph you'll need 1.4kw at your disposal. For just that 4-mile climb, you'll need between 280 and 350Wh. Assuming the rest of her commute is on flat ground, add in 20Wh/mile at 20mph or 28Wh/mile at 25mph for the rest of the trip. If she is unable to recharge her battery before the return trip, be sure to account for it (and make sure she has decent brakes for the downhill leg). If she wants to go faster, it's certainly possible (and rather fun), but it does take a toll on the energy requirements. Mind you, all of those Wh numbers are nominal ratings, factoring 80% motor efficiency and assuming you get only 90% of the battery's rated capacity. The 1kw and 1.5kw figures are "at the wheel", after motor losses, and not the V*A being sucked from the battery.

To elaborate on what pwbset said about motor requirements, you could do the climb on a Golden or Wilderness or Clyte 400-series, but you'll have to run it at a high voltage (though to be fair, any hub motor setup will need >60v to accomplish the climb). The other issue with those smaller motors is heat - running those smaller ones at >1kw for 10min will make them hot to the touch. It isn't too likely burn them out immediately (that is, demagnetize the rotor magnets or burn off the stator coil insulation), but I'd be very worried about the long-term survival of such motors. Not that they can't take that sort of power, just they can't handle it for a prolonged ride.

Perhaps a Clyte 408 at 72v would do it fine, but it'd be in the outer range of the motor's abilities.

That pretty much leaves the Crystalyte 5300-series of motors. They're big - the diameter of a large dinner plate - and they weigh ~25lbs. However, I love 'em. They're the best motor out there if you need power, period. Because of their greater mass and surface area, they have excellent thermal characteristics; my 5303 only gets warm after commutes of 10-15min at 45mph. And they tend to live very long lives at those power levels.... Of course, I suspect your wife does neither require nor necessarily desire that sort of power...

Anyway, a 5304 at above 60v will get the job done. More volts is faster, anything in the 72v and higher will outperform a 50cc engine, and there are no reliable controllers that can handle >90v. You'll want to use lithium, of course, and there's a lot of discussion about that in these forums. No, your leftover ThunderSky packs aren't suitable for this particular build... but they do make for interesting options for other builds...

Link, how've you been? Good to see you! Been a while!

I'll disagree with needing a 5305 or a 20" wheel (the 5305 is the torquiest flavor of the 5 series). True that it'll climb anything, but using the 5305 winding with a 20" wheel compromises on top speed (that is, it won't be able to hit 30mph), and the 20" wheel introduces its own set of complications. It wonks with turning radius and pedal clearance, both of which the rider may find irritating.

 

[Link]

Seconding the "head over to ebikes and have a looksee" sentiment. There's actually more info to that site than there is store. :wink:

I'll disagree with needing a 5305 or a 20" wheel (the 5305 is the torquiest flavor of the 5 series). True that it'll climb anything, but using the 5305 winding with a 20" wheel compromises on top speed (that is, it won't be able to hit 30mph), and the 20" wheel introduces its own set of complications. It wonks with turning radius and pedal clearance, both of which the rider may find irritating.

Hmm, I dunno. The ebikes sim says it should do somewhere around 25mph on 72V (flat, anyway...), which is a good top speed for those who aren't total performance freaks or crazy like us.

Guess it'll depend on what kind of speed she wants. If she's okay with normal bike speeds uphill, then the 5305 in a 20/24" would be a bit more efficient. If she wants to be a bit more superhuman, then the 5304.

You'd be okay with a 20" if you used something that was built for it. A BMX might not be her style, but the people here seem to like their folders.


Hmm, I think we need a little input on capabilities from the missus...

Link, how've you been? Good to see you! Been a while!

Being lazy on my summer vacation (which, sadly, ends in a few weeks ). Playing SSBB until 6:00AM. The usual.
(That, "Whoa, I'm a senior. " thing just hit me again...)

 

[DahonElectric]

Thought I'd post this to ES... Dennis is definitely a bright light on the EVDL, but out of his depth w/power-assist...
Ya might post here then I/we can hand Dennis the link! (Hehe... where's Randy when you need him?)

From: "Bill Dennis" <wjdennis@qwest.net>
To: "Electric Vehicle Discussion List" <ev@lists.sjsu.edu>
All right all you Electric Bike guys out there, I need your advice. My wife has asked me if I can build her an electric bike to ride to and from work. Her commute home ends with a 4-mile uphill climb with an elevation gain of 1700 feet. During that climb, she would like to be pedaling as if she were on a flat road, or maybe just a little bit harder. I know there are commercial electric bikes that make this claim, but what kind of motor would I need to pull it off for a home-built EV? And do you have any estimates on a battery pack that would have enough kilowatt and kilowatt-hour capability to handle it?
Thanks.
Bill Dennis


Geeesus... I am only familiar w/401ft up over 15kms or so... Yah, Canuck but also mixed up between land and sea and air (hence Statute and Kms and Knots)... ES ppl... whadda you think Missus Dennis needs?
tks
Lock

If missus Dennis is looking especially for a climbing bike, then a folder equipped with either a Bionx PL-350 or an eZee kit would probably suffice. JVbike's owner had a Youtube demonstration of a Birdy folder bike equipped with a PL-350 (brushless) going up the Cypress Bowl road which has an 8% grade and an elevation gain of 1200m, or 3937 feet over 12km from the Transcanada Hwy 1, with hardly any effort at all plus he beat a normal roadie by 20 mins. The small wheels will give you the best torque going uphill, but lower top speed on the flats as opposed to say a 26" or a 700c wheel. That was the main reason why I converted my Dahon into an electric in the first place, and my commute route is very hilly, with one 15% section which my 250w motor can not make up by itself, but needs me to pedal with a low gear to assist it.
Secondly, think light weight. My Dahon package weighs about 38lbs, certainly beats others at 60 to even 100lbs. The lighter the ebike package, the easier you can take it up any hill with lesser effort. Ever wonder why some many pro cyclists ride stripped bikes as opposed to a normal flat lander bike on any hill climbing routes? Instead of using Shimano or Campagnolo brifters (that's shifter and brake lever combined), they use a brake lever with a friction shift lever. If pro people shave every little ounces to go up a hill easier and quicker, what does that message tell you?

Here's the problem.. So many people want power. Power comes with a price and that's the price of weight! Bigger and more powerful motor needs more battery capacity. More battery capacity means more weight and although you can mitigate that with better batteries (Lithium variants), you are going to be taking that weight up regardless. A good compromise is when she pedals normally without electric assistance on the flats and only use it going up the hill. If that is the case, a planetary geared hub like an eZee would be a good compromise (planetary geard hub freewheels better than brushless) and she can run with a lesser capacity battery which lightens up the weight. Stay with a 26", which gives a good compromise between hill climbing power, good flat cruising speed and good steering characteristics (20" folders can be a bit squirly if not used to) and make sure her bike is equipped with a good set of climbing gears if she wants to assist the motor. Usually, a 26" bike comes with a 44-32-22 (chain ring) and a 11-32(34) 9 speed cassette and with full throttle and at 22-34, she should be able to climb any steep hills, as opposed to 700c bikes which comes with a 52-42-30 and a 11-30 cassette or so -- ideal for fast flat landers, but geared too high for steep hills.

 

[dogman dan]

I agree with about half of each of the previous posts. A geared hub motor at 36v will be perfect if she is not into high speed. If she is, it sounds like she'll get her fix going down for sure. Especially since the gearmotors freewheel. A brushed hub is a good climber and putting one in a small wheel, like a 20" folder or bmx will climb well with just about any brand motor. But since this is a serious climb, you risk burning up a brushed motor like I did this summer. A 20" wheel with the hill climbing x5 chrystalite would be great, but you may do NO peadaling with that one! Might go through tires too! Chances are the torqueier 400 series brushless hub in a smaller wheel will be fine running on 48v. One Idea I'm toying with is a 26" mtb with a 24" rear swingarm and wheel bolted on. But your wife may fit a 24" Mtb if she is petite.

 

[pwbset]

The other issue with those smaller motors is heat - running those smaller ones at >1kw for 10min will make them hot to the touch. [snip] Perhaps a Clyte 408 at 72v would do it fine, but it'd be in the outer range of the motor's abilities.

Yes heat... a 4011 at 84v and 20-40amps after climbing 1,600ft is way too hot to touch... like burn your fingers hot (not that I've done that over and over ). The first thing I do when I get to the office is put a big fan on the motor to cool it down. Working so far, but were I to do this again I would have saved up a couple hundred extra and gotten a 5305 in a 24" wheel... like Doctorbass setup, but I would have run it at only 48-60v/40a instead of his insanely powerful rig. :lol:

Anyway... I don't expect my 4011 to last very long at these 2,000+ watt sustained power levels. :|

 

[dogman dan]

At stock 36v and stock controller, my climb in 100+ F cooked a BD36 in 400 miles. One hour ride was tooooo long for it. So length of ride is also an issue. This stuff is designed for about 8 usable ah of power avaliable. I need a motor with a fan inside for my ride.

 

[Joey]

I would caution against using a stock eZee or similar BMC geared hub motor at greater than 20A and 36V without increasing the size (reducing the gauge) of the phase wires and using PTFE (teflon) insulated wire. Shortening the exisitng wires and running thick gauge from there to the controller is inadequate. I fried my stock but shortened BMC motor phase wires running 56V and 35A controller while hill climbing in an attempt to stress-test my Milwaukee batteries. Similar problems have been encountered by others (e.g. jonathan's "BMC Motor Burnout" story). I rewired with 14 gauge PTFE and have had no problems since. The motor itself handles way more power than its rated, but the stock phase wires are a weak link. I haven't had problems with my nylon planetary gears ... yet. Steel replacement gears are becoming available -- noisier but beefier.

-- Joey

 

[lawsonuw]

My personal favorite is getting a motor to drive the chain or pedals so the motor can take advantage of all the bike's gearing. This does have the disadvantage of limiting the maximum power to what bicycle gearing can take. That's still like 1000w total power.

http://www.cyclone-tw.com/order.htm makes commercial kits. Reports I've heard say Cyclone kits are a more challenging to install, but work well once they're installed.

http://www.elationebikes.com.au/ another Kit.

Also, some german makes a kit similar to the eLation kit.

Anywho, if you're a bit more adventurous an imitation of the setup on my Linear Recumbent might be worth a try. http://endless-sphere.com/forums/viewtopic.php?f=6&t=5919 One advantage is that since my setup runs at 12v, 90Ah ThunderSky cells are more reasonable. Understand, this is the first version of this and I've got many ideas on how to make it better.

Marty

 

[dogman dan]

I agree about overvolting stuff, fine on flatter terrain but more juice to climb hills can just cook stuff. I had some help from the climate though, my other motor, used in under 95 F is fine. The cyclone type kits look real good, but on my cheapie wallmart bikes, I suspect the gears and shifters would fail. Slow and easy with a bmc or such would be the best approach for stuff to last on a huge daily hill I think.

 

[wjdennis]

Thanks for all the advice. I've been doing some research. In Utah, the law limits electric bikes to 1000W and 20 mph. so I'm thinking a 36V 35A controller with a 1000W Crystalyte motor on a 20- or 26-inch. My question is this: does the motorized wheel go on the front or the back?

Thanks.

Bill Dennis

 

[Link]

That's the same limit we have in Cali.

Just, FYI: The "1,000W" X5s are capable of far, FAR more than that. 8)

You can order them either with no sprocket cassette (front) or with (rear). There could be balancing issues depending on where you put the battery, though. Rear motor and batteries near the back can make it pretty squirrely or prone to wheelies. Front motor and rear batts are a good combo, but not good for higher speed, IMO.

I use a rear motor and rear batts, myself. The balance point on the bike used to be about 5 inches in front of the seatpost. It's now behind it.