Electric assist bicycles
 

It was suggested I look into electric bicycles for my commute to work. I looked into this when I got the job last year, but it never went anywhere. So, I am now looking into it and am wondering if I could get some more info.

My commute is roughly 7 miles one way, there are some decent hills. I am not in the worst of shape and believe I could fairly easily work my way up to biking it, but I do have a bum knee from ACL surgery about 10 years ago.

So, what is out there? I know there are conversions out there as well as production bicycles. Suggestions?

Having only had one ebike and one test ride on another, I don't have a great first hand experience base with what all is out there. But I've had that Songi for a couple years now and I absolutely LOVE IT! You would not believe how often and how long the car remains parked on the sidelines when you have one of these! The Songi has a 25 mile range- flatland of course. It has pedals and I have used them when pushing past the batt pack's capacity; do that a few times and you know exactly how far it'll go. It has a basket and I use it for shopping and general errand running. It has full fenders also with flaps and I'll even ride it in the rain, or after the rain. My riding season ends when the streets get icy and they start salting the roads. Still, that is a nice chunk out of the year to leave the car parked.

There are a ton of options ... I'd start with considering what you want ... not just from the finished product but from the process.

Meaning for some people like me the conversion , the modifications , etc ... where fun activities in and of themselves ... I wanted to do them.

That isn't the case for everyone ... many people are all about the use it ready.

The use it ready by far is easier and such ... it will save some headaches that end up happening in a 'project' ... the quality of the project will depend heavily on the skill and time invested of the project builder ... but a project does allow you to customize much more than a ready made product ever could.

If you don't have a specific need for it ... I would recommend avoiding the folding bicycles ... some are not bad ... but unless you specifically need that feature it will just cost more money and have bike design compromises you don't need.

That having been said mine is a folding ebike ... I personally prefer it , for a few reasons ... but there are cons to them ... so if you don't need that feature don't bother with it.

My bike is chainless ... It has a drive shaft going to a mini 8 speed transmission built into the rear wheel ... I like it for the removing of the chain issues , maintenance , grease and dirt , etc ... but it isn't free ... so if you are used to and don't mind the comparatively minor issues with bicycle chains ... just stick to those , it opens up a lot more options for you.

Make sure the bike itself a base is comfortable ... if it starts off uncomfortable , it is likely to always be uncomfortable.

If you only are considering some assist to make those bike rides and commutes easier and such ... and you are not looking for an electric scooter where you don't plan to pedal at all ... Then there is not much reason to go with anything more than the mini motors rated around 200 to 300 watts.

If you want that scooter like pure EV like mode with zero pedal power from you ... than that is when the higher over 300 watt motors can become useful.

Be mindful that many places will legally consider a ebike with more than about 700watt rated motor as a scooter or moped like device , and may not be allowed on bike trails and paths ... where as many places a eBike under 700 watt rated motor is still legally a bicycle and can still use those bike trails and paths and such.

Regenerative braking on a bicycle is mostly useful if you plan to use it for training ... meaning if you get in great shape and you want a hard work out , you can use that extra resistance for additional exercise the human efforts ... other wise it can pick up a bit more energy efficiency ... but there is usually a price to pay for that feature ... a price larger than the price of electrical kwh are ever to likely recover ... so it is good for some applications ... but if that isn't your thing ... it is a feature that might not be worth the cost.

Many eBikes that do not have regenerative braking instead offer a better free wheel ... allowing the bike to coast further and generally require less energy to go a mile ... this better free wheel often tends to be not as expensive as the regenerative braking feature.

There are some nice power monitors and displays ... I like my Cycle Analyst ... but most of the eBike kits have safety minimums already built into the electronics ... so , such a fairly expensive monitor is mainly for the user ... it has nice features that I like and wanted ... but it may not be cost effective for many people ... who mainly are just going from point A to point B... and having a monitor that logs the distance tells you your speed monitors battery voltage amps Ah watts wh etc ... those things are not worth it to everybody.

Make sure you put a little consideration into weather proofing / resistance ... even if you don't plan to use it in the rain ... there are some simple and easy steps that can be taken ... things that can be useful latter if you get caught by an unexpected shower and such.

There are many battery options as well ... but keep in mind the use and application ... 100 watts of assist for ~15 miles at ~10 MPH is only 150Wh of battery power ... even 300 Watts under the same conditions is only ~450Wh ... unless you want a very long range ... or you are going up into the over 300Watt pure EV like scooter range ... there really is extremely little need for anything more than ~500Wh of battery power ... from 36V this is at most about ~14Ah ... But if you are going to do it make sure you have at least enough to able to use it freely ... I'd say about ~200Wh as a free use entry point for a under 300Watt just giving assist to your pedal efforts type of riding ... at 36V this is ~5.5Ah.

So once you have some ideas of the basic kinds of things you are looking for ... do and don't want ... etc ... then I think you can take those choices to go out and look at specific options and models , etc.

I got a hub motor built into a wheel from ebikes.ca. I loved it, until my math class destroyed it doing experiments at like 40 mph with a guy that weighed close to 300 pounds. We weren't using a controller, just an on/off switch. haha.

ebikes.ca Hub Motor and Ebike Simulator

I have a Crystalite rear hub motor from Electric Rider that I really like, I just don't use it much so it's up for sale if you have a reason to come up to west central Wisconsin any time over the winter, right now it's a full bike, with a 36v controller (some people say you can run the motors up to 96v but they were designed as a 72v motor), I also have a 36v 10ah Ping battery and am willing to sell the whole set up for $600 or just the motor/wheel, with speed controller, throttle for $500, no battery and no bike frame.
When I was running that bike with 33v dewal batteries it would go 27mph without pedaling and I'm 250lb so at a true 36v and with someone smaller on it it's going to go faster! that is why I bought that motor, I liked the idea of being able to go faster!

If I don't sell it, I plan to build a cafe racer Ebike using a Chinese scooter's title and vin so I don't have to have pedals on it.

Are there any possibilities in the under $500 range (not you specifically Ryland)?

Yes.

Most easily if you are starting with a donor bike ... and in either the used category or the DIY category for the project.

For example I got my front hub motor and motor controller for about $150 for both of them ... that isn't the whole electrification part of the project, but it's part of it.

Once I had the core Motor and controller in hand ... the 3rd and last major component was a battery ... on the cheap you could use any battery you happen to have that can do the volts and amps ... I did splurge a bit for a higher capacity LiFePO4 battery but that is not necessary to go that far.

The 4th part is all the little bits and pieces ... things like:

• Connecting wires
• Controls ( Throttle and such )
• Getting the motor spoked to a wheel ( any bicycle shop can do this for you if you don't want to DIY )
• Securing the battery pack to the bike ... can be as simple as strapped to a bike rack ... or more complicated like the one I have has a lock , quick disconnect from the bike , a handle , etc ... but as long as it is securely on the bike , and functional , that is all it needs to be.

Off you go.

Staying under $500 when you have a donor bike ... is doable for a used system , or for a more DIY basic system.

Of course if you want more battery capacity ... lighter ... faster .. more power or torque ... better controls ... more displays ... etc ... etc .... more / better cost more.

- - - - - -

For example ... my 1st eBike was lead acid batteries strapped together ... my 2nd was NiMH D cells I soldered together ... as long as it is secure and functional it doesn't matter if it is pretty or not , unless that's what you want to pay for.

I was kind of thinking this would be a fun DIY project.

I just happen to have a 350W PM scooter motor. I also happen to have 12V worth of A123 20Ah cells. While it may not be the perfect setup, all I would need is a controller and charger to get things going...

As long as you enjoy the DIY road trips , highs and lows together ... It will be fun ... it was for me.

From what you happen to already have you are off to a good start.

As long as you are only intending on using it to assist and make your pedaling easier ... ~350W should be fine ... do you know what voltage the scooter motor was originally used at?

Yeah, it is a 24V motor. That means it is setup for ~14.5A, and if I only use 12V I'll only get half the power output, so 175W.

As I mentioned in the first post. I think I can fairly easily work my way up to a 7 mile commute, but this would just help get up the bigger hills and not get to work all sweaty.

Is your motor a hub motor or a chain driven brushed motor?

The motor I have is very similar to this one. It is made for an electric scooter.

Brush DC Motor for Electric Bikes, Scooters, Mopeds, Motorcycle - 24V 250W

I used a motor just like that for the scooter I built for my son this summer. Endless-sphere.com • View topic - Stand up to Mobility scooter conversion it works quite well but I think you will need to run it with a 24v pack it you want it to have enough power to do any good. Also, a controller for it will be 24 volt. Check out the online scooter parts sites. Parts are pretty cheap and since you are in the US shipping shouldn't be too bad. I didn't buy any thing from them because of the high shipping to Canada. If you could find a good deal on 4 more A123 cells, you should be able to stay within your budget. I have the scooter geared really low, but it has lots of torque. I think, even with higher gearing for a bike, it should be fine for a pedal assist if you don't need too much speed. The only problem might be figuring out a way to mount it. I think you will need a second freewheel or something.
Another cheap option might be to pick up an ebike kit off ebay, but I have no idea which sellers are reputable.

Hey Daox,
I built this ebike for about $600 (see attachment). IMO it has a lot of advantages over a hub motor ebike like
1) You can shift gears to get the best use of the motors power
2) You can pedal if you want but you don't have to
3) Top speed of 25 mph
4) 20-25 miles of all electric range

If your interested in more details let me know. You could do this with your motor but, you will need more cells. 175W will be nothing and even 350W is severely underpowered. I'm running 500W and I still want more. I would really like a 36V/1000@ motor but its just not in the cards for now. I'm using lithium (LiFePO4) batteries as well. My pack is 24V/30ah and it is sufficient for my 17 mile round trip commute.

Looks pretty nice Govman6159. That is pretty much what I was thinking of doing. More info would be great.

Puddleglum, that is pretty cool too! I love how it folds up. Very nice work.

I would be happy to be of any assistance to you on your build and happy to provide you with whatever info you need. What specific questions do you have for me?

Here is a pic of how I mounted the motor.

Where do you get the gears?

I got some from sickbikeparts.com and others from electricscooterparts.com. The gear you see is a 96 tooth #25 sprocket from electricscooterparts.com. Its off of a Schwinn S500 scooter. I ordered the front freewheel bearing from sick bike parts. Both sites have a myriad of parts you can use for converting your bike.

govman, nice job. It looks like your motor is driving the crank through a freewheel, right? How do you keep your motor from overspeeding your crank at full throttle? Unless you have a really low speed motor, the gearing doesn't seem low enough. Am I missing something?

Do you have any form of BMS for your batteries?

I checked prices on the controllers on the electric scooters site. They're way cheaper than other ones I've seen. Is the quality any good? $30 for a controller makes me wonder.

Yes, I believe you are missing something. If you look at the close up of the motor/drive sprocket, you will see the crank is attached to a freewheel bearing. When the motor turns (clockwise) it only drives the sprocket and not the crank. This in turn, turns the stock sprockets which turns the chain as if you were pedaling but the pedals do not turn. If you do pedal, the freewheel locks and the crank powers the stock sprocket or if you apply power and pedal, the motor will provide assist. It is truly a hybrid w/ 3 possible power sources (the motor only, pedal only or motor and pedal).

As for the gearing, I can change that to match the terrain just like on a regular bike. The front sprockets are 48/38/28tth and the rear is a 14-34 tth 7 speed rear freewheel cassette.

All this makes for an excellent ebike that is suitable for riding over various terrains. This is really just my proof of concept bike. I am experimenting with various gear ratios to see which one best suites my performance desires. So far I have migrated from a 11-28t rear cassette to a 14-34. The 14-34 is better for all electric riding and I still have high enough gears for normal city riding. My next mod will be switching the front triple spocket to a 24/34/42 setup for even more low end torque. This should allow for better hill climbing capability and faster takeoffs and still allow for full speed operation.

Yes I have a BMS and his name is Govman6159 (lol). IMO, there isn't really a need for a BMS on this bike as long as I monitor cell voltage periodically. What I do is periodically monitor the individual cells as its charging. If I see one getting too high, I will stop charging that cell and continue charging the others. I am using a 24V/1.8A charger to charge the pack. I find I get nearly equal charging up to 27.1V (29.2 is the max for the pack). Once it hits that voltage, I have found it is at this point when cells may become unbalanced. So from this point forward I closely monitor individual cells. This has allowed me to id which cells are prone to overcharging (I only have one set of cells prone to overcharging). 27.1V is about 92% charge for the pack so I usually just stop at this point. I have found that by doing this, I get less than a .08V variance between cells (whereas .3V is considered normal).

As for the controller quality, I'm happy w/ the performance of mine. I've had this controller for 7+ years and its still working (YMMV). IMO it does a fine job.

I think they were asking about the gear reduction from the motor. What is the motor rpm rated and what is the crank rpm if you want to pedal to add to the top speed? What is top speed while pedaling on top of a 500 watt motor?

The gear reduction from the motor to the sprocket is 96/11 or 8.73:1. The final reduction ratio to the rear wheel in 1st gear is 9.553:1, 2nd gear is 8.612:1 and so on.

The motor is 0-2500 (variable, obviously) rpm max.

The crank rpm is dependent on the selected gear. In 1st gear, you will not be able to pedal fast enough at top speed to assist but simply shift into 5th and you can begin to add pedal assist and can add more by shifting to a higher gear.

As for top speed, I haven't been able to "maintain" speeds in excess of 30.4 (flat surface) with pedal assist. I can get above that but wind resistance is high and hard to overcome. This is honestly an area I haven't studied much b/c I tend to rely on all electric (I'm lazy). I will do some tests and report back.

Top speed in all electric is 25mph and is limited by wind resistance (little to no wind, flat surface). I'm guessing a 350W motor would get you about 18mph (if your lucky).

So I guess it is just normal that the electric motor will be running at only 800 rpm when you are pedaling.

Yeah, I'd say that's about normal for all electric mode. If I'm doing 30mph with pedal assist, my calcs put motor rpm @ 1100 (about). This may change once I put the new sprockets on up front. I'm hoping for 0-20 in 6-10 seconds with that swap. Right now its about 8-15 sec's to 15mph depending on terrain. I'm also hoping to be able to maintain 15mph up most hills. Right now I can only maintain about 9mph up the worst hills and 12-13 up other hills (which is painfully slow). All of this is with no pedal assist of course.

What parts are needed to attach a sprocket to the crank with the freewheeling mechanism?

What you need
 

Here's what you need.
1) one freewheel crank set (Sick Bike Parts)
2) one front freewheel bearing (Sick Bike Parts)
3) one extended length crank spindle (your stock one wont work because you will be extending the attachment point for your crank arms to fit the additional sprocket. You will have to measure for this, each bike varies)(Sick Bike Parts)
4) 90 tooth #25 sprocket (#25 Sprockets for Electric Scooters and Bicycles - ElectricScooterParts.com)
5) bolts and nuts (you pick the size, I went w/ M5)

I've tried two different controller/motor combinations with the scooter now, and both seem to work well. I can't speak to their durability, but they both seem to deliver their rated power without getting hot and they cut back power at low voltage. According to my wattmeter, I can get over 800 watts peak from the 35 amp controller and 600 watts from the 25amp one. You will also need a throttle control and a set of brake levers. You could use a Cellog8 as a cheap BMS to cut power to the charger or maybe a simplified version of the one you already designed for your Enginer pack.

This was what I was getting at with my question about gearing. If your motor is rated for 2500 rpm and you are pulling it down to 800-1100 rpm that seems like too much to me. I would think that more gear reduction to the motor would give better performance. Thanks for explaining the freewheel mechanism though.

This is pretty cool - self contained hub motor/battery/controller and a wireless accelerator lever:

Green Wheel - 3 in 1 wireless electric bicycle hub motor | Electric Vehicle News

This might be awesome on velomobile, as well.

That's a great idea. Plug and play. I'm not seeing much room for a battery pack though. They say 25 miles but I wonder what the rating is.

I'm really not into hub motors b/c they don't allow you to shift (the motor). With my setup it has the advantage of allowing you to shift the gear ratio the motor sees. A hub motor cannot do this. This severely limits at least one aspect of all electric riding (either takeoff acceleration, hill climbing or top speed). I know hub motors look nicer and provide good assist but I guess that's just my personal preference.