Greetings from new member, 300 miles and counting on E-bike

[caleb]

Hi all,

I have enjoyed reading this forum and thought I would share a little about my story and pose a question where to go next.

I have a hub motor ebike, got 2 co-workers and myself into buying electric motor kits for our bikes. I thought the golden motors were the best at the time so they both bought front GM hubs for their bikes. I for some reason held out a few weeks and ended up buying an Ebay 1000W 48V motor.

With some years of electric R/C experience and sucesssfully using Dewalt 123 drill packs on my large electric heli as well as large Lipos on airplanes, I was ready to build up my own battery and charging configuration for our bikes. I went with a 4 way Hobby King charger and 4x 6s 5000mAh Zippy batteries in 2 x 6s2p config resulting in 12s2p, or 48v 10Ahr battery. I put my system together in a night and was off to work Monday on my 5 mile commute. Haven't looked back since, have been riding 6 months through the winter without any problems. I keep tinkering with battery location and haven't settled on anything yet, but have tried it rear mounted, handlebar bag, and water-bottle cage mounted as well. Bike was an old schwinn w/o shocks, but upgraded to a Wal-Mart special full suspension to help with the potholes. Ready-to ride weight is 56 lbs, I am about 180, and I can get to 28.5mph straight and level, 33mph down a hill, verified with GPS Google Tracks. I use an astroflight watt meter and have seen 1200+ watts at the battery, and average 700-800 watts at full speed.

Video of ride to work with old Schwinn and squeaky brakes...sorry http://vimeo.com/19626509

I like the rear motor setup and have good power, acceleration, but battery has been dying earlier than I expected. I thought I could get around 20 miles conservatively, but recently only getting 13 miles or so on a charge. Balanced charging puts in about 4Ahr on each 5Ahr battery pack, but I run out of motor at 44 volts on the 12s battery system. So I am not discharging all 5000mAh, but all in all it’s pretty good.

For my next bike build, I would like to try gearing a motor, to get better acceleration, and decrease my large watt consumption starting off from all the red lights. I guess regenerative braking would also be good, but not sure if I want to do a hub motor or not. Was thinking a small brushless driving the chain on a internal geared 7 speed Shimano Nexus would be cool. Any thoughts on if I can get better acceleration/efficiency/endurance on a battery if I gear down an outrunner motor rather than using a hub motor?

Thanks for reading.

Cheers,

Caleb

 

[dogman dan]

Looks like you are getting close to my often repeated rule of thumb. 1 ah per mile at 36v which should leave you a small reserve to go easier on depth of discharge.

Basicly, you just need to carry a bit more battery. 14s 15 ah would get you a bit more snap off the line, and the range you want, 20 miles at fast speed.

The other option would be to improve motor performance some by going to a slower winding motor with better and more efficient slow speed performance, then volt up till it's top speed is faster. Something like a 2810 9 continent, running 20s lipo, and higher amps on the controller. That's realllly heaving some battery at the problem.

The easiest thing of course, would be to just buy two more 5 ah 6s packs. Paralell them, and your charging setup remains the same, and you increase your range by 1/3. 12s is a pretty handy way to go with lipo, unless you really need the extra speed or power of 14s. You might need that extra to climb hills for instance.

 

[theRealFury]

Hello Caleb,

Sounds like you have your head pretty much screwed on right from the start which is more than i can say for my first e-bike purchase... looks like a nice kit. I have found out though with practice that range is a factor of speed rather than AH. You could get 30miles out of that 10AH pack if you cruise arround at 10MPH. Its the 20+MPH speed that saps the battery capacity. Basically if im correct as you speed up your power consumption increases exponentially so going 10MPH would take 1x power but going 20MPH actually takes 4x power.

Basically your battery pack seems fine although your LVC might be a little conservative unless the 44v is your resting voltage and not your under load voltage. 44v is 3.67v per cell, i beleive the average cutoff per cell that people run is 3.5-3.6v depending on how conservative you want to be so you might find another mile in the pack if you drop LVC to 42.5 or 43v but technically speaking taking 4AH out of a 5AH lipo pack is about right.

On geared motors i can give you two points from my personal experience.

1) Geared motors still crave high currents on the startup if you just give it the throttle, no different to a DD motor in that respect. I believe that any motor starting from stalled under load will draw the maximum power it can do unless you regulate it with the throttle.
2) Geared hubs generally dont do regen unless you can find one without a freewheel in it.

I have no personal experience with outrunners but from my time reading other peoples build notes and experiences it would seem that an RC chain drive will give you more torque and more speed for the same ammount of watts than a geared or DD hub motor because of the direct use of the gears on your bike. the main downside that i can see to an RC drive is that you sound like a 150lb angry wasp as you zip along.

 

[Ypedal]

hehe.. welcome to ES !

Easiest and least expensive way to get the range without slowing down is to add capacity, as dogman pointed out.

The hub motor rig is more efficient unless you have severe hills to climb that are bogging down the hub to the point of current-limitting of the controller, going to an outrunner pulling the chain allows mechanical advantage of gearing but is not more efficient imo.. ( and a very experienced opinion it is ! ) and the stealth factor also comes into play if that matters to you.. the RC drives are not quiet and not really weatherproof by nature..

A geared hub motor will lighten the load a bit, but if you like going 30mph a direct drive is more robust and abuse tolerant.. and as said above you do not get regen with a geared hub but you can pedal it with very little restriction ( pedals like a regular bike with added weight vs slight magnetic resistance on a DD setup ) .

I say up the capacity and run it until it breaks. .then upgrade to something else ! :wink:

 

[wesnewell]

If my math is right 12s2p is 504w. 14s2p would be about 588w. 12s3p would also be a good option for more range, about 756w. Optimum would be 14s3p. Also range should improve as the temp rises. As for the brakes, yours aren't near as bad as mine were. Rubbing alcohol and a scrubby on the pads and cleaning the rims cured mine of all squeaking.

 

[Ykick]

Looking good and welcome to the forum - 'nice to see some tunnel action too! Your RC background is a huge advantage IMO.

Couple things - Wh/mile seems spot on especially for what looks like a 30A controller. You simply need double Lipo capacity and you'll be in great shape.

As a regular commuter (NYC) I've struggled for years with Vee brake squealing - Tried Kool Stop, Salmon color pads, Clarks, etc. All the compounds I could find and in the end - cheap, relatively hard black rubber generally squeals less than anything else I've found. It also doesn't stop as well, but...

You may be able to minimize squealing regardless of compound by drastic toe-in/out adjustment. That's what I've had to do with some of my "expensive" pads to shut 'em up.

For your type of riding I also highly recommend a loud Automotive type horn, Can usually be powered by whatever 12V lighting supply you're likely already using. I'm a believer in running quiet as possible until I need to make my presence known.

Nice job! Enjoy...

 

[caleb]

Thanks for the reply's, great info. I should say again that my commute is 5 miles one way, so my 10AH battery is ok to get me to work and home, but I had been trying to go 2 days before charging, but that hasn't been the case since I don't pedal much and I have a "lead thumb" I guess and have lots of stop lights, so lots of high-amp starts. My buddy with as 12 mile one-way commute is upgrading (2 more zippy LiPo's) from 48-10 to 48V 15AH to cover him for 24 miles without pedaling.

I upgraded from my squeaky old bike to full suspension with disc brake front, so no more squeaks...need a new video though, I know.

Happy E-biking!

 

[FMB42]

Welcome aboard caleb.

That's some nice work you've done there.

Your previous electric RC experience seems to have given you an edge when it comes to the patience and electrical/electronic skills needed to achieve your goals.

This, imo, is especially true of those who get past the learning stages of flying and maintaining the larger class electric RC helicopter$...