Help Narrowing Ebike Kit/Battery Selection

[chardin]

Warning: Long post, I'm trying to get help narrowing the massive amount of information out there. Leave now if you don't like reading.

I live in silicon valley, south of San Francisco and am looking into going a bit more green. I'm looking at selling my car and building an ebike instead. My commute is about 12 miles each way, but fairly flat (413ft up and 240ft down). I'm hoping to cruise at about 30mph on the trip. I have a giant xtc2 mountain bike that has served me well, that I'm thinking about using as the base.

https://www.giant-bicycles.com/en-US/bikes/model/xtc.2/3878/36269/

I did quite a bit of research and I'm hitting the point where I have many options to choose from, but need advice of people with experience on where I might be making foolish mistakes. I hit a point of information overload on all the options I could choose from, so I decided to make 4 different kit/battery options at increasing price points and see where that put me. Here are the results of that:

Option 1: Ebay kit like this one:

http://lunacycle.com/hot-new/golden-motor-v5-magic-pie-complete-kit/

LaEbike 10ah battery:

https://laebike.com/collections/48v-battery-1/products/48v-10ah-lithium-ion-battery-aluminum-case-top-discharge

Total estimated cost: $520

Estimated range at 30mph: 11 miles

Comments: Very low cost. How is the quality on ebay kits? Battery has no rated max amperage on website, likely fine for this kit, but no room to upgrade to a bigger motor later. Will need to rely on pedal assist to hit needed range.

Option 2: Golden Motor V5 kit

http://lunacycle.com/hot-new/golden-motor-v5-magic-pie-complete-kit/

LaEbike 48V, 20AH battery:

https://laebike.com/collections/48v-battery-1/products/battery-48v-20ah

Total estimated cost: $985

Estimated Range at 30mph: 23 miles

Comments: Nicer kit, but with no display. Battery is a great deal, but I can find little on the reputation of LaEbikes batteries.

Option 3: Crystalyte Rear H Kit, Advanced PAS

http://www.ebikes.ca/shop/conversion-kits/direct-drive/crystalyte-rear-hs-kit-advanced-pas.html

Luna 72V, 11.6AH battery:

http://lunacycle.com/72v-panasonic-pf-11-6ah-with-luna-charger/

Total estimated cost: $1365

Estimated Range at 30mph: 20 miles

Comments: I have zero doubt this would meet my needs, nice controller, good battery manufacturer, but it's very expensive considering how it's not much more to move to a 3kW setup.

Option 4: Kinaye 3K-Turbo Power Kit:

https://kinayems.com/Store/KitBuilder Battery:

Ping Battery 60V, 15AH battery:

http://www.pingbattery.com/servlet/the-19/60V-15AH-V2.5-LiFePO4/Detail

Total estimated cost: $1721

Estimated Range at 30mph: 22 miles

Comments: Absolutely awesome, but perhaps a bit of overkill? Might cost additional money in speeding tickets.

I put together a spreadsheet with all of the cost, analysis, links, etc. if anyone wants to look at it:

https://docs.google.com/spreadsheets/d/1_TZGRcSWmYGLsIK8RHNVyBTojv9RpiTDiHzpS-CbeUU/pubhtml?gid=0&single=true

Now comes the real question, what do I really need?

Should I invest more in a battery? or more in a kit?

I've been looking at ~800-900WH of battery capacity, is this overkill for my needs?

Is my bike a good donor or should I buy a Genesis 2100, like many do?

If you've made it this far I'd like to thank for your time. Any advice is appreciated.

 

[wesnewell]

And i don't like typing.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=66302

 

[ScooterMan101]

For 30 mph, you are going to want a motor that will run continuously at 1,200 watts minimum ,
so then you will need a better battery than what you show from that LA Dealer,
the Place to Buy Batteries in the L. A. area is Luna Cycle LLC.
You want a high amp discharge battery, 30 amps minimum for speed.

Good Disc Brakes, like Avid BB7 or Shimano Deore,

There is a place near you, don't know if they sell the e-conversion parts , or just sell complete bikes.
Go in talk with them and take a test ride and get back to us on what you think.


http://vintageelectricbikes.com/

 

[wesnewell]

30 mph only takes 1000W motor power, Nowhere close to 1200W. Check the simulator. The best battery to buy imo is rc lipo. You won't have to worry about power output from it and it will cost about a third or less than a weak ass 18650 pack. My last 888wh 20ah 12s pack of 20C rc lipo cost $180 and is rated for 400A output.

 

[LI-ghtcycle]

Depends on the system,I travel at that speed all the time on closer to 500w. :wink: Usually hauling a heavy trailer (150lbs approx.)

It's going to take A LOT more power for say a DD hub motor in the wheel vs a mid-drive that uses the bicycles' gears.

Sure, getting there generally takes more, and if you must have break-neck acceleration, there go all our calculations, more speed = feed the beast, empty the wallet!

 

[teklektik]

It takes 1000W power to propel a 'typical' MTB at 30mph as shown in the ebikes.ca simulator:



However, that's the power that comes out of the system, not the power that goes in.
Motors are rated by the continuous power out, so you theoretically would need a 1000W motor - if you can believe the manufacturer.

Assuming an 80% efficient system (motor+controller+BMS+drive) this will require that the battery provide

• 1000W/0.80 = 1250W

It is impossible to propel that bike at 30mph with less power.
The figure from the simulator is simple physics - it has nothing to do with the motor, drive, battery, or controller or any motor modeling.

However, if you want to cruise at 30mph then you want to have a higher top end than that - rule of thumb is 25% higher (or cruise speed = 80% top speed) so the motor is not wound out. At 100% speed it has no extra torque for minor inclines, wind, maneuvering, etc. Even shaving that back a bit, the simulator shows 1532W to propel the bike at 35mph. This means you need to be able to push 1915W into the system.

• 1532W/0.80 = 1915W

So - assuming your cruising speed of 30mph, you need to be able to continuously push 1250W with a maximum of 1900W at a design top speed of about 35mph.

Since you have a 12mi run, the motor will need to dissipate the corresponding heat - this isn't a short 3-4mile jaunt where you could rely to some extent on motor mass to soak the heat to stave off eventual overheating. If you are accelerating hard in stop and go traffic, the heat situation gets worse in a hurry. High ambient temperatures also reduce the dissipation so some derating is a good plan.

• Again - this is independent of the motor or drive type - no amount of gearing is going to make power appear from thin air.

From this baseline figure of 1250W at 30mph, we can see that your consumption will be about:

• 1250W/30mph = 41.66Wh/mi

You can diminish this slightly by pedaling, but your contribution at 30mph is essentially inconsequential.

For a 24 mile round trip you will need:

• 41.66Wh/mi * 24mi = 1000Wh

Derating this to 80% (capacity degradation over the life of the battery) gives you a battery size of no less than

• 1000Wh/0.80 = 1250 Wh

Again, repeated hard accelerations will eat into this.

So for a 52V pack (without adjusting for mean discharge voltage and partial charging to extend life), you are looking very roughly at about:

• 1250Wh/52V = 24Ah

The exact nature of your trip and the speeds you attain can change all this, but these are '30,000ft view' figures based on what you provided - you can jiggle them if you have better information or changed design criteria...

Thoughts:

• slow down - aero drag is the major contributor to drag and goes up by the square of the velocity (see Load Line in above plot). Even running part of your trip at lower speed will dramatically improve these steady-state 30mph estimates.
• possibly consider charging at work

 

[Ebike4me]

OP. Thanks for the post.. I just purchased a paratrooper pro and currently in the process of researching hub motors for this bike. I plan to use it mostly for recreational kickback type riding. Your spreadsheet came in pretty handy for me as I have looked at these kits as well. Just to add some information regarding the golden motor magic pie five, The latest version of the five has Bluetooth built into the controller and you can use your smart phone to display various real-time information. I have also read that the 30 mph out of the box experiences seem to be valid. This set up is also one of my choices. The only issue I have with it is weight as it is pretty heavy. I am now considering a geared hub motor but I am concerned about
Reliability of these types of designs. Great thread.. Keep us posted on your progress

 

[dogman dan]

In general, a 2016 geared motor only breaks if you jump it, and land with the motor on, or overload it, ( like you weigh 300 pounds) or you over watt it past 1500w. Rough terrain, little pops, fine as long as you just get off the throttle to land those pops. Harder to control how you land it though, with pas. Throttle only kit for off road, IMO.

A geared rear motor works well for off road riding like you describe. It has great torque, but still a pretty light rear wheel compared to monster 3000w dd motors. Good for riding using the motor to help, vs a dirt ride that is really just a motorcycle type ride.

A stock 48v geared motor kit should do what you want fine. Riding real hard off road, I tend to get one mile from one ah of 48v. You can double that with pedaling though, if you are not a tired old fart like me.