TexasElectric - eBike build

[Shortie771]

Originally Posted by vskid3

Some kits/controllers support regen that's enabled through either the brake switch or another switch. They're good for recovering some power when braking, but you're better off to power the wheel directly with the pedals than trying to charge the battery. It's more efficient to power a bike with electricity than a human/food, so trying to use a human to charge the battery will just make the human power that much worse (PDF of a paper comparing ebike to human powered bike). You can pedal in addition to the motor for increased range or acceleration, but it doesn't actually charge the battery.

Just the kind of of info I was looking for... And more. Thanks.
I wasn't aware that you could pedal along with the motor to increase range by taking some of the load. That does seem much more efficient. I just never thought of that I tend to over complicate things in my head.

[Grant-53]

Shortie771: First check all state and local ordinances on bikes and e-bikes. Interstate highways are usually off limits to limited use vehicles, e-bikes, horses, and pedestrians. A reverse trike or tadpole design with a body shell is also known as a velomobile. There is an enormous amount of information at recumbents.com on building trikes. The least expensive way to go is to build a trike from square tubing and get the body from Blue Sky Designs. The only drawback is the low seat heights may make it difficult to see and be seen in traffic. I suggest having your eye level at 36+ inches when your seat back angle is 45 degrees. A good aero package with a ventilation system copied from sailplane designs helps too.

[Shortie771]

Yeah I don't think I would ever take a bike (of any sort) on that interstate. The speed limit there is 75mph and most people go 80mph, not me ofc. I used Google maps to see if there is another way without highways and there is. It's about the same distance on county roads. Didn't mean to sidetrack the thread...

How is the project going? Any updates?

[Grant-53]

Balky shifters and too much run out on new chain rings. I need to double check the frame alignment too. Still fine tuning the rear tailbox design as it is critical to low drag.

[TexasElectric]

Here's where I stand on this project...

The items highlighted in red are on order (should arrive in the next week).

eBay
$289.99 - 1x, 48V 1500W Direct Drive REAR 700C eBike Kit Electric Bicycle Ebikeling
$119.99 - 1x, NEW Box of 80 Tenergy LiFePO4 32650 3.2V 5500mAh Rechargeable Batteries 5.5Ah
$48.49 - 1x, 48V 60A LiFePo4 Battery BMS LFP PCM SMT System 16S 16x 3.2V eBike Battery 16x 3V
$42.90 - 1x, Topeak TT9646B MTX EX Rigid Trunk Rack Bike Bag QuickTrack System 480ci
$39.84 - 1x, Topeak Bike Rack Rr Explorer Mtx 29, Black
$24.04 - 1x, 8 Gauge Silicone Wire 20 feet 8 AWG Silicone Wire Flexible Silicone Wire
$22.49 - 1x, Joe Rocket Velocity 2.0 Street Motorcycle Gloves
$20.99 - 1x, 20 feet of Pure Nickel Battery tabs for spot welding 0.2mm Heavy Duty DIY Pack
$15.88 - 2x, 6 Modes COB 1 LED Bicycle Bike Cycling Front Rear Light USB Rechargeable Battery
$8.30 - 1x, 25 mm x 33 m Gold Kapton Tape Polyimide High Temp 1" x 36yds 25mm; US stock

Amazon
$78.66 - 1x, HJC FG-X Legendary Lucha Off-Road Motocross Helmet (MC-3H, Medium)
$43.23 - 1x, Cygolite Metro 700 USB Rechargeable Bike Light, Black
$19.90 - 1x, SCOTT Recoil XI Adult Motocross MX UTV ATV Goggle Black Anti-Fog Clear Lens

Richardson Bike Mart - Frisco (Local Bike Shop)
$676.56 - 1x, 2017 Specialized RockHopper Sport 29r (XL Frame)

Home Depot
$21.42 - 2x, (4'x0.5"x3.5") Oak wood
$3.00 - 8x, Washers
$1.35 - 4x Screws

Still needed:
- battery charger
- Matte black spray paint
- EVA foam
- wire connectors
- 1/4 inch wood paneling (for the sides of battery box)

Total up to this point:
$1477.03

This past weekend I purchased the bike from a local bike shop. I decided to buy the Specialized RockHopper Sport 29er (one model up from the base RockHopper) because this bike has hydraulic brakes. I figure hydraulic brakes should preform better over mechanical brakes when braking from high speeds.

I estimate that I should have the bike completely built and functional in about 2 weeks. Once complete I'll be riding it 70 miles a day (35 miles each way to work). I plan to use a combination of pedal assist and motor only. I would like to be able to maintain an average speed of 25-30mph on the flats. I will do some testing on watt usage as soon as I finish building the bike.

[samwichse]

So you're going to do 16S5P?

Where did you find the cells so cheap? That's a heck of a price.

EDIT: NM, it's DougDeals on Amazon. ~$30 shipping, still a good deal. If only they were easier to connect.

[TexasElectric]

samwichse
Yes, I will be doing 16s,5p for a total of 27.5 amp hours.

I bought the cells on eBay (brand new):
NEW Box of 80 Tenergy LiFePO4 32650 3.2V 5500mAh Rechargeable Batteries 5.5Ah | eBay

Picture of the bike:


Picture of the wooden frame for holding (most, but not all of the cells). The remaining cells will be stored in the rear mounted bike rack.


I also decided to buy a motocross helmet and goggles. I figure if i'm going to be traveling at speeds of 25-30mph, should I have a crash I want my head/face to be well protected. I regularly hit speeds of 30-40+mph on my cyclocross bike, but only for a few seconds (5-15 seconds at a time) and I feel comfortable wearing a regular bicycle helmet.

My thinking is that since this eBike will weigh around 75lbs (compared to my cyclocross bike at 13lbs), if I had an accident I'd have more mass accelerating me toward the ground or a tree. Think of two vehicles traveling down the road at 30mph, one is a semi truck with a full load, the other is a 4 door sedan. Both slam into a wall and come to a full stop. The likelihood of the semi truck driver walking away is slim because of the large mass, vs the driver of the sedan. (I don't know... that's just my 2 cents. Maybe i've watched too many YouTube videos of car crashes, lol.)

[TexasElectric]

Some other things i'm thinking about...

After reading a lot of different articles online about eBike speeds and watts, and watching a bunch of YouTube videos of people scientifically testing their eBikes I've decided I want to do the same. For example...

1. I've seen similar build eBikes use 400-450w to maintain 20mph. This would mean I could hypothetically get 61-68 miles on a full charge at an average speed of 20mph (assuming minimal wind and relatively flat roads). I am curious to know how many watts will be used at 25mph and 30mph (or even 35mph)? Plus I need to test watts used for pure electric vs pedal assist.

2. I plan to use the tires that came on the bike (29x2.1) knobby tires until they are bald. Once they are ready to be replaced, I am looking to replace them with a 700x35, 700x40, or 29x1.5 non-knobby tire. The idea being that I'd have less rotational mass and rolling resistance but still have good contact with the ground. Plus (in theory) a smaller/smoother tire should use less watts to maintain speed.

3. Lastly, I'm giving consideration to buying a few more LiFePo4 cells for 16s,7p for a total of 38.5 amp hours. The total weight of the battery with the addition of 2 additional cells in parallel would be 36lbs (compared to my current setup at 27lbs). If the addition of 2 more cells in parallel would allow me to ride at an average speed of 30mph (for my ride of 35 miles, one way), i'd consider it. But, i'll make this decision after doing a bunch of testing.

[samwichse]

My bike has a 500w motor. All out on level ground is about 27-28mph without pedaling (I run out of pedals around 24-25mph with my gearing).

Actual battery watts drawn is more like 700-750 at that speed, if that helps your calculations any. Let's say you need ~800w for 30mph cruise with pedaling and slight elevation changes. Your upgraded battery would be 1.85 kwh. That means you'd go 69 mi at 30mph. Your current setup is good for 50 mi at that speed.

The upgrade doesn't sound worth it unless you can't charge at that 35 mile destination.

[vskid3]

Originally Posted by TexasElectric

Some other things i'm thinking about...

After reading a lot of different articles online about eBike speeds and watts, and watching a bunch of YouTube videos of people scientifically testing their eBikes I've decided I want to do the same. For example...

1. I've seen similar build eBikes use 400-450w to maintain 20mph. This would mean I could hypothetically get 61-68 miles on a full charge at an average speed of 20mph (assuming minimal wind and relatively flat roads). I am curious to know how many watts will be used at 25mph and 30mph (or even 35mph)? Plus I need to test watts used for pure electric vs pedal assist.

My ebike used 25-34 wh/mile over a trip with me doing 25-28MPH and mainly only pedal assisting when accelerating (you'll likely have to change the gearing to be able to pedal at top speed). Your battery is about 1400-1500wh, 35wh/mi would give you a range of about 40 miles.

Originally Posted by TexasElectric

2. I plan to use the tires that came on the bike (29x2.1) knobby tires until they are bald. Once they are ready to be replaced, I am looking to replace them with a 700x35, 700x40, or 29x1.5 non-knobby tire. The idea being that I'd have less rotational mass and rolling resistance but still have good contact with the ground. Plus (in theory) a smaller/smoother tire should use less watts to maintain speed.

How smooth are the roads you'll be riding? 30MPH on a hardtail can be hard on the backside. Do some research about the skinny tires, I believe I've read that the "logically" best route of skinny and high pressure isn't necessarily the lowest rolling resistance.

Originally Posted by TexasElectric

3. Lastly, I'm giving consideration to buying a few more LiFePo4 cells for 16s,7p for a total of 38.5 amp hours. The total weight of the battery with the addition of 2 additional cells in parallel would be 36lbs (compared to my current setup at 27lbs). If the addition of 2 more cells in parallel would allow me to ride at an average speed of 30mph (for my ride of 35 miles, one way), i'd consider it. But, i'll make this decision after doing a bunch of testing.

Going to 6p or even sticking with 5p might be good enough, as I figured above. It comes down to just how much power your setup actually ends up using, how much you're willing to push the batteries, and how much cushion you want to have to account for headwinds or days that you don't pedal much.

For a charger, check out the Cycle Satiator. It's expensive, but you're certainly getting what you pay for. You could take it with you to charge at work and not have to worry about it falling apart like most chargers.