TexasElectric - eBike build

[TexasElectric]

7/5 update

The eBike is basically complete. I need to touch up a few cosmetic things and clean up wiring, but other than that it's done!

I made a short YouTube video of a test ride, thoughts, concerns, etc...

https://www.youtube.com/watch?v=JGDQzF3B3-E

I won't be riding the bike to work today because they are calling for rain this evening, but tomorrow and Friday I'll ride it into work.

[Daox]

Wooohoo, congrats!

[TexasElectric]

Daox

Thanks!



In the video I make a claim that the bike has a "theoretical" range of 192 miles. I know, I know 192 miles... really? After I put the battery through a few charge/discharge cycles from riding around I'll plan to ride the bike for as long/far as I can on one charge to put this claim to the test.

[vskid3]

Congrats on getting it up and running! You're very right about it not being something you can just throw together in an afternoon. Controllers can take a decent amount of heat, but like some airflow, especially with the Texas heat and the power of your bike.

There is an issue with your theoretical 192 mile range (at least at those speeds). The discharge curve for lithium batteries is very flat, so there's not much voltage drop for the first ~80% of discharging. The voltage starts to drop dramatically at that point. The way you're estimating range doesn't take that into account. The best way to estimate the state of charge is using an ah or wh meter and compare that to your battery's total ah or wh.

I never recorded the voltage at the beginning of a ride, so I'll have to go off the voltage after riding to work and then hours later after riding home. There was a voltage decrease of 0.34v and I used 2.252Ah according to my meter over a ~4.6 mile ride with at tailwind. Going off the voltage drop and using the same voltage range as your battery, that gives about 6% usage of the battery, while the Ah shows the ride used 15% of the battery's advertised 15Ah.

[Grant-53]

A good aero package could push that to 250 miles. Everything looks great.

[California98Civic]

That is astonishing speed and range. At 27.5ah you have twice my 14ah. And your 48v system should get more range than my 36v system. Still... amazing. Are there speed restrictions for ebikes in your jurisdiction?

You will want to do something about the heating of the motor controller, though. Get it out of that battery box above the rear tire. Maybe on top of that box is the easiest way to deal with it for now.

[TexasElectric]

California98Civic
In Texas (where I live) the law is 750w motor, 20mph top speed, and weighs less than 100lbs. I meet the weight criteria at least . I passed a few cops on while I was out and nobody seems to care (i'm not acting like a hooligan).

Relocating the motor controller is on my list of things to do.

Grant-53 & vskid3

My initial estimation of 192 miles range is off, but I'll be able to better calculate the estimated range once I get my new watt meter installed.


7/11 Update
I rode the eBike to work on Wednesday last week. I rode it for 14 miles the weekend prior and I did not charge it after riding. I got 35 miles to work (with 2 miles to go) and the bike died on me. More specifically the motor controller decided to turn off because the voltage was low. I pulled over immediately and checked the voltage, my multi-meter read (50.3v). I thought it was kind of weird that the controller would cut me off at 50.3v because 50.3v is above 48v. Maybe there is a setting I can adjust somewhere.

How I have been riding the eBike... Because of the bikes weight (80lbs) (and my desire to remain cool when it's 90+ degrees Fahrenheit outside) when starting from a stop I pedal just enough to get my balance then ease in the motor. I don't do any additional pedaling after that.

I really enjoy cruising at 30mph, that feels very natural. On both my 14 mile weekend ride and my 35 mile work ride I was averaging 25-30mph on the flats. The power usage varied from 450w to 650w when cruising at 25-30mph, there are so many factors (wind, gradient, terrain, etc...)

The biggest problem with my ride to work on Wednesday is the route. There are way too many stops. I reprogrammed my Garmin yesterday to take me on surface streets (less back roads) with a lot less stop signs.

I need to be more mindful of the throttle, because I found myself using 1000w+ during acceleration at times which obviously kills the batteries range.

I will be riding the bike to work today, Wednesday and Thursday. I'll post my experience with the rides later this week. (approx 220 miles of riding)

[vskid3]

So about 50 miles on the charge? That's pretty sweet!

You probably hit the low voltage cutoff of the controller because of the voltage drop when putting a load on the battery. Looking at one of my rides, the battery was at 52.29v at the end, but the voltage had gone down to 49.45v at some point in the ride. You might have been able to continue on at a lower speed/load to keep the voltage from dropping too much.

[California98Civic]

Originally Posted by TexasElectric

California98Civic
In Texas (where I live) the law is 750w motor, 20mph top speed, and weighs less than 100lbs. I meet the weight criteria at least . I passed a few cops on while I was out and nobody seems to care (i'm not acting like a hooligan). ....

... I'm sure you'll still watch that 25-30mph speed preference a little as you pass officers... one day, one of 'em might get curious and look closely at you, wondering... then come investigate. There's a chance of it anyway.

Thanks for the updates. Is it possible your controller is misreading voltage? I'm still dumbstruck by the range you are estimating. 192 miles seems really long for the setup you describe. (I guess I might just be envious!)

[samwichse]

Originally Posted by TexasElectric

California98Civic
7/11 Update
I rode the eBike to work on Wednesday last week. I rode it for 14 miles the weekend prior and I did not charge it after riding. I got 35 miles to work (with 2 miles to go) and the bike died on me. More specifically the motor controller decided to turn off because the voltage was low. I pulled over immediately and checked the voltage, my multi-meter read (50.3v). I thought it was kind of weird that the controller would cut me off at 50.3v because 50.3v is above 48v. Maybe there is a setting I can adjust somewhere.

That's the resting voltage, but under load that's going to sag.

My 36v LiFePO4 system is 12s, with a nominal 38.4 volts (full charge voltage 43.8). That gives it space to voltage sag under load and stay over 36v. Yours is 15s, which is exactly 48v, so at nominal you're going to sag below that. I'm not sure about your controller/computer, but there should be a cutoff voltage setting (there was on my BBS02). You may need to drop this a bit since you're running so close to the metal if you want your full range.

EDIT: NM, looks like you switched to 16s partway through the build?