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Luke 07-27-2011 05:45 PM

Electric trail bike

I'm just getting started, but here's what I have. An electric trail bike based on a '99 YZ125. Everything is assembled, wired, and running. It needs a lot more work to get it into a useful state. I don't have much to show right now, but I'll get some pictures of the components and go into what it took to get to where it is now.

Until I figure out embedding vimeo videos;

alphaBETAdog 07-27-2011 06:22 PM

Excellent Luke! :clap Keep pluggin away (pun intended)!

DaveRMS 07-27-2011 06:37 PM

Awesome Luke!!!

oregoncoast 07-27-2011 06:41 PM

Luke is da man. Where's that link to the video of it running though??? :1drink

Luke 07-27-2011 06:44 PM


Originally Posted by oregoncoast (Post 16495110)
Luke is da man. Where's that link to the video of it running though??? :1drink

Right at the bottom of the post.

It embeds perfectly in the 'test your embed video' thread, but not here. Go figure.

Here, I'll try again:

<iframe src="" frameborder="0" height="300" width="400"></iframe>

Edit again: One message to the mods and it works! Embedding wasn't turned on for this forum yet. Thanks Johnjen!

oregoncoast 07-27-2011 06:47 PM

Yep. I could not get it to work here :lol3

Zachsv 07-27-2011 06:50 PM

I hope you get it worked out right! I would love to have an electric dirtbike capable of a couple hours of medium riding. Would be amazing to tear through some woods w/o bothering the houses that are near.

OaklandStrom 07-27-2011 07:40 PM

Cool project!

Just out of curiosity, exactly which city in Oregon is idiotville? I think there's more than one possibility. My vote is for Springfield.

Luke 07-27-2011 09:10 PM

So I have a few goals for this bike. They may be modest, but they're goals.

1: Built like a real woods bike. I'm basing this on a full sized bike's chassis, and it needs to not weigh much more than the original bike. The YZ has a claimed weight of around 210 pounds, I didn't check the actual weight before stripping it and I'd like it to end up the same after conversion, but I figure if I keep the weight under 250# that'll be good enough. That's the weight of a modern 250 4 stroke. I'd prefer lighter (sub 225#) but we'll see what I get.

2: Good performance. It needs nice smooth power delivery, especially since there is no clutch to mask any thottle issues. It also needs to wheeley. Top speed should be good enough for local trails, which is around 25 mph.

3: 10 miles of range. That's not much, but if it can be recharged quickly and/or have swappable battery packs then that's good enough for around here. My trials bike has about a 20 mile range and that's enough for a good multi-hour trail ride.

Luke 07-27-2011 09:27 PM


Originally Posted by OaklandStrom (Post 16495619)
Cool project!

Just out of curiosity, exactly which city in Oregon is idiotville? I think there's more than one possibility. My vote is for Springfield.


No, it's not Springfield. With all respect due our beloved Springfield ADVer's, that's a pretty good guess though.

I actually live in Beaverton; Idiotville is an old logging camp in the coast range where I usually go trail riding.,_Oregon. Surprise, it's a real place. :lol3

Luke 07-27-2011 10:44 PM

Anyway, since I have some pictures of them, let's start with the batteries.

There are a zillion different kinds available. It turns out, though, that only one type will deliver the sort of power* that I want. They are a lithium cell made by A123. They're the same one used in the electric drag race bikes, and in the lightweight replacement starter batteries. The bad news is that they are only made in a long-C cell size, not a big rectangular pack. So I would have to build a big pack out of a lot of little cells.

*Batteries are usually rated by how much energy they hold, which translates into the range of the bike. Almost as important is the amount of power they can deliver, which translates into the power of the bike.

The cells are expensive, and would be hard to pack into the available space. A little math showed that 100 cells would make a pack that would deliver most of the power that the motor could use. So I paypalled $800 to some guy on ebay and crossed my fingers.

He delivered.

And one pack is filled. It isn't wired yet. The two packs are different sizes due to the way everything mounts on the bike. This one is smaller, a grid of 9 cells in series, 5 parallel. The other is 11 series, 5 parallel.

Lithium cells require management, and I couldn't find anything off-the-shelf that I liked, so I built these:

They limit the voltage to each cell to prevent overcharging, tell the charger when each cell is nearly charged to get the charger to slow down, and tell the bike if the cell voltage gets to low so it doesn't discharge them too much.

earwig 07-28-2011 07:20 AM

Sweeeet!!!! :clap

What an amazing project, and the bike rides really nice already. I can't wait to see how it feels after some of your power delivery tweaks!

Luke, you are an inspiration. Majorly impressive accomplishment!

Grider Pirate 07-28-2011 09:19 AM

What motor are you using? Brushless?
Nice project!

DireWolf 07-28-2011 01:32 PM


a1fa 07-28-2011 02:48 PM


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