Build Help - Commuter (10Mi RT) For GF. (Update: Now for me)

[nlhaines]

Well if I screw up the BMS I'll just get myself a good 2 or 4 channel RC Charger. What do you do for LVC? Does the yescom kit handle that or do you have to add something?

If you do end up running without a BMS, get some Lipo alarms to handle the cell level LV warning. They are cheap and loud so you know when there is a problem. Lipo is most dangerous when its over charged or over discharged. The manufacturing tolerances are pretty bad on these packs so having bad cells in the bunch is common. Controllers do LVC for the whole pack total but they are blind to the individual cell voltages. If one cell fails and is about to explode but the rest are fine you can still be above the LVC at the controller. Cell level monitoring through BMS or at least warning alarms is an absolute necessity with LiPo in my opinion.

I learned more about batteries in just a few hours watching my RC balance charger than I learned from all of my reading online. A balance charger is a good thing to have around anyway. You can cycle your packs and make sure they all behave the same way before you hook them up to the BMS.

As far as paralleling the balance leads without checking them, that is a bad idea! There are varying opinions about how much difference you can have between cells when you parallel but I wont do it if they are off by more than .05v. High output batteries like these will try to balance instantaneously through those small gauge wires. I'm probably more careful/paranoid than most but its just not worth risking burnt fingers or the entire house. You can form your own opinion about how much imbalance you are comfortable paralleling but at least measure so you can base that opinion on something!

I'm not trying to talk you out of what you have already bought but keep in mind that these packs are dangerous and make sure the girlfriend understands that before you let her out of your sight with the bike. Might be easier said than done but maybe she should help you hook up the pack and the BMS so she has an understanding of how it works. You could always pick up a turn-key pack from ping or em3 that is as easy to charge as a cell phone. Then keep the Lipos for your own personal hotrod bike.

I should update the thread title, because my girlfriend is no longer convinced she needs an e-bike commuter. I'm doing a personal build now, and I'm sure she will eventually want one (if I can make it look pretty).

When I do get to building hers I'm just going to get her a safe, easy lifepo4 pack.

 

[anon0973923]

I just wanted to say that I've been following your progress because I was in a similar situation in regards to building my ebike (same budget, needs, experience, etc). I'll share with you the direction I went, hopefully it's of some use to you.

If you want a cheap, sturdy, reliable bike there are two options IMO.

1. Scour craigslist for 80's and 90's steel rigid MTBs like a Trek Antelope or something similar. These mountain bikes have what is considered by modern standards a hybrid geometry, which is perfect for commuting. You are high enough up to see over cars and the frames are strong.

2. Purchase a bike off of bikesdirect.com (you should go 700C since you're in NO) and put it together yourself. Make sure you are comfortable with basic bike maintenance and wheel truing. The Sheldon Brown and Park Tool websites are invaluable for this kind of stuff.

I've built two ebikes, one for my girlfriend with a budget (I went option 1 and bought a '95 Marin) and one for myself (I'm 225lbs and very tall so I went the bikesdirect route and got myself a huge 700C hybrid).

As far as kits, I weighed all of my options and the best route was buying the 48V Aotema 850-1100W (23A) kit off of eBay (http://www.ebay.com/itm/301009247892?_trksid=p2059210.m2749.l2649&var=600165093404&ssPageName=STRK%3AMEBIDX%3AIT). The Aotema is a front hub, which means I didn't have to sacrifice my freehub or anything else on the bike to retrofit it. I also found that when I'm commuting and carrying a load in the back my front wheel was normally too feathery so having the hub motor upfront has improved the feel of the bike. The Aotema is sensorless, which is more reliable, but it's a good idea to get the bike up to 2-3mph before you kick it on for the smoothest experience. You can google around about the aotema kit, but it's highly regarded for its weight to power ratio among other things.

For batteries, I broke middle ground between what you are trying to do and a LifePO4. I bought 4 6s 5000mAh HobbyKing lipos and run them in 2s2p for 10Ah at 48V. It's slightly more expensive than the 4s solution you've chose but it's so much easier to deal with and a lot less soldering. I bought a cheap 10A 6S balancing charger off of eBay and repurposed an old computer PSU to drive it. Each pair of lipo is permanently paralleled using bullet to t-plug (deans) adapters (you can buy the parallel adapters for $3 on hobbyking) at the mains and also the JST plugs (balancing wires) and then I have a series plug on the bike leading to the controller. All I have to do is plug the two t-plug leads coming from my battery bag to the balancing charger using the parallel adapter and the two jst plugs to another parallel jst on the charger. I plug those same deans leads into the serial t-plug adapter on the bike.

It's nearly foolproof and I didn't have to solder a thing. Plus I get the advanced readouts on the balancing charger about the individual cells instead of having to trust that the BMS is doing its job properly. I use the charger for both battery packs.

Estimated costs, shared:
Charger: $35
PSU: $30 (free to me)
Adapter plugs: $15

Estimated cost, bike one (hers):
Bike: $100
Kit: $250
Batteries: $200
Adapter plugs: $15
Torque arm: $20

Estimated cost, bike two (mine):
Bike: $400
Kit: $250
Batteries: $200
Adapter plugs: $15
Torque arm: $20

So if I average the shared costs, her bike (for a 48V, 850W nominal motor and 10Ah battery) is ~$620 and mine is ~$920.

I think the best choice I made was the kit, followed by going with 6s batteries, which meant I had to do zero soldering. If I didn't already have a PSU I may have gone your route with an on-board BMS and a bulk charger but since the PSU was free to me, buying a balancing charger was the smartest way to go.

 

[nlhaines]

Thanks anon!

I like your battery solution a lot. I think making a few cables to parallel the batteries or adapt the balance leads from 3x4s to 12s or 2x6s won't be too difficult, but we shall see. I knew there would be easier more expensive solutions, but I enjoy going through the process of building and learning. I'll look into those adapters you mentioned though.

Connecting the BMS may be difficult, and I may fry it, but then I'll just start working towards a balance charger setup. I think it's definitely a good idea to have a balance charger around anyway.

I'll keep an eye out for the bikes you mentioned. I snagged a recumbent tadpole for $300 because I thought it would be fun to motorize, but I'm thinking I'll do a mountain bike as well. With one battery between the two of them it should be pretty cheap to have a second build.

 

[wesnewell]

I know what Kv is, I just don't see 731 RPMs, or 50V anywhere in the info for the leafbike motor. Did you calculate the 731 or is that provided somewhere?

All data used, including the the rpm and voltage is provided if you click on the "Performance Data:" link at the bottom of the page. And you get this for that motor.
http://www.leafbike.com/u_file/images/13_06_18/f415a5c455.jpg

 

[nlhaines]

1. Scour craigslist for 80's and 90's steel rigid MTBs like a Trek Antelope or something similar. These mountain bikes have what is considered by modern standards a hybrid geometry, which is perfect for commuting. You are high enough up to see over cars and the frames are strong.

2. Purchase a bike off of bikesdirect.com (you should go 700C since you're in NO) and put it together yourself. Make sure you are comfortable with basic bike maintenance and wheel truing. The Sheldon Brown and Park Tool websites are invaluable for this kind of stuff

Why do you like this particular frame geometry more than a standard mountain bike? I feel like mountain bikes generally ride pretty high, and are strong. The one advantage I see is that those old bikes might be steel.

I found a 2011 or 2012 Trek Marlin 29er on CL for ~$250 or so, which I was considering, but I want to get one done before I start amassing pieces for a second build.

 

[Chalo]

1. Scour craigslist for 80's and 90's steel rigid MTBs like a Trek Antelope or something similar. These mountain bikes have what is considered by modern standards a hybrid geometry, which is perfect for commuting. You are high enough up to see over cars and the frames are strong.

Why do you like this particular frame geometry more than a standard mountain bike? I feel like mountain bikes generally ride pretty high, and are strong. The one advantage I see is that those old bikes might be steel.

Pre-suspension MTBs have shorter forks, and are stronger and stiffer as a result. They are generally much better rigid bikes than modern suspension-ready bikes fitted with suspension-corrected forks.

That said, it would not be a bad idea to have a decent quality suspension fork to ride on the streets of Orleans Parish. Suspension for the street is something I usually recommend strongly against, for several reasons. In your case, I think it could open up more route options for you.

 

[nlhaines]

1. Scour craigslist for 80's and 90's steel rigid MTBs like a Trek Antelope or something similar. These mountain bikes have what is considered by modern standards a hybrid geometry, which is perfect for commuting. You are high enough up to see over cars and the frames are strong.

Why do you like this particular frame geometry more than a standard mountain bike? I feel like mountain bikes generally ride pretty high, and are strong. The one advantage I see is that those old bikes might be steel.

Pre-suspension MTBs have shorter forks, and are stronger and stiffer as a result. They are generally much better rigid bikes than modern suspension-ready bikes fitted with suspension-corrected forks.

That said, it would not be a bad idea to have a decent quality suspension fork to ride on the streets of Orleans Parish. Suspension for the street is something I usually recommend strongly against, for several reasons. In your case, I think it could open up more route options for you.

Would you recommend sticking to hardtail or would full suspension work better? I'm sure it depends on which bike, but any guidance would help.

 

[Chalo]

Full suspension would yield a better ride, but with the obvious drawbacks of higher cost, more weight, more maintenance, less room for electrical components, fewer mounting options, and more ways to break and fail.

It's a matter of personal judgment, but for my own bike, I'd keep it simple and use a rigid frame.

 

[nlhaines]

Thanks Chalo....I think a hardtail would work fine, but if I see a great deal on a FS bike I might jump on it.

To get the speed I'd like I either need to go to a 20s setup (and stick with the yescom kit) or go to a faster wind motor. Is the LVC typically something that can be adjusted? If so I'd be more inclined to ditch the BMS and beef up the pack a bit.

 

[nlhaines]

Still trying to decide between the fast wind leafbike and the yescom kit.

I'm thinking the fast wind leaf motor might be okay in a 20" wheel, plus I'll mostly be using it on flat ground (I think New Orleans has one (artificial) hill). On the other hand its about $175 more for the leaf kit. I could probably just use that money to upgrade the battery/controller and get just as much speed out of the yescom kit, plus I'd have something with significantly better torque. This all has me leaning towards the Yescom kit, but the problem is I'd have to build the motor into a 20" wheel, which is the only thing holding me back at this point.

How difficult is it to build a wheel? It looks simple enough, but it seems like one of those things that's easy to do poorly and hard to do well. Could I just slap it together and have a local bike shop true it?

 

[docnjoj]

Could I just slap it together and have a local bike shop true it?

Yep that is what I do. With a smaller motor you can lace it on your lap during TV time. Just make sure you get the spokes the right length so the bike shop has some room to adjust them and tension them.
otherDoc

 

[nlhaines]

Could I just slap it together and have a local bike shop true it?

Yep that is what I do. With a smaller motor you can lace it on your lap during TV time. Just make sure you get the spokes the right length so the bike shop has some room to adjust them and tension them.
otherDoc

Thanks! I guess I'll try it. What rims should I get? Does it matter much? I think the trike comes with 20x2.0 tires. I wouldn't mind going up to 20x2.25 if I can.

How do I configure the spoke calculator for the yescom kit?

 

[Chalo]

Just make sure you get the spokes the right length so the bike shop has some room to adjust them and tension them.

Thanks! I guess I'll try it. What rims should I get? Does it matter much?

First, use 14ga spokes (or 14-15ga, or 13-14ga, or 13-15-14ga) rather than the silly thick spokes that many around here seem to think are appropriate. The bike shop will do a better job with your wheelbuild if they can use their normal spoke wrenches, tensiometer, and techniques-- including acquired feel. Normal gauge spokes are much more likely to remain tight in use, but thick ones tend to loosen.

The strength of the wheel is in the rim, so use a sturdy double-walled rim. You'll be asking a lot of your rims not only because you'll side load them in a way a two-wheeler can't, but because you won't be able to stand up on the pedals and use your legs as suspension.

Wider rims are better, up to a point, for a trike that side loads its wheels and tires. Ideally, use a rim with an inside width not less than about half the nominal width of the tire you want to use. But don't use a rim that's as wide on the outside than the nominal width of your tires. So for example, if you want to use 2.25" wide tires, use rims that are at least about 1.125" wide on the inside, between the sidewalls. But don't use rims wider than about 2" outside. Narrower rims will make your tires slew from side to side more; wider rims will make your tires ride more harshly, and will be easier to damage because they get less protection from the tires.

The Alex DM24 is a great economical rim that would be ideal for a trike with tires between 1.75" and 2" wide. The Alex DX32 would be a good choice for fatter tires.

 

[nlhaines]

Thanks Chalo. Those DX32 rims look great. I'll try to get a nice 2.5" tire for those.

Would it be crazy to buy the yescom kit and use it with the motor from leafbike? Would save me the hassle of having to build the wheel, and would only cost slightly more than the leaf kit by itself. I could use the Yescom Motor on my next build, or sell it and recoup maybe $100. Also it looks like a more complete kit (two brakes, freewheel, bag)...

What I don't see is any information on the controller with the yescom, but they all look pretty generic....

 

[wesnewell]

Info on yescomusa kits.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=49638&p=733752#p733752

 

[nlhaines]

Info on yescomusa kits.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=49638&p=733752#p733752

Thanks for that. The spreading of the dropouts worries me, because I've never done anything like that, and I don't want to screw up the frame. Because of that I'm very close to going with the leaf motor, though I wish it wasn't wound quite so fast.

One other thing I'm weighing is getting a moped tire if it will fit. I figure a huge tire will act almost like a suspension, but I'm not finding a ton of options.

 

[wesnewell]

I don't think you need to spread the dropouts on the newer kits, at most you only need a few mm. And although I don't, and will never own a bike with aluminum dropouts for conversion, I think even they will spread up to 5mm without damage. And that's more than enough to mount even the older model kit. And if you want to take the time to shorten the spacer that goes on the left side, you can get it to mount in 135mm or less dropouts. There are a lot of happy people on the forum with yescomusa kits.

 

[nlhaines]

I don't think you need to spread the dropouts on the newer kits, at most you only need a few mm. And although I don't, and will never own a bike with aluminum dropouts for conversion, I think even they will spread up to 5mm without damage. And that's more than enough to mount even the older model kit. And if you want to take the time to shorten the spacer that goes on the left side, you can get it to mount in 135mm or less dropouts. There are a lot of happy people on the forum with yescomusa kits.

Oh, so you just force it in there, and when you pull the wheel out the frame goes back to normal? Sounds doable.

I think with a KV of ~9.7, and 44V, in a 20" wheel I'll have a top speed of around 20 MPH, which means I'll probably want to up the voltage. Can I setup some kind of LVC appropriate for 20S?

 

[wesnewell]

I've spread them like that, butthen it's a pita, because you have to do it every time you pull the wheel. I just take a board and place between the dropouts and pound it in until I get the static width I want when I remove it. This is not a problem with steel. Not sure with aluminum, because I've never bought a bike with aluminum dropouts and never will. At least not to put a motor on. i've also never used a torque arm/plate on steel dropouts, in over 10K miles of riding with regen. I would not do that with aluminum dropouts. They'd be toast in a short time.
In a 20" wheel top speed will be ~23.5 mph under normal level load.

 

[wesnewell]

You can set LVC to whatever you want if you know how to do it on the controller you have. I've set mine to 88V on the 72V controller I have. Default was 62V. I used a VAR so I could change it from 62V up to whatever I wanted.

 

[nlhaines]

I've spread them like that, butthen it's a pita, because you have to do it every time you pull the wheel. I just take a board and place between the dropouts and pound it in until I get the static width I want when I remove it. This is not a problem with steel. Not sure with aluminum, because I've never bought a bike with aluminum dropouts and never will. At least not to put a motor on. i've also never used a torque arm/plate on steel dropouts, in over 10K miles of riding with regen. I would not do that with aluminum dropouts. They'd be toast in a short time.
In a 20" wheel top speed will be ~23.5 mph under normal level load.

Dropouts are steel. That was a top priority for me. Steel is cheaper and seems better for an e-bike. Of course there is a weight/speed penalty, but I'd rather have the savings/strength/safety of steel dropouts. If I end up doing a traditional bicycle next, then maybe I'll end up with aluminum, just because nice steel bikes are pretty rare.

I ordered the Yescomusa kit from their ebay seller xxceries. $244 shipped. Eyeing some Alex DX32 rims, but I can only find lots of 2 or more ($40). Having a spare wouldn't be so bad.

I calculated 20 using 44.4V, 80% of unloaded speed, but I guess voltage could get at high as 50.4V (12*4.2). 23 MPH will be fine to start with while I get used to driving the thing. Once I'm accustomed to that speed I can bump up to 16S or 20S and have some real fun.

Anybody know the relevant measurements for the newer YescomUSA kit and the Grin spoke calculator?

 

[wesnewell]

You got the 1000W kit for $244? Or did you get the 500W kit? You won't get the speed or power from the 500W kit. In fact you won't even get 20mph from it in a 20" wheel.

 

[nlhaines]

You got the 1000W kit for $244? Or did you get the 500W kit? You won't get the speed or power from the 500W kit. In fact you won't even get 20mph from it in a 20" wheel.

You scared me there for a second, but yeah it's the 48V 1000w kit.
http://www.ebay.com/itm/291107275178

I guess its on sale at $255, and there's a promotion for $10 off every $150 spent with Yescom or something.

 

[wesnewell]

Wow, that's a heck of a deal. It was $309 for the new model not long ago.

 

[nlhaines]

Wow, that's a heck of a deal. It was $309 for the new model not long ago.

It almost seems to good to be true, but a lot of people on here seem happy with it so I'm willing to bet it's a great value. Do you know how I set up the spoke calculator for this motor?