New commuter build

[KipMcSkipster]

Hello,
New to ebikes here, planning my first build. I've been doing a lot of reading on here (fantastic resource), and was wondering if I could get some recommendations, and maybe have a few questions answered.

First, my commute: Boston area, about 7 miles each way, all pavement, hilly but nothing really steep, roads in okay condition. I'm not looking for any crazy speed, certainly don't need any trouble with the law! I mostly want to keep my commute time fairly short and not break out in a sweat. How this translates into maximum speed I don't know, but I'm guessing in the 25mph range?

I'm looking to add a kit and lifepo4 battery to a mountain bike, none of which I've purchased yet. I'm no engineer or metalworker, but am reasonably handy. I could certainly just buy everything from ebike.ca or ampedbikes, but honestly I'm a bargain hunter and would love to save some money a) without compromising safety or reliability and b) without having to delve into a project involving skills and equipment which I don't possess (although I hope to learn a thing or two). If I can keep the whole project under a grand, that would be great.

First the bike. I'm planning on a hardtail, still not clear on whether a steel frame is crucial, whether the fork should be steel, in what circumstances I need a torque arm (always? both front and back?), and whether I should have disc brakes both front and rear? On a side note, I'm planning to mount the battery within the triangle. One possibility is a Walmart cheapie such as the Mongoose Snarl (http://www.walmart.com/ip/Mongoose-Snarl-26-Men-s-All-Terrain-Bike/15711161), or Mongoose Deception (http://www.walmart.com/ip/Mongoose-Deception-29-Men-s-All-Terrain-Bike/14956326) , both with aluminum frames and front/rear discs. I could also do some hunting on craigslist or elsewhere if someone has a better suggestion.

Next the kit. I'm pretty sure I want a DD, rear mount. I inquired to cell_man about his 36V 500W Direct Drive Ebike Kit, although I'm a little concerned that it won't be fast enough? He indicated the possibility of upgrading to an Infineon controller (IRFB4100) suggesting that then it would be safer if I decided to use a 48V battery. I might have misread what he said, if I'm wrong, please let me know!

Finally, the battery. Leaning towards 48V as I said, probably 10AH. Could be a ping, something from ebay (e.g. daoji666), or one of cell_man's. As I said I would love to mount it inside the frame triangle, not sure whether this would mean buying a FalconEV bag, although I like the look and potential ease of ampedbikes' battery tubes.

Any thoughts? Am I on the right track? Anything I've missed? As I said, I'd welcome any suggestions from this knowledgeable group!

Ezra

 

[wesnewell]

10AH would be enough for a 14 mile round trip, but a ping is only rated for 2C max. Either consider 15ah or more or go with a better C rated pack like A123 or lipo. I went through 4 Walmart bikes (love their 30 day return) before settling on the NEXT Avalon FS comfort bike. $108 with tax. Got over 2K miles on it now, and about 1K miles with the motor kit.
http://www.walmart.com/ip/NEXT-Avalon-26-Men-s-Cruiser-Bike/14272884. I got a rear 48V 500W kit from yescomusa.com (off ebay because it was cheaper @ $227.90 shipped) and it was in the US. Using 5AH 15C Zippy Flightmax lipo ($114) I get about 10 miles without pedaling. There's some pictures in this thread, http://endless-sphere.com/forums/viewtopic.php?f=2&t=28043&start=45#p409153. The motor kits, http://www.yescomusa.com/home.php?cat=48.

 

[jonathanm]

Wes, which walmart bikes did you reject before settling on the Next, and what were the reasons?

 

[wesnewell]

Wes, which walmart bikes did you reject before settling on the Next, and what were the reasons?

Roadmaster. It just wasn't comfortable for a short person and quality sucked too.
Schwin Meridian trike. Solid bike. Would have loved to convert to front hub but I bought it mostly for my wife to ride and she couldn't even ride it straight so I retruned it and she now rides a stationary bike.
Huffy single speed. Solid, but slow and rough riding. No suspension.
NEXT Avalon ladies bike. Only got rid of this to get the mens model.

I also bought a Kent Sierra Madra from Amazon. It's pretty much just like the NEXT Avalon just with 21 spd and better components at twice the price. Still have it but don't ride it much since going electric. I put the motor on the Walmart Avalon because I didn't know how much I'd like it or if it would tear up the bike.

If I weren't so short I'd probably electrify a Genises 29er.

 

[dogman dan]

One thing worth considering for a mid battery carry, is a ladies bike. Wineboyrider did that for the death race, and it was just amazing to me how good it worked. He bolted a rear rack onto the steel frame's top bar, and strapped the toolbox with a 48v 15 ah ping on there easy as pie. Handled great, with his cellman mac motor in the rear.

I'm refering to one like this. http://www.walmart.com/ip/26-Ladies-Schwinn-Sidewinder-Bicycle/11089190 With the low top bar, you simply mount the battery on top. Can still straddle it nicely, since the battery is only about 5 inches tall when laying on it's side.

Ping battery needs to be at least 15 ah, to adequately power a 48v 20 amp controller.

For your ride length, a cellman 10 ah battery is also a good choice.

The Cellman DD kit on 48v will run fast enough to exceed comfortable pedaling cadence. You should have 20-23 mph on a 36v battery. With no hills, I'd actually recomend the 36v if you want to pedal along for the fitness benefits of spinning to work. Even faux pedaling is good for the heart. At 48v, you'll end up needing a huge front gear, not pedaling, or riding slower anyway. Easier to ride max throttle on 36v, than to ride part throttle on 48.

 

[wineboyrider]

One thing worth considering for a mid battery carry, is a ladies bike. Wineboyrider did that for the death race, and it was just amazing to me how good it worked. He bolted a rear rack onto the steel frame's top bar, and strapped the toolbox with a 48v 15 ah ping on there easy as pie. Handled great, with his cellman mac motor in the rear.

I'm refering to one like this. http://www.walmart.com/ip/26-Ladies-Schwinn-Sidewinder-Bicycle/11089190 With the low top bar, you simply mount the battery on top. Can still straddle it nicely, since the battery is only about 5 inches tall when laying on it's side.

Ping battery needs to be at least 15 ah, to adequately power a 48v 20 amp controller.

For your ride length, a cellman 10 ah battery is also a good choice.

The Cellman DD kit on 48v will run fast enough to exceed comfortable pedaling cadence. You should have 20-23 mph on a 36v battery. With no hills, I'd actually recomend the 36v if you want to pedal along for the fitness benefits of spinning to work. Even faux pedaling is good for the heart. At 48v, you'll end up needing a huge front gear, not pedaling, or riding slower anyway. Easier to ride max throttle on 36v, than to ride part throttle on 48.

Yes, it worked well Dogman and I was getting 27mph plus on 36vlifepo4.
Edit : (saved for picture of ladies bike when I find it...)

 

[jonathanm]

I was in Walmart today and saw that Mongoose Deception 29er, quite a nice looking bike actually....for the price, obviously...What did you get Ezra?

 

[BikeFanatic]

Do you live in Boston Ezra? I have a few electrics you could try.

 

[oatnet]

I think you are heading in the right direction with LiFePO4 and a rear motor. The DD is pretty solid and I would recommend it if you want to hod-rod the bike, but geared motors are light, stealthy, and effective on a commuter, either will work great. Torque arm with the motor in the rear, don't need it in the front. Steel forks are required for front motors, but since you are looking at a rear motor...

I still have a few of the factory-sealed TidalForce purpose-built-electric-bike frames available in silver:
http://www.endless-sphere.com/forums/viewtopic.php?f=31&t=18112

-JD

 

[KipMcSkipster]

Just a little update to this build.

I've ordered almost all I will need:

Motobecane 400HT from bikesdirect (I first bought a dirt cheap Giant MTB on craigslist, needless to say, you sometimes get what you pay for)
cell_man kit rear DD 36v 500W with an upgrade to a 12 fet Infineon controller
36V 15ah lifepo4 from daoji666 on ebay
FalconEV triangle bag for the battery (and controller?)

Still need a torque arm, and also waiting for the kit to arrive (I underestimated how long surface shipping from China can actually take!). Really hoping to get this up and running before the summer is through.

Thanks for all the help and suggestions, ES people are the best.

 

[Pure]

You need to do some research on C rates of batteries. The pack you bought (looking at what he has on ebay now) are 1C discharge. So with a 15Ah pack you can only pull 15 amps continuous. To pull more will significantly shorten the life of your pack. At only 15 amps your acceleration is going to be painfully slow, unless you weigh under a hundred pounds and have a very light bike. Even then it would be a boring ride. On my old 48 volt pack with my current motor, it was a 1C, and I would usually run out of road before hitting 25 MPH having the amp limit set to 20 amps. It would take a seriously long road for me to get up to speed, granted I'm a big dude, and my bike is pretty heavy.

With this pack you really need to have a cycle analyst to set your max amps limit, so you do not kill this pack.

 

[dogman dan]

Yeah, what controller? if it's not a 25 amp or lower, you just screwed yourself. You can't go buying the hot controller and still have a ho hum battery. You'll need to get a 20 amp controller for that battery. You won't pull all 20 amps all the time, so that 15 ah battery should be able to handle a 20 amp controller.

You can save the hot controller for later, when you have money for hot batteries.

 

[KipMcSkipster]

Okay, sounds like it's time to swallow the old pride and admit that going cheap on the battery was a crappy idea. Is the consensus that the battery is where I screwed up or the controller, or both? The controller I ordered was, if I have this right, a 12 fet infineon IRFB3077. I'm not clear on what you mean by "hot controller", dogman - could you spell it out for my addled brain?

I think I get the C-rate concept; I know the no-nonsense lifepo4 is a ping, which appears to be 2C. Is that sufficient for decent acceleration?

Sorry for the newbie questions. Hopefully, this stuff will start to sink in.

 

[Pure]

By hot, I'm pretty sure he means high powered.

Pings 2c are definitely better. That's what I have, but even still because of amp limits (I like speed) I'm not using the full potential say a 60V (actually 68V hot off of the charger) LiPo pack could provide.

But for your uses it sounds like ATM you want just a tame means of transportation. The current battery with some form of Amp limiter (a CA) will certainly do that. But yes at such a low Ah rating on the pack a 2 C Ping would have been mucho better, and Cellman A123s would have been great, and LiPo would be awesome.

At this point I think if you want to correct this. You need to get a different pack, or a Cycle Analyst. If you go the new batter way, LiPo would really be the cheapest most economical. Especially at such low Voltage and Amp Hours. Just be sure to research Lipo in the Bat forums..It's not something to be played with.

 

[oatnet]

I think I get the C-rate concept; I know the no-nonsense lifepo4 is a ping, which appears to be 2C. Is that sufficient for decent acceleration?

2c Ping is passable. 5c Headway is midrange. 20c a123 is top of the line; the cells get lighter, smaller, and longer lived as you go up the range.

Dogman is asking for the amp rating on the controller you want to buy, 20a, 30a, 35a, 50ah... To size the battery to your controller, the formula is AH x "C rating" = discharge amps. For example, if you are sizing to a 50amp controller, and you want to use a 2c battery, the pack will need to be at least 25ah to be able to deliver 50a @ 2c. If you used a 5c headway pack instead, the pack would only need to be at least 10ah to be able to deliver 50a @ 5c.

Note that if your pack uses a BMS, it might supply less amps than the battery is rated for, so you need to make sure the BMS can also deliver the controller's rated current.

You need to size the pack to your range, as well. The more powerful the controller you buy, the more AH your pack needs to have to keep up. The AH (amp-hour) rating of a battery describes how many amps it can deliver over the course of an hour. A 10ah battery drained at 10a (1c) will be empty in one hour. Drain that 10ah battery at 50ah (5c), and it will be empty in 12 minutes - not much of a commute. I try to size the pack so that it will supply at least 1/2 hour of juice, which works out to a 2c discharge.

One would expect that a 72v 10AH pack would have twice as much "juice" as a 36v 10ah pack, so you can see AH aren't a good measure of how much energy it stores. The formula for WH (watt hours) also includes voltage, so it is far more accurate than AH. WH is calculated as Volts x AH. For example, a 50v pack with a 10ah battery has 500wh. If you know how many WH you consume in a mile, you can figure out how many WH the pack needs to have. My CycleAnalysts show that I typically use 35-40whm in spirited hilly riding, and I use that as my rule of thumb.

Also consider what is known as using an 80% DOD (Depth of Discharge). To protect the cells, you can only use 80% of the AH or WH from the pack - ie 8ah from a 10ah cell, or 400wh from a 500wh pack. You could still use the last 2ah or 100wh, but that ages the battery and reduces the number of times you can recharge the pack. If you have a BMS it will probably stop you at an 80% DOD anyhow. Be glad we aren't using Lead Acid anymore, which only has a 50% DOD. :lol:

So, for a 14 mile commute, 14m x 40wh/m, means you would need @480wh. Given an 80% DOD, 480wh/.8 DOD = 600wh you need to have in the pack. At your planned 48v nominal (which will average around >>> 50v <<< over the discharge). 600wh / 50v =12ah. A 12ah pack can deliver 24a @2c, 60a @ 5c, or 240a @20c.

-JD

PS - I lived in Boston (Brookline) as a young man and honed my driving skills there, where offense is truly the best defense. Dunno how it is now, but back then I'd be scared on a bike. I wish every city's public transport was as effective as the "T" was when I lived there.