First Timer Building an E-Bike - Input Welcomed

[yosquire]

In recent months I've become quite fascinated by e-bikes and have been lurking around here behind the scenes. This is my first post and I'm looking for some input before I start spending money. I'm gearing up to start buying components. My current plan is to nearly copy Russ's Ultimate Seattle Hybrid as it fits my preferences quite well. http://visforvoltage.org/forum-topic/bicycles-and-pedelecs/998-ultimate-seattle-hybrid-bike. I have a 12.5 Mile commute and am recovering from Knee Surgery, so may need to be able to lean on the batteries pretty hard at first. Of course, I can always call for a ride should I run the batteries flat. I can charge the batts while at work. The commute consist of 12 miles along a river bike path, so the only hill is climbing (60ft) to cross a bridge. Even so, there are a minimal number of hills in my area.

1) Wal-Mart full suspension & full disc brake Mongoose. ($180 usd - give or take)
2) Crystalyte 408 Rear motor with disc
3) Crystalyte 40 amp controller (Maybe 50 amp controller for upgrade purposes...input?)
4) 4-pack DeWalt 36v, 2s2p for 72 DeWalt Marketed Volts (or 66v actual)
5) Direct Plug-in Cycle Analyst (This should provide the LVC, correct?)

I've read a good amount about the DeWalt BMS (Battery Management System) and understand it's pretty mediocre for this application. I also understand that the charger is junk too. However, at first I plan to use the unmodded 36v packs and chargers. Hopefully I can keep it that way since I'm going to buy a DeWalt 36v power tool set as well. I'm planning on building my Battery tray large enough to accommodate 6 batteries for future upgradability.

Motor: Based on everything I've read, the 408 provides a good balance between performance and efficiency. It seems the 500 series motors give up efficiency for performance. I have automotive racing experience and love speed, but I think the 408 should keep me out of trouble, especially since I'll mostly be on bike paths with pedestrians and their leashed dogs.

Controller: 40 amps should be more than adequate. Does anyone know if the 408 motor can handle the 50 amp controller? I may want to upgrade to a 500 series motor in the future.

 

[Drunkskunk]

Welcome to the addiction!

It looks like you're realy done your homework. Russ over on V has a good bike, but his rear rack is still a weak point. I think he said his is steel, and most are aluminum. Those tend to crack and fall off with repeated use.

My 408 at 74volts will just creep up to 40 amps if I hit the throttle hard, going up a hill from fully stopped, and only for a few seconds while it starts rolling. 50 amps would be overkill, but it won't hurt the motor. The motor won't draw more than it needs at that point.

 

[EMF]

In recent months I've become quite fascinated by e-bikes and have been lurking around here behind the scenes. This is my first post and I'm looking for some input before I start spending money. I'm gearing up to start buying components. My current plan is to nearly copy Russ's Ultimate Seattle Hybrid as it fits my preferences quite well. http://visforvoltage.org/forum-topic/bicycles-and-pedelecs/998-ultimate-seattle-hybrid-bike. I have a 12.5 Mile commute and am recovering from Knee Surgery, so may need to be able to lean on the batteries pretty hard at first. Of course, I can always call for a ride should I run the batteries flat. I can charge the batts while at work. The commute consist of 12 miles along a river bike path, so the only hill is climbing (60ft) to cross a bridge. Even so, there are a minimal number of hills in my area.

1) Wal-Mart full suspension & full disc brake Mongoose. ($180 usd - give or take)
2) Crystalyte 408 Rear motor with disc
3) Crystalyte 40 amp controller (Maybe 50 amp controller for upgrade purposes...input?)
4) 4-pack DeWalt 36v, 2s2p for 72 DeWalt Marketed Volts (or 66v actual)
5) Direct Plug-in Cycle Analyst (This should provide the LVC, correct?)

I've read a good amount about the DeWalt BMS (Battery Management System) and understand it's pretty mediocre for this application. I also understand that the charger is junk too. However, at first I plan to use the unmodded 36v packs and chargers. Hopefully I can keep it that way since I'm going to buy a DeWalt 36v power tool set as well. I'm planning on building my Battery tray large enough to accommodate 6 batteries for future upgradability.

Motor: Based on everything I've read, the 408 provides a good balance between performance and efficiency. It seems the 500 series motors give up efficiency for performance. I have automotive racing experience and love speed, but I think the 408 should keep me out of trouble, especially since I'll mostly be on bike paths with pedestrians and their leashed dogs.

Controller: 40 amps should be more than adequate. Does anyone know if the 408 motor can handle the 50 amp controller? I may want to upgrade to a 500 series motor in the future.

This is quite similar to my bike, only difference is the bike frame and I have a front hub motor. My post is about 13 down from the top.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=235&st=0&sk=t&sd=a&start=75

I really like my bike a lot and it has plenty of power and speed for me. At 72 ( 66 ) volts you will get that bike to just over 30 MPH. Having said that, I *think* that if you don't pedal that much, you will have to go quite slow, maybe 15 MPH if you want to make 12.5 miles with 4 batteries. I guess it all depends on terrain, wind etc. I would reccomend 2s3p, or at least make sure you can add 2 more batteries in the future if you are not satisfied with your range...

The CA is real nice to have ( Invaluable ) and yes the LVC does work. The speed limiter works well also. I like to set mine on 21 MPH and then just hold the throttle wide open for "cruise control" .

 

[Dr. Shock]

If you use six DeWalts at 66v, you should be ok with the stock BMS and charger for a while. Try to isolate each battery with a diode.

I use four at 36v with no problem, but I found using 2 was too much strain on them, and fried one bms. Split the amp draw 3 ways (3p2s) and you'll probably do better. 4 ways would be better still. If you use a larger number of batteries, your stock BMS and charger will do better.

 

[ngocthach1130]

Just open up the battery and run tap going out from the battery. I ran wire into the battery with minimal intrusion and doesn't look that much different. Took some slight clipping and grinding on the inside to remove some ridges to clear the path for the 12guage wires, but not hard.

 

[Dr. Shock]

ngocthach1130 wrote:

"Just open up the battery and run tap going out from the battery. I ran wire into the battery with minimal intrusion and doesn't look that much different. Took some slight clipping and grinding on the inside to remove some ridges to clear the path for the 12guage wires, but not hard."

You know, I did that to bypass the bms and it still fried one bms when I only ran 2 DeWalts. Never had a problem running four, though.

 

[yosquire]

Dr. Shock,

I like the idea of isolating each battery with a diode. What size Diode would I need? (Assuming a 2p2s at this point) I did the math and am not sure it worked out correctly.

Assuming 40amp maximum total system draw:
Each battery should see 20amps at 2p2s or 14amps at 3p2s?

A 20amp 100v Diode like this: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=IRD3900-ND?


EMF,
A few weeks ago I watched your videos on YouTube. Thanks for the input on range & packs.


Ultimately, I think I will go to a 6 pack, but to offset the initial outlay of cash I'll probably start with a 4 pack. Or at least I'll justify the last two batteries after dragging my butt home for 4 miles with dead batteries.

 

[EMF]

It will be interesting to see how far you can get on a 4 pack. I hope you post this information somewhere so we will know!

 

[Dr. Shock]

Yosquire,

You probably saw my recent post on my diode board, but if not, look it up.

Generally, in selecting a component, you want to build in a margin of tolerance, so if you think the maximum amps you'll draw is 40A, and each parallel pair of batteries will provide half of that, you want diodes that do a bit more than 20A. I'd look for 25A diodes as a minimum.

Also consider that if you order from a place like Digi-Key, you should try to order from what they have in stock if you want to order small quantities with quick shipping. I did a quick search and I saw some 30A 100v diodes in stock (V30100S) that would probably suit you very nicely. I always look on ebay to see if there's anything suitable.

If you do a diode board, to get 66v out of DeWalt packs, you can do a 2 sided board with side A's pos connecting to side B's negative, and use A neg and B pos for the lines out to the controller.

For information purposes, running 4 DeWalts at 33v, I easily get through a course of errands taking in about 5 miles of travel without drawing down the batteries very far (about 20 min recharge time each pack). Not sure how that would change for a 2s2p configuration. Theoretically, you'd use the same total power, but I suspect that in the real world, you'll burn a lot in acceleration.