Dougt
100 mW
Hi Everyone,
Planning my first ebike build. Been reading these forums for a month now, and I'm sure some of the answers are already here somewhere, but some are a matter of opinion based on experience and goals, so I would like feedback that takes my goals and build concept into account.
A) My background: Engineer with good electrical and mech. skills. Access to test equipment, tools, friends w/ nuke/aerospace cert tech welder & some machinists. Used to road bike 7000+ miles a year and race cross country mt bike, so have decent bike handling skills and in-traffic experience. Have gone over 50 mph on steep road downhills many times (full tuck). No motorcycle experience. Enjoy building stuff, hate repairing stuff. Would rather build my own ebike than buy a used Stealth Bomber or such
B) My goals:
1)budget about $4k (USD). Quality build, but not insane. aka Strong, safe, reliable. Can spend more if needed, but thats my target
2) Usage: 95% road / 5% dirt. Dirt only hard pack trail to cut between roads, maybe pop a curb or two at low speed. No jumping, but should be able to survive average pothole at 40mph. My body is too beat up to do any serious off road stuff anymore,
3) desired performance
i) 40+ mph capable (for a few minutes for fun), most time at 25 mph.
ii) acceleration: don't care much, as long as it doesnt overheat getting to top speed
iii) capable of mild 6% grades for 1 mile before overheating. Very short (100 meter) 9% grade. Any speed
iv) range 18 miles at 25 mph
v) battery to last 800-1000+ cycles
4) practicality
i) charging simple...no separating or removing pack to charge or balance. 4 hrs ok.
ii) doesnt scream ebike to casual observers from distance. Don't want cops to take interest
C) my concept
1) frame: ??? havent decided between hard tail, FS, or rigid. road use means dont need suspension - cost savings? strength? safety? availability? Seems most ebike frames are FS and expensive ($1500).
i) front shock ?, strong with good tire clearance. Since road use, big travel not needed.
ii) brakes 203mm hrdraulic with E-cutout, front and rear. Tektro Dorado. Stopping really important to me.
2) motor: crystalyte fast wind (40100) or cromotor. Allows for future upgrades, rather do it right the first time. drawback wide...need special frame. torque with big dia tires a problem?
3) wheels:
i)rims 21" motorcycle. Strong, and want MC tires so no flats. Equiv tire diam to 26" mt tires?
ii) tires: prob Shinko 244 Dual Sport Front - Rear Tire - 2.75-21
ii) front hub ????
4) battery:
i) 20s 72v 20 ah. havents decided on chemistry. will make pack myself. have spot welder.
ii) charger: use two 10s balance chargers in series. (iCharger 1010b+) Use isolation power supplies on each to allow this. rewire/upgrade to custom coonectors for simplicity and idiot proofing.
iii) bms: none? need one if balance charge every time? will fuse battery.
5) controller: 60a? 72v? 80v?
6) gears: single speed ok. only plan to pedal in emergencies or for appearances sake. Prob geared to pedal 70rpm at 15 mph.
D) Questions:
1) frame...front suspention only ok or asking for trouble at high speed? any ebike frames with good triangle battery capacity? or use DH frame, but I prefer the clean look, assembly convenience, and added strength of ebike frames though. I'd prefer not to spend $1500 on a frame, $450 on a front fork and $350 on a rear shock for on-road use seems overkill and wasteful. I definitely want to put batteries in the triangle - no racks. maybe the E-kross frame with cheaper suspension components? opinions?
2) suspension:
a)fork: inexpensive, low travel, but strong and clear 3" wide tire + brake? suggestions? used ok. suggestions?
b) rear shock/spring (if full susp): again don't need much travel for road use. Suggestions?
3) batteries: suggestion for cells to build 72v20ah that can source 3C without sacrificing cycle life. Desire 700-1000 cycle life.
a) I'm thinking the panasonic NCR18650PF in 20S8P. They are 10 amp each and good cycle life...expensive though.
b) I see cells for half the price on alibaba, but are they likely fakes? suggestions for reliable sourcing?
c) i assume I can use two 10S iChargers in series if I run them off isolated powr supplies, but not sure if motor controller truly looks like open cicuit during charging. Anyone done this? (I will have beefy wires for each bank, esp the first and last, and charging at 8 amps is plenty fast for me.
4) Controller: handle 60amps, 72V. suggestions? dont need regen, but may want flux weakening if not much cost added (20% more $ ok).
a) its not clear to me that a controller will limit its current to its current or temp rating. - adjustable? How do I make sure I don't blow up my controller? suggestions for sources?
5) motors...ok the ones I've speced are overkill and restrict frame selection, but I rather start with more in case I want to upgrade.
6) wheels: Will lace myself for proper dishing. The 21" MC rims have same tire diam as 26" MB. I know people frown on large diameter wheels, but I don't care about big acceleration and prefer the front wheel stays on the ground. And I think normal sized tires will draw less cop attention. Contrary to what ive read, frame stress should be the same, because if you motor puts out 150 n-m peak torque, then it doesnt matter how far away the reaction force (tire/ground interface) is, the frame or torque arm will see 150 n-m. A bigger wheel means the bike will accelerate slower, and the motor need to work harder for the same lower speeds or on hills...right? The eBike similator says I can do my combo. comments?
a) BTW I love the similator, but wish it had a feature that showed the total heat deposited into the motor and/or contoller to get to a certain speed. Since the simulator says I can be at max throttle at max speed (41 mph) for 40 minutes before overheat, then that implies that I should have no prob getting up to max speed as long as I dont go full throttle at <5 mph.
I know there are many more components, but those seem to be the major ones.
Thanks in advance for any guidance,
-Doug
Planning my first ebike build. Been reading these forums for a month now, and I'm sure some of the answers are already here somewhere, but some are a matter of opinion based on experience and goals, so I would like feedback that takes my goals and build concept into account.
A) My background: Engineer with good electrical and mech. skills. Access to test equipment, tools, friends w/ nuke/aerospace cert tech welder & some machinists. Used to road bike 7000+ miles a year and race cross country mt bike, so have decent bike handling skills and in-traffic experience. Have gone over 50 mph on steep road downhills many times (full tuck). No motorcycle experience. Enjoy building stuff, hate repairing stuff. Would rather build my own ebike than buy a used Stealth Bomber or such
B) My goals:
1)budget about $4k (USD). Quality build, but not insane. aka Strong, safe, reliable. Can spend more if needed, but thats my target
2) Usage: 95% road / 5% dirt. Dirt only hard pack trail to cut between roads, maybe pop a curb or two at low speed. No jumping, but should be able to survive average pothole at 40mph. My body is too beat up to do any serious off road stuff anymore,
3) desired performance
i) 40+ mph capable (for a few minutes for fun), most time at 25 mph.
ii) acceleration: don't care much, as long as it doesnt overheat getting to top speed
iii) capable of mild 6% grades for 1 mile before overheating. Very short (100 meter) 9% grade. Any speed
iv) range 18 miles at 25 mph
v) battery to last 800-1000+ cycles
4) practicality
i) charging simple...no separating or removing pack to charge or balance. 4 hrs ok.
ii) doesnt scream ebike to casual observers from distance. Don't want cops to take interest
C) my concept
1) frame: ??? havent decided between hard tail, FS, or rigid. road use means dont need suspension - cost savings? strength? safety? availability? Seems most ebike frames are FS and expensive ($1500).
i) front shock ?, strong with good tire clearance. Since road use, big travel not needed.
ii) brakes 203mm hrdraulic with E-cutout, front and rear. Tektro Dorado. Stopping really important to me.
2) motor: crystalyte fast wind (40100) or cromotor. Allows for future upgrades, rather do it right the first time. drawback wide...need special frame. torque with big dia tires a problem?
3) wheels:
i)rims 21" motorcycle. Strong, and want MC tires so no flats. Equiv tire diam to 26" mt tires?
ii) tires: prob Shinko 244 Dual Sport Front - Rear Tire - 2.75-21
ii) front hub ????
4) battery:
i) 20s 72v 20 ah. havents decided on chemistry. will make pack myself. have spot welder.
ii) charger: use two 10s balance chargers in series. (iCharger 1010b+) Use isolation power supplies on each to allow this. rewire/upgrade to custom coonectors for simplicity and idiot proofing.
iii) bms: none? need one if balance charge every time? will fuse battery.
5) controller: 60a? 72v? 80v?
6) gears: single speed ok. only plan to pedal in emergencies or for appearances sake. Prob geared to pedal 70rpm at 15 mph.
D) Questions:
1) frame...front suspention only ok or asking for trouble at high speed? any ebike frames with good triangle battery capacity? or use DH frame, but I prefer the clean look, assembly convenience, and added strength of ebike frames though. I'd prefer not to spend $1500 on a frame, $450 on a front fork and $350 on a rear shock for on-road use seems overkill and wasteful. I definitely want to put batteries in the triangle - no racks. maybe the E-kross frame with cheaper suspension components? opinions?
2) suspension:
a)fork: inexpensive, low travel, but strong and clear 3" wide tire + brake? suggestions? used ok. suggestions?
b) rear shock/spring (if full susp): again don't need much travel for road use. Suggestions?
3) batteries: suggestion for cells to build 72v20ah that can source 3C without sacrificing cycle life. Desire 700-1000 cycle life.
a) I'm thinking the panasonic NCR18650PF in 20S8P. They are 10 amp each and good cycle life...expensive though.
b) I see cells for half the price on alibaba, but are they likely fakes? suggestions for reliable sourcing?
c) i assume I can use two 10S iChargers in series if I run them off isolated powr supplies, but not sure if motor controller truly looks like open cicuit during charging. Anyone done this? (I will have beefy wires for each bank, esp the first and last, and charging at 8 amps is plenty fast for me.
4) Controller: handle 60amps, 72V. suggestions? dont need regen, but may want flux weakening if not much cost added (20% more $ ok).
a) its not clear to me that a controller will limit its current to its current or temp rating. - adjustable? How do I make sure I don't blow up my controller? suggestions for sources?
5) motors...ok the ones I've speced are overkill and restrict frame selection, but I rather start with more in case I want to upgrade.
6) wheels: Will lace myself for proper dishing. The 21" MC rims have same tire diam as 26" MB. I know people frown on large diameter wheels, but I don't care about big acceleration and prefer the front wheel stays on the ground. And I think normal sized tires will draw less cop attention. Contrary to what ive read, frame stress should be the same, because if you motor puts out 150 n-m peak torque, then it doesnt matter how far away the reaction force (tire/ground interface) is, the frame or torque arm will see 150 n-m. A bigger wheel means the bike will accelerate slower, and the motor need to work harder for the same lower speeds or on hills...right? The eBike similator says I can do my combo. comments?
a) BTW I love the similator, but wish it had a feature that showed the total heat deposited into the motor and/or contoller to get to a certain speed. Since the simulator says I can be at max throttle at max speed (41 mph) for 40 minutes before overheat, then that implies that I should have no prob getting up to max speed as long as I dont go full throttle at <5 mph.
I know there are many more components, but those seem to be the major ones.
Thanks in advance for any guidance,
-Doug