Monkey proof 1st ebike build parts list recipe? 88.8v

[iLearn]

*monkey proof = easy to use, least amount of tinkering to get working, and reliable.*

Hi Endless-Sphere ebike community!

I'm inspired by all of your accomplishments to try to build my first ebike based on a full suspension mountain bike. My only experience in electronics is basic car wiring upgrades and soldering wires, so I'm no expert yet. So far, I'm considering these parts based on my research here and playing with the ebikes.ca simulator that's kindly provided by Justin:

BMC v4 high torque motor (rear wheel)
74v or 88.8v 8aH battery packs from HobbyKing.com
Some type of Battery Charger built into the bike's triangle so I don't have to remove batteries for every recharge.

Given the fire danger of lipos, I had a few questions for all you experienced folks.

1. Is there a bidirectinoal active balancer for Lipo batteries like the one from Linear Technology that always ensures the batteries are balanced during discharge & charge use?
2. What is a good Monkey-proof Battery Management system and charger?
3. What is a solid monkey-proof motor controller?
4. What is the best pressure valve for the rear motor that only allows air to pass through so any atf oil from oil cooling does not leak out of the motor?

 

[spinningmagnets]

If you have the funds to build a serious E-bike, and you care about "first try" reliability...using 88V I recommend a diect drive Crystalyte HT35XX rear hub in a beefy 20-inch rim with a Pirelli moped tire (ends up with a 22-inch diameter tire). Controller would be a Lyen 12-FET run in sensorless mode capped at 35A.

Don't try to pump more power through the motor or controller until you have temp probes in each, and have data-logged the heat from your normal rides. Once you have temp data, you can raise the amps to 40A, and then possibly even 45A. Direct-Drive (DD) hubs seem to take well to oil-cooling if you want more amps than that.

I'm liking full suspension (FS) DownHill (DH) frames these days, but they can be problematic for mounting a large battery, requiring some creativity. DH frames have a good head-tube angle for street stability at your top speed. I'd recommed dual-disc BB7's as adequate.

BMC geared hub is a great motor, but until you are experienced, pumping high power through one is risky. Low copper mass, poor heat-shedding path. Great kit at 48V and 30A = 1,400W, and your first set-up I recommend is...88V X 35A = 3,000W

 

[dnmun]

batteries are not balanced during discharge. the BMS balances them during the charge cycle when it get s to the end of charge and some cells are already fully charged so the BMS diverts current around the fully charged cells in order to allow the current o flow into the undercharged cells until it reaches full charge on all cells. you cannot balance a pack by undercharging it.

we have no idea what batteries you are talking about. 88.8V is 24S of lifepo4, not lipo. 24S of lipo is 101V.

do you know how many cells in series you can use with the controller you are buying? do you know which controller yet?

 

[John in CR]

If you want reliability, forget the 24s, because it's too close to voltage limits of components in the controller, unless you spend some extra for a high voltage controller.

If you want monkey-proof, low maintenance, and low hassle, forget the RC Lipo route. Most of the guys using it have a second hobby called fiddling with your batteries, and despite experience and knowledge are quite prone to mistakes that turn fingers a scary black which luckily isn't as bad as it looks immediately after the plasma event.

BTW, you quoted the Lipo 24s correctly at 88.8V . Batteries are described by their nominal voltage with top of charge voltage requiring that specific wording.

 

[parajared]

24s for me has been more of a pain in the rear than it's worth due to motors that get really hot at sub 15mph speeds. 12s (44 volts) can be a pain too because the phase wires to your motor get hot with high amperage. I have enjoyed 18s the best.

I have heard that BMC motors don't do well with high voltages.

I have had more grief fiddling with the BMS on Lifepo4 than I have messing around with lipo, but I just solder my lipo into 6s 20ah packs and parallel the balance wires with a EPbuddy parrallel harness. I did accidentally drop a lipo and have it burst into flames however.

I have had a bad time with the cheaper 20a controllers and Hua Tong. They would just kind of poop out on me after a while. So far Lyen's controllers have worked great.

I have had issues with hall sensors and hall wires. If you get the wires too hot, aka running 50a down the stock wires, the hall wires get brittle and break. If you get the motor too hot, the hall sensors in the motor will break.
I have had much better luck with just running sensorless controllers.

My Crystalye H series ate my wire harness and destroyed my motor after 3 months. So far my 9C and MXUS motors have been performing best.

It's easy to keep a charger in your garage and have long wires from the charger to the bike. I welded my frame to lock my batteries to my bike so I don't have to remove mine either.

I have never oil cooled a motor.

Honestly it does not matter much if your cells are out of balance during discharge. Right around 3.65volts per cell your voltage will start dropping off more rapidly. This should be pretty noticable on your volt meter your "fuel gauge".

 

[wesnewell]

Please go to the User Control Panel, select Profile, and then enter your city, state/province, and country into the Location field (country minimum) and save it. This will help people help you. Example: Wylie, TX, USA. Without knowing what country you are in it's hard to make any recommendations. Thank you.

 

[iLearn]

You guys have given me a lot to think about, so thanks! 8)

Since it's my first project, I'm now considering a mid-drive unit located near the pedaling hub instead of putting the motor in the wheel. It seems like it would be easier to retrofit a bike to this mid-drive setup instead of making another wheel w/ added expense. What would you guys recommend to be a good mid-mount brushless motor that can handle 66.6 volts and has smooth engagement from a stop (not jerky like some direct drive motors)? Also, do they make good geared mid-drive motors that have internal gears? (I had 3 8000mah 22.2v Turnigy packs wired in series in mind). Top speed in mind is 31-35mph for the bike with the right gear set.

 

[dogman dan]

Seems to me that monkey proof would be running a lot less wattage.

For example, a typical 9c or muxus motor or equivilant, and a 72v 20 amps controller. You get about 35 mph, but not enough watts at 1500 to get seriously into melting motors. No, it won't take off like a 40 amps, but you can ride all you want without melting motors unless you find some steep wall to stall it on.

Or a bigger motor at 2000w, like a crystalyte and a 30 amps controller, run on 18s instead of 20.

BTW, 30 is pretty fast on an ebike. If you plan on mixing it up with fast traffic on 45 mph roads, get a motorcycle. You won't fly under the radar going 40 mph on a bike.

One option for managing lipo is sold by Methtek.

 

[iLearn]

It seems like a mid-mounted motor with internally geared hub on the rear wheel will suit my preference the best. This way I can run lower volts (maybe 48v?) with the mid-mount motor and take advantage of bike gears, and retain better overall bike balance. What do you guys think of retrofitting one of these old Norco mountain bikes like so in the attachment?

To answer your question, I don't need more than 30mph on say a 0.5% incline, so yes I have no intentions of mixing with traffic in 35+ mph .

 

[wesnewell]

Depending on what part of Dallas you live, you could be within 10 miles of me. If you want to try my bike, let me know.

 

[iLearn]

Depending on what part of Dallas you live, you could be within 10 miles of me. If you want to try my bike, let me know.

That sounds good to me Wes 8) .

 

[John in CR]

monkey proof = easy to use, least amount of tinkering to get working, and reliable.

That does not describe any DIY mid drive solution.

Jerkiness has little to do with motor selection other than speed wind direct drive hubbies will have smooth takeoff and acceleration until you push extreme amounts of current using an immediate start high power controller, so in that respect they are easier since it's hard to make them jerky on takeoff. Jerky can almost always be cured with proper settings using a direct drive controller. I'm partial to speed wind DD motors, because I prefer an ebike that has a top speed higher than I actually ride, so I can ride at whatever speed is warranted for a given situation, AND because with relatively simple mods they're capable of higher power than an identical motor with a slower wind due to voltage limitations of available controllers.

Since you don't really mention looking for the cheapest route in, then as long as you're not looking for extreme power and speed, I'd suggest a full kit from http://www.ebikes.ca . There's no more knowledgeable outfit, so all you have to do is tell them what you want it to do and the bike you're starting with, and they'll fix you up including service after the sale.

 

[iLearn]

John,

thank you for your input and same goes to everyone who posted great information . Regarding "easy," I was planning to Tig weld a good mounting solution to the frame for the mid-drive motor because I've been Tig Welding sing 2009 and am proficient at it 8) . So, now I'm looking for a motor that has good optimization of the following parameters.

1. Reliable & least maintenance
2. quiet
3. light weight
4. as small as possible
5. 48 volts

 

[spinningmagnets]

With TIG, you have many options.

An "ultimate" setup can involve buying a good used chromoly DH full-suspension bike, and using everything but the main frame triangle. By making a new frame triangle, you can use a hub as a mid-drive, or even if using a rear hub, you can make a great battery mounting solution in the triangle.

Re-read, just saw you want quiet, recommend Crystalyte HT series rear-wheel hub using a sine-wave controller.

 

[John in CR]

John,

thank you for your input and same goes to everyone who posted great information . Regarding "easy," I was planning to Tig weld a good mounting solution to the frame for the mid-drive motor because I've been Tig Welding sing 2009 and am proficient at it 8) . So, now I'm looking for a motor that has good optimization of the following parameters.

1. Reliable & least maintenance
2. quiet
3. light weight
4. as small as possible
5. 48 volts

1 and 2 are in direct opposition to 3 and 4.

 

[iLearn]

1 and 2 are in direct opposition to 3 and 4.

I'm willing to compromise . How about this for criteria in order of most important, to least important?:

1. No less thn 48v
2. Reliable w/ least maintenance
3. Quiet
4. as small as possible
5. as light as possible (Given the above criteria)

 

[Chalo]

Top speed in mind is 31-35mph for the bike with the right gear set.

Have you gone 35mph on a bicycle before? You might not like it as much as you think you will. If that speed requirement is relaxed, everything else gets easier and cheaper.

35mph takes twice as much energy to maintain as 25mph, makes twice as much wind noise, and requires twice the distance to stop. It'll chew up your tires and beat up your wheels a lot faster too. And that's more or less the speed at which you'll attract the attention of police, who may or may not know applicable e-bike laws. (Yours won't be a legal e-bike at that speed, though it might squeak by as a "motor-assisted scooter" under Texas law.)

My suggestion is to start with a bike that is satisfactory to you without added power. (Like, not a Wally World bike.) Then juice it with forty-something volts, choosing components such as the controller that are compatible with a higher voltage if you so choose. After accommodating to the speed that you get on say 44-48V, you might decide that 60V is enough and save yourself a bunch of money and hassle.

If monkey-proofness is your goal, don't think Hobbyking.com. You should be using quality lithium iron phosphate or lithium manganese batteries if you want them to be like an appliance rather than a dangerous pet.