First bike build, consultation needed!

[Anonymous]

Hello everyone!

So, I am a newbie to this scene. I just started to google around about electric bikes and stuff, and after a while got stuck here
reading for days about everything

So I am considering building a bike for travelling to school and also further away, maybe 50+ km with battery power only.
As stated above, need for long distances gets me to big and heavy battery packs

Enough blahblah, lets get to the business! Below I will list the build I have been thinking about:

- Upgrade Mac kit from em3ev.com, rear hub motor. They state that the upgrade version has composite gears
and upgraded phase wires for the motor.
- Controller would be 9fet with IRFB4110 FETs, because I would like to have 60-72volts battery pack.
- MAC 8T motor, because I won't be climbing steep hills, maybe a few moderate ones, and I want some speed
- Battery pack and charger from bmsbattery.com, 72v15ah or 60v20ah.
- CA v2.3 from em3ev.

So to the consultation then I would like the bike to have top speed around 40+ km/h. I don't need very torquey motor because the
bike I am putting it into is cruiser/city bike style. Range is also needed for long distance travels, that's why the large Ah pack is needed.

The bike itself looks like this.

It's a pressed steel frame city bike, legendary here in Finland because it's made in Finland quality work
24" wheels, which I will be upgrading with 3,2mm spokes and disc brakes front and rear.

Rear and front wheel forks are lousy thin steel tube full of rust and would probably not handle the power of the motor so they will be upgraded by replacing
them with DIY thicker steel tube forks. This part is not yet planned fully ready.

MAC motor would be my choice of weapon due to its lightness and small size, and because power requirement is not very high.
Also it would probably get modified by filling it with oil and replacing original bearings with SKF or FAG ones.

Battery would be placed on custom mounts above the frame. These are still to be made.

So actual questions would be:
-Will the Mac be able to handle something like 72V * 20-25A= 1440-1800 Watts or 60V * 25-30A= 1500-1800 Watts?
Especially with oil cooling mod and the bearings?
- Is bmsbattery source for reliable battpacks? They have low pricing especially on 72V packs and they use 40152 or 38140/38120 cells
which are from Headway(?) Or should I consider custom made pack for example made by schwibsi ?

Any recommendations are welcome

Greetings from Finland

 

[Ykick]

Hello and welcome to ES.

Maybe I'm looking at the wrong bike but where will you put a front brake? Dangerous business to ride a "faster & heavier" eBike with only one brake. Especially, a coaster brake which can completly fail should your chain hop off the sprocket. Nevermind a rear motor which is incompatible with coaster brake.

I run 67V hot off the charger using 3077 FETs with no issues for several months. The 3077 FETs appear to be significantly more efficient than the 4110's because whenever I use the 3077 controller on the same motor, bike & battery, I experience between 20-25% more range.

I would be very cautious dealing with BMS Battery packs. If you have an issue you'll pretty much be SOL. I know it sucks to bite the EM3 batteries but it's a MAJOR component and attempting "cheap" often results in sadness and more money spent than simply buying a GREAT battery to start.

 

[Anonymous]

Hello and thank you!

The brakes etc. would be no problem since I am manufacturing my own rear and front forks with all the necessary mounting points.
Original ones are like 10-12mm mild steel tube and are known to fail even on normal use. My bike has been laying around
for couple of years and I am restoring and modifying it to suit my needs

Yes I know the most essential part is the battery. Could you recommend a good and reliable source for them?
I have been snooping around the internet about this for a week now
Would this be any good ? With high rate BMS and charger upgrade maybe ?

So you recommend using the 3077 fets. I am believing more experienced ones and will probably be buying that
And I have also considered making my own pack, but my knowledge about electronics is fairly low, and I would not take the risk of burning someting up
This sounds maybe ridiculous because I am starting school next month and will graduate to an Electronics Engineer

And how about pack made by schwibsi ? I red his thread on Sales section and saw some happy comments about his work

I am all ears, please advice a newbie

 

[docnjoj]

All of the MAC motors have the composite gears these days. EM3EV has very high quality batteries. Extremely well made. Ping is good too, but heavier. 60-72 volts is a lot for a MAC or most geared motors. Paul (EM3EV) recommends no more than 48. Don't know about Schwibsi but his thread is really classy.
otherDoc

 

[Tench]

A point I would like to make is your plan for the spoke upgrade to 3.2mm is not a good idea, very heavy spokes will not tension correctly in bicycle rims creating a wheel that will constantly suffer from loosening spokes. Upgrade yes, but 13g would probably be the best choice, certainly no bigger if the rest of the wheel is made up of bicycle components.

 

[The fingers]

Welcome to ES. Steel is good, rust not as good. Wise to upgrade to new steel and still use torque arms.

 

[Anonymous]

Hello!

Thanks people for all those advices Yes I will upgrade spokes to something more rigid, maybe the 3,2mm was a bit overshooting
13awg seems to be around 2mm. That also sounds sturdy enough

I have a fixation to make everything pretty hardcore, that's why I suggested so thick spokes. As I am metalworking professional/welder
I have seen more than enough crappy quality chinese bikes, steel etc. They are constantly being broken and brought to me to be fixed.
It's hard to make anything good out of them and then people are nagging why it broke again So it's "turd polishing"

So as I mentioned earlier the rear fork/frame and front fork will be removed and upgraded versions will be welded on place.
Also the pressed/stamped steel mainframe will get some improvements. Although I won't be welding some 8mm steel plate to frame
But some, so it will handle 50-60km/h easily. It will not go that fast but I want to do so because of safety first

Front hub will be aftermarket bought/salvaged from broken bike with disc brake mount and proper bearings. Not some "groove, loose balls held in place
with grease" type. Good rigid ball bearings with both sides shielded(2RS)

Torque arm will be fitted. Does it only need one for rear axle or should I/must I put one on the front for disc brake ?

I've made now a decision that I will stay a mile away from cheapo batteries and save some more bucks for proper one.
I was thinking this one with 22Ah upgrade. Description states that it will handle continuous max. 35A with 29E Cells(22Ah upgrade)

So that would leave me with 14S7P pack 50V*30A limited by controller. Is this good limit for MAC 8T or will it melt
This would leave me with 1500Watts of power which is enough for me.

Does anybody know what chemistry the INR18650-29E uses? Is it LiFePo4?
Am I right with the conclusion that LiFePo4 has best durability etc. for e-bike usage? Lot of people recommend them.

 

[motomech]

If you want to go "hardcore", Lipo is the way.
If you order from two or more vendors, you will pay add. shipping.
Maybe you should get everything from Cel_man. He is great to work with.

 

[Drunkskunk]

Hello!

Thanks people for all those advices Yes I will upgrade spokes to something more rigid, maybe the 3,2mm was a bit overshooting
13awg seems to be around 2mm. That also sounds sturdy enough

I have a fixation to make everything pretty hardcore, that's why I suggested so thick spokes. As I am metalworking professional/welder
I have seen more than enough crappy quality chinese bikes, steel etc. They are constantly being broken and brought to me to be fixed.
It's hard to make anything good out of them and then people are nagging why it broke again So it's "turd polishing"

So as I mentioned earlier the rear fork/frame and front fork will be removed and upgraded versions will be welded on place.
Also the pressed/stamped steel mainframe will get some improvements. Although I won't be welding some 8mm steel plate to frame
But some, so it will handle 50-60km/h easily. It will not go that fast but I want to do so because of safety first

Front hub will be aftermarket bought/salvaged from broken bike with disc brake mount and proper bearings. Not some "groove, loose balls held in place
with grease" type. Good rigid ball bearings with both sides shielded(2RS)

Torque arm will be fitted. Does it only need one for rear axle or should I/must I put one on the front for disc brake ?

I've made now a decision that I will stay a mile away from cheapo batteries and save some more bucks for proper one.
I was thinking this one with 22Ah upgrade. Description states that it will handle continuous max. 35A with 29E Cells(22Ah upgrade)

So that would leave me with 14S7P pack 50V*30A limited by controller. Is this good limit for MAC 8T or will it melt
This would leave me with 1500Watts of power which is enough for me.

Does anybody know what chemistry the INR18650-29E uses? Is it LiFePo4?
Am I right with the conclusion that LiFePo4 has best durability etc. for e-bike usage? Lot of people recommend them.

As someone who has been building wheels for a few decades, I can tell you 13g is still too thick for your bike. Spokes are actually a type of torsional spring to suspend thew hub in the rim. they take the various types of shock loads that get placed on the rim and help to evenly distribute it to the whole wheel. The spoke is part of an integrated system, and has to be matched to the rim, as well as the bike.

Just imagine if you took a car and replaced it's springs with steel rods. Would it be drivable? sort of. would it survive long? No, it would shake it's self apart. You would have stress fractures from the rims all the way to the roof line. parts would be failing through the whole car. The same is true of spokes. If the spoke is too thick, it can't do it's job, and will pass those forces on.
14G is about as thick as you want to go on a bicycle unless you're running a heavy rim and have excessive amounts of power in the motor or excessive weight on the bike. A butted spoke like a 13/14 might be even better, with it's heavy elbow end, but for a bike like yours, 15g might be a better option. Let me show you how hard 14g spokes get pushed reliably.
[youtube]Hv_DRJZZ2qI[/youtube]


When you have a car, you think of it's motor being it's heart. With an Ebike, it's not. The battery is the heart of an Ebike. Well, think of the Battery as the bike's pistons, and the motor as it's crank shaft.. its a complicated analogy. the point is the battery is the most important part.

That ping battery is fine. Mr Ping is well respected here, and even a member of the forum. but shipping will be high. EM3ev.com's batteries are better, and you can combine that high shipping cost with the motor, so it's not that much more expensive than buying the Ping battery separate.

INR are LiNiMnCoO2 (also called NMC).
Its IFR that are LiFePO4 . LiFePO4 are the best durability, but INR and IMR have better power density, and are a good trade off between ICR (the round can version of LiCoO4, what we call Lipo) and IFR (LiFePO4).