I've done a bit of searching, but haven't found much... Has anyone here ran a Crystalyte 408 motor at 72V? I'm currently running a 36V 10.5Ah Lithium Ion battery pack and would like a few more MPH. I'd like to add another 36V 10.5 Ah battery in series if the motor can handle it.

Am I the only one crazy enough to consider doing this?

Motor can handle it. Controller may not.

Check with the seller to make sure your controller is able to handle up to 72v.

https://www.ebike.biz/Crystalyte_408-..._Hub_Motor.htm


Under specifications 36-72v

am I reading this correctly?

Yes. Those controllers are made for up to 72v. Make sure you set your amp limit, as not to burn it up.

I have it running at 48 volts and have seen it documented at 72 volts.

This is where I've first seen the 72 volt build using 408 crystalyte hubmotor: https://technorati.com/videos/youtube...?v=zKKvP9wWrlY

https://endless-sphere.com/forums/

Many users here regularly run their Crystalyte 4XX wheels at 72 volts. However, you may need to upgrade your controller to handle the higher voltage depending on what controller you currently have. With my 24V-48V controller, too high a voltage would definitely blow a mosfet as those things are what limits the voltage. See https://www.ebikes.ca/store/ for a list of controllers. Also, running at such a high voltage tends to incur higher resistive losses in the 4XX so you'll notice the motor getting significantly warmer. At higher voltages, one way to reduce losses is to upgrade your motor to a 5xxx but you'd also need a large-amp controller to handle the extra amps it draws.

There are 72v Crystalyte 408s in Power in Motion (ItsElectric) here in Calgary fairly often. The motors are capable of handling that level of current without issue, but as mentioned, you *do* need an appropriate 72v controller.

The typical 36/20 controller for the 408 will work fine at 48 volts, but will not withstand 72 volts.

Thanks for the feedback. I expected a new controller would be required. Thanks for the links. My main concern was whether or not the motor could handle it. I deal with brushless motor technology in my field of work, but it's limited to 12V (9-16V real world). Typically, the electronics are the limiting factor for increased power applications. FETS are usually the first to show weakness. Anyone know of durability issues with these motors in high voltage applications?

Abneycat - I actually bought my kit from Ken at Power in Motion. I emailed him a few days ago, but no response. I know he's busy, but thought his lack of response might be indicative of not supporting 72V for these motors.

Oh, the motor itself will pretty much handle ANYTHING(within 'reason'). These motors have been tested upto 110V with no problem, they just tend to get really hot.

Thanks for the feedback - off to my first 24 mile one way commute tomorrow. So far, I've had a blast with the 36V setup... managed to put just shy of 100 miles on the setup within a week and a half putsin around town here and there. My commuting will be the real judge of whether or not I go with the 72V setup, but knowing how I tend to be with things like this - I will.

Generally, do not overvolt your controller, regardless if your fets can handle it

And there are two points to consider, not just one:
1) Controller
2) Bike frame

A typical 26" wheel, running at 72V, 20A, will push about 53km/h, with a 408 motor
your bike frame may not be able to handle it, assuming a rear mount, but with a front mount, your fork may not be able to handle it

load up torque arms or you will regret it
crescent wrench the right night, then clamp the wrench tight against the bike frame with hose clamps/fasteners

I never planned to push the controller. My discussion about FETs and such is in regards to my experience with brushless engine cooling fan motors which often have integrated PWM controllers... as far as I can tell, in bike applications, the PWM controller is always external so no concerns with the motor from a FET overload standpoint.

Nice suggestion with the wrench as a torque arm. Simple yet effective. I've also seen some stamped pieces on Ebay for less than $20.

I have a rear motor setup so I'll take your suggestion with the torque arm if I move forward with the 72V setup.

53 km/hr would be plenty for me. I'd be happy if I could cruise at 40 kph (25mph). With 36V, I average around 18-20 mph. My 24 mile commute today took me exactly what I expected - 80 minutes. It'd be nice to be closer to an hour, but it's still a lot of fun either way. I'm enjoying the E Bike!

Maxximum,
Re your note "load up torque arms", can you explain what a torque arm is (and provide a picture if possible)?

Also, I didn't understand your note "crescent wrench the right night" Was "night" a typo?

Finally, when you say "then clamp the wrench tight against the bike frame", are you suggesting to clamp a wrench to a bike frame?

Hi Element116,
I've got the same setup as you (although I'm only averaging about 15-16mph, probably because of all the darn stoplights on my route) and I was contemplating the same thing.

I'm curious, assuming you buy a new 36V 10.5 Ah battery and hook it up in series with your older battery, will there be any problems with using 2 batteries which are not exactly the same ie presumably the older battery will have slightly less capacity.

You need torque arms. Otherwise the motor's axle will rip out the the dropouts from your bike.

The wrench is a crescent wrench that goes on the right nut. Because of the direction of the force of the motor, the axle on the right side has an urge to turn counterclockwise, this in effect causes the right nut to tighten. If the nut is held stationary, it will prevent the axle from twisting, thereby preventing the axle from ripping out the dropout. However, I do not know how strong this is. Btw, you attach the wrench with pipe clamps.

Btw, a 48V controller can handle upto 100V, provided it is using the newer FETs. 16mph is EXPECTED at 36V.

Thanks Snowsurfer. Your comments re torque arms make sense. But just so I'm clear, in the context of this thread, is the crescent wrench meant to act as a torque arm?

Also, re your comment "16mph is EXPECTED at 36V", I guess I don't feel so slow. "Reaching" 20mph (and slightly above) is no problem. But "averaging" 20mph in city riding seems very fast to me.

ha ha ha yeah, it is.

it increases r, with a constant torque, so it must better counter the force

tau is equal to f r cos theta or something like that

watch out for the controller and batteries though
the cut off voltage is lower than what your batteries should be subject to if you over volt

for instance, if you have a 48v controller, the cut off voltage might be 36V, and if you are overvolting to 72V, the controller could still keep sucking electricity from the battery to below 1V/cell, or below 60V which could damage the batteries, or cause an explosion or fire depending on the chemistry

I'm maintaining an average of 18-20 mph but I pedal the entire time. I haven't pursued the 72V since my motor has fallen apart already at 36V. The axle separated from the case!! Luckily, Ken at It's Electric has been very prompt to replace the motor. Unfortunately even the replacement doesn't work properly. He suspected a defective controller, but that didn't fix it. It's going on 3 weeks now with no E-bike. I'm really bummed especially with the perfect weather forcast for this week and the steep gas prices. My commute is far too long to brave without the motor assist.

Yeah, that sucks to hear about your ebike man. Are you able to purchase a hybrid bike, or a road bike? It could help with long commutes.

What controller are you using? The 48V controller is very robust. The 408 motor can handle 100V. Though I don't know what life to expect from it there though.

the ebikes.ca website has a simulator thats made for just
such a question...check it out

I was able to get the bike going again. It took a jaw puller and a bit of cobbling between the two motors. It looks like a wire was shorting inside the second motor they sent me. I used the armature from the first motor and put it inside the case of the second motor.

As for my commute, I like my mountain bike, but it would be nice to pick up the speed a bit. That being said, I found a bus route that shaves 10 miles and about 20 minutes off my commute. They have bike racks on the front and a ride is $1.50. I plan to take the bus for 10 miles and bike the rest and figure it will get me close to an hour one way. That's more like it.

Element116,
FYI, kudos to you for even considering biking for a 24 mile one-way commute. My commute is 17 km (about 10 miles) and to me, that's far enough even with an ebike motor. On a separate note, I see that your location is Detroit. I've always had the impression that the majority of Americans (especially in the 'motor city') are addicted to their cars and would never consider biking as a commuting alternative. So I'm even more impressed (I'm from Canada by the way)

For anybody that's actually ridden a 408 on 72 volts, how's the acceleration rate? Is it brisk? I'm running 74 volts on a 5303 and performance is perfect for me, but the motor is so darn heavy. In theory, a 408 on 72 volts should top out mid 30's mph which is fine for me, but how is the acceleration?