ebike simulator: why hasn't everyone's hubs burnt up?

[parajared]

Hi,
I bought a 9C hub motor 12s setup with a 50a controller, and I have tried to keep the watts to the motor under 2000 watts in order to avoid overheating.

Recently I have been playing with the simulator at ebikes.ca and I think I may be pushing my motor too hard.
http://www.ebike.ca/simulator/

My commute to work is nothing, but I take on steep hills when I use my bike as a trail riding machine. According to the simulator a 6% hill will kill a 9c 2807 in nine minutes flat, and a 12% will kill it in three. This is pushing 1558 watts according to the simulator.

Even if I limit watts to 1000 and full throttle up a 6% it overheats in 15 minutes according to the sim.
Should I be worried?

***update 8-8-12: VT sensor sucks, can't see readout in daylight, TG3 temp sensor works great, the motor was burnt before I got the sensor in. Motor continued to run crappily for the last several months but died completely about a week ago.

 

[Ykick]

I do similar levels and motor and seems to be okay for my 3300 mile habits. More a matter of duty cycle, me thinks? 10-15Ah battery and stop/go you can push a lot of heat through a 9C. Large battery, hills, sustained high speeds, hot weather, can be much worse, ya know?

'noticed a slight gooey'ness to phase wires when pushed long and hard in hot conditions so I do feebly remind myself: this is a bicycle, this is a bicycle, this is a bicycle, repeat as needed...

 

[MadRhino]

So your motor was virtually dead long time ago, and every mile that you've done since, is a bonus.

 

[parajared]

So your motor was virtually dead long time ago, and every mile that you've done since, is a bonus.

Well that's a bummer. I love trail riding. I may end up burning up my 9c hub.
I think I need a bigger hub or better heat shed. Magic Pie 3 maybe? Hubzilla? Toyota Prius motor bolted to my bike?
no seriously though 1500 watts up a long hill is nothing right?

 

[MadRhino]

So your motor was virtually dead long time ago, and every mile that you've done since, is a bonus.

Well that's a bummer. I love trail riding. I may end up burning up my 9c hub.
I think I need a bigger hub or better heat shed. Magic Pie 3 maybe? Hubzilla? Toyota Prius motor bolted to my bike?
no seriously though 1500 watts up a long hill is nothing right?

I recall some here feeding much more than that to a 9c, and most are still riding happily

Just remember that: The harder you ride, the better you need to be prepared to fix or replace components.

 

[pwbset]

no seriously though 1500 watts up a long hill is nothing right?

I used to pump 2-2.2kw into a measly little Clyte 4011 for about 15-20 minutes straight climbing 1,600ft over 3.5mi for my commute to work. It got hot, but never went tits up on me in over 1,000mi of doing that. I just got a rear 9C 2810 for the same commute that I'm hoping to start up again next week once my new battery is completed. I'll let you know if a 9C 2810 can take 2kw+ for 20min daily or not. If it's not up to it stock I'm going to oil bath it and see if that helps.

 

[keysersoze310]

So your motor was virtually dead long time ago, and every mile that you've done since, is a bonus.

Well that's a bummer. I love trail riding. I may end up burning up my 9c hub.
I think I need a bigger hub or better heat shed. Magic Pie 3 maybe? Hubzilla? Toyota Prius motor bolted to my bike?
no seriously though 1500 watts up a long hill is nothing right?

If you're particularly worried about burning up your motor, just install a temperature probe. Then you'll always know if you're overdoing it and can dial down the power a bit if you're reaching the limit. This way you can get the full power out of your motor and never worry about burning it up.

Or, with no difficulty at all, you could just put a temperature sticker on the motor to give you a ballpark idea of how hot it is.

 

[neptronix]

I think their definition of an overheat is different than ours.

Might be about 100c. Whereas some of us abuse our tiny motors up to 150c-175c - riding right along the melting point and getting awful efficiency as a result.

 

[waynebergman]

Can you tell me more about this temp sticker. Who sells them?

 

[amberwolf]

Depends on the motor--I have twice overheated a Fusin geared hub (meant for 500w max, pushing 500-1200W thru it sometimes for short bursts) so hot that I couldn't touch the outer casing. I don't want to think what temperature it was inside. Both times it was so hot the halls stopped working and the controller couldn't sync to drive the motor, yet it didn't kill anything either time, just slightly darkened the windings. Like a toaster on the lightest shortest setting. :lol:

Dogman actually heated two other Fusins up so hot that they stopped working completely...but it was becuase the solder melted on components on the hall sensor board, and the little SMT resistors and capacitors fell off, preventing hall signals from getting back to the controller. I fixed that, and now both motors still work. Though they are the darker side of toasty.

Dogman also heated a DD 9C so hot that it died, but it turned out to just be a phase wire unsoldered itself, and it worked again when that was fixed.


In the above cases, those would be severe overheat conditions that end your ride. That's what I consider an overheat. If I can't keep using the motor because of it, even if it's only temporary, that's a fatal condition.

If it just gets realy hot (without smoke!) but it keeps working continuously, then it's not overheated yet.

 

[keysersoze310]

Can you tell me more about this temp sticker. Who sells them?

I've seen these recommended in another thread:
http://australia.rs-online.com/web/p/products/0286175/

I actually tried buying a few a while back but they were way overcharging for shipping so I changed my mind. Maybe I should buy a bunch a sell em' cheap on ES...

 

[neptronix]

 

[iovaykind]

The ebike simulator is also for stand-still.. which I don't think anyone has mentioned thus far. Real world you can push quite a bit more into your motors.

 

[parajared]

awesome picture neptronix. Excellent info, that could really save me money down the road.

I think a bbq sensor would be fairly easy to install on a magic pie, or a crystalite, but on a 9c, I'm not so sure. The opening to the motor on the 9c is through a tiny hole through the axle. I mean the phase and hall sensor wires only just barely fit as is (even though they look quite undersized). I presume putting a bbq sensor wire through a 9c axle would involve completely chopping hall sensor and phase wires off, re-wiring everything and somehow trying to wad the whole bundle back in there. Has anyone done this mod before on a 9c?

 

[sn0wchyld]

The ebike simulator is also for stand-still.. which I don't think anyone has mentioned thus far. Real world you can push quite a bit more into your motors.

+1 this... I remember justin saying somewhere that these are 'worst case scinario, with no airflow on a bench' and overheat wasn't 'dead motor' but getting the motor past 110/150deg or something. Also, the load curve of his sim's are worst case scinario too (atleast for a mtb). its basically the load of a upright mtb with low psi tyres, so his overheat times are very conservative.

I'd still suggest adding a temp probe. the Hobbyking VT monitor is the best if you ask me... has a built in alarm + flashing lights, so you can basically ride like a maniac all you want, safe in the knowledge that youve got an alarm to tell you to slow down for a while. You can get the probe to touch your windings too, unlike the bbq probes, which gives much faster feedback on motor temps.

 

[parajared]

Perfect!
It's small, looks easy to zip tie to handle-bars, and it's $7.80. I'm getting one.

*edit: got one- $10.86 shipped
Also scooped up a lyen dc dc reducer $15, so I can plug my headlight, tail light, and temp sensor in and use the e-bike battery instead of double a batteries.

 

[neptronix]

awesome picture neptronix. Excellent info, that could really save me money down the road.

I think a bbq sensor would be fairly easy to install on a magic pie, or a crystalite, but on a 9c, I'm not so sure. The opening to the motor on the 9c is through a tiny hole through the axle. I mean the phase and hall sensor wires only just barely fit as is (even though they look quite undersized). I presume putting a bbq sensor wire through a 9c axle would involve completely chopping hall sensor and phase wires off, re-wiring everything and somehow trying to wad the whole bundle back in there. Has anyone done this mod before on a 9c?

Surely you can fit 2x 24ga. wires down there

You add a temp sensor in conjunction with a phase wire upgrade mod, so you end up already chopping off the wires and redoing them anyways. All my motors have fat gauge after the axle, so this worked out.

Notice that i replaced that thick heatshrink on the wires with some fairly thin stuff? that's one way how you can jam more wire in there. Another trick is to replace the phase wire heatshrink with something super thin.

 

[dogman dan]

Back to the original question.

It's a simulator, and the motor is run differently in the real world. In the real world, it's quite difficult to get a motor to behave the same for a long period of time. You pull spikes, but mostly you really don't run continuously at the same wattage you see on the graphs. So the motor heats, then cools some.

If I am correct, I don't think the sim takes wind cooling into account either. So weather matters, and in the sim weather is set at some temp, but I don't know what temp. And there is no wind.

We all know the best way to cool a motor fast, slow way down, but keep moving. Stop, and the motor heat will actually spike quite a bit when the wind cooling stops. If you stop, and want your motor cooled you have to throw water on it.

So in the real world, the wind and ambient temp cool the motor a bit better than shown in the sim. Generally, in my motor heating observations, I see a tendency for a motor run under 1000w to reach an equilibrium temp where motor heat stops rising. The wind and weather combine to cool the motor as fast as it heats, and the temp settles in at about 150F max. Even in 110 F weather, the motor will still cool enough if it's run not to far from its spec wattage.

Once you go above 1000w, you can still keep a motor at a safe equilibrium temp, but you may need to stop riding uphill to let the motor cool from time to time. Once you go to 3000w, you generally will see a motor such as a 9c go hotter than you want it to, if you run it on flat ground long enough. It gets enough load just from wind at 40 mph, to keep the motor temp steadily climbing. Climb it at 3000w very long, and it really heats up.