Will stock 9C 2807 like being powered by 72V 40A controller?

I currently have completely stock 9C 2807, with stock 22A controller. After only a month I've decided that's not enough .

I'm considering upping the voltage (20-22S LiPo) while using HuaTong 72V 40A controller, so I'm concerned about cruising capabilities of 9C. I know I can't dump 3-4KW in stock motor (and wiring) for a long time, but will it be able to cruise at 30mph on level ground without cover holes, without overheating? Actually, should I even consider upping the voltage and power that much with stock phase wires?

I see lot of you exceed 9C 1000W rating by at least two to three times, but I couldn't find any information about cruising capabilities at lower speeds. I've just read at ebikes.ca that maximum continuous power for 9C 2807 is ~600W, and at 30mph it's 1.1KW according to ebikes.ca Simulator.

According to simulator, you can cruise at up to 33.5mph using 84V (20s) and 81% throttle without ever overheating. 70% will get you 30mph at slightly over 1KW.

Yes, I saw that as well, but on the same site it's written that 9C will take only about 600W continuous.

The motor and stock wiring will start overheating at 40a unless you watch the power on hills or vent it. If you replace the phase wires with 12ga it will help a lot. If you replace the wires between motor and controller with 8ga it will really help shed heat from the motor and controller.


I was running a controller at 35a on a stock 9c with stock wiring. Replaced the in-between wires with 8 gauge and saw a 20 degree drop in controller temp. Couldn't tell if motor got cooler, but it had more power and top speed.

I ran a 9c front at 100V 45a for a long time. My experience is that it can take 1500W (15a) in 95F ambient heat all day. Beyond that, you have to use some judgement. I peaked at 4500W and would run for a mile or two at 45mph. Later I opened the motor, and it looked brand new. Keep in mind that around here, the terrain is pretty flat.

itchynackers said:

I ran a 9c front at 100V 45a for a long time.

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You forgot to mention did you upgraded stock wiring? I guess you did if you peaked at 4.5KW.

johnrobholmes said:

The motor and stock wiring will start overheating at 40a unless you watch the power on hills or vent it.

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I'm completely aware I mustn't hammer it on hills or at low revs.

When I first saw stock wires I was like "What the hell?", but nevertheless I tought they would cope. After a month, first time I've touched them today and noticed they get very warm when going WOT on hill after just 10 or so seconds. So if they're barely coping with stock controller (and they really look pitiful) I'm struggling to see how would they cope with three times over stock power.

johnrobholmes said:

If you replace the wires between motor and controller with 8ga it will really help shed heat from the motor and controller.

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I would, but I've never previously worked with DD hubs, and I'm really reluctant to thinker with it, especially as I have sensored controller (more wires), and it would be nice to add temp probe when it's already taken apart, and that's even more hassle.

That's why I'm interested in seeing how much stock wiring (and motor) can take, to weigh in wether I should buy that powerfull controller at all, or should I just stick with stock one (and tune it up a bit, perhaps).

My CrazyBike2 uses a mostly-stock 9C 2807, no upgraded wires, and even before putting the vented covers on it didn't have a problem with pulling 300lbs+ around all the time (bike and I weigh the same, just about), with 48V up to 40A+. Typically it handles about 2KW at startup from a stop ok, which lasts a few seconds and then it's 500-800/900W for another several/many seconds getting up to speed (20MPH), if I keep full throttle until then and back off when at speed.

It doesn't take much power to cruise at 20MPH on that bike, less than 500W, usually 350-400W when I glance at it these days; depends on wind and stuff (mostly flat terrain here).

I don't remember what it took for power when I ran it at the Undead Race at 60-72V, up to 31.5MPH, full throttle all the time I wasn't braking, but it didnt' have a problem with that, either, and I didnt' have vented covers then.

Even now, the windings still look brand-new, so they haven't ever heated up enough to notice, and that's in the Phoenix (and Tucson, for the race) heat, typically over 100F (right now it's usually over 110F and sometimse over 120F, and on the roads at it's height it's probably 130-150F).


It's certainly possible to kill one, though--Dogman smoked one pretty well during the last Death Race in Tucson, thanks to a nearly-flat tire for (several?) laps that forced him to use a lot more power thru it than expected. (but it's possible that motor actually still works and just has desoldered phase wires...that *also* happened to him with another one, which had been heated enough to suspect it was dead, but resoldring the wires fixed it). That fixable fried motor was cooked on hills.


So it depends...with a lot of hills you may well run into trouble. Ventilating the motor may or may not make a difference, depending on how *fast* it heats up inside, and on hills a direct-drive (DD) motor is going to heat more and faster than a non-DD, as more of the power is wasted because it's not going as fast as it needs to to keep the currents down.


I'd say go for it, but...maybe go easy on the throttle on hills, charging up them as fast as you can on the approach, and cutting throttle back as you get partway up and current starts shooting up if you have to (but this will make the hill take longer to do and increase current even more, etc.). I'm not sure how to deal with reducing power usage on long hills--if you can't charge up it with momentum to help reach the top and coast down the other side, it's going to heat the motor a fair bit.

Add a temperature monitor even if all you can do is stuff the sensor into the axle thru the wire bundle. It's better than nothing, and you can figure if it's alarm is going off you need to stop and let it cool off *now*. Possibly pouring icewater over it (with it wrapped in rags or something to keep the water from just running off before cooling it much).

Your stock 9 c should be able to take about 1500 w pretty much continuously. It may eventually overheat, but it will be after you run 600 or more wh through it. So you should be able to cruise at 30 mph, using 1200-1500 watts for ten miles or more easily. At 30, you should remain in the safe wattage zone unless riding into stiff wind or uphill. So maybe back off to 1500 w if in those conditions if you need longer range, even if it means riding 25 mph.

I know from experience, you can WOT it at 20s lipo and 40 amps for 8 miles. You will return with a nice hot motor, but not overheated. Lots of starts and stops will heat the motor more, since you will pull full amps for awhile each start

amberwolf said:

My CrazyBike2 uses a mostly-stock 9C 2807, no upgraded wires, and even before putting the vented covers on it didn't have a problem with pulling 300lbs+ around all the time

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So you didn't upgade phase wires at all? Bike and me add up to slightly over 200lb, so I guess I should be ok in 2KW burst region.

amberwolf said:

Even now, the windings still look brand-new, so they haven't ever heated up enough to notice, and that's in the Phoenix (and Tucson, for the race) heat, typically over 100F (right now it's usually over 110F and sometimse over 120F, and on the roads at it's height it's probably 130-150F).

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I don't ride in temperatures exceeding 90F, so I guess I'm ok with that as well.

amberwolf said:

It's certainly possible to kill one, though--Dogman smoked one pretty well during the last Death Race in Tucson, thanks to a nearly-flat tire for (several?) laps that forced him to use a lot more power thru it than expected.

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Oh I certainly won't race it, and I won't go WOT for more than 30-60 seconds.

amberwolf said:

I'd say go for it, but...maybe go easy on the throttle on hills, charging up them as fast as you can on the approach, and cutting throttle back as you get partway up and current starts shooting up if you have to

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Such strategy is no-go because hills (where I'm going to ride e-bike) are usually longer, and up to 5%, so there's not much point in charging up on the approach.

amberwolf said:

Add a temperature monitor even if all you can do is stuff the sensor into the axle thru the wire bundle. It's better than nothing, and you can figure if it's alarm is going off you need to stop and let it cool off *now*. Possibly pouring icewater over it (with it wrapped in rags or something to keep the water from just running off before cooling it much).

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Well I'll certainly do at least that, if not insert it properly inside. And icewater sollution is a bit extreme .

dogman said:

Your stock 9 c should be able to take about 1500 w pretty much continuously. It may eventually overheat, but it will be after you run 600 or more wh through it. So you should be able to cruise at 30 mph, using 1200-1500 watts for ten miles or more easily. At 30, you should remain in the safe wattage zone unless riding into stiff wind or uphill. So maybe back off to 1500 w if in those conditions if you need longer range, even if it means riding 25 mph.

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Well I guess I should stick to 25mph cruising, just to be on a safe side. After all, I'm not that much in a hurry.

72v is not a problem, but I think 40A on an unmoded motor is unwise. I ran my 9c at 74v 30A with no mods and never had a problem. For months I regularly took 12 mile trips at 40+ mph most of the way. I only stopped becasue I messed up my batteries while charging them, the motor is fine..

So 9C unmoded will take 1.5KW of sustained power nicely. I will then consider snipping one shunt in controller because it has three of them.

bobale said:

So 9C unmoded will take 1.5KW of sustained power nicely. I will then consider snipping one shunt in controller because it has three of them.

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Don't do that. you need to add to the shunt not take away from it if you want to run more amps through the controller.

I was talking about 72V 40A controller. And we discussed here that with stock wiring can't cope with that much power (3KW burst), so the next best thing would be to snip one shunt (out of three) of that new controller and keep power to tolerable levels.

When we're already talking of shunts, I've added 0.6 inch long piece of 24AWG wire (half thickness of original shunts) to shunts in my stock 22A 9fet controller, so could anybody hazard a guess how much I've upped the current limit? I currently have no wattmeter or ampermetar capable of measuring such high currents, so I tried WOT carefully and only on level ground, and it accelerates much better.

alot probably, I added alittle solder to my old 22 amp controller and it can pull 30 amps now. Best(easiest) way to test is with a watt meter on the battery while applying the brakes and WOT.

I would, but I don't have any wattmeter, that's the problem.

On a double shunt controller, I wrapped wire around both for about that much and then soldered. It went from 30A to 42A max and a noticeable improvement in torque.

With this shunt mod it goes much better, but God knows how much current I'm pulling because 9fet gets really hot, so before smoke comes out, I'll better take this shunt mod out and order HuaTong .

If your brain can do the volt amp watt thing on the fly... Spend the $30 on ebay stuff. voltlmeter and ampmeter

Problem is here in Serbia we can't use Paypal, so I'm at the mercy of HobbyKing as I can pay directly with my credit card there. And Turnigy Wattmeter is nowhere to be seen for a month or so.

bobale said:

With this shunt mod it goes much better, but God knows how much current I'm pulling because 9fet gets really hot, so before smoke comes out, I'll better take this shunt mod out and order HuaTong .

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If you can source a very small fan, you can cool that little controller quite a bit by ventilating it. That almost doubles the surface area for cooling the fets by utilizing the inside of the housing, and it cools the other components too. I've successfully used that to more than double factory performance of stock controllers, and that was using a very hard to drive high speed motor.

John

I almost melted down my 9C/MXUS DD motor running 76v ( 20S lipo ) and 36A constant on the flats at night when it was cold. Would have burned my hand if i left it on there for more than a second. That was after 20 minutes of continuous operation.

That is about 3000 watts continuous and this motor was designed for 500 watts continuous..

That is way too much power for this motor. I would say don't run it any higher than 14S - 16S.
And keep the amps around 35a. Should be reliable unless you are riding it in very hot weather.

I would just keep the amps lower unless you prefer acceleration to top speed. More volts = more fun

Yeah but.. there is a point where you need higher amps to cruise..

Like at 36a, i could only go about 37mph on the flats. 72v ( 83V charged ) should have gone about 46mph. I probably needed about 50-60 amps or more to cruise at the speed that 72v can go.

36a x 82v = 2952w constant on the flats.

So let's say 50a x 82v = 4100w constant on the flats at around 40-45mph..
So why fork over for high voltage that you can't use.. That's crystalyte 5xxx series power. the 9C can take peaks of 3000w but it really likes 1500-1750w constant, no more.

John in CR said:

If you can source a very small fan, you can cool that little controller quite a bit by ventilating it.

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Even just opening the ends so air can flow thru it, if it's in a place on the frame where that's possible without getting wet inside, will help some. But the squirrel-cage fans forcing air into one end or sucking it out of the other will do much better.

bobale said:

So you didn't upgade phase wires at all? Bike and me add up to slightly over 200lb, so I guess I should be ok in 2KW burst region.

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No upgrading at all. I repaired them once for a broken wire (cut in a fall on the axle end) but I simply opened the hub and pulled them in further, resoldering them beyond the cut point. Same wires, though. (at the moment I am considering upgrading them, simply because I have to do a similar repair again, and they're already a bit short, but first I have to locate suitable wire of sufficient length out of some other junked item I already have).

And icewater sollution is a bit extreme .

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Sometimes it helps to have it with you anyway, just to cool *you* off, if it's ever hot enough to worry about (or hydrate you, which is usually needed on long rides even if you don't pedal). If you do, you can then avoid destroying a motor that you did push too hard, as I recently did with a geared front hub.
http://www.endless-sphere.com/forums/viewtopic.php?p=447022#p447022

John in CR said:

If you can source a very small fan, you can cool that little controller quite a bit by ventilating it. That almost doubles the surface area for cooling the fets by utilizing the inside of the housing, and it cools the other components too. I've successfully used that to more than double factory performance of stock controllers, and that was using a very hard to drive high speed motor.

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Thanks, but I've decided I'll beter buy generic HuaTong 72V 40A, and then poke around with it, this stock 9FET has 75NF75s, and they do heat up a lot even at 22A, and as HuaTong is considerably cheaper than I paid for 9FET, I'll just jump on the generic wagon .

neptronix said:

I almost melted down my 9C/MXUS DD motor running 76v ( 20S lipo ) and 36A constant on the flats at night when it was cold. That was after 20 minutes of continuous operation.

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I certainly won't have that much power in battery pack to do 20 mins at that pace, at least not anytime soon.

nomad85 said:

I would just keep the amps lower unless you prefer acceleration to top speed. More volts = more fun

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Well I'm not sure about top speed, my bike is not that good, so for now I'm more interested in acceleration.

neptronix said:

Like at 36a, i could only go about 37mph on the flats. 72v ( 83V charged ) should have gone about 46mph.

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How come you managed only 37mph, is your motor slow wind? I easily do 30mph on level ground with 57V charged.

neptronix said:

the 9C can take peaks of 3000w but it really likes 1500-1750w constant, no more.

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As I said in the first post, I was mostly interested at cruising at 30mph, and that was 1.1KW continuous, so I guess I'm within safe(ish) limits there.

amberwolf said:

Even just opening the ends so air can flow thru it, if it's in a place on the frame where that's possible without getting wet inside, will help some. But the squirrel-cage fans forcing air into one end or sucking it out of the other will do much better.

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I don't have any place to put it where it won't get wet, and anyway I've decided not to tinker with it much, and to just go for cheap generic, so if I smoke it I won't regret that much .

amberwolf said:

Sometimes it helps to have it with you anyway, just to cool *you* off, if it's ever hot enough to worry about (or hydrate you, which is usually needed on long rides even if you don't pedal).

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Well I don't do long rides, so I don't need that much hydration.