250w motor with 500w controller?

[g1nko]

I set up a '72 Peugeot with a Bionx 48v system and I really love it. Due to the nature of the Bionx system, that really required little thought and little planning. I want to convert my '11 Workcycles Secret Service, as well, and this one, I'm finding, requires a lot of thought and a lot of planning.

I want to keep the nuVinci n360 hub on the rear, so I'm going with a front hub motor. Since I also want to keep the Shimano Roller Brake on the front, I'm pretty much channeled into using a Q85 250w motor which I plan to source from BMS Battery. I'm resigned to losing my front dynamo hub for my B&M lighting system in the process, but I'm hoping I can keep the lights and power them from the battery.

I liked the price of the LiFePO4 36v 10ah and 12ah batteries from BMS Battery, but was shocked at the $280+ shipping charges. I found a North American source for the batteries/case/rack that will save me $$$ on the total cost. They're even offering to ship a 500w controller for free. Here's where my ignorance kicks in: I know I can't use a 250w controller with 500w motor, but can I use a 500w controller with a 250w motor? Or do I need a 250w controller?

Also, I ruined a nice IQ Cyo by attaching it to the 6v auxiliary output on the Bionx battery, so I'm a little shy of trying again. Again, my ignorance is showing as I'm not sure what fried the Cyo (flashed bright for a second, then continued to stay light, but much dimmer), but I'm suspicious it has something to do with the output from the dynamo hub being AC while the output from the battery is DC.I've tried Googling "convert dynamo light to battery" but I'm not getting much. Anybody done this successfully?

 

[dogman dan]

First of all, a 250w motor should be able to handle double that rating with no big problems. Pretty small motor wires can still carry 500w IMO.

However, there is an issue here with how they rate controller wattages. It's nearly random. The identical controller would produce differing wattage depending on the voltage it is run on, and in addition, some vendors will call anything any wattage to make the sale.

Find out what the controllers amps limit is. That number times the voltage you will use, is the max potential continuous wattage. For 36v, which is actually 42-44v fully charged, a 10 amps controller on that motor should be no problem at all. 400-440 watts. 400w is enough wattage to reach 20 mph, if the motor windings max rpm allows it.

As for the lighting, you would need a dc to dc converter to get the right voltage to it. I'd just use a second rechargable battery to run the lights myself. Nicads might be the most convenient.

 

[wesnewell]

Watt ratings on motors and controllers are continuous duty cycle ratings. Not max ratings before they blow up. A 500W controller could put out 1000W or 4000W depending on it max amp rating. A 500W controller with a 40A max on 50V will draw 2000W. VA=W. Most motors will take 5 times or more of their watt rating for short periods of time.

 

[friendly1uk]

I know I can't use a 250w controller with 500w motor

I do. I have a 500w cst and 6 fet controller. It has a 15 amp limit, and I use 44.4v, making 666w. However, a 6 fet won't generally take 48v.

Edit: Converting a 6 fet is not a lot of work if you can solder.

 

[d8veh]

A Q85 with the BMSBattery 500w controller will melt before you get to the end of your road. It's a tiny motor. 15 amps will be about the max. Some forum members tried the 22 amp 350w KU93 with the Q100, which has a higher rating, and they didn't get far.

 

[g1nko]

Thanks; there's some good info there.

I ended up buying a 36v 10ah LiFePO4 battery for $260 delivered. I also ordered the Q85 motor, again, because I want to use my existing roller brake and the idea is for commuting at a reasonable 15-20mph clip, not going 40mph.

I passed on the 500w controller and picked up the 250w S06S 250w controller from BMS.

I still want to pick up a Cycle Analyst v3. I really like the torque sensor with the Bionx kit. It works so well, I don't even have the throttle installed on that bike. I'd like to try and duplicate that. Since the S06S is a "torque simulation sine wave" controller, would pairing that with a 12-magnet PAS work similarly to the much more expensive THUN unit? Or is the THUN the way to go?

 

[Drunkskunk]

The THUN is the only way to go if you want something of the quality of the Bionix. Those magnet rings don't sense torque, and no amount of simulating it will ever be as good as really sensing how hard you're turning the crank.

Since you're considering a THUN and a CA, you should also consider a controller with a direct connection for the CA. that gives you greater flexibility and control

 

[NeilP]

I do. I have a 500w cst and 6 fet controller. It has a 15 amp limit, and I use 44.4v, making 666w. However, a 6 fet won't generally take 48v.

Nonsense...number of FET's is irrelevant to voltage
The number of FETs has no bearing at all on the voltage it will take .. it is the type of FETs and capacitors and component values that determine the voltage that the you can use.

I run all my little bikes with 6FET 4110 controllers at 20 series, so 70-84 volts, only occasionally running at 24 s (100volt) if I want a bit more speed.

 

[friendly1uk]

I do. I have a 500w cst and 6 fet controller. It has a 15 amp limit, and I use 44.4v, making 666w. However, a 6 fet won't generally take 48v.

Nonsense...number of FET's is irrelevant to voltage
The number of FETs has no bearing at all on the voltage it will take .. it is the type of FETs and capacitors and component values that determine the voltage that the you can use.

I run all my little bikes with 6FET 4110 controllers at 20 series, so 70-84 volts, only occasionally running at 24 s (100volt) if I want a bit more speed.

Thanks Neil lol
I said generally a 6 fet controller will not handle 48v. Which is true. I also said he could mod one, which between you and me means high voltage caps and fets, but I didn't tell the OP this as he is not going to do it. If by some chance he is interested I would of painted the whole picture. Rule of thumb though, If he is selecting a controller for 48v then don't get a cheap 6 fet. They are aimed at typical 36v installs and the capacitors won't like over 50v although for his needs the fets would be ok. Well worth changing them though. They would be a weak point otherwise.

It was not nonsense, You just didn't read it properly.

 

[NeilP]

buy saying

generally a 6 fet controller will not handle 48v.

is implying the number of FET's determines voltage..

You can't say that, it is just wrong. Implying that number of FET;s determines voltage is nonsense, no "Generally" about it. I have three different bikes all with different little controllers all 6FET and they all can handle up to 50 volt....I also have another 4 on the bench not fitted, not even unwrapped, from e-bay all capable of 100volts

Going on the controllers i have here, you would have to say that Generally all 6 FET controllers can easily handle up to 100volts, but soem are only good to 50 volts.

As I said, nothing to do with the number of FETs all down to component values

 

[ddk]

lol- all my 6-fet controllers are good to go up to 60V, therefore 6-fet controllers are good up to 60v :wink: (j/k)




except when they're not.
I use 23A-30A controllers running 40V-58V on my little geared-hub motors, but I've -0- experience with a Q85.
Mine are all MUXUS 350s and Bafang 250s
I've yet to melt a motor (knocks on organic material that simulates "wood" )

 

[sammyg]

Hello all,

I have the same question yes I am new at the game but do have a 12 FET 4110 Mark II Extreme Modder LYEN Edition Controller that was set up for a 500W hub motor with a 48V 15 Ah lifePo4 and cycle analyst. and want to use it on a 250W motor rated at 49V all due to some activity from the things that like blue.
Can It be done ?
Would running the C.A on a lower power speed make it work?
Yes, sorry for not getting the answer in the first post.

 

[NeilP]

Hello all,

I have the same question yes I am new at the game but do have a 12 FET 4110 Mark II Extreme Modder LYEN Edition Controller that was set up for a 500W hub motor with a 48V 15 Ah lifePo4 and cycle analyst. and want to use it on a 250W motor rated at 49V all due to some activity from the things that like blue.
Can It be done ?
Would running the C.A on a lower power speed make it work?
Yes, sorry for not getting the answer in the first post.

Hi
I see this is your first post.

First, please go to your user profile, and add your location, so we can get an idea of where you are and the language you speak. If English os not your native language, we can make allowances when trying to understand what you ask. and also there may be others in your local area who can help. Also helpful to know when recommending suppliers of parts


For instance:

Would running the C.A on a lower power speed make it work?

Is pretty meaningless to me. Maybe you know what you mean, but I am not sure. I can take a guess, but lots of time and typing wasted if I guess wrong.

the CA will work whatever the speed or power of the bike, and may only affect the oration of the motor, depending on the model of the VA..a V2.23 or a v3



The motor will work fine on that controller, at anything up to 98 volts or so.

How long the motor will last at very high power levels is another question completely

Some hub motors are 'labelled' as 250 watt to comply with regulations, but will happily take 5000Watts, and 10,000 or more peaks.
Other will get fried very quickly at 1500Watts.

A geared hub motor will take less power before something breaks, like one of the gears.


Need more info from you first.

 

[dogman dan]

Just limit the amps on the CA, if you want to run the motor at 500w. Using the value 50v for the voltage, set the amps limiter on the CA to 10 amps.

Then your 2000w-3000w capable controller will deliver only 500w to your little motor. If that works fine, you could likely get away with a few more watts. 700w or so sounds reasonable, as long as you don't weigh 250 pounds.

 

[sammyg]

Excellent. Great Thank for you answers, I will limit the amps on the CA and see how is all goes.

Also I will do the profile thing soon.