Controller Thoughts and Questions ...
I purchased a Navitas 100-36 controller for my mountain bike conversion. It's rated at 30A continuous and 100A max. It has "current and thermal limiting the unit is fully protected".
Used for: 24V 650W Scott (3/4hp) Permenant Magnet DC Motor rated at 30A.
I don't know what my actual load is with a 10:1 ratio or with the 12.68:1 ratio that I plan on changing it to. (there are just too many variables, weight, temperature, friction, hills etc)
The Navitas controller fried the other day.
I emailed the retailer about it and they said that before they issue me an RMA# they need to know the specifics of my drive system.
I emailed back with the information and a general electrical and mechanical schematic of my system.
I'm not very happy with my original choice, I thought it would work well for this conversion. Perhaps I was wrong.
I'm looking at alternatives. If they warranty it fine, I'll baby it and hope it holds up but it sounds like no matter what, I'll eventually need to get another, higher amperage, controller. It's a bummer, the one above cost me $150.
Curtis and Alltrax controllers come to mind but I wonder why there are so many rebuilt Curtis's if they are so good. It probably has to do with using contacts which arc and deteriorate after repeated starts and stops.
I don't know anything about Alltrax other than some of you have them.
I looked at some Curtis and some Alltrax controllers but it looks like I would need to go to a 200A. They sure are spendy!
Any suggestions on a good controller that has a Great warranty? I want one that is definately not going to fry, hopefully it's not going to run me more than $175-$250.
Would something like this work with a 24V system?
Thanks for any info that might help.
I share your disappointment. I have been following your posts the last few days. I have been to busy with work. I make wrought iron outdoor furniture and I am in "season".
Let's break the current "amp" issue down. "And please, anyone out there, put your 2 cents in if I am wrong".
The motor is 80% efficient. Thats about 30 amps. Without doing the math, on a flat road, no acceleration, 18 to 20 mph, with the motor very close to its design rpm the motor will be drawing 30 amps. Up a decent long grade, maybe 5%, the motor will be drawing 50 amps, but, it is no longer in its efficient range, probably 60% effiecent. Probably closer to using 80 amps. IF the motor is not near its peak rpm it will use all the amps you supply it.
I use the alltrax controller npx 200 amps non programable. I chose this controller because it does not spark when it is switched on. This sparking slowly destroys contactors. On the curtis controllers you supply the controller a "pre-current" bypassing the contactor with a wire from the battery to the controller that has an inline resistor. I did not want any current drain, no matter how small, so I chose the alltrax.
Ken at KTA services sent a letter with my purchase of motor and controller that no one makes a reliable controller that is sized right for the scott motors. In this letter Ken felt a 60 amp controller would be ideal. Ken also, on a phone conversation, strongly advised me not to volt this motor at 36 volts.
I am using odyssey batteries. I can supply over 2000 amps for 5 seconds, over 1000 amps for a minute. My fuse is rated at 180 amps. On a cold very windy day. I climbed a long 1/4 mile grade, I am guessing about 4% at 20 mph, 9.6 to 1 ratio, 40 mph headwind and blew my 180 amp fuse.
Now that it is summer, my motor gets very hot, I can hold my hand on it only for a few seconds, it will burn you. I am really guessing here, probably more than 125 degrees and not more than 150 degrees F. My controller, absolutely no increase in temperature. The controller has no heatsink. I do need a method to control current. Fechtor has designed current limiting into some controllers, I will probably start working on limiting my current to save my motor .
So it seems my controller is oversized and very reliable. My motor has been performing well, I do worry about the magnets in the motor weakening. I only have about 2000 road miles of experience behind me.
Well, thats all for now Dave,
I just reread my last post. When I said I had only 2000 miles of road experience, let me expand a little.
All of my riding is on streets. Both to and from work I have to climb a long grade that slows me down from 26 mph to about 21 mph, then a couple of short very steep grades with, of course, stop signs. I am not 2 careful when it comes to throttle usage. In 2000 miles I have had one flat, and one blown fuse. I am going a little faster lately, I don't know why, about 27 mph on the flats. I don't charge my batteries properly, I use a 24 volt solneil charger and am using four batteries and connect the charger to charge all the batteries at once. By the book, 400 discharges at 15 miles a discharge should mean my battery pack will last about 6000 miles. I thought my problem would be with the batteries. It looks like, after 2000 miles, heat is going to degrade my motor. My batteries seem to be better than when new. I don't think this is a temperature issue in the batteries, they are always inside and are only outside for the 20 minute ride to work. They might be 10 degrees max warmer than in the winter. I should change that sprocket to a 13 tooth for a 10.5 to 1 ratio, but, I will get more chain noise doing that. This is the main reason I hav'nt changed that sprocket is that the chain was silent when I had a 15 tooth, the 14 tooth is, I don't know how to describe this, is bending the chain just a little bit more which causes a whirring sound.
EV Controller Collaborative Hand Books are in the works, we just need to figure out how many Hand Books are needed for the various type of EV Controllers.
Any suggestions on how many we should start with?
Thanks, good idea. We'll probably start with E Bike Controllers, since that seems to be where the most inquiries are located, and link it to Building E-Bikes Collaborative Hand Books rather than lump them all together.
Hope I'm not making you feel like your on a tightrope with my writing style. I try to get as much in as I can before my keyboard locks up on this forum. I think it is a motherboard issue, just not ready to buy another computer when usually it happens just here. My dad is degreed mechanical, electrical, hydraulic and degreed in electronic controls. My dad can make me feel like I am on a tightrope. He is retired, still answers the phone, "Johnson". I have worked around him for all of my life and he just assumes I know what he is talking about. I learned a lot from him, and from 2 1/2 years of physics in college. I never liked electricity 25 years ago when it came up during my studies, I learned enough to pass the tests. I liked hydraulics and thermodynamics, earthmovers and big engines. Wish now I had studied more, the electrical elements that I was forced to learn dealt a lot with electric motor design.
Both the Bidwell book and Ken at KTA services put the fuse just before the main on/off switch, "contactor", between the battery pack positive and the contactor.
So, battery pack + cable attaches to the fuse, the fuse attaches to the contactor, the contactor cable then goes to the battery + on the controller. This is confusing, I just don't know how Chas Stevenson draws a diagram. Hopefully he will draw it for you.
I hope you can get over that tightrope feeling and get back on the bike.
I guess I should start my own blog. Main reasons that I have not. My computer skills are weak. Converting files is a real task for me, ie posting photograghs. To make a drawing and posting I found to be impossible. I used to have a program called coral draw which would convert any cad drawing into code to run machine tools using xyz axis or into jpeg images. It was a breeze to use. When I use my kodak camera to take pictures its own software steals them, I think it is kind of a default issue, whatever opens the pictures first hoards them. If I use different software to open my kodak pictures I loose clarity, kodak must be putting a little code in the image that makes it better to use kodaks proprietory software. Kodak pics are tooo big to post. So, I use image shack to re-size. I like things to be plug and play.
My fuse does not have a delay, it will blow at 180 amps. My alltrax controller is not programable. The npx 4834 has a built in ramp up to limit current, ie, acceleration. I can feel this ramp up from a stop. I twist my throttle fully, I accelerate nicely, then at about 10 mph I can feel a good increase in power as the controller gives out more current. I went on the alltrax site, they list all of the data for their atx line, but nothing for the npx. The atx series are programable, I have not looked at their site in months, but, I am pretty sure limiting current is programable. Ramp up is definitely programable. If you investigate their website it should answer all of your questions on their controllers. In fact, I am going to relook there now.
No problem on the Computer skills, help is available from your world wide Moderator Team.
If you are planning to use images, all we need you to do is upload them to http://visforvoltage.org/user/65/imce , and we'll insert them where you want them for you. (Example: Insert 1stbikevc3.jpg here) You can also send them directly to us at firstname.lastname@example.org
You can also contact one of your Moderator Team Captains to set up something.
If you share the knowledge, we'll provide all the necessary Computer skills.
The VisforVoltage Forum will resize the photos for you when you upload them so they are the correct size for posting. Please give it a try, we would love to see some pictures.
My Bicycle Pages
You asked earlier if there was a drawback to getting a controller that was too big. I am not completely sure how the controllers you are buying are set up, but I do know that in order to overcome the capacitance of the gate in the power driving mosfets, a driver circuit of suitible size must be used. If too small a driver, it will take a bit longer to activate the base threshold energy, and the mosfet will not be able to swich on and off as quickly. For a 200 amp controller, this could be as much as 6 amps of power to drive the mosfet! So the bigger the controller, the more power it takes to run. This is a little intuitive, but useful none the less. I gues I would just figure out what your max energy usage will be (motor at stall is an extreem case) and have a good safety margin.
Well.....I am no electrical engineer, But I do have an engineering degree and love to tinker around (so feel free to correct me anybody that knows more than I do, and I am sure there are plenty) so here goes my advice based on your questions as far as what I know.
"Do you think a fuse placed between the batteries and the contoller will help if it is rated less than the controller maximum rating?
What about a fuse between the controller and the motor? Or both?"
There are two main systems within your setup. There is the PWM (pulse width modulation) system that runs at farily low amprage, and there is the power system running from the mosfets to the motor (with the battery as a supply of course). Both of these systems are running in parallel to each other. BUT...Each system alone has the main components running in series, which means that the amprage across each component (especially in the power mosfet section which is of the most concern) will be virtually the same. This means that the amprage at the battery to the controller will be roughly the same as the controller to the motor, will roughly be the same as the amprage from the motor back to the battery. (This will not be exact due to the driver circuit, temp control and other power drawing sub circuits, but these will be small).
SO...theoretically it does not matter where you put the fuse in these parts of the circuit, because if the power is high in one part, it will simultaniously be high in the other parts as well. BUT...and isnt there always a but???...many controllers use a large capacitor to smoth out the PWM square wave, so that it isnt so "sharp" between on an off cycles. This means a slight delay between power delivered from the battery through the controller to the motor. So high amp draw goes fromt he battery, charges up the capacitor (this is an example of a power spike) and the capacitor levels it to an avarage power, and then a bit later delivers it to the motor (not sure if there is an acutal delay, however the point is that there is no voltage spike that is very severe). Your sensitive piece of equipment is the controller, so you probably want to protect between the battery and the controller. Im sure though that putting a fuse between will be redundant, but its not going to hurt anything.
"What about additional cooling (a fan) to disipate heat from the sink, do you think this is a wasted effort since an overload situation would tend to happen rapidly rather than over a long time span?"
the overload may be a quick occurance within the circuittry of the controller, howeve if you have a really beefy one, it could be a slow process that builds up heat in the motor. My advice would be, dont take chances, heatsink everything, more than you think you need. The cooler the system runs the longer the component life, and the less chance of a blow out.
"I will be changing my reduction ratio from 10:1 to 12.68:1 which should help lessen the load on the system."
As you probably know, power, is amprage times voltage. or in motor terms, torque times speed. So changing the gearing ration does nothing, a ration of 2:1 with 10 amps and 10 volts is the same as a ratio of 1:2 with 10 amps with 10 volts ( 10 x 20 is the same as 20 x 10) so gear ratio doesnt really matter that much. However remember that when it comes to betteries, more voltage and less amp hours will go further than high amps and lower voltage.
Again, I could be mistake on alot of this and would value input. but I hope this helps.
Yea, you got it right, at stall the motor is stops transfering energy into kennetic motion, and begins to act like a large resistor, with low impedance, you can figure out how much power it will want to draw using homs law. Test the resistance of the motor you will use... and use the formula Voltage = amprage x resistance, solve for amprage (as you know your voltage) and you will find out exactly how much amps your motor will draw at stall full throtle. But yes, a lower gearing ratio will help against stalls...and take your top speed down a notch proportionally to the ratio. This can be good and bad, In flat areas, you are getting alot of torque but that same energy might be better used for top speed (there will be a sweet spot where your torque, rpms your weight and wind and rolling resistance all balance out to give you maximum efficiency). But in your case, protection from hills sounds important.....of course you could always do what I do up hills.......pedal.
Went to the Alltrax site. It has been extensively updated since I last visited. This is a very young company, started in 2001. This may be the reason they have not had has many controller failures as Curtis.
It is worth going to their site and spending an hour or so. I educated myself on my own controller. Looks like Alltrax wants a pre-charge circuit across the contactor now, before they advertised that the x in npx or axe meant sparkless contacting. I will have to get with Ken at KTA services where I bought my controller to clarify this.
Specs for my npx 4834 controller. 300 amps peak, 275 amps for 2 minutes, 125 amps for one hour. Ramp up rate is 1.5 seconds.
Rating on my Scott 1hp motor, from the motor plate, 41 amps continous.
Rode my bike as hard as I could last night, full throttle at each start. 17 stops from work to home. 5.7 miles. At the end of the ride I put my hand on the motor, was able to keep my hand on the motor for 15 seconds before I felt I would be burned. Outside temperature about 90 degrees. From what Fechtor says, unless spit sizzles on the motor, most magnets will not degrade. So I feel my motor case temperature is probably a little less than 125 F and I should be in the higher end of the safe zone.
Controller, no perceptable increase in temperature.
To repeat on my gearing, belt motor sprocket - 21 tooth, jackshaft belt sprocket - 64 tooth, jackshaft chain sprocket - 14 tooth, wheels chain sprocket - 45 tooth. Gates pg2 drive belt 15 mm, #41 chain final drive. 9.79 ratio.
When I had a 15 tooth jackshaft sprocket, for a 9.14 ratio, I did not have any drive noise, but, the bike did not have as much top end speed and did not have good acceleration.
With the current setup, 14 tooth sprocket, I don't like the chain noise, Stanton Inc. now has a 48 tooth wheel sprocket, I think I'll try that for a 10.45 ratio. The results hopefully from this setup will be I go faster and decrease my motor temp. The chain noise (I just don't like hearing it, it's not very loud) will be eliminated. I will need to put that 15 tooth sprocket back on which will mean a different jackshaft belt sprocket.
I looked at htd belts, I chose the Gates pg2 because of a claimed 3 to 5 db decrease in belt noise. My belt is reasonbly quite and they seem to be very durable.
Thats all for now
Answer to what to add to the controller page:
The axe product family (progamable) and the npx product family (nonprogrammable). These controllers are for brushed series wound motors, including permanent magnet motors like the scott, etek brushed, pmg, advanced dc, and lemco motors. The other product families are for shunt wound and other types of brushed motors.
Is this correct?
AXE Mini Manual [Doc100-004-A_OP-AXE-Mini-Man.pdf] Revision A, 439kb, 6/29/2006 [Series Motor Controller] and NPX Mini Manual [Doc100-013-B_OP-NPX-Mini-Man.pdf] Revision B, 464kb, 8/30/2006 [Stock Series Motor Controller]
Moderator Team Captain
You've gone a long way on this already, but a few thoughts:
"I will be changing my reduction ratio from 10:1 to 12.68:1 which should help lessen the load on the system."
As you probably know, power, is amprage times voltage. or in motor terms, torque times speed. So changing the gearing ration does nothing, a ration of 2:1 with 10 amps and 10 volts is the same as a ratio of 1:2 with 10 amps with 10 volts ( 10 x 20 is the same as 20 x 10) so gear ratio doesnt really matter that much.
You're right that reducing load will avoid that stalled on near stall state. It looks like the nominal 27A load (650W) was at full speed. At stall, the draw is going to go way up. In addition to figuring out stalled current from Ohm's law, you can get an idea of what's happening underway with a BrainDrain, or test in a shop with the Craftsman clamp-ammeter 82372
If you're in contact with the motor supplier, you should be able to get information on what current limiting the motor needs.
I have just bought an electric bike. There are a few un-used cables on the controller, and I am trying to figure out what the function might be. Would you be brave enough to make a "guestimate" on what the function might be for each free or un-used cable?
Please see my picture attached to this forum for details: http://www.pedelecs.co.uk/forum/electric-bicycles/1022-control-box-cabels.html
thank you very much,