Im so angry, because Ive just blown another controller on one of my bikes. They are so easily frazzled - all I did was disconnect one of the brakes and connect the wires so that the break cut out wouldnt be active. Goodness knows why that affected it.
Anyway last time this happened I just stripped out all the wires and connected the battery into the motor, with one of the wires running up to a push button on the handlebars. It was great - never went so well. Jerky when u start tho!
However having all 30amps running up thro a push button meant that one day the button unexpectedly welded shut and I went into the back of a lorry.
This time I would like to find a simple foot switch to go inbetween the battery to motor set up. Are there any simple variable resistor type switches that would allow me to get a graduated start without me having to delve into the merky world of unstable controllers?
One way of improving your milage is to always disconnect the main battery before doing any work on the controller.
If you insist on a resistor-based control, you are actually going down a path that was used for decades in trams (some still used in daily traffic) and other electric vehicles. For example, you could add a resistor in series with the motor, and a switch to bypass it. That way you have two speeds. The resistor and switch will have to be large. You could add more switches and resistors if you want more steps. Electric vehicles of the era could have a whole network of resistors and switches like that, and with clever selection of the resistors and switch logic you could have say 10-20 steps. Often this was combined with several windings on the motor (your motor probably has only one winding). If you ever go with an older tram or subway you can actually feel the stepping as speed increases.
One reason your switch fails can be the inductance of the motor. When you turn the power off, the motor will briefly continue pushing current through the switch, and there will be an arc. The arcing will destroy the switch after a number of operations. To reduce this arcing, you can connect a so called free-wheel diode, in parallel with the motor (directed so that normally there is no current through it). Any diode that can take the voltage and peak current will do.
In any case, all this involves many mechanical parts and will be more expensive and less reliable than using a controller. And less efficient, since the resistors take power.
Thanks for useful answer. Perhaps u havent had as many problems with controllers as me, but I think their flimsy design makes the real cost of electric bike ownership high, because Ive seen so many 'written off' as not working when its just down to the controller.
I think the trams had it right lol!
where could I get a variable resistor from that could cope with 30amps. I dont care about the 'wasted power' as Im usually full on or full off. Anyway that would less than waste the heat produced by the controller.
I even thought of just making my own switch out of two metal plates that can be pushed together - but would be much easier if there was something already made
one other thing, about that arcing, as my bike doesnt have a freewheel, wont the motor be trying to generate current all the time when its rolling and the switch is off? I note u mention its 'briefly' trying to push a current back?
IMHO there needs to be a move back to a physical switch invention, these controllers are holding back development of cheap electric transport. Who ever thought having a few semiconductors controlling many amps of power as a good idea anyway?
I think the manufactures like them because they can sell u a bike for £1000 then charge u £400 every six months to replace the controller! Im wising up to this wicked Scam lol!
colin9876,
Apparently the controller you had was designed to control the current to 30 amps. That is the only reason the motor only pulled 30 amps. I believe you are assuming some very bad information. The controller is your friend not your nemesis. The real problem with using a switch and no controller is the motor will draw max current when the switch is on. If the batteries are capable of putting out 100 amps the motor will draw 100 amps as soon as the switch is turned on. Motors are dumb they have no way to regulate themselves. Look at it this way, a motor is nothing more than a very long piece of wire. If you take 1000 feet of wire, lay it out in a big circle and connected the ends to a battery you would have a short circuit. Lots of amps would flow through the wire until one of 3 things happened.
1. The wire would get hot enough to melt in two breaking the connection.
2. The battery would get hot enough to explode, in your face.
3. The battery would discharge rapidly to 0-volts and be worthless.
Another item I think you need to know is "Current (amps) equals torque", "Voltage equals RPM". Adding more amps to the motor will not make it turn any faster. This just makes it get to top speed quicker. Adding voltage will make the motor turn faster or give you more RPM.
If you take a 24-volt motor that runs at 2600 RPM and add another 12-volts to it so it is now running at 36-voltage the RPM of the motor will increase to something around 3800 RPM. This is know as over volting the motor, I am sure you have seen that term here on V in other posts.
I have one e-bike which uses a 24-volt motor. I replaced the controller with a 36-volt controller and added another 12-volt battery to my pack. With the 24-volt battery pack and controller @ 26 amps the bike would top out at around 18 MPH, with the 36-volt battery pack and controller also at 26 amps the bike tops out at 23 MPH. I have over 800 miles on the 36-volt conversion and the motor is still running great. If I did not have a controller on this bike the motor would draw over 100 amps and get to 23 MPH very fast, if the motor did not toast in the first 8 seconds, then the motor would let go it's magic smoke and the ride would be over. Using a switch as your throttle is both dangerous and waste lots of power and can cause your batteries irreparable damage.
I have 3 bikes running using very inexpensive scooter controllers and have never blown a controller. I even connected one backwards one time applied power, saw smoke, disconnected it, reconnected it the right way and it still works. I have over 500 miles on that controller after the mistake. Here is where I got my controllers. I am not affiliated with this site. You will need to scroll down to see the controllers.
Grandpa Chas S.
+1 to Chas.
It may have been a 30A switch, but the motor will have been drawing a lot more current than that depending on voltage. I'd say upwards of 100A easily if you were running 48V or better. You'll get going quick, but that's really hard on everything from the batteries to the motor.
The relative lack of speed control and efficiency compared to a controller would be...not so good for higher-powered vehicles, and brushless/induction motors can't even run without a proper controller.
There ARE large wirewound/heatsunk resistors like that, but they're very expensive and heavy, not to mention ill-equipped to be adjusted while riding something.
IDK what happened in the past, but even cheap controllers are fairly reliable, brushed ones in particular. I've never had one break, myself, save for one due to human error (backwards battery). My recommendation would be to give it another shot.
The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai
Thanks - that explains alot. Probably also explains why NiMH batteries always failed on me - probably the SLAs were the only ones that could cope with my abuses.
One more thing, as V=IR, doesnt ur analogy 24v 26amps mean that by physical laws if u up the volts to 36 u must also up the current x1.5 to 39amps, as the resistance of the motor hasnt changed?
Old fasioned golf carts worked like you describe. they had a big contactor that would turn on various resistors for three speeds. The contactor was huge to deal with the sparking and weighed about 10 pounds. Not real suitable for an ebike. Brushed controllers are so cheap, shop around for one you like better than the one you have been using.
Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global
Thanks again - one last thing when u say 'brushed controller' does that mean the controller has brushes in it, or that its for a motor which uses brushes?
My bike is an standard bike with a 450w 36v motor attached to the frame, chain drive to the back wheel. Is that likely to be a motor with or without brushes?
colin9876,
From everything I have read about your bike here I would guess you have a brushed motor. To know for sure just count the number of wires coming out of the motor if it is only 2 then it is a brushed motor. A brushless motor will normally have either 5 or 7 wires.
I have been thinking about this. If I remember correctly the switch on the brake would close when the brakes are applied. So by connecting the wires together you are in effect telling the controller the brakes are on all the time. Try breaking that connection and see if the controller returns to a working status.
Grandpa Chas S.
Spot on! It works now. I just assumed the brake circuit would be be broken when the brakes are applied - but as u say its the other way round - so just leaving the wires unconnected fixed it!
So if I used a relay operate the button to motor circuit, although I would then avoid my button switch fusing issue are you still saying I would have problems? OK the motor would always operate On/Off at the batteries MAX current but would that be a proble,?
Incidentally in my 36v system could the power for a relay come from my SLA battery pack, or would it be better just to have a small 9v battery for that?
There are 2 problems with this type of operation.
1. Damage to the motor could occur due to excessive heat problems.
2. Damage to the batteries in 2 ways:
Using a relay would not be a good idea. A contactor would need to be used. This is a very large relay designed to switch large inductive loads (i.e. motors). Look at the golf cart industry and find a contactor with a 36-volt coil so it can be connected through the push button switch to a 36-volt battery pack. Using a small relay could cause a problem if the contacts fused together. Full power with no off switch is never a good thing.
Grandpa Chas S.
P.S. Glad to hear your controller is working again.