Cheap controller, dumb question

[Chalo]

I'm putting together a very cheap, very simple, easy to operate e-bike for my girlfriend. It uses a Q128 front hub motor. Mechanically, I've had the thing sorted out for a while.

I had a small pile of suspect BLDC controllers that I hoped to use one of, but I was unable to get anything but smoke out of them. So I got a cheap 350W controller on eBay:

http://m.ebay.com/itm/36V-48V-350W-Electric-Bicycle-E-bike-Scooter-Brushless-DC-Motor-Controller-/371239291127

I replaced the connectors I'll be using with either Powerpoles or JST-SM plugs. Except for the battery connector. The connector as furnished contains three wires, not two. There is a fat black wire and a fat red wire, which I assume are to carry juice from the battery. But there's a second red wire, smaller gauge but not tiny, in the same plug.

I don't know where to connect the second, smaller red wire. The diagram from the eBay listing is not of any help, except that it shows no enable/ignition wire pair.

I'm all ready to test this thing, but I don't know whether I need to crimp the small red wire along with one of the power leads.

Any advice would be appreciated.

 

[spinningmagnets]

Since the connector for the battery has only two sockets, the small red wire is energized every time that controller will be plugged in. That wire is located external to the case to make it easier to add an ON/OFF switch.

Cut the middle of the thin wire and add any DC rated switch that can handle the volts you plan to use. If for some reason this is wrong, and doing this fries this controller, I have a spare I can send you at no charge.

 

[Chalo]

Thanks for your prompt advice. While I was waiting for someone to bite on this question, I clipped the large power leads in place, but the motor did not respond to throttle input. So I attached the small red wire to the + terminal and it came to life. I put in spade connectors as a dumb switch for the moment.

I appreciate the help.

 

[Rassy]

I didn't quite follow what SM said, but I think it might be just me. In my experience the smaller red wire must be connected to the battery positive for the controller to work. You can either hook it up permanently or via a switch as SM said.

I don't have a spare controller to send you.

Edit: Okay, I see you got it sorted while I was typing.

 

[e-beach]

Ok a dumb replay because I can only figure the small red wire does what has already been stated and found to work. But here is a diagram that seems to show the type of wiring needed.
http://www.elizabethrudolph.us/e-bike-wiring-diagram

 

[spinningmagnets]

Although it will certainly work to use an on/off switch that carries the full current of the system through it (as in the diagram above), such a switch must be rated for high currents, or it will be permanently self-welded into the "on" position. By providing the thin wire, a positive voltage is provided to a single FET that is located internally to the controller case.

Either option will work.

 

[Chalo]

I got the bike running. It's not fast or fancy-- but it is fun and easy to ride, and my entire outlay for it was just under 100 bucks (plus a lot of stuff I salvaged for free, or had left over from other projects)

 

[d8veh]

The thin red wire is what many call the ignition wire. It should be connected to the battery positive, through a switch if you want to switch the controller on and off. When switched off the leakage is so small that you don't eed a separate battery switch, since you already have one at the mosfets. It carries the power for the controller and the sensors (throttle, pas, brakes, halls, mosfets and cpu). The main power goes direct to the motor but it's blocked by the mosfets. Only the cpu can open the mosfets tolet the power reach the motor. That red wire carries about 100mA. It gets cut down by the big resistor, then by the 12v regulator, then by thev 5v regulator, which is the voltage at which all those things mentioned above work.

Running a nice motor like the Q128 with a crappy controller is a wasted opportunity. A decent controller, with a PAS, like the one from PSWpower, will transform that bike into something that's really pleasant to ride. I thought you were the one that's always preaching that it pays to get proper quality, Chalo. IMHO, it applies more to the electrical system than the bike itself.

 

[Chalo]

I'm not sure what there is to distinguish a crappy controller from a nice one, if they both turn the motor when you twist the handle. PSW Power has good pricing and seems to be worth trying out in due course. My prospective upgrade from a salvaged battery and a $16 eBay controller was going to be one of the bottle batteries with integrated sine wave controller from BMS Battery.

I am sure that PAS isn't really applicable to this bike and its rider. I would want it on my own bike, but that's another story.

 

[motomech]

That controller may turn the motor over, but that's about all that can be said for it. It would have been considered bare bones 10 years ago.
She may not need(or want)a sinewave/SLCD display, 5-level "Torque Imitation PAS controller, but a modern square wave w/ the 3-speed LED display, like this one from Elifebike would be a big improvement;

http://www.ebay.com/itm/36V-48V-500W-9MOSFET-ebike-Electric-Bicycle-Brushless-Motor-Controller-with-LED-/222373438906?var=&hash=item33c67d65ba

It features;
Soft start and quiet operation
Convienent on/off button w/ timed turn off
3-speed limiting
cruise control
LED "fuel gauge"

PAS is more than a way to pedal along, it offers a way to give the rider's wrist/thumb a break.
Even if PAS is not installed, setting the cruise and adjusting the speed w/ the limiter and pedaling "on top" of that, is a good way to have a "poor man's" PAS
And the "fuel gauge" is more useful than one would think a 3 lite LED could be. 3 lites when "full", then 2, then one and finally, w/ about a 1/4 left, the last lite starts blinking. I spaced out the other nite and was heading away from home when the blinking caught my attention. I had left w/out really ck'ing my batt., thinking it had more charge than it really did. I would have been pedaling my guts out if I hadn't been alerted.
Lastly, the linked 9-FET controller would be a much better match for the Q128 than that anemic 6-FET. That genaric you listed doesn't give much in the way of specs, but I would think it's a 12 or 13 Amper. There's two versions of the ELB 9-FET, a 17 or a 20A. Enough to actually climb a hill, but w/. the soft start, not be overly powerful to be hard for her to control. If you wanted to stay w/ a 12 A controller, you could have ordered a Q100.
I need to use a square wave because the sine waves don't care much for my odd LiPoly Voltage and I have used at least a half dozen, everything from a basic genaric, to the mid quality BMS Battey KU series to Infineons and these low-cost ELB units are far and away the best.

Down-sides? Well possibly two. The 9-FET is larger than the 6 Fet and if the cruise is to be used, at least one Ebrake would have to be installed. But there are inexpensive and easy work-arounds, especially for mechanical systems.

 

[Alan B]

Just to be precise, the thin red "ignition" wire powers the voltage regulators that feed the logic in the controller. The thick red wire feeds the capacitor bank which in turn feeds the power FETs that send power to the motor.

The power FET leakage current is very small, but in some controllers there is a resistor that draws a few milliamps to bleed the capacitors for safety, and this resistor, if present, can drain batteries in a few weeks. If there's no BMS this can overdischarge and ruin the battery pack. Some folks remove this resistor, and some controllers don't have it in the first place.

If you monitor your battery voltage occasionally in storage you will find out if your controller has this "feature". Hopefully before it drains your pack.

 

[d8veh]

I'm not sure what there is to distinguish a crappy controller from a nice one, if they both turn the motor when you twist the handle. PSW Power has good pricing and seems to be worth trying out in due course. My prospective upgrade from a salvaged battery and a $16 eBay controller was going to be one of the bottle batteries with integrated sine wave controller from BMS Battery.

I am sure that PAS isn't really applicable to this bike and its rider. I would want it on my own bike, but that's another story.

Lets put it another way. That $16 controller compared with a Kunteng with LCD, is like comparing a $50 wally bike with one of your $2000 ones. In the same way that controller turns your motor, the pedals on the wally bike turn the wheels.
Try the KT one and you'll see what I mean. You need the PAS, LCD and speed sensor to go with it. Throttle is optional.

 

[Chalo]

Try the KT one and you'll see what I mean. You need the PAS, LCD and speed sensor to go with it. Throttle is optional.

By and by, I'll do that. But probably not with this bike. For this one, cadence sensing PAS and gauges are not wanted. My girlfriend doesn't even shift when she has a shifter available, and the longest distance she's likely to go on any bike is about three miles. The more stuff on her bike there is to be aware of, the less she likes it.

If she gets interested enough to use the thing more than just to go to work nearby, the next step would probably be a TSDZ2.

Given that a "crappy" controller and a "nice" controller are moving the same number of electrons with the same EMF, and are made in the same way from the same sort of components in the same manufacturing environments, and that they don't get any further tuning or adjustment after assembly, I don't believe the BSO/real bicycle analogy is valid. I think you're comparing features to the lack of features. So it's more like comparing a single speed bike with no accessories to multi-speed bike with convenience features.

Thing is, the customer for this bike prefers it to be simple. So it's an unembellished single speed bike, with a minimal controller. A "nicer" controller would not be nicer to her.

 

[d8veh]

Given that a "crappy" controller and a "nice" controller are moving the same number of electrons with the same EMF, and are made in the same way from the same sort of components in the same manufacturing environments, and that they don't get any further tuning or adjustment after assembly, I don't believe the BSO/real bicycle analogy is valid. I think you're comparing features to the lack of features. So it's more like comparing a single speed bike with no accessories to multi-speed bike with convenience features.

That's exactly the same argument turned around. An expensive bike with a motor and "quality" components transports you from A to B. So does a wally bike with a motor if you're just going to sit on it and use the throttle.

 

[spinningmagnets]

This thread asks the question "what is the thin ignition wire, and what should I do to get this generic controller to work?"

The question was asked and answered. Any further OT discussion will be moved to its own thread, where we can continue to exchange ideas about component selection philosophies...