GoldenMotor.com Forum
General Category => General Discussions => Topic started by: Barry on June 30, 2009, 12:01:18 AM
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My friend was riding his bike with the key off to save battery power so he would have some left for a big hill he had yet to climb. But before he got to that hill he was going down another hill and applied the brakes. He said that the bike came to a stop very quickly presumably due to the regenerative braking but it was much stronger braking than normal.
To make a long story short, his battery fuse burnt out and the wheel would no longer roll easily until he unplugged the motor wires from the controller. Apparently the controller shorted the three motor power wire terminals together when it burnt out. I suppose all the FETs shrt circuited instead of open circuited.
So now his problem is that the battery fuse blows immediately when he turns on the power switch and the brushless motor hub will only spin freely if unhooked from the controller.
Any ideas what can be done to fix this? It appears that the problem was all caused by applying the brakes with the power switch turned off, while going down a steep hill.
If you have any questions I will get him to sign up for this forum and answer them cause this is all the middle man stuff I am gonna do. ;-)
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If you have any questions I will get him to sign up for this forum and answer them cause this is all the middle man stuff I am gonna do. ;-)
I am now registered Barry so I will take over. Thanks
Gregte
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G'day Greg,
I'm not sure how to fix the problem. Frankly your controller may be fried. As soon as I read your post I seemed to remember that using regen with the power off is a very bad idea as the power that goes to recharge the battery has no where to go. It seems to be similar to an old thread that was on here: http://goldenmotor.com/SMF/index.php?topic=408.0
Muzza
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I was told to disconnect or disable regen when riding with the battery off. The electricity generated by the motor has no place to go if the battery is turned off. With the Magic controllers, it's simple. disconect the brake wires from the controller. I'm not clear as to how to disable regen if it's activated by the throttle.
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Thanks for the input Muzza.
I am pretty confident that what happened to me is much like what was discussed in the thread you referred me to. When I applied my brakes, which have regenerative braking, and my key switch was turned off, thus disconnecting the battery so it could not absorb the power being generated by the motor, the voltage went very high and burned out diodes and/or FETs.
The thing that really bothers me is this: the whole system could be easily designed so that this cannot happen by doing something so innocent as applying your brakes while going down a hill with the key turned off. There could be a high power zener in place and a fuse that would blow in this situation thus saving the electronics.
At the very least, there should be big WARNING stickers on the controller, the key switch and the owners manual that would warn you to never ride the bike with the key turned off because it could cause an electronic failure if the brakes are applied.
I would still like to hear from anybody who might know which components are likely to be the defective ones so I could replace them. I expect this info would have to come from someone who has had this same failure with this same controller (Golden Motor 36v Cruise Controller).
TIA for any help anyone can provide.
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I did figure out what was wrong and have fixed my controller. It has three pairs of FETs, one each for the yellow, green and blue motor wires. It turns out that both FETs of one of the pairs was defective in the shorted mode, not open mode. I was able to detect this with all components in circuit. I removed the two bad FETs and replaced them with good ones and now it works perfectly.
But, I had to figure out a way so this failure could not happen again. I cannot count on my memory always have the key ON while riding. I screw up too often for that. Situations will come up where I take off coasting down a hill and have not yet turned the key on. Or perhaps a friend will do it.
While riding the bike this afternoon the solution to the problem hit me, and it is so simple that I cannot believe that it had not been implemented from the factory. The solution is to connect a diode of ample current and voltage capacity across the key switch (on/off switch), but in a direction such that battery current cannot flow through it to the controller when the key is OFF. However, current WILL flow through this diode from the controller to the battery, to charge it, with the key OFF and the bike moving and brakes applied.
The only cost of this fix is the cost of buying and hooking up a diode across your off/on switch. I used one diode of a 25 amp full wave rectifier because that was the only device I had that I felt could carry the potential current that the hub motor might generate.
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I am not sure that does what you think it does.
The problem is not that there is noplace for it to go, the problem
is that the spinning wheel is generating a large reverse EMF
across the FETs.
The diode won't change that end of the circuit.
I don't know that this is right, it's just how I think it works.
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Well, you will just have to try it as I have. Think about it, when the hub motor charges the battery through its regenerative braking, what is happening is current is flowing to the battery instead of from the battery. This diode allows that to happen. If the diode were turned around the other way then current could flow from the battery which would serve no purpose more than turning the key switch on.
Anyway, like I say, just try it and you will see that it works. I have to be going 12 or 15 mph for it to generate enough power to operate the controller, and also I am using the Golden Motor Cruise Controller and brushless hub motor. Maybe other controller and motor combinations will not work like this, I don't know.
Another way to look at it is like this.... during normal operation current flows from the battery to the controller and then the motor. But during regenerative braking current flow just the opposite. Current does NOT flow from the battery to the controller and also from the controller to the battery at the same time, that is impossible and nonsense to think.
So, since we have established that current can flow from the controller to the battery then it can do it through a diode instead of a key switch. It is DC, not AC and it only flows one direction at a time.... that is, it is either charging or discharging the battery and when it is charging the battery all it needs is the diode as pictured. And we know that it can charge the battery since this model has "regenerative braking".
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Excuse my ignorance, but I'm new to this sort of thing. It seems that in effect, this diode is an electrical version of a flow check valve that's used in plumbing, which allows water to flow in only one direction. Is that correct? Do all diodes act this way, or do we need a certain type? Your solution makes perfect sense to me.
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Yes, your assumption is correct.
Some diodes have more specific functions but they all have the one way flow to some degree. A zener diode will pass current both directions but in one direction the 'zener voltage' must be reached before it will pass current in that direction.
An LED is a Light Emitting Diode whose main purpose is to emit light but it also passes current in one direction only.
Diodes can be configured in a manner to turn AC (alternating current) into DC (direct current). In this capacity they are generally referred to as a rectifier, but they are performing the same task of allowing current to flow in one direction only.
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Thanks. That's a good idea you have. The only time I don't turn the key is when I forget, so I'll install one just in case.
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I am trying to find a diode as described for my kit. What exactly should I ask for? I tried to find one with a web search but not sure what I need. It should be 25 amps but what voltage? My kit is 36 volts so should the diode be rated for 36 volts? As you can see I am not an electronics person. Will Radio Shack carry these or where should I be looking? Thanks from Lagrange, Georgia USA
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Hi guys, I hope this picture is self explanatory, thanks greg!
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Has anyone tried this yet,was it sucessful.
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I have tried it and yes, it does work. My method for trying it was to get at the top of a steep hill and go down fast with the key turned OFF. Then I hit the brakes. The voltage went as high as 43 volts (I have a voltmeter permanently mounted on my handlebar) but no damage was done to the controller. I tried it several times with the same result. The battery itself only sees 42.3 volts because there is a 0.7 volt drop going thru a silicon diode.
For the diode, I used a 35 amp, 200 PIV (Peak Inverse Voltage) full wave rectifier. There is no need for the full wave part since that means the device contains four diodes, but it is the simplest and cheapest solution I could find. It cost $1.25. It has male spade terminals. This rectifier is normally used for changing AC to DC but we are just using one diode in it. The others just come along for the ride.
You just use two of the four terminals. The four spade terminals will be the green dots on the picture. Never mind the other 3 diodes, just pick one and wire it according to the picture above.
I got my rectifier at:
http://www.bgmicro.com/index.asp?PageAction=VIEWPROD&ProdID=11660
Note the + marking and the AC marking on the body of the rectifier. They can be used just like the terminals in the picture on this post with the + and AC being the same thing. Use the + and either one of the AC terminals.
If you connect the + and AC terminals to your key switch backwards what will happen is your key switch will not turn off your power. No harm will result but your power will not turn off and your controller will NOT be protected from regen braking with key off.
Conversely, if you connect to two terminals of this rectifier and your key switch does turn the power off then you have connected it correctly. The exception to this would be if you use two spade terminals that are diagonally opposite. If you use one of the possible diagonal combinations your system will work except there will be a slightly higher voltage drop between the controller and battery. Again, no problem but do it the right way just to keep things straight forward and sensible.
If it helps, think of each of the 4 diodes as being one way water valves and water can only flow the direction that the arrow points. That is the direction that the positive electrical current will flow. For the purists, electricity actually flows from neg. to pos. but it makes no difference to think of it as flowing from pos. to neg. This way the arrow used in schematic symbols of diodes and transistors have an intuitive sensibility as to direction of current flow.
ONE LAST THING: if your key switch is in the Negative (-) line of your system instead of the Positive (+) side then your diode needs to point the other direction than the above picture. Just remember what it is you are trying to do; you are trying to allow electrical current to flow from the controller to the battery when the key switch is open (off). And as I said, as a test to see if you are wired correctly all you need to do is see to it that your key switch still turns your power off. If it doesn't then reverse the wires going to the diode.
One more one last thing :) If you use too small of a diode it will burn out and not do any good at all. So be sure you know what the rating is of your diode.
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This all made sense to me until I was about to install the diode. It occured to me that the regen is built into the controller. If the battery is off, then there is no power to the controller, so pulling the brake lever will do nothing but stop the bike mechanically. Furthermore, the motor acts as a generator whether going forwards or backwards, when no power is feeding into it.
So if the battery is turned off, it still produces electricity back to the controller. Why aren't all controllers fried when the battery is turned off? I'm assuming there are diodes that prevent this from happening. Which goes back to the regen braking. If there's no battery power to activate the regen, then there's no signal to make the motor reverse itself or stop.
I have a rear 9C motor with a GM magic controller. Regen is activated with the brake lever only with this controller. I propped the wheel up and left the battery off. I operated the pedals by hand, until the wheel was spinning quite fast. I released the pedal and pulled the brake lever for the front brakes, and nothing happened. The rear wheel just kept spinning. I did it again, and pulled the lever for the rear brake. Nothing happened, but the wheel stopped. I put the bike back on the ground and tried using motor only. No problems whatsoever. If there's a problem with the motor frying the controller with the battery off, then there must be a problem with the controller to begin with.
So how would you know if the problem was caused when braking, or while just riding with the battery off? The motor still acts as a generator when it's spinning.
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1. When riding with the battery switch turned off the motor produces a small amount of current.
2. When that current and voltage is sufficient, i.e. wheel speed is fast enough, the controller is now powered, just as if the battery were connected.
3. Now, if you pull the brake to activate regen, the now-powered controller will cause the motor to supply a much larger current and voltage.
4. This larger current and voltage has no load (small load-controller is a load), the battery is missing, and thus the voltage rises.
5. The voltage escalates beyond the rating of the controllers components and they burn out.
All of my experience was with the Golden Motor controller and motor.
The results of applying the brakes with key switch turned off and the bike going fast (didn't look at speedo) were instant and dramatic in my case. Upon returning home I discovered that two FETs were burned out in the shorted mode, in my controller. I replaced them and all was well again. I installed the diode across the key switch and have tried the bike with switch off (open) and the voltage does not rise above 43 volts at the controller or 42.3 volts at the battery.
Install a voltmeter across the power wires but on the controller side of the key switch, not the battery side. Mount the meter on your handlebars. Now go for a ride down a steep hill with the switch OFF and watch your meter from 0 to 35 mph. If it never rises above the normal battery voltage during regenerative braking you don't need a diode and your controller will not likely burn out.
When I do this the meter reads fairly low voltage ( a few volts) until around 10 or 12 mph at which time it instantly rises. This is the speed for me that the controller got enough voltage and current to be normally energized, as though it were connected to the battery. It is now capable of generating full regenerative braking power.
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Another thing to note; I have the Golden Motor motor and controller and it includes a 'fuel gage' on the handle bar. This gage is 3 LEDs that are nothing more than a crude voltmeter.
Anyway, when I merely push the bike at 1/2 mph one of the LEDs will light up. This is with key OFF or even with the battery removed from the bike. This is proof that the motor is generating power to the controller, even at 1/2 mph.
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That's my point. It's not supposed to send current to the controller. You'll get a reading on a voltmeter because the circuit is complete. But the circuit shouldn't be completed by feeding back into the controller. I tried it again, this time actually riding the bike, reaching speeds in excess of 15mph, with the battery turned off. The longest run without having to stop at those speeds was 15 minutes or so. Even when stopping from those speeds, I didn't hear the regen kicking in. I then turned the battery on, and there are no problems. I'm no electronics expert, but I do have years of experience working for electricians. You could spin a generator from now til doomsday, but if there's no load to complete the circuit, no electricity will be generated.
I wondered about this a couple of years ago, and asked on another forum about current flowing to a controller when the battery was off or disconnected. One member experienced in electronics said there were safeguards in the controller to prevent that from happening. I don't remember exactly what he said, but it was something to the effect of switching off the current between the motor and controller, or disengaging the regen if a problem arises where the current can't get back to the battery. There was also a mention of diodes, but I didn't fully understand what he was saying.
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You could spin a generator from now til doomsday, but if there's no load to complete the circuit, no electricity will be generated.
But there IS a load. The load is small. The load is the controller. Also, this is a permanent magnet DC motor. They will produce a voltage with NO load and a current will flow if there is any load for it to flow into.
. One member experienced in electronics said there were safeguards in the controller to prevent that from happening.
This depends entirely on the particular controller. They are not all made by the same company.
It may very well be that your setup behaves exactly as you say it does. I do not doubt it one bit. But my setup definitely produces power with no battery on the bike. If I pedal it at around 10 or 12 mph with NO battery I can honk the horn and all 3 fuel gage LEDs will lite up. That means that at that speed the controller is getting at least 37 volts from the motor/generator. It has to be 37 volts in order for all 3 LEDs to light. If I then apply the brakes the voltage will rise even higher.
Again I will say this;
1. Remove your battery.
2. Connect a voltmeter to the wires that go to the battery.
3. Ride the bike and watch the voltmeter.
Whatever voltage you read is what the controller is seeing. This obviously assumes your key switch is turned ON unless it is part of the battery you removed.
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I tried it again, this time actually riding the bike, reaching speeds in excess of 15mph, with the battery turned off. The longest run without having to stop at those speeds was 15 minutes or so. Even when stopping from those speeds, I didn't hear the regen kicking in.
You shouldn't get any affects of regen braking without a battery in circuit, or at least it should be very minor if detectable at all. In order for regen braking to slow your bike the regen system has to take on a lot of energy. If there is not battery (a substantial load) there is no place for the energy to go and you will not be slowed. You are driving a generator that has a very small load to drive. It is not hard to turn that generator. But attach a heavy load to that generator (a battery) and it will not turn so easily. It will slow your bike.
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My two cents, as I have been following this thread. I, too, have a GM motor and controller. The GM motor generates electricity any time it turns, going backward or forward. I have "lit" the power meter LEDs on the throttle and honked my horn. After hearing about what happened to Gregte I quit doing that. If I do more than walk the bike from one parking spot to another I turn the key on, thus completing the circuit to the battery, jic. After monitoring this for some time I went to Radio Shack and got a diode. I put it on. I sleep well.
And, as for regen, it is awesome. Not so much from a power saved perspective as from a "it feels so cool" perspective. When I am hauling a$$ up to a stop light and pull my brakes it feels like the scifi scenes where ships are coming out of hyperspace. I go from near 20mph to NOT fast. Of course, any observers nearby do a double take. It is most satisfying.
I expect that different combinations of motors and controllers behave similarly or very differently depending on the design, efficiency, quality of the parts and such. As for me, I really enjoy my toy.
John
Bike E Recumbent e- Bike
Driven by a GM 36V 750W 20" rear
Powered by a GM 36V 16Ah LiMn battery
Ridden by a MadMan
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You'll get a voltage reading because the voltmeter completes the circuit. But there should be no current going through the controller with the battery off. It should have safeguards to protect it. With the battery turned off, I get nothing to the LED's on the throttle, so in that regard it's working correctly. However, the regen works for a second, then the wheel keeps turning. At any speed, there is no difference between braking with the battery on or off. It's the same even if I don't connect the motor to the controller at all.
I bought this controller because it had features that the Infineon controller that came with my 9C kit doesn't have, particularly reverse and regen. Reverse woks perfectly, as does cruise control. But I'd really like to be able to stop using regen only, as the motor on my delta trike does. My trikes are quite heavy, and so am I. Since adding the motor to my delta, I haven't had to adjust or replace the disc pads yet. I had to adjust them almost every week before that, and replace them every few months.
My point is that these GM controllers seem to vary from one to another. I just found out my Infineon can be modded so I can get all the same features I wanted in the GM. I ws going to order the Magic Pie when it comes out, but now I think I'll go with another brand for my next trike build.
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After monitoring this for some time I went to Radio Shack and got a diode.
Just be sure the diode is rated to carry the current (unknown by me but must be several amps) and a high enough PIV (again, unknown by me but may see 100 volts, maybe more, just a guess).
And, as for regen, it is awesome. Not so much from a power saved perspective as from a "it feels so cool" perspective.
Ditto! The power saving is not worth much for my road riding but when trail riding it is. I am always going up a steep hill or down. When going down I most always need to apply brakes, so the regen is doing some real good.
I often stop and enjoy scenery at the top of a hill. I then may jump back on the bike and start coasting down, forgetting to turn on the key. If my speed is not too great the first time I hit the brakes, no problem. But when going fast the diode saves the day (or FETs rather).
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With the battery turned off, I get nothing to the LED's on the throttle, so in that regard it's working correctly.
Where is your key switch?
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The key switch is on the battery pack
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I guess your motor is enough different than my Golden Motor motor to make the difference.
Also, I am using the Golden Motor "Cruise Controller". I assumed you are also since you have the cruise function.
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Yes. Magic controller, 9C motor. But I don't think it's the difference in the motors. It seems to me that there are differences between the controllers. Maybe programming, or maybe components that vary from one controller to another.
I'm learning more about Infineon controllers, since that's the one that came with my kit. I just found a MS Word document that explains how to install jumpers and switches to enable regen, cruise, and reverse. It also explains how to program the regen for different size wheels and/or degree of regen, as well as speed parameters for both forward and reverse.
As I said, I only bought the GM controller because I didn't know my Infineon could be modded with the features that the Magic controller has. But I have no idea how to get the regen to work the way I want it to in the GM, but I now know how to do it with the Infineon. I'll keep the GM as a backup.
I had no problems dealing with GM, they sent everything I ordered very quickly, within 6 days, except for the battery, which was out of stock. But they gave me notification without having to ask them when the battery was shipped. I received it 5 days later, which was a total of 17 days. They also gave me the upgraded battery at no extra charge. I ordered the older battery that didn't slide on a rack.
From what I'm seeing on the Net, it seems there are various problems with the Magic controllers, or none at all, which leads me to believe there are inconsistencies in the manufacturing of these controllers. That makes me leery of ordering the Magic Pie at the early stages.
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Maybe this has nothing to do with your situation but are you aware that the GM controller can be configured to work with non-GM motors, i.e. with motors with different phase angles than the GM motor? The following is a copy/paste from a GM pdf.
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The controller can work brushless motors with different phase angles other than defaulted 120 degree. Below are procedures to let controller match the motor phases:
•Cut-off power to controller and motor
•Grip and hold power brake lever, turn throttle to maximum speed position, depress the cruise control button, turn on the power switch (using battery key)
•Connect battery power to the system, release throttle, release brake lever, release cruise control button.
•Listen 2 beep sound, turn the motor wheel forward and reverse once
•If hear 1 beep sound, motor phase calibrating successfully completed. Otherwise, swapping any two of three motor phase wires, and repeat above steps.
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That's the first thing I did. It calibrated on the first shot. I set the controls on some tubing so I could hold the brake lever, cruise button, and throttle with one hand, while turning the key switch with the other.
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You must have a SLA battery pack for this to work.
Following another thread on this forum, if you have a LIFEPO4 pack the BMS stops the reverse flow from the diode.
http://goldenmotor.com/SMF/index.php?topic=1068.0
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You must have a SLA battery pack for this to work.
Following another thread on this forum, if you have a LIFEPO4 pack the BMS stops the reverse flow from the diode.
http://goldenmotor.com/SMF/index.php?topic=1068.0
I have a Golden Motor brushless front hub motor with a GM Cruise Controller. I also have a LiMn 36v battery and a LiFePO4 battery. The regenerative braking works with both batteries. It will also work without the key switch turned on but it will burn out the controller if you are going fast enough.
If you cross the keyswitch with a diode in the manner shown in the diagram shown in this thread the regen braking will work with the key off and will not burn out the controller. I know this to be true with the equipment I have as I have done it.
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We have recently enhanced the cruise controller to detect if the battery pack is in place. If the battery is switched off, or is not connected at all, the controller will check the back EMF voltage, if it exceeds the preset limit, the controller will disable the regenerative braking to protect controller from being damaged. Now our new version of cruise controller is much more reliable than before. I'd like to take this opportunity to thank all contributors who gave us feedback and suggestions, to help improve the quality and reliability of GM products.
The regenerative braking function will be resumed automatically when the battery is switched back on.
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My 48v system was shipped on july 13 2009. It was promised this diode would be installed in all systems shipped after july 6 2009. Does this mean my system has the diode? is there a way of checking it?
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We do need a diode anymore, read the post.
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We do need a diode anymore, read the post.
I assume you mean "we do not need the diode anymore" and yes I did read the post, it was written on july 25th. If you read my post you will see my system was shipped on july 13th. Does "recently enhanced" mean before july 13th or after. I'm just looking for some clarity or a way of telling what I have. So i'll ask again, how do I know if I have the new "enhanced controller' a diode fix or no fix at all.
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lately my colleague has also totally grilled is BAC controller by simply trying to recharge the battery on a downhill after the BMS has switched off the GM battery pack:
(http://). The 'diode solution' offered in this thread will not solve this problem since the BMS will keep the battery disconnected and the FETs will burn out. Solutions could be to disable the controller (as implemented recently by GM) or adding a breaking resistor (which could be the motor wiring?) - both require reprogramming the controller (that's why I'd like to see a USB connector for firmware updates). r
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I have a Golden Motor brushless front hub motor with a GM Cruise Controller. I also have a LiMn 36v battery and a LiFePO4 battery. The regenerative braking works with both batteries. It will also work without the key switch turned on but it will burn out the controller if you are going fast enough.
This is quite interesting, does your batteries have BMS, and if so, is it from GM?
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This is quite interesting, does your batteries have BMS, and if so, is it from GM?
Yes, both batteries have BMS circuits and one of them, the LiMn is from Golden Motor.
But the fact that the regen braking supplies a high voltage current to the controller with the key turned OFF does not have anything to do with the type of battery you are using because the key is OFF, meaning the battery is completely out of the circuit.
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I was told by Li Ping that the BMS on his batteries will prevent regen braking to protect the battery from the higher than 5a regen current. I assumed that was also correct for the GM LiFePo4 batteries as well. When I use the GM battery, regen kicks in for a split second, then stops, and the wheel continues to spin. When I installed an SLA pack, the regen worked fine for a while, but then it started doing the same thing as with the LiFePo4 pack. Then I discovered this only happens with a fully charged battery. It seems as though the controller stops the regen from working with a fully charged battery. I also have one of the older GM regen controllers, and the same thing happens. With the LiFePo4 battery, no matter if it's fully charged or not, regen doesn't work with either controller, but it does work with a less than fully charged SLA pack.
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This may be regarded as a dumb question but I just want to be sure:
The problem with burned controller from generative breaking is only present if you have both a "magic controller" and a regenative braking controller installed together (regenative braking controller = the black controller box on the web site).
If you only have the "magic controller" installed then there is no risk of burning it from regenerative braking...right!?
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This may be regarded as a dumb question but I just want to be sure:
The problem with burned controller from generative breaking is only present if you have both a "magic controller" and a regenative braking controller installed together (regenative braking controller = the black controller box on the web site).
If you only have the "magic controller" installed then there is no risk of burning it from regenerative braking...right!?
Sorry Bengt,
But unfortunately it's not right.
Only one of the above mentioned controllers would usually be fitted, not both.
Two controllers would only be used if two separate hubmotors were fitted. (One controller for each motor)
As far as I am aware, unless you have a very recent controller, there is still a risk that the controller may be damaged by the regenerative braking current generated at higher speeds while the battery is either turned off or disconnected.
As of today, 22/7/2009, the day of the eclipse, all GoldenMotor controllers have a new function to deal with the issue of regen braking burning out the controller while battery is off.
Alan
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I bought a 36V 250 Watt MiniMotor kit in June 2009 with "Magic Controller" (to be installed next week)
So I am apparently at risk of burning it.
Suppose I happen to ride the bike until the battery cuts out (forgot to recharge).
Is the battery in this case defined as "unconnected" (although it is physically connected).
Will the battery in this state absorb the current created from "regenerative braking" or will the controller be at risk of burning if I continue pedalling home without support from the battery? Will I have to walk home leading the bike by hand???
Can I disable the generative braking function by a command to the "magic" controller - or unplug a wire there - thus avoiding this potential problem?
I see that there is a diode solution that can be applied to my "non-fixed" controller but I am an electric novice not knowing how to fix that or what components to get (and where).
I think that this "add-on" solution for nonfixed controllers should be available to order (with detailed instructions how to install it) from Golden Motor website at reasonable cost.
Additional information added:
I have the 36V 16ah Golden Motor battery.
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Liared,
The mini motor has a freewheeling hub so it will never generate any power during braking. So you have nothing to worry about.
Actually I think the mini motor is one of the best solutions available for a hassle free moderate powered eBike.
Good luck with your new bike!
Helge
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Liared,
The mini motor has a freewheeling hub so it will never generate any power during braking. So you have nothing to worry about.
Actually I think the mini motor is one of the best solutions available for a hassle free moderate powered eBike.
Good luck with your new bike!
Helge
Thank you Helge!
I feel really relieved.
For a electric bike novice user like me, participating on this forum is a great learning experience.
I am grateful that you more knowledgeable people have the patience and will to answer an guide a non expert !!
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I was told by Li Ping that the BMS on his batteries will prevent regen braking to protect the battery from the higher than 5a regen current. I assumed that was also correct for the GM LiFePo4 batteries as well.
If you open a GM Lithium battery it has a BMS with a FET for charging and dual FET for discharge. These FETs have built-in protection diodes against reverse voltages. So during regen the discharge FET will conduct current to the charge FET via this diode. You will get around 0.7 V voltage drop over this diode (unless it is a schottky type which has much less). Then current flow until it exceeds the maximum allowed by the BMS. When the BMS senses that the charge current is higher than the limit it will open the charge FET to protect the cells from damage. Then with no load, the voltage generated will increase above the maximum ratings and the magic smoke will start leaking...
To make regen work on Lithium batteries, you need a BMS that is designed for regen, and use battery cells that is able to handle the maximum regen current. In addition, you should also have a braking resistor as often used on AC variable speed drives. This resistor handles the regenerative load when the battery is full. I am currently designing my own BMS using the new Texas Instruments bq78PL114 BMS chip where I implement this function. My BMS is specially designed for regenerative ebikes/velomobiles so it has a built-in regulator for cycle lights as well (fixed voltage or fixed current for LED).
Maybe I can talk GM into producing and selling it (if it works as planned ::)).
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To make regen work on Lithium batteries, you need a BMS that is designed for regen, and use battery cells that is able to handle the maximum regen current. In addition, you should also have a braking resistor as often used on AC variable speed drives. This resistor handles the regenerative load when the battery is full.
If I understand correctly and if the 2 discharging and the 1 charging FETs of the BMS are all connected to the same battery terminal then it would be possible to connect a braking resistor to the charging socket of the battery, as the charging FET of the BMS is switched on by the controller if the battery is fully charged? that would be an elegant solution to prevent the burning of the controller! r
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If I understand correctly and if the 2 discharging and the 1 charging FETs of the BMS are all connected to the same battery terminal then it would be possible to connect a braking resistor to the charging socket of the battery, as the charging FET of the BMS is switched on by the controller if the battery is fully charged? that would be an elegant solution to prevent the burning of the controller! r
It is a bit more complex than this, but yes, it is possible to have the resistor switched into the circuitry when the battery is full. The problem is that you also have freewheeling diodes in parallel with the FET's making matters a bit complex. In my BMS I have added a logical function that connects the resistor to the speed controller (ESC) only when the BMS turns of the charge and precharge FETs due to fully charged battery. To add such solution to an existing BMS without schematic is IMHO both difficult and dangerous.
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The problem is that you also have freewheeling diodes in parallel with the FET's making matters a bit complex.
As far as I understand the circuits of the GM BMS and BAC there is never a condition where regenerative current is actively managed by the built in MOSFETs if the back emf is higher than the battery voltage - regen current is then always conducted by the free wheeling diodes and therefore regen current is completely uncontrolled in this condition!? The BLPMDC-motor always generates a back emf proportional to the rpm (with permanent excitation there is no control over emf). If the back emf is larger than the battery voltage all the freewheeling diodes start to conduct (the bridge in the controller and the twin discharge MOSFET in the BMS). The induced current which creates the braking torque in the motor (in this case generator) is the charging current of the battery. If the battery is not connected, there would be no load and no braking torque, thus the e-velo speeds up and the voltage would rise continuously in sync with the rpm. If the battery is full, there is no way to cut off the regen current other than disconnecting or stopping the generator/motor!
If the back emf is smaller than the battery voltage (braking at normal travel speeds) charging the battery is not obvious as the back emf is too low. How to switch the bridge so that it works (PWM ) can be found e.g. here http://www.4qdtec.com/bridge.html
r
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I thought of an idea. An electronic switch that has large capacitors and keeps the controller engaged until the a breaker switches on the brake switches. It only needs to happen in a couple of seconds, This is by no means an idea that is a sellable device.
Ive had a couple of controllers burn out and learned to avoid it. I need Regen for the braking capabilities because I drag some heavy SLA's and shopping around. I make sure I install a big fat 50 amp fuse and place the switch where it wont be bumped. It is a temptation to switch the bike off down hills on those controllers that need to be switched off to disable regen. unlees you got the new one with issue solved just don't do it.
I learned the hard way. Once you have a good controller going just leave it and it should live for a long time.
Stop the bike before switching off and on.
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The transistor gate drivers and fets put a reverse phase signal in against the forward operating phase that can control the regen, and another fet is installed to milk the regen into the batt input. It is initiated when you decrease the throttle. Well on my controller.
If you look at the gate drivers there are two per channel and both different and faced opposite, and one of these these could well be triggered by what look to be a nearby dual inverted opamps but the part numbers are beyond my spectacles. When the motor outputs voltages above the input voltage and by the throttle decrease the opamp switches the reverse phase gate into gear. Possibly depletion mode drivers, so when the hall is on or off respectivly the gate driver is a depletion or normal causing the opposite to happen. How this is works variable to the throttle I have no idea but is quite intellegent as you can controll the amount of regen with the throttle.
On the new controllers I like the idea of full braking regen on the brake levers but doesnt this lose variable braking and regen systems that the old controller had. I guess you cant have your cake and eat it so to say.
I'll admit still haven’t analysed the fet bridge properly on my controllers as yet but I swear some half of the fets outputs go straight to the battery input.
The tvs diodes do filter the current into the right cables also to clamp spikes from inductive switching.. You can turn these hubs into a really good wind generator just by placing diodes on the phase wires. But to rev up the current a reverse to phase input can really pull out the juice at lower RPM.