Converted alternator on ebike controller

Ekart

10 mW
Joined
Aug 18, 2019
Messages
22
Location
Perth West Australia
Hi guys, just a new member and have a question if anyone has experience in connecting a brushed car alternator (I rewired it to a 3pole motor -Delta connection), connected to a 1500w 48v controller. It runs fine with wheels off ground but when under load moves a few inches then stops? The controller is both brushed/brushless and sensor or not. I’m wondering if there is a setup procedure to tell it no sensors are in use? Cheers
 
Hi eee291, thanks for your reply, no did not put magnets on rotor. Are they used for sensor triggering or some kind of pulsing back into the stator windings? I followed this chaps video.... https://youtu.be/IKqy3rRWJQE and he dosen’t seem to use any? Cheers
 
Hi Flat tire, and thanks for your reply. Yes I think so I have reduced it to about 4:1 and the tacho reads about 3200 rpm at the alternator sprocket flat out. Sitting in the kart you get a definite jolt of a few inches then stops, almost like the controller is waiting for a “tacho” signal and not getting one, or some form of feedback not being received.
 
If you're not using magnets did you at least separately exite the rotor coils? You'll get no torque otherwise.
 
Hi eee291, yes I have a separate 12v battery running to the rotor windings through the brushes. I have contacted the guy that did the youtube video also ... https://youtu.be/IKqy3rRWJQE
my controller is supposed to be a sensor or sensorless type so hopefully he can shed some light on it.
 
Alright, it sounds like like it's just battery or controller then.

Do you have a battery with a BMS? If so, is the BMS Amp rating at least that of the controllers peak Amp rating?
When it cuts-out, does it recover after a few seconds or do you have to cycle power or plug/unplug the controller?
Your battery voltage could also be sagging so much that the controllers LV cut-off gets triggered.
 
Hi there, yes you have some very good points there... no BMS just 4 of 12v 18Ah gell batteries in series to make 48v for the stator windings and one 12v lipo battery for the rotor winding. Rotor winding draws about 1.5A max.
Once the wheel turns slightly under load and stops I then have to reset power to try again.
Just thinking about it now you mention it the under voltage limit (42v I think) may be tripping it out at the controller.. thanks for the tips!! I will get back to you! Cheers!!
 
Ekart said:
The controller is both brushed/brushless and sensor or not.

What controller is it? I haven't seen a complete controller that can do both brushed and brushless, though there is an old motorola chip (MC3303x) that can be built into a controller that can do that. (thread by Jeremy Harris on using that chip to build a controller is somewhere on the forum).
 
Hi amber wolf, it’s a AUD$40 AliExpress controller model 2922043 brushless controller... here’s the specs
Strong driving stability
Phase 120/60 compatible
Start the anti-speed function
Waterproof and moistureproof
Hall/Hallless Dual Mode Compatible
Turn the line short-circuit protection function
Specifications:
Input voltage:48V
Power:1500W
Current limit: 45A
Undervoltage protection:42V
Braking: high and low
Phase angle: automatic
Function: anti-theft three-speed reverse
First look at your electric car battery voltage levels,corresponding to the selected voltage controller,look at the size of the current controller previously used,such as the current is 16A-18A 350W controller,22A-24A controller is 450W,28A -30A controller is 500W,31A-33A is 600W controller,33A-35A is 800W controller,36A-38A is the 1000W controller,40A-43A is the 1200W controller,50A is about 2000W controller.Such selection controller,if the original car is 350W controllers we recommend the use of bigger,so you can take advantage of the highest motor speed and power.
Size:25.2x10.6cm/9.92x4.17inch
Having said that I’m wondering if the problem is that I’m using a “brushed” motor ? The thing is it runs fine with the driven wheels off the ground?? Maybe the battery capacity 48v x 18Ah is the problem..just too weak to drive it?
 
Are you using a 'Brushed' motor though? kind of, it's just that the rotor has coils instead of the usual magnets.
The controller still 'sees' this motor like any other 3 phase brushless motor.


The problem is obvious, you are asking for about 3x the amount of current those lead acids can provide. you would need low IR ~25-50Ah SlAs if you want to get anywhere. Try using 4 starter batteries in series for a test, I'm sure it will work just fine.
 
Thanks eee291, I think you have it! I do not know enough about those batteries and how much instantaneous current they can/could provide. We will try better batteries .. I guess you guys use lithium iron cells in a pack? Lighter and able to provide 45amps??
Cheers
 
Sure, I use all types of Lithium batteries not just Lifepo4.
My favorite chemistry is lithium manganese oxide.
 
Either the batteries cant provide the discharge. You'd just destroy the battery.
OR
Your batteries sag to below the LVC (while under load) and cuts off. Most probable.
OR
Your LVC is set to low. Probable.
 
Hi markz, I watched the original idea video again here: https://youtu.be/IKqy3rRWJQE and his battery pack that apparently works is made up of 4 of 12v 12Ah gell cells and ours is 4 of 12v 18Ah gell cells so I’m thinking it should be ok??
Battery sag on full load goes down to 46v and LVC is 42v so should not be that. Thanks for your thoughts ... still thinking.
 
Ekart said:
Hi amber wolf, it’s a AUD$40 AliExpress controller model 2922043 brushless controller... here’s the specs

Well, I don't see any thing in those specs that says it will run a brushed motor at all, so it's not very likely to be capable of both brushed and brushless...just brushless.


Having said that I’m wondering if the problem is that I’m using a “brushed” motor ? The thing is it runs fine with the driven wheels off the ground??
If you are driving the three phases of the motor with it, then it's doing what it can.

If you were driving a single phase (like a brushed motor) then it shouldn't work. (well, it might be able to spin it becuase it will pulse it, but the phases reverse so it would probably just buzz).


Maybe the battery capacity 48v x 18Ah is the problem..just too weak to drive it?
Since the low cutoff (LVC) is 42v, then if your pack sags below that the controller will shut off until voltage recovers above that. So you'd have to measure voltage while testing to see this.

A wattmeter generally keeps the minimum votlage stat until you disconnect power, so it's handy ot see voltage sag.
 
Yes a rolling start has been tried and same problem..just stops, but will recheck, we've done some changes since then. My son thought of reversing the polarity on the rotor winding battery but have not yet heard of the result.....cheers!
 
:bigthumb: hi guys, just an update albeit a few weeks later! The Ekart is working!! I rewired the alternator for “Star” connected and away it went ! Draws about 14Amps at 46v whilst running at about 25 mph.
 

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Had you tried wiring for 24v? I'd played around with powering alternators a bit and for some reason the (cheap 6s RC) controller I was using was happy at 12v but would stutter with any kind of load at 24v. I never dug into why but it suggested a rewind would be needed for high voltages so got put on the shelf.

Do you have a means of varying the field current? It will allow a much wider range of rpm, with a fixed 12v you'll have a good amount of torque but peak rpm will be very low. A brushed RC ESC is ideal for the job, idealy with something like an arduino to vary field with rpm and load but a cheap servo tester will work just fine to vary field manually.

If you can find a way to add magnets to the rotor it would be a good idea, if the brushes lose contact under load there's nothing for the current to "push" against and that can result in a fried controller. Some small magnets to make sure there's a bit of field at all times will help prevent that while still allowing the field windings to be used for high starting torque and a wide rpm range. Somewhere here on the forum there's a very good thread from a few year back on using an automotive alternator as a motor including dyno tests, well worth a read.
 
You still using 12V to excite the alternator?
Also, what kind of a shaft was on the alternator when you pulled the pulley off?
Was there a gear that fit? What gear tooth count did you install?





Ekart said:
:bigthumb: hi guys, just an update albeit a few weeks later! The Ekart is working!! I rewired the alternator for “Star” connected and away it went ! Draws about 14Amps at 46v whilst running at about 25 mph.
 
Hi markz, yes 12 volt on the rotor windings via a separate battery now. The shaft on the pulley was 5/8" threaded at the outer end to take the Fan and split pulley with lock washer and nut. These were replaced first with pulley and "V" belt and eventually replaced with sprockets and a large chain. I think 9 tooth on the alternator (similar to one in Pic) and 48 tooth bolted to a plate welded directly onto the drive shaft. see pics.
 

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