Twin brush controllers

[dumbass]

My question is can I use 2- 48v 1500 watt BRUSH CONTROLLERS in series to run a single 48v 2000 watt motor? And of course use a single throttle. These are the throttles.

https://www.amazon.com/gp/product/B096LB7RGK/ref=ox_sc_saved_title_1?smid=A20EV1HFK23EFH&psc=1

This is why…

Last year I stripped down an old mini lawn mower converting it to electric. My intent is not for mowing but simply a drivable lawn cart but it needs enough power to pull a waste cart. I’ve already installed a 24v to 72v brushed motor (I’m running on 48v batts.) with the following rating..

No-load rpm: 5600 at 48 volts; Can be used with voltages ranging from 24V to 72VDC
Maximum power: 790 watts (1.1 horsepower); Maximum stall torque: 5.4 Nm (760 oz-in)
Peak efficiency at 48V: 77% at 8 amps and 5000 RPM
Power and torque at peak efficiency: 296 watts (0.40 horsepower) and 600 mNm (85 oz-in)

https://www.amazon.com/gp/product/B086Z86WC5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The tractor has a 5 speed trans. At full power it was pulling 900+ watts. It did very well on pavement in all gears but once it hit the grass it was so dogged down it struggled in 2nd. gear. And that was without towing a cart.

I’m looking at 2 options…1) upgrade it to ether a larger motor (2.7hp vs. the current 1.1hp but with the same mounting). The problem is the new motor pulls over 2000 watts. Finding a 48v 2000 watt brush controller isn’t easy to find. Option 2 is to add a second (twin) motor that I’m already using. But twin motors have their own set of problems.

These are the specs for the possible new motor…

No-load rpm: 5800 at 48 volts; Can be used with voltages ranging from 24V to 72VDC
Maximum power: 2000 watts (2. 7 horsepower); Maximum stall torque: 13 Nm (1860 oz-in)
Peak efficiency at 48V: 82% at 15 amps and 5300 RPM
Power and torque at peak efficiency: 600 watts (0. 80 horsepower) and 1060 mNm (150 oz-in)
Any thoughts and/or recommendations are greatly appreciated.

https://www.amazon.com/gp/product/B086Z86W4H/ref=ox_sc_saved_title_6?smid=ATVPDKIKX0DER&psc=1

BTW, I prefer to stay with this type of brush motor due to it’s physical mounting and shaft size.

 

[amberwolf]

My question is can I use 2- 48v 1500 watt BRUSH CONTROLLERS in series to run a single 48v 2000 watt motor?

In series? No.

Depending on which series method you mean, then:

To do it by putting hte controllers in a series set (one after the other), you'd have to feed the power output of one into the battery input of the other, and the second would not have a consistent power supply unless you used separate throttles, and always held the throttle at one specific level on the first one (and even then, because of the PWM output of the first one, you'd probably have to add series chokes or parallel capacitors or both to the output of the first one to smooth it enough for the second to reliably operate ffrom it).

To do it by putting the controllers' battery inputs in series (+ of one to battery +, - of that one to + of other controller, - of other controller to battery -) and then controller's motor outputs in series (+ of one to motor +, - of that one to + of other controller, - of other controller to motor -), it would divide the battery voltage in half between the two controllers, so if they have an LVC for a 48v battery, neither will ever turn on. If they have a lower LVC so they work on 24v or less, then they might drive the motor, but you don't get any benefit from doing this. (no extra power to motor)


You *might* be able to *parallel* two of them to do this (battery +'s together, battery -'s together, motor +'s together, motor -'s together), but it depends on their output stage design--some of them may not operate reliably or predictably. You'd have to try it out and see.

And of course use a single throttle.

THat depends on how the controller reads the throttle. Some brushed controllers have active "throttle disconnected" circuits that don't work correctly unless they use a resistive potentiometer throttle, with no other connections to their throttle input port. If yours is one of those, it may operate incorrectly or unpredictably when both ports are wired in parallel or if only the throttle signal wire is provided to one of them. You'd have to try it and see what happens.

I recommend only connecting the signal wire (no 5v or ground) to one controller, and running all three throttle wires to the other one.

I’m looking at 2 options…1) upgrade it to ether a larger motor (2.7hp vs. the current 1.1hp but with the same mounting). The problem is the new motor pulls over 2000 watts. Finding a 48v 2000 watt brush controller isn’t easy to find.

There are some pretty big golf cart controllers out there (Curtis is probably the most well-known brand, Alltrax is another) for their brushed motors. As long as they are not sepex, they'll work on PMDC motors or ones with series-wound field coils. THere are also the 4QD brand controllers (I used a 2QD on one version of CrazyBike2, just before I tried an old Curtis), driving a powerchair motor with gearbox)

(if you find a used golf cart being parted out, the golf cart motor would also probably easily handle the load your tractor would put on it, too).

 

[dumbass]

Well I’m not surprised it’s not as easy as I was hoping. Looks like I’ll just sisterup a second duplicate motor and buy 2 new matching controllers. I’m guessing there will be some small differences in ether the motors or controllers that will force 1 motor to pull harder and get a little warmer. But I can live with it. It’s not like they are going to be run hard all day.

Thanks for the assist.

 

[amberwolf]

If you have to use separate motors and controllers, and you want to tune them to operate the same from one throttle, you can use a 5k-10kohm potentiometer between the throttle signal and one controller's throttle input (wired so one outer leg of pot goes to ground, other outer leg goes to incoming throttle signal, and center leg goes to controller's throttle input). Then you can turn down the signal to that controller to reduce it's motor output (by reducing the speed it attempts to drive the motor to).

Alternately, you can add a pot from the current sensor to the MCU, to alter the current the controller thinks it is providing the motor (I recommend always turning that *down* rather than up to prevent controller damage). This I don't have specific wiring advice for, as it depends on the exact design of that part of the controller.

 

[dumbass]

I’m thinking that with my limited talent these days maybe I’m best off to settle a bit. I’m thinking to just buy 1-48v 1500w controller and run it to 2- motors rated at 825ish watt. I’ll lose some of the top end speed and torque but I’ll live with it. I’m guessing most controllers give out more then their actual rating anyway.

 

[amberwolf]

Wiht 2 identical brushed motors and one controller, you can run the motors in series or in parallel.

In parallel, they will receive equal voltage (speed), at whatever the average is that the controller outputs. Current will be approximately split between them, depending on their individual characteristics and loading.

In series, they will receive equal current (torque). Voltage on each will be approximately half of whatever the average voltage the controller outputs, depending on their individual characteristics and loading.

Assuming the motors are not exactly identical, there's no simple way of equalizing the motor output / loading this way, unfortunately, unlike if you use separate controllers (where you can tune it with the throttle input as previously noted).

There's probably not enough difference between the motors to worry about, for two of the same make and model, though you'll be ablet o see the difference as more heat in one than the other if there is.

 

[E-HP]

There's probably not enough difference between the motors to worry about, for two of the same make and model, though you'll be ablet o see the difference as more heat in one than the other if there is.

It's unclear to me whether the two motors are combined through one drivetrain, or whether they will the discreet, each driving its own wheel. I guess the latter could be an issue, if they are driving a left and right wheel, depending on the difference.

 

[dumbass]

In another life I have run 2 motors on one controller in parallel. One motor always over worked harder and got hot. Another issue is the controller and battery must be twice the input voltage and current capacity of the motors (96v). Not an option I’m interested in.

So basically as I said I am likely to just run 2 motors with 1 controller but is series. Being a budget project I can buy a single 48v 1500w controller on Amazon for $40, a second $80 motor, a second $10 gear pulley and $16 for a bigger belt.

 

[dumbass]

It's unclear to me whether the two motors are combined through one drivetrain, or whether they will the discreet, each driving its own wheel. I guess the latter could be an issue, if they are driving a left and right wheel, depending on the difference.
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Actually I can do ether. I can simply install a second motor and link the 2 motor with a single belt drive to the gearbox. Or I could install them independently. Running 2 separate belts to the gearbox. Each has its advantages and disadvantages. If a single belt system is used it’s more stress on the belt and potentially requires an idler. Whereas, independent drives are much kinder on the gear belt but significantly more involved.

 

[E-HP]

It's unclear to me whether the two motors are combined through one drivetrain, or whether they will the discreet, each driving its own wheel. I guess the latter could be an issue, if they are driving a left and right wheel, depending on the difference.
————————————————————————————————-
Actually I can do ether. I can simply install a second motor and link the 2 motor with a single belt drive to the gearbox. Or I could install them independently. Running 2 separate belts to the gearbox. Each has its advantages and disadvantages. If a single belt system is used it’s more stress on the belt and potentially requires an idler. Whereas, independent drives are much kinder on the gear belt but significantly more involved.

Since it sounds like the design is flexible, how about if each motor contributes to the drivetrain via freewheels? That way one motor won't have to deal with the drag of the other if they aren't 100% synched up at every RPM while cruising, but both will contribute when the load is high.

 

[amberwolf]

In another life I have run 2 motors on one controller in parallel. One motor always over worked harder and got hot. Another issue is the controller and battery must be twice the input voltage and current capacity of the motors (96v). Not an option I’m interested in.

If you have them in parallel, you do not need twice the voltage; each motor sees the same voltage across them, whatever the controller outputs. (each one just sees half the current, depending on motor characteristics).

So basically as I said I am likely to just run 2 motors with 1 controller but is series.

If you have them in series, then you do need twice the system and controller voltage to get the original voltage on each motor; Each motor sees half the voltage, depending on motor characteristics. (but each sees the same current, whatever the controller outputs)

 

[dumbass]

Since it sounds like the design is flexible, how about if each motor contributes to the drivetrain via freewheels? That way one motor won't have to deal with the drag of the other if they aren't 100% synched up at every RPM while cruising, but both will contribute when the load is high.

I guess that would work but add cost and complexity. My ratio calls for a very tiny gear pulley that barley handles the bore.

 

[dumbass]

I did eventually find a 50a brushed motor controller. I coupled it to my new motor and battery and it does work. However, it’s not what I would call ideal. The speed control is very harsh to say the least. The slightest touch on the throttle and the cart jumps to life. Actually jerking your neck back. Once moving it’s fine though. Any thoughts on how to calm this beast would be appreciated.

Here’s are links to what I am using for my setup.

Battery: Amazon.com

Motor: https://www.amazon.com/dp/B086Z86W4H?psc=1&ref=ppx_yo2ov_dt_b_product_details

Controller: Amazon.com

Foot throttle: https://www.amazon.com/gp/product/B07TKVZ7GV/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1