Using two drivers to drive one motor

Hi! I have a powerful motor that draws a lot of current at full load. I also have a power supply that can output enough current and a driver that may be able to handle it, but its current rating is a bit lower than what I think the current draw will be.

So the driver I am using is the IBT-2 / BTS7960 with a max current rating of 43A. My power supply can output ~62A and the motor will be drawing at most 60A and I don't think the motor driver is going to like it.

My idea is to use two drivers, so that each one "controls" one of the two wires of the motor, but the Arduino will control them as if they are one (the logic inputs will be tied together).

So far I have come up with two ways of doing this (please forgive the ugly mspaint "schematics").

Method 1:

Here, you can ignore the connections from the "enable" pins of the driver to the Arduino, in method #2 I just tie them permanently high.

(From now on, I will refer to the first driver's pins as "pin(1)" and the second driver's as "pin(2)")

The RPWM(1), RPWM(2) and LPWM(1), LPWM(2) are tied together, so the motor must have one wire connected to R(1) and R(2) and the other wire to L(1) and L(2) ('R' and 'L' being the outputs of the driver, as noted in the picture).


Method 2:

Now, the enable pins are tied high to avoid clutter, as I will not disable outputs in my code.

Both RPWM and LPWM pins of each driver are tied together and are controlled by a single Arduino pin each, and the outputs R(1), L(1) and R(2), L(2) are connected to each other.

This means that one wire of the motor goes to R(1) and L(1) and the other wire to R(2) and L(2).


In both methods, the downsides and possible risks I can see are that if some wire which was tying the logic inputs together somehow disconnects, one of the shorted-together outputs can become high and the other low, resulting in short circuit / bad day.

That aside, is there any other downside or risk in any of the methods? Personally, I want to go with method #2 because it looks tidier.

The main question, after this wall of text, is whether or not this helps with my initial problem.
Does connecting them like this boost the maximum output current from 43A to 86A?

Thank you.

Here we go again. Designing something based on what you "think" applies, rather than find the actual or documented values.
Find or measure the ACTUAL stall current value for the motor and get a controller that can handle that current.
Paul

Thank you for your reply.

This motor has a gearbox and to get it to stall I will need a lot of force. I could remove the gearbox, but it has an intricate worm shaft that I don't want to damage trying to stop it. Also the rig it will be used in doesn't exist yet.

My question was pretty much theoretical, I only want to know if such a configuration doubles the rated max current, whatever motor I am using.

Thanks again.

Being on the theoretical side you can develop, design, debug, and build a driver circuit by the time this becomes real. as far as operating them in parallel it depends on the parts. If the logic is not faulty, and the IC's are on the same heat sink it might give you maybe about 170% but this is theoretical. From what I can tell the motor does not reverse so designing a simple MOSFET driver would not be that hard, just be careful of the PCB traces and the heatsinking. You can use smaller ones and parallel them if you want. A secret for paralleling MOSFETs is to place them on the same heatsink with good thermal coupling between. Use something in the 33 Ohm range in each gate and the sources and drains are connected with as low as resistance as reasonably possible. MOSFETs increase RDSon when they get warm so when thermally connected they will share. To sumrize: A) Make a symmetrical layout of circuit wiring. B)Assemble MOSFETs to one heatsink so that the thermal dissipation condition is the same for each MOSFET. C) Use an external gate resistor for each MOSFET.
D) Secure a large current margin, considering current imbalance. The gate resistor helps eliminate oscillation in those rarer cases.

Domnulvlad:
Hi! I have a powerful motor that draws a lot of current at full load. I also have a power supply that can output enough current and a driver that may be able to handle it, but its current rating is a bit lower than what I think the current draw will be.

So the driver I am using is the IBT-2 / BTS7960 with a max current rating of 43A. My power supply can output ~62A and the motor will be drawing at most 60A and I don't think the motor driver is going to like it.

No, it has over current detection circuitry anyway...

My idea is to use two drivers, so that each one "controls" one of the two wires of the motor, but the Arduino will control them as if they are one (the logic inputs will be tied together).

Hmm, not sure if it makes much difference (even if the overcurrent failed to kick in), the BTS7960
is two big MOSFETs in the same package, and probably has about the same thermal resistance to
the heatsink for both MOSFETs.

For really high currents you need to go to a discrete MOSFET bridge, driven from a gate driver such as
the HIP4081A. Then you can choose even beefier MOSFETs, and perhaps double them up.

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