Can the same driver be used on both 12V and 24V systems?
The ST42, KS250 and PT500 all run on 12V and 24V DC, so no module change is needed; the current limit is independent of voltage: KS250 15 A, PT500 30 A.
Yes. All three of the ST42, the KS250 and the PT500 work on both 12V and 24V DC systems; the KS250 is defined as 12V/24V and the PT500 in the 12-24V DC range. You can move the same module between two systems without taking it apart. The point not to be confused is this: the voltage range is flexible, the current limit is not.
The current limit does not change with the voltage
The KS250 carries 15 A continuous at 12V and at 24V alike; the PT500 is 30 A in both cases. What changes is that you can obtain the same mechanical power at a higher voltage with a lower current. On an application moving to 24V, if the motor power stays the same the current drawn falls to roughly half and the thermal load on the driver decreases. That is, 24V does not enlarge the capacity of the driver, it reduces the current demanded of the driver.
The reverse is true as well: if you bring a 24V application down to 12V, the current for the same work roughly doubles. The driver still works, but you reach the continuous current limit far sooner.
What to check when changing voltage
| Item | Check |
|---|---|
| Motor label | The rated voltage has to match the supply; feeding a 12V motor from 24V raises the speed and the current excessively |
| Input signals | The levels arriving at the IN1-IN5 inputs of the KS250 and the A-E inputs of the PT500 have to be consistent with the system voltage |
| AntiSwitch thresholds | When the voltage changes the current profile changes; set the A1/A2 adjustments again |
| Fuse | Since the current falls the fuse rating falls too; leaving the old rating means being left unprotected |
| Auxiliary loads | 12V equipment such as the receiver, a lamp or a horn cannot be fed directly from a 24V line |
Do not overlook the fuse side: the fuse rating to be fitted to the driver is determined by the continuous current, not by the supply voltage. On the cable side the cross-section is most often determined not by current carrying capacity but by voltage drop; that is why choosing the cable cross-section in a 12V and a 24V system gives a different result for the same motor.
The most frequent mistake on site
The most commonly seen mistake is assuming that because the driver works at both voltages the motor will work too. The driver tolerates the voltage range, the motor does not: connecting a 12V motor to 24V raises the speed and the current together and shortens the life of the brushes and the windings. The second frequent mistake is mixing up the negative when a vehicle has both a 12V and a 24V rail. Whichever battery group the negative of the driver belongs to, the negatives of the motor and of the signal source have to belong to the same group; that is the rule for using the same kit on vehicles with 12V and 24V batteries as well.
Where this flexibility ends
The supply range is limited to 12V and 24V; these modules cannot be used on a 36V or 48V system. Putting a converter in between is not the right solution either, because the whole current of the motor passes through that converter. There is a similar situation at the lower limit: when the battery weakens and the voltage falls, the current profile changes and the board may behave differently from what is expected. The AntiSwitch threshold coming in early is most often not a setting error but a symptom of a supply problem of this kind.
What to do
If you are changing the voltage, review the motor, the fuse, the cable cross-section and the AntiSwitch thresholds together; you do not need to change the driver. After the change, do the first run with no load, then measure the current under load and verify that it stays below the continuous rating.
The full topic: DC Motor Driver Selection Guide