If I switch from 12V to a 24V system, what changes on the driver and cabling side?
Doubling the voltage for the same power roughly halves the current and quarters transmission loss; the driver current limits and module choice stay the same.
For the same mechanical power, doubling the voltage roughly halves the current. The gain comes from there: the transmission loss falls to a quarter, the cable cross-section requirement decreases and your voltage drop budget widens. On the driver side, however, nothing changes; the KS250 and the PT500 already work at 12/24V and their current limits stay the same.
What changes on the cable side
- Since the transmission loss is P = I² × R, the cable and connection losses fall to roughly a quarter.
- You can go a longer distance with the same cable cross-section. On low voltage systems the cross-section is most often determined not by current carrying capacity but by voltage drop; at 12V a 3% drop is only 0.36 V, whereas at 24V you have a budget of 0.72 V.
- The fuse rating falls along with the current; the general rule is 125-150% of the continuous current.
- The heating on terminals and connectors decreases; the likelihood of a fault caused by a connection working loose drops.
When you make the calculation, add the outward and the return length of the cable together; that is the reason the voltage drop formula is multiplied by 2. The resistivity of copper is taken as roughly 0.0175 Ω·mm²/m. The practical meaning of the 3% rule is this: the voltage lost in the line never reaches the terminals of the motor, it comes straight off the torque.
What does not change on the driver side
| Item | 12V | 24V |
|---|---|---|
| KS250 continuous / peak current | 15 A / 45 A (5 s) | 15 A / 45 A (5 s) |
| PT500 continuous / maximum current | 30 A / 40 A (15 s) | 30 A / 40 A (15 s) |
| 3% drop budget | 0.36 V | 0.72 V |
| Current drawn for the same power | Reference | Roughly half |
You do not need to change the module. The current limit of the driver is a hardware limit, it does not grow with the supply voltage; the distinction between continuous current and peak current holds in the same way at both voltages.
What gets overlooked in the changeover
- The motors: they have to be rated at 24V. If you have a fleet of 12V motors on hand, the real cost comes out not in the cable but in the motors.
- Auxiliary equipment: 12V loads such as a lamp, a horn, a receiver or a compressor either have to be changed or fed from a separate line.
- Input signals: the levels arriving from a button, from the panel or from an RF receiver have to suit the new voltage.
- AntiSwitch: since the current profile changes, calibrate the thresholds again; on the PT500 the A1 and A2 pots are for this job.
- The fuse: do not leave the old rating, choose the fuse rating again according to the new continuous current.
Where moving to 24V does not help
If the distance is short and the current small, the gain is too small to be measured; the cable is already of adequate cross-section. If the vehicle electrics are 12V, a second battery group, a separate charging arrangement and a converter are needed; that is far more complexity than the cable cross-section gained. If the problem is not current but mechanical, raising the voltage corrects nothing: a jamming guide, a misaligned shaft or a dry bearing produces the same strain at 24V.
What to do
First measure the current under load in the existing system and the voltage at the driver terminal. If the drop is marked and the distance is long, moving to 24V gives a real gain. If you have made the decision, gather the motor, the auxiliary loads, the fuse and the signal levels into a single list and change them all at the same time; a changeover left half done is the situation that produces the most faults.
The full topic: DC Motor Driver Selection Guide