24 V, 48 V, 72 V: How Battery Voltage Decides Your Motor Drive

When designing an electric machine — or modernising an existing one — battery voltage is the earliest decision to settle. Voltage does not only define the battery; it defines cable cross-section, contactors, fuses and, above all, the current class of the motor drive. A project that starts at the wrong voltage cannot be fixed later by swapping the drive.

Why Voltage Comes First

Power is roughly voltage times current. Produce the same power at a higher voltage and you draw less current. Less current means thinner cable, smaller contactors, lower copper losses and less heat. On the drive side, a smaller current class does the same job.

Losses are the reason this matters: heat loss in cables and joints rises with the square of the current. Halving the current cuts that loss to a quarter. On vehicles with long cable runs the difference is not small.

Same Power, Three Voltages

Take a traction system drawing 3 kW continuously. Setting efficiency and peak demand aside for a rough calculation, the continuous current expected from the drive changes like this:

• At 24 V, around 125 A — this calls for a 300 A class drive (TULPAR 300).
• At 48 V, around 63 A — a 75 A rated drive handles it comfortably (TULPAR 275).
• At 72 V, around 42 A — a 50 A rated drive is enough (TULPAR 250).

Same machine, same work; only the voltage changed, and the drive’s current class dropped to a third. These are rough figures: in a real project, efficiency, starting peak current and duty cycle push them up. They still show the scale of the difference correctly.

What to Weigh When Choosing a Voltage Class

• Existing battery and charging infrastructure: if your fleet already runs on 48 V batteries and chargers, making one machine 72 V adds a new stock item on the operations side.
• The motor nameplate: a motor is wound for a particular voltage. Changing voltage may mean changing the motor as well.
• Cable cross-section and routing: high current needs thick cable, and on tight chassis the bend radius can be a real constraint.
• Peak current demand: on start-up, ramps and lifting, current goes far above the continuous value. Drive selection must be validated against peak current, not continuous.
• Safety and insulation requirements: as voltage rises, insulation, isolation and service safety requirements increase. Where exactly the threshold sits depends on the standard applied to your machine — settle this with your safety engineer.

Voltage Ranges Across NESDrive Models

Filtering by voltage first is the quickest way to narrow the selection. Current ranges:

• TULPAR 300 — 12–48 V and 48–120 V. 300 A rated / 450 A peak. Brushless BLDC / PMSM.
• TULPAR 275 — 12–48 V. 75 A rated / 120 A peak.
• TULPAR 250 — 12–72 V. 50 A rated / 75 A peak.
• TULPAR 200 — 12–48 V. 50 A rated / 55 A peak.
• TULPAR 150 — 12–48 V. 20 A rated / 60 A peak.
• TULPAR 100 — 12–48 V. 10 A rated / 30 A peak.
• BAMSI 300 — 12–72 V. 300 A rated / 450 A peak. Brushed DC.
• BAMSI 200 — 12–48 V. 50 A rated / 100 A peak. Brushed DC.

Worth noting: for a 72 V system, TULPAR 250 covers the brushless side, or the 48–120 V version of TULPAR 300 where high current is needed; on the brushed side, BAMSI 300 sits in range. The 12–48 V band is covered across almost the whole line-up.

Renewing the Drive Without Changing the Battery

A scenario we meet often: the machine runs, battery and motor are in place, but the control board is obsolete or out of spare parts. Here the voltage class is already fixed; the task is to pick a drive that matches the existing voltage and current profile.

On machines with brushed DC motors, modernisation with the BAMSI series is possible without replacing the motor — you gain control, protection and regenerative braking. Moving to a brushless motor means changing motor and drive together, so that decision belongs with the voltage class decision.