Choosing a 48 V Motor Controller: Watts and Amps

“48V 1000W controller”, “48V 30A controller”… In the battery-vehicle and e-bike world, controllers are usually named by voltage and power. To choose the right one, though, the value that really matters is current. This article explains the relationship between watts and amps on a 48 V system with a simple calculation.

From Watts to Amps: A Simple Calculation

Power is voltage times current: P = V × I. A 1000 W motor at 48 V draws about 1000 ÷ 48 ≈ 21 A. Motor and controller losses push this up a little, so adding a 10–20 % margin is a good starting point.

• 500 W → about 10–13 A
• 1000 W → about 21–25 A
• 1500 W → about 31–38 A
• 2000 W → about 42–50 A
• 3000 W → about 63–75 A

What Really Decides: Peak Current

The power on a motor label is for continuous operation. At start-up, on a ramp or under load the motor can briefly demand two to three times that current. The controller’s peak current must cover these moments, otherwise the vehicle struggles on slopes or the controller goes into protection.

Mind the Fully Charged Battery Voltage

48 V is the nominal battery voltage. Lithium packs can exceed 54 V when fully charged, and energy recovered while braking raises the voltage briefly. Check the controller’s maximum allowed voltage against your battery’s fully charged voltage; if in doubt, ask us with your battery pack details.

The Motor Type Decides the Controller

Most products listed as “48V controllers” are for brushless (BLDC) hub motors. If your vehicle has a brushed DC motor, a BLDC controller will not work; you need a DC motor controller. We explain the difference in BLDC or brushed DC.

NESDrive Models for 48 V

• TULPAR 100: 10 A rated, 30 A peak — compact BLDC applications around 500 W.
• TULPAR 150: 20 A rated, 60 A peak — light vehicles up to about 1000 W.
• TULPAR 200 and TULPAR 250: 50 A rated (55 and 75 A peak) — 2000 W class traction.
• TULPAR 300: 300 A rated, 450 A peak — heavy industrial vehicles.
• For brushed DC: BAMSI 200 (50 A rated, 100 A peak) and BAMSI 300 (300 A rated, 450 A peak).

If the voltage choice is still open, see 24 V, 48 V, 72 V: choosing a motor drive by battery voltage.