Question

Calculate the number of 12 V batteries (capacity 120 Ah) needed to run a 3 kW DC motor that operates in 240 V. How many hours the motor will run with 20 of such batteries connected in series?

Answer 1

• 20 batteries
• 9.6 hours

Step-by-step explanation:

To obtain 240 V from 12 V batteries they must be connected in series. The number needed is ...

240/12 = 20 . . . batteries needed

__

The current draw will be ...

(3000 W)/(240 V) = 12.5 A

Then the time available from the battery stack is ...

(120 Ah)/(12.5 A) = 9.6 h

The motor can run 9.6 hours from the series connection.