Question

. You have completed your design of a new surgical headlamp. You have decided to power the headlamp using four AA rechargeable batteries. Each battery is rated at 1.2V, 2550 mAh. Your design uses an LED light that consumes a constant 3W. The LED is driven by a current source that takes power from the batteries and provides a constant current to the LED. The current source is 95% efficient. How long will the LED run before the batteries are depleted?

Answer 1

Answer:

LED run before the batteries are depleted is 3.87 hours

Explanation:

given data

battery = 4 AA

battery is rated = 1.2V, 2550 mAh

power = 3 W

efficient = 95%

to find out

How long will the LED run before the batteries are depleted

solution

we consider here power delivered by battery is = x

so power = x × efficient

3 = x 95%

x = 3.15 W

and

voltage by 4 battery is = 4 × 1.2 = 4.8 V

so current will be = $\frac{x}{volatge}$

current = $\frac{3.15}{4.8}$

current = 0.6577 A

so total discharge hours = $\frac{2550}{current}$

total discharge hours = $\frac{2550}{657.7}$

time = 3.87 hours

so LED run before the batteries are depleted is 3.87 hours