A rechargeable battery can be modeled as an ideal emf in series with a resistanc
ID: 1618287 • Letter: A
Question
A rechargeable battery can be modeled as an ideal emf in series with a resistance. You recharge the battery by connecting it to a power supply with a higher voltage than the emf of the battery. The current goes the "wrong way" through the battery, reversing the chemical reactions in the battery and recharging it. A higher voltage power supply means more current, faster charging, and also means the battery heats up more due to power dissipated in the internal resistance.
A typical battery has an emf of 1.2V and an internal resistance of .75 ohms.
Sketch a recharging circuit that includes the battery and power supply.
What voltage power supply would be needed to provide a typical current of 300mA to recharge the battery?
With a 300mA recharging current, what power is being dissipated as heat in the internal resistance of the battery.
Explanation / Answer
a.
b. power supply = emf of battery to be charged + potential drop due to internal resistance
=1.2 + 300 x 10-3x0.75 = 1.425 V
c. power dissipated as heat = current2 x resistance= ( 300 x 10-3)2 x 0.75 = 0.0675 j