Specifications

Charge and Discharge Batteries in Less Time

Using a power supply in constant-

current mode (Figure 1) is a simple

way to recharge batteries, and it also

lets you achieve 100% charge levels.

On the downside, this method is slow,

taking as long as 14-16 hours because

the charging current is only a fraction

of the battery’s amp/hour rating.

Pulse charging, also called transient

mode, shortens the charging time, yet

still charges the battery to over 90%

capacity (Figure 2). The electronic

load acts as a switch, providing the

current pulses. (Note that you can

also use an electronic load to program

constant-current charging.) Figure 3

shows a typical pulse-charging current

waveform.

To simulate battery drain, you can

also program the electronic load to

discharge batteries with either con-

stant or pulse current waveforms. In

some cases, pulse discharging does

a better job of mimicking a product’s

energy-saving features. Simulating

cellular phone battery discharge,

for instance, is complex due to the

phone’s various operating modes—

standby, dialing, and talking. You can

create the necessary tri-level discharge

current wave-form shown in Figure 4

using the electronic load.

Figure 1: Constant current charging is simple and effective, but

it can be very slow. (The diode prevents the battery from dis-

charging through the power supply if the supply voltage drops

below the battery voltage.)

Figure 2: Pulse charging using an electronic load is much

faster, while still achieving 90% recharge.

Figure 4: A complex waveform that simulates the energy-saving

features in portable, battery-powered products

Figure 3: A typical pulse charging waveform created with an

electronic load

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