Power for portables

Energy density requirements and available flashlight cells suggest the use of lower voltages in power supplies for hand-carried portables. Optimum time utilization of rechargeable batteries requires high charging rates, yet portable radios tend to insulate the batteries thermally, making overcharge at normal rates undesirable. A dual-rate charger with voltage sensing alleviates the overcharge problem. For maximum time utilization, this concept can provide a 15-minute charge to 70 percent capacity. Description is provided of this high-rate charger, with suitable precautions for use in two-way radio environments.