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Improve Battery Performance with Proper Charging Methods Understanding different charging methods is key to extending the life of batteries destined for medical electronics. To a large extent, the reliability and longevity of a battery hinges on the quality of the charger. In a price-competitive market, chargers are often given low priority, especially for consumer products. This article assesses the charger as the quintessential provider and guardian of the battery. It also examines recommended charge methods to increase the performance of nickel-cadmium (NiCd), nickel­metal hydride (NiMH), and lithium ion (Li-ion) packs. Well-performing batteries and chargers are especially important for instruments where battery failure is not an option. A battery should always remain cool during charging because high temperatures shorten battery life. However, some temperature rise cannot be avoided when charging nickel-based batteries. The temperature peaks when the battery approaches full charge, then moderates after the battery switches to trickle charge. The battery should eventually cool to room temperature. If the temperature remains above room temperature after a few hours in ready mode, the charger is performing incorrectly. Remove the battery when ready because any prolonged trickle charging will damage the battery. The caution applies especially to NiMH because this chemistry cannot absorb overcharge well. A lithium-based battery should never get warm during charge. If this happens, either the battery or the charger is faulty. Discontinue its use. Nickel-based chargers are grouped into three categories: slow, quick, and fast. The slow charger, also known as , applies a fixed charge of about 0.1 C (one-tenth of the rated capacity) for as long as the battery is connected. The charge time is 14­16 hours. The C rate is a unit by which charge and discharge currents are scaled. A charge current of 1000 mAh (1 C) will charge a 1000-mAh battery in slightly more