Assessment of Battery Smart and Pulse Charging

The rapid growth of battery systems for portable power of computers, communications devices, tools and entertainment devices has created a need for better batteries and better electronics for charging these batteries. Although there are some forces decreasing the electrical load on batteries such as the use of 3.3V CMOS logic instead of 5V TTL logic, there are other forces increasing the electrical load, including faster clock speeds on microprocessors that require higher currents. There is the need for longer operating time on each discharge and a longer battery cycle life to amortize the initial battery cost.

Smart battery charging allows faster charging, improvement of the battery cycle life and in many cases, allows the battery user to monitor the battery state of charge. Smart charging involves implementing basic charging methods, such as constant current or constant potential, and adding the measurement of parameters, such as temperature, voltage and current in the battery during charging. The data is used in a feedback loop to determine what the charger does to optimize the charge cycle, or to protect the battery and the user from harm. The advantage of smart charging is that the battery is charged much more quickly without undercharging or overcharging.

It is important to consider battery chemistry when developing charger systems. Guideline believes that lithium-based batteries will continue to evolve to fill many, but not all, market niches. Lithium battery chargers require redundant safety systems to prevent fires. These systems must include monitoring of temperature and voltage, along with watchdog timers.

For lower energy density requirements, NiCd and NiMH will be predominant. For some market niches, small sealed lead-acid cells will be the best choice. For very small, very specialized markets, a variety of different batteries are available, including zinc-air, aluminum-air and silver-air.

In Guideline's opinion, successful smart battery charging systems depend on incorporating the smart charging chip into the battery pack itself. This means that battery parameters are measured at the source and simpler chargers can be produced to implement the charge regime called for by the chip on the battery. Any smart charging product should conform to the de facto smart battery standards jointly developed by Intel and Duracell.

Pulse charging is a controversial topic in the field of battery charging. It has been shown empirically to be effective in charging some batteries faster and may extend the life of a battery. Teltech feels that there are benefits to pulse charging. However, the electrochemical mechanisms behind pulse charging are not understood and none of the available pulse charging techniques have been optimized. Patents and products have been developed by small companies without the resources to thoroughly evaluate their processes. The reputation of pulse charging has suffered as a result. A multidisciplinary study sponsored by a major player is needed and, potentially, government funding.