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Smart Battery Workshop

Smart battery design starts with knowing the details of the system that is using the battery power. A battery does not make a system battery-powered. For operational lifetimes measured in days, weeks or years, power must be a design consideration from the ground up.

Companies such as Raveon Technologies in Carlsbad, CA that produce mission critical devices rely on smart engineering to extend battery life to a maximum. The company’s wearable UHF/VHF personal tracker is intended for multi-day excursions into the wilderness where cellular solutions are not available. As such, the unit has a battery life of several days while maintaining continuous communication with a base station at 5W output power.

Watt-hours can help. Battery research at Raveon yielded more than 50% increase in capacity. Still, battery technology can only yield so much power-per-pound. In terms of usefulness, battery research falls somewhere near the middle of the list of design considerations for battery-powered systems.
These are 10 Tips for smart battery implementation:

  1. smart battery workshopSnooze and sleep. Always consider how speed can be reduced. Try to sleep even for short periods between operations.
  2. Start up faster. Shorter startup yields longer sleep. Cache anything that will speed the process.
  3. Design in parts that can be turned off. Select parts that support receive-only modes when transmission is not necessary. Try to turn on peripherals periodically. Number two (above) applies to any hardware that can be used sparingly.
  4. Lean on wall-powered peers. Receive circuits may be turned off periodically if it’s acceptable for another unit to attempt “first contact” multiple times. Look for ways like this that the system can wait for something to happen. Be as interrupt driven as possible.
  5. Use a co-processor. Allow it to be the arbiter of power modes and battery charging. This will allow almost all components to be turned entirely off. With a co-processor, deep sleep systems can be created that measure their operational lifetime in years.
  6. Research and increase watt-hours. Once the above has been fulfilled, an increase in capacity will result in incredible gains.
  7. Understand the environment. Battery life can be reduced dramatically by ambient conditions. Ensure battery life is acceptable in the most extreme temperature.
  8. Remember “off” current. A unit must not discharge its battery if it is expected to be off. As a rule, a battery should still be half-charged after three months on the shelf.
  9. Add a swappable battery. If all else fails, this can more than double the run time between charges.
  10. Create levels of power reduction and implement full-power modes. Some operational modes are impossible while maintaining longevity. Create configurations that enable features at the cost of battery.

Filed under: Installation Information, System Design | Posted on August 6th, 2012 by chris sonnenberg

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