Aug. 11 2006 12:34 PM

Sometimes it's the little things that make a big difference. Or, perhaps, another saying describes it best: out of sight, out of mind. Regardless of the phrase, logistics professionals don't always look "inside" and consider the impact batteries have on operations. And unfortunately, poor battery management is common among transportation companies using mobile computers negatively impacting employees, operations and the bottom line.


Most mobile computers can operate for no more than six hours per charge. If an employee has to change batteries twice in a shift, that can easily consume 10 minutes a day far more if the employee has to walk to another location to access a fresh battery. That's almost an hour in a five-day workweek, with a likely soft cost of more than $20, or about $1,000 per year. Also add the cost of 40 hours of lost employee time in a year as well as the difficult-to-measure, but significant costs of employee stress caused by the risk of a computer shutting down with little warning.


To combat the loss of countless dollars annually due to battery-related hard and soft costs, many companies using mobile computers turn to high-capacity batteries to lengthen per-charge run times. This typically extends sustained operating times to less than eight hours still less than a work shift. A battery change-out would still be required to keep most mobile computers up and running.


The Solution: Superior Power Management

Obtaining sufficient battery life to enable a mobile computer to run for a full shift (with a significant safety margin) demands intelligent power management in addition to high-capacity batteries. There are five components to intelligent power management, and their implementation impacts not only run time per charge, but also the useful life of mobile computer batteries and management of the battery replacement process.


1. Battery Capacity and Charging

Even before businesses get their hands on their mobile computers, manufacturers are choosing from a wide variety of batteries. Key variables that manufacturers consider include battery capacity and intelligence that can be built into the battery pack. Unfortunately, battery specifications can be confusing and must be clearly understood by the purchaser to better match the end-users' needs. ·


For example, a battery pack with a rating of 3000 mAh (milli-Ampere hours) at 3.7 volts has less capacity than a pack with a rating of 2000 mAh at 7.4 volts. Watt hours (Wh), which is a more meaningful measure of capacity than mAh, takes voltage into account. It's determined by multiplying a battery pack's mAh rating by its voltage. In the example above, the 3000 mAh battery pack has a power capacity of 11.1 Wh, while the 2000 mAh pack has a power capacity of 14.8 Wh. More sophisticated portable designs that come with higher battery capacities usually have multiple cells and higher voltage ratings for example, 7.4 volts instead of 3.7 volts.


Increasing capacity increases run time, but that is not the only benefit: Higher capacity batteries may need less frequent replacement. Lithium-ion batteries are durable and efficient power sources; however, like virtually all battery types, their abilities to store power declines with each charge.


Most battery types used in portable computing have a typical lifespan of 500 complete charge/discharge cycles. But if the battery is routinely recharged before it is fully discharged, it can be recharged more times. Instead of being replaced after 500 discharge/recharge cycles, it might last for as many as 1,500 discharge/recharge cycles three times as long. With a mobile computer that can operate for longer than a full shift on a single battery charge, the battery can be recharged well before it is fully discharged.


Temperature is also a factor in battery recharging. If batteries are rapidly recharged at too high or too low a temperature, damage results, and battery life is shortened a common occurrence when batteries are charged in parked trucks. When the intelligence to sense temperature and communicate with a charger is built into a battery pack, an intelligent charger can respond with smart charging that prevents battery damage. Unfortunately, most mobile computers are not equipped with intelligent batteries.


2. Power Conversion

The power-consuming components in a mobile computer memory, the display and its backlight, the processor, the imaging system and the wireless communication system operate at a number of different DC voltages. DC voltage regulation reduces or boosts voltage from the battery to supply the proper voltage to all components. Mobile computer manufacturers have a wide variety of voltage regulators available. All lose some power in conversion, but the high-efficiency regulators lose relatively little, thereby lengthening per-charge run time. Most mobile computers are built with less costly, comparatively inefficient voltage regulators.


It's more efficient to convert voltage down to meet a component's requirements than it is to convert it up to a higher voltage. And it's far easier to avoid up-conversion with stacked-cell battery packs providing 7.4 volts than it is with battery packs producing 3.7 volts.


3. Load Management

Optimum load management requires the selection of the most energy-efficient mobile computer components. As with batteries and voltage regulators, these high-quality components are typically more costly than the less-efficient equivalents found in most mobile computers. Maximizing per-charge run times also requires intelligent operation of all power-consuming components to minimize power consumption. Some of this intelligence is built into the computer's operating system (most commonly in Windows CE or Windows Mobile). Manufacturers can build additional efficiency intelligence into the computers themselves.


4. Battery Charge Monitoring

Like the gas gauges found in cars, the accuracy of mobile computer battery monitoring varies greatly. Many mobile computers have battery monitoring that is insufficiently precise. If a mobile computer user cannot be sure how much battery charge remains, the only way to avoid the risk of having the computer shut down prematurely with potential loss of valuable data and compromised customer service is to change batteries more often than necessary. Without precise battery monitoring, mobile device users must carry spare batteries an additional cost.


5. Battery Condition Analysis

Because the ability of lithium-ion batteries to accept a charge declines with use, battery condition analysis is a useful tool to help determine when a battery should be replaced typically when a battery's capacity has been reduced to between 60% and 70% of what it was originally. Analysis capability can be built into a battery charger, enabling easy condition monitoring. With constant, accurate condition monitoring, it's easy to replace batteries as required avoiding premature replacement, a potentially great expense for companies with many mobile devices.


The Result: Enhanced Productivity and Lower Hard Costs

To find the best value in mobile computing, it's essential to look at the big picture and consider soft costs, including employee time and stress, as well as hard costs, including number of batteries required and battery service life.


If mobile employees can be assured of a full work shift's computer uptime, they won't have to worry about tracking power use, carrying spare batteries (or getting to where they are available if not carried). They will not have to interrupt their deliveries with a need to change batteries, and they will no longer face losing real-time LAN communication for data downloads or information access or risk losing data. With a major headache eliminated, mobile employees can focus on what's really important: delivering consistent, excellent service to customers.


Kevin Ahearn is Vice President and General Manager , Mobil and Wireless, for Hand Held Products. For more information visit