What's the best battery for wheeled and stationary applications?

Consumer products have benefited the most from the advancements in battery technology. The size and weight reductions achieved for the high-end cell phones, PDA's and laptops have not trickled down to batteries for wheeled and stationary applications in an expected fashion. Only marginal improvements have been gained on larger batteries. One of the reasons for the apparent lack in progress is the loyalty to the classic sealed lead-acid battery.

The wheeled and stationary industries have several reasons for their unwillingness to change: [1] lead-acid is mature and inexpensive. [2] The low energy density is no major drawback because the battery is either on wheels or is stationary. [3] The limited cycle life can, to some extent, be compensated by using larger batteries. Unlike portable devices, most wheeled and stationary batteries are replaced due to age rather than wear out effect induced by high cycle count.

What's the best battery for wheelchairs?

Wheelchairs and scooters are almost exclusively powered by sealed lead-acid batteries. Regular car batteries are sometimes used for cost reasons. There is, however, a danger of spillage if overturned. Neither are regular car batteries designed for deep cycling. The demanding cycling regiments of wheelchairs and scooters cause an undue strain on these batteries and shorten their lives. nickel-based batteries would be lighter than lead-acid but are more expensive and maintenance prone. Lithium-ion would simply be too delicate, not to mention the high cost.

A new generation of wheelchair is being developed that is able to 'stand up' and climb chairs. These high-tech devices use gyroscopes for balancing. To obtain the extra power needed to run its internal computer and electric motors without adding too much weight, nickel-based batteries are used. The two-wheeled Segway scooter being touted to solve city transportations problems also uses nickel-based batteries.

What's the best battery for the electric bicycle?

Anyone serious about the electric bicycle would use nickel-based batteries. Sealed lead-acid is simply too heavy and does not provide the cycle count needed to satisfy daily use. In addition, lead-acid requires a long charge time of 10 hours and more. Lithium-ion would simply be too expensive and delicate. The lack of a suitable battery that is light, durable and inexpensive is, in my opinion, delaying the public acceptance of the electric bicycle.

What's the best battery for the electric vehicle?

The electric vehicle will gain public acceptance as soon as a battery emerges that is inexpensive and provides 10 years of reliable service. The high cost and limited cycle life of the batteries used in hybrid vehicles negate the savings achieved in burning less fuel. The benefits are more environmental in nature rather than in cost savings. Higher fuel prices could change this equilibrium.

nickel and lithium-based batteries have been tried but both chemistries have problems with durability and stability. lithium-ion has an advantage in weight but this gain is offset by a high price. Similarly, nickel-metal-hydride used for the hybrid vehicle is expensive and requires forced air-cooling. No battery manufacturer is willing to commit to a 10-year warranty. After excursions into new battery chemistries, design engineers always come back to the old but proven lead-acid.

The fuel cell may still be two decades away before offering a viable alternative for cars. An executive from Ford stated recently that the fuel cell may never be feasible to replace the internal combustion engine. Cost and longevity remain major drawbacks.

Since the invention in 1839 by Sir William Grove, the advancements in the fuel cell have been slow. Much attention was then placed on improving the internal combustion engine. It was not until the Gemini and Apollo programs in the 1960s that the fuel cell was used to provide power and water in space. During the 1990s, renewed activities took place and the fuel cell stocks soared. Unlike the rapid developments in microelectronics, which generated income in its early stages, fuel cell research continues to depend on government grants and public investors. It is our hope that one day the fuel cell will become a viable option to the polluting combustion engine.

What's the best battery for stationary applications?

Until the mid 1970s, most stationary batteries were flooded lead-acid. The Valve Regulated Lead Acid (VRLA) allowed batteries to be installed in smaller confinements because the cells could be stacked and mounted in any position. Although VRLA are less durable than flooded lead-acid, simple mounting and lower cost make them the preferred battery system for small and medium sized installations. Most UPS systems repeater stations for cell phones use VRLA. Large installations, such as internet hubs, hospitals, banks and airports still use the flooded lead-acid.

Heat is the main killer of batteries. Many outdoor installations for communication systems lack proper venting, not to mention air conditioning. Instead of the expected 10-year service life, the batteries need replacement after 2 to 5 years. Many batteries in the field are in such bad conditions that they could only provide power for a short time, should a major power outage occur. Stationary batteries are often installed and forgotten.

A Canadian manufacturer of lithium-polymer batteries is taking advantage of the heat problem. They offer lithium-polymer for standby applications, a battery that needs heat to operate. The dry lithium-polymer lacks conductivity at ambient temperature and must be heated. The battery includes heating elements to keep its core temperature at 60°C (140°F). The mains provide the energy for heating. On a power outage, the battery must also provide power for heating the core. To conserve energy, the battery is well insulated. Unlike the VRLA, the high ambient heat does not shorten the lithium-polymer battery. The high cost remains a drawback and only a few lithium-polymer batteries are used for stationary applications today.

Flooded nickel-cadmium batteries have been used for many years in applications that must endure hot and cold temperatures. This battery system is substantially more expensive that Lead-acid but the improved longevity makes up for the higher investment cost. The flooded nickel-cadmium batteries are non-sintered and do not suffer from memory. It should be noted that only the sintered sealed nickel-cadmium cells are affected by memory and need regular discharges.

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world.
Cadex Electronics is a manufacturer of advanced battery chargers, battery analyzers and PC software. For product information please visit www.cadex.com.