Secondary batteries have lower capacities but are more resilient at a load of 1C

June 21 [Fri], 2013, 15:14
The growth has been in secondary batteries (rechargeable) but non-rechargeable or primary batteries are equally important. They continue to fill an important niche market in applications such as wristwatches, remote controls, electric keys and children’s toys. Primary batteries also assist when charging is XPS 14 laptop battery
Other applications of primary batteries are tire pressure gauges in cars and trucks, transmitters for bird tracking, pacemakers for heart patients, intelligent drill bits for mining,as well as light beacons and remote repeater stations. High specific energy, long storage times and operational readiness make this battery well suited for such applications. The battery can be carried to remote locations and used instantly, even after long storage. Most primary batteries are inexpensive, readily available and environmentally friendly.

Carbon-zinc, also known as the Leclanché battery, is the least expensive battery and comes with consumer devices when batteries are included. These general purpose batteries are used for applications with low power drain, such as remote controls, flashlights, children’s toys and wall clocks. One of the most common primary batteries for consumers is the alkaline-manganese, or alkaline for short. Lewis Urry invented it in 1949 while working with the Eveready Battery Company Laboratory in Parma, Ohio. Alkaline delivers more energy at higher load currents than carbon-zinc. Best of all, alkaline does not leak when depleted, as carbon-zinc does. On the negative side, alkaline is more expensive than carbon-zinc.

Primary batteries have one of the highest energy densities. Although secondary batteries have improved, a regular household alkaline provides 50 percent more energy than lithium-ion. The most energy-dense primary is the lithium battery made for film cameras and military combat. It holds more than three times the energy of lithium-ion and comes in various blends, such as lithium-metal, lithium manganese dioxide, lithium-sulfur dioxide, lithium-thionyl chloride, lithium oxygen and others. Figure 1 compares the typical gravimetric energy densities of lead acid, NiMH, Li-ion, alkaline and lithium primary batteries.

Specific energy indicates the energy a battery can hold. This, however, does not guarantee delivery. Primary batteries tend to have high internal resistance, which limits the discharge to light loads such as remote controls, flashlights and portable entertainment devices. Digital cameras are borderline ― a power drill on alkaline would be unthinkable.

Manufacturers of primary batteries only specify specific energy; the specific power (ability to deliver power) is not published. While most secondary batteries are rated at a discharge current of 1C, the capacity of primary XPS 17 laptop battery is measured by discharging them at a very low current of 25mA, or a fraction of a C. In addition, the batteries are allowed to go down to a very low voltage of 0.8 volts per cell. This evaluation method provides impressive readings on paper, but the results are poor under a more demanding load.

Figure 2 compares performance of primary and secondary batteries on a discharge of 1C. The results are indicated in Actual and Rated. Actual is the Wh/kg derived at a 1C discharge, Rated is the Wh/kg the manufacturer specifies when discharged at a much low current. While the primary batteries do well on a discharge representing entertainment device, secondary batteries have lower capacities but are more resilient at a load of 1C.