Is the runtime of a portable device directly related to the size of its battery? While the logical answer should be “yes”, the runtime is actually governed by attributes other than battery size.

We’ve learned that the amount of charge a battery can hold gradually decreases due to usage and aging. Specified to deliver 100% capacity when new, a battery should be replaced when the capacity drops to below 80% of the nominal rating.

The energy storage of a battery can be divided into three imaginary sections: available energy, the empty zone that can be refilled, and the unusable part (rock content) that increases with aging.

In nickel-based batteries, the so-called rock content is present in form of crystalline formation, also known as memory. Restoration is possible with a full discharge to one volt per cell. However, a full repair becomes increasingly more difficult the longer service is withheld. To prevent memory loss, nickel-based batteries should be deep-cycled once every one or two months. Nickel-cadmium and nickel-metal-hydride batteries are used for two-way radios, medical instruments and power tools.

Performance degradation of the lead-acid battery is caused by sulfation and grid corrosion. Sulfation is a thin layer that forms on the negative cell plate if the battery is being denied a fully saturated charge. We already learned that sulfation can, in part, be corrected with cycling and/or topping charge. The grid corrosion, which occurs on the positive plate, is caused by over-charge. Lead-acid batteries are used for larger portable devices and wheeled applications.

Lithium-ion batteries lose capacity through cell oxidation, a process that occurs naturally during use and aging. The typical life span of lithium-ion is two-three years under normal use. Cool storage at 40% charge minimizes aging. An aged lithium-ion cannot be restored with cycling. Lithium-ion is found in cell phones and mobile computing.

As with our human bodies, usage and aging makes batteries increasingly more tired, and in need of proper recharging. So, a healthy lifestyle is key to both longer battery runtime, and a longer life!

For additional information, visit www.batterygiant.com

Do you realize that a typical North American cellular phone provider with about 12 million subscribers receives roughly 70,000 warranty returns per month? Wow. Out of these returned handsets, 50% have mechanical failures; 30% are performance related issues; 15% have battery or charger related problems, and 5% have miscellaneous faults.

Cell phones that use lithium-ion batteries fail less during the warranty period than those cell phones that use the nickel-based chemistries. There are many reasons for the battery failures. The battery may not have been properly charged before use. Perhaps the battery packs remained on the shelf too long or the charger is not functioning correctly. Lack of battery understanding may also be to blame.

To satisfy the customer and honor warranty obligations, stores usually provide a replacement battery, no questions asked. Competition makes it tough to do otherwise. The faulty batteries are then returned to the manufacturer for replacement. Phone manufacturers are aware that 80-90% of the returned batteries have either no problem or can easily be restored with a battery analyzer. The remaining 10-20% can often be revived by reactivating the safety circuit with a boot program and by applying charge/discharge cycles. Only a small percentage of batteries returned under warranty exhibit non-correctable faults.

To reduce the flow of warranty goods, some manufacturers began charging $35.00 for no-fault battery returns. With the added cost, the dealers had no other option than to continue accepting and replacing returns from fickle customers. Warehouses started to fill with dead merchandise; and in 1997 a critical mass was reached. The cost of exchange, lost time by retail staff, shipping, warehousing and paying a subsidy for a replacement phone became a multi-million dollar problem.

A service manager of a leading cell-phone manufacturer hinted that coffee submersion is a common cause of battery failure. The acid in the coffee manages to corrode the electrical conductors in the handset and the battery.

For additional information, visit www.batterygiant.com

While older cell phones were powered with nickel-based batteries, most newer phones are now equipped with lithium-ion. This chemistry is preferable, as it is lightweight, offers high energy density and lasts long enough to span the typical life of the product. Plus, lithium-ion contains no toxic metals.

To obtain thin geometry, some cell phone manufacturers have switched to lithium-ion-polymer. This satisfied consumer requests for slim battery designs. In the meantime, technological advancements also made low profile lithium-ion possible. Thus, lithium-ion packs are now available in 3 mm, a profile that suits most battery designs. Lithium-ion has the advantage of lower manufacturing cost and better performance, plus it has a longer cycle life than the polymer version.

Lithium-ion is a low maintenance battery. No periodic discharge is needed and charging can be done at random. A random charge means that the battery does not need to be fully depleted before recharge. In fact, it is better to recharge the battery before the battery gets too low. Full discharges put an unnecessary strain on the battery. A recharge on a partially charged battery does not cause memory because there is none.

Charging lithium-ion is simpler and cleaner than nickel-based batteries but the chargers require tighter tolerances. Lithium-ion cannot absorb overcharge and no trickle charge is applied on full charge. This allows lithium-ion to be kept in the chargers until used. Some chargers apply a topping charge every week or so to replenish the capacity lost through self-discharge while the battery sits idle in the charger. Repeated insertion of the battery into the charger or cradle does not damage the battery though overcharge. If the battery is full, no charge is applied. The battery voltage determines the need to charge.

On the negative side, lithium-ion loses charge acceptance as part of aging, even if not used. And lithium-ion batteries should not be stored for long periods.  Rather, lithium-ion batteries need to be rotated like perishable food. The buyer should be aware of the manufacturing date when purchasing a replacement battery. Aging affects battery chemistries at different degrees.

So… just like when purchasing food, check the dates, and once in the refrigerator… ROTATE!

For additional information, visit www.batterygiant.com

Batteries for laptops have a unique challenge – they must be small and lightweight. In fact, the laptop battery should be invisible to the user and deliver enough power to endure a five-hour flight from Detroit to San Diego. But we know this rarely happens, as a typical laptop battery provides only about 90 minutes of service, and many of us complain of much shorter runtimes.

Computer manufacturers are hesitant to add a larger battery to the laptop because of increased battery size and weight. A recent survey indicated that, given the option of larger battery size and more weight for longer runtimes, most users would settle for the laptop battery that is being offered today. For better or worse, we have learned to accept the short runtime of a laptop battery.

Laptop batteries age more quickly than in other applications because of heat. During use, the inside temperature of a laptop rises to 45°C (113°F). The combination of high temperature and the battery’s full state-of-charge promotes cell oxidation, a condition that cannot be reversed once present. The battery’s life expectancy when operating at high temperature is half compared to a battery running at a more moderate 20°C (68°F) temperature.  Leaving the laptop battery in a parked car under the hot sun, for example, will aggravate the situation. While all batteries suffer permanent capacity loss as part of elevated temperatures, lithium-ion batteries are affected more than other batteries – and most laptops are powered by lithium-ion batteries. The chemistry in a lithium-ion battery has a high energy density and is lightweight. Alas, there is no immediate breakthrough on the horizon of a miracle battery that would provide more power than the current electro-chemical battery.

So, as with your skin, keep the laptop battery out of the sun.

For additional information, visit www.batterygiant.com