Time: Monday,Aug 04,2014

How to Prime Batteries

Caring for the Battery

In many ways, a battery behaves like a human being; it senses the kindness offered and delivers on the care and attention given. Looking after the battery well will return the benevolence bestowed and deliver good performance over a long life. There are exceptions, however, as any parent raising a large family will know, and the generosity given may not always deliver the anticipated returns.

To become a good custodian, we must understand the basic needs of a battery, a subject that is not taught in school. This section teaches what to do when the battery is new, how to feed it the right “food” and what to do when putting the pack aside for a while. The next articles also look into restrictions when traveling with batteries by air and how to dispose of them when their useful life has passed.

Just as we cannot predict a person’s life expectancy at birth, we cannot date-stamp a battery. Some packs live to a great old age while others die young.Incorrect charging, harsh discharge loads and exposure to heat are the battery’s worst enemies. Although we have waysto protect a battery, the ideal situation is not always attainable, and as battery custodians we try to do our best. This chapter discusses how we can get the most from our batteries.

Priming a new Battery

Rechargeable batteries may not deliver their full rated capacity when new and will require formatting. While this applies to most battery systems, manufacturers of lithium-ion batteries disagree. They say that Li-ion is ready at birth and does not need priming. Although this may be true, users have reported some capacity gains by cycling these batteries after long storage.

What’s the difference between formatting and priming? Both address capacities that are not optimized and can be corrected with cycling. Formatting completes the manufacturing process and occurs naturally during early usage when the battery is being cycled. Priming, on the other hand, is a conditioning cycle that is applied as a service tool to improve battery performance during usage or after prolonged storage. Priming relates mainly to nickel-based batteries.

Formatting of lead acid batteries occurs by applying a charge, followed by a discharge and recharge as part of regular use. Do not strain a new battery by giving it extra-heavy duty right away. Gradually work it in with moderate discharges like an athlete trains for weight lifting or long-distance running. Lead acid typically reaches the full capacity potential after 50 to 100 cycles. Do not over-cycle on purpose; this would wear the battery down too quickly.

Manufacturers advise to trickle charge a nickel-based battery for 16 to 24 hours when new and after a long storage. This allows the cells to adjust to each other and bring them to an equal charge level. A slow charge also helps to redistribute the electrolyte to eliminate dry spots on the separator that might have developed by gravitation.

Nickel-based batteries are not always fully formatted when they leave the factory. Applying several charge/discharge cycles through normal use or with a battery analyzer completes the formatting process. The number of cycles required to attain full capacity differs between cell manufacturers. Quality cells perform to specification after 5 to 7 cycles, while others may need 50 or more cycles to reach acceptable capacity levels. Lack of formatting might cause a problem when the industrial user expects a new battery to work to specification right out of the box. Organizations using batteries for critical applications often verify performance through a discharge/charge cycle as part of quality control. Automated analyzers (Cadex) apply as many cycles as needed to achieve full capacity.

Cycling also restores lost capacity when a nickel-based battery has been stored for six months or longer. Storage time, state-of-charge and the temperature under which the battery was stored govern the recovery. The longer the storage and warmer the temperature, the more cycles will be required to regain full capacity. Battery analyzers help in the priming functions.

Some scientists believe that with use and storage, a passivation layer builds up on the cathode of a lithium-ion cell. Also known as interfacial protective film (IPF), this layer restricts ion flow and increases the internal resistance. In the worst cases, the phenomenon can lead to lithium plating. Charging, and more effectively cycling, is known to dissolve the layer. Scientists do not fully understand the nature of this layer, and the few published resources on this subject only speculate that performance restoration with cycling is connected to the removal of the passivation layer. Some scientists deny outright the existence of the IPF, saying that the idea is highly speculative and inconsistent with existing studies. Another layer is the solid electrolyte interphase (SEI), which is said to form at the anode on the initial charge. SEI is an electric insulation yet provides sufficient ionic conductivity for proper function.

Whatever the truth may be, there is no parallel to “memory” of NiCd batteries, which require periodic cycling. The symptoms may appear similar but the mechanics are different. Nor can the effect be compared to sulfation of lead acid batteries.

Lithium-ion is a very clean system and does not need formatting when new, nor does it require the level of maintenance that nickel-based batteries do. The first charge is no different than the fifth or the 50th. Formatting makes little difference because the maximum capacity is available right from the beginning. Nor does a full discharge improve the capacity once faded. In most cases, a low capacity signals the end of life. A discharge/charge may be beneficial for calibrating a “smart” battery, but this service only addresses the digital part of the pack and does nothing to improve the electrochemical battery. Instructions to charge a new battery for eight hours are seen as “old school” from the nickel battery days.