Batter Tips

Battery Knowledge

Battery Classifications

Primary Battery – energy is exhausted when active materials are consumed (carbon-zinc dry cell, lithium battery, silver oxide battery, alkaline battery)

Secondary Battery – active materials are regenerated by charging (nickel cadmium (NiCd), nickel metal hydride (NiMH), Lithium Ion, Lithium Polymer, Sealed Lead Acid.

Nickel-cadmium Battery- mature but has moderate energy density. Nickel-cadmium is used where long life, high discharge rate and extended temperature range is important. Main applications are two-way radios, biomedical equipment and power tools. Nickel-cadmium contains toxic metals.

Nickel-metal-hydride Battery- has a higher energy density compared to nickel-cadmium at the expense of reduced cycle life. There are no toxic metals. Applications include mobile phones and laptop computers. NiMH is viewed as steppingstone to lithium-based systems.

Lead-acid Battery- most economical for larger power applications where weight is of little concern. Lead-acid is the preferred choice for hospital equipment, wheelchairs, emergency lighting and UPS systems. Lead acid is inexpensive and rugged. It serves a unique niche that would be hard to replace with other systems.

Lithium-ion Battery- fastest growing battery system; offers high-energy density and low weight. Protection circuit are needed to limit voltage and current for safety reasons. Applications include notebook computers and cell phones. High current versions are available for power tools and medical devices.

Memory Effect

The condition of rechargeable nickel cadmium and nickel metal hydride batteries in which it continues to hold less of a charge over time. It is said to “remember” how full it was when last charged because it will not charge past that point the next time. This is why you should completely drain nickel-based batteries every month or so.The memory effect is caused by a combination of chemical reactions; however, the cadmium in a nickel cadmium battery is the bigger problem and why nickel metal hydride batteries fare somewhat better. In a fresh battery, the anode’s cadmium crystals are approximately one micron across. If the battery sits in the charger too long or is not fully discharged, over time, the crystals grow to as much as 100 microns. This conceals more of the active material to the electrolyte and reduces battery life

Do & Don’t Battery Sheet

	Nickel-cadmium (NiCd)	Nickel-metal-hydride (NiMH)	Lithium-ion (Li-ion)	Lead-acid (Sealed or flooded)
Used in	Two-way radios, power tools, medical.	Similar application as NiCd; higher density.	Cell phones, laptops, video cameras.	Motorcycles, cars, wheelchairs, UPS.
Charging	Do run the battery fully down once per month; try to use up all energy before charging. Do not leave battery in charger for more than 2 days because of memory. Avoid getting battery too hot during charge. Charge methods: Constant current, followed by trickle charge when full. Fast-charge preferred over slow charge. Slow charge = 16h Rapid charge = 3h Fast charge = 1h+	Do run the battery fully down once every 3 months. Over-cycling is not advised. Do not leave battery in charger for more than 2 days because of memory. Avoid getting battery too hot during charge. Charge methods: Constant current, followed by trickle charge when full. Slow charge not recommended. Battery will get warm towards full charge. Rapid charge = 3h Fast charge = 1h+	Do charge the battery often. The battery lasts longer with partial rather than full discharges. Do not use if pack gets hot during charge. Check also charger. Charge methods: Constant voltage to 4.20V/cell (typical). No trickle-charge when full. Li-ion may remain in the charger (no memory). Battery must remain cool. No fast-charge possible. Rapid charge = 3h	Do charge the battery immediately after use. Lead-acid must always be kept in a charged condition. The battery lasts longer with partial rather than full discharges. Over-cycling is not advised. Charge methods: Constant voltage to 2.40/cell (typical), followed by float held at 2.25V/cell. Battery must remain cool. Fast charge not possible; can remain on float charge. Slow charge = 14h Rapid charge = 10h
Discharging	Full cycle does not harm NiCd. NiCd is one of the most hardy and durable chemistries.	Avoid too many full cycles because of wear. Use 80% depth-of-discharge. NiMH has higher energy density than NiCd at the expense of shorter cycle life.	Avoid full cycle because of wear. 80% depth-of-discharge recommended. Re- charge more often. Avoid full discharge. Low voltage may cut off safety circuit	Avoid full cycle because of wear. Use 80% depth-of-discharge. Recharge more often or use larger battery. Low energy density limits lead-acid to wheeled applications
Service needs	Discharge to 1V/cell every 1 to 2 months to prevent memory. Do not discharge before each charge.	Discharge to 1V/cell every 3 months to prevent memory. Do not discharge before each charge	No maintenance needed. Loses capacity due to aging whether used or not.	Apply topping charge every 6 months. Occasional discharge/ charge may improve performance.
Storage	Best to store at 40% charge in a cool place. Open terminal voltage cannot determine state-of-charge. 5 years and longer storage possible. Prime battery if stored longer than 6 months.	Store at 40% charge in a cool place. Open terminal voltage cannot determine state-of-charge. Prime battery if stored longer than 6 months.	Store at 40% charge in a cool place (40% state-of-charge reads 3.75-3.80V/cell at open terminal. Do not store at full charge and at warm temperatures because of accelerated aging.	Store always at a full state-of-charge. Do not store below 2.10V/cell; apply topping charge very 6 months.
Disposal	Do not dispose; contains toxic metals; must be recycled.	Should be recycled. Low volume household NiMH may be disposed.	Should be recycled. Low volume household Li-ion may be disposed	Do not dispose; must be recycled.

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