Friday, July 31, 2009

Rechargeable Battery Care

Nowadays, rechargeable batteries is a must for our gadgets and is commonly used in mobile phones, notebooks and home electrical appliances. Very often we take them for granted and provide the wrong battery care! Not taking care of your batteries properly not only shorten their lifespan dramatically, but can also cause harm and damage to you and your surroundings. Below, I would cover two commonly used battery types in our household, Nickel-Cadmium (NiCd) and Lithium-Ion (Li-ion).

Nickel Cadmium (NiCd)

Charging / Discharging

NiCd batteries suffer from memory effect, if they are are recharged and discharged to the same level of charge regularly. This is usually obvious when the battery voltage suddenly drops dramatically. However, the capacity is not reduced substantially. To recover this lost capacity, perform a deep or full discharge to INDIVIDUAL CELLS once in a while by using the battery until its fully discharged (or even better, with your battery charger if it came with a deep discharge function). It is not recommended to discharge your battery pack as a whole, as some cells may be discharged earlier, and this will result in a cell reversal charge condition. If you do not have any of these dischargers at your disposal, just use your batteries with an electrical appliance until its near dead flat for the FIRST time (If you have a voltmeter, stop the discharging sequence when the battery pack voltage drops to 1.0 V). After that, recharge it like normal. Individual cells can be discharged to zero voltage without harm.

Do not perform deep discharge too often as it will shorten the lifespan of the battery. (Once a month should be fine)

Lifespan

Typically, 1000 charge cycles before its capacity drops below half of its original capacity.

Storage

If not used, the battery should be discharged to maximum 40% of its capacity and store it in a cool dry environment.

Other precaution measures

Do not mix old and new batteries together. Old batteries loses its capacity quicker and could be damaged due to cell reversal charging. It could also cause damage as hydrogen gas is produced when this occurs.

Lithium Ion (Li-Ion)

Charging / Discharging

Unlike NiCd batteries, Li-Ion batteries do not suffer from memory effect. In fact, they should be charged as often and regularly as much as possible and should NOT be fully discharged. Discharging it fully will damage the battery (below 2.4V) permanently. Good Li-Ion batteries will always self discharge slowly from time to time, since it has an internal safety circuit that will prevent a “dead” battery to be charged (recharging a dead Li-Ion battery can be very dangerous). Since its charging process is a non linear process, its therefore dangerous to charge a Li-Ion battery without any monitoring mechanism. The charging sequence usually consist of 3 parts as quoted from Wikipedia:

Part 1. Apply charging current limit until volt limit per cell is reached.

Part 2. Apply maximum volt per cell limit until the current declines below 0.03C

Part 3. Periodically apply a top-off charge about once per 500 hours.

Some devices may have optimization charging mode when you charge the battery “in-house” together with the device turned on. It is recommended that you turn your device on while charging so that the device is able to monitor and prevent overcharging from occurring. Most dedicated chargers have this circuitry as well. If you are to charge it unmonitored, do not charge it for more than 3 hours or manufacturer specified time.

Lifespan

Typically, 1200 charge cycles. However, it is important to note that Li-Ion batteries age with time, even if not used.

Storage

Charge/Discharge it to 40% and store in a cool place to reduce the aging effects. Do not store a Li-Ion battery at 100% charged.

Other precaution measure

Li-Ion batteries are sensitive to heat. You should consider removing the battery from your equipment like notebook if you are going to connect it to a direct power supply for long hours. You should also buy Li-Ion batteries only when you need it due to its aging effect.

Sources – BatteryUniversity, Wikipedia


3 comments:

Kelvin said...

wah...ur physics is good right haha.
Thanks for the info. Totally dun know these before i read ur post:P

Looi Hong Aun said...

Wow, you're really quick at leaving comments =P. Well, I figure these info is very important because we're using these batteries in almost all our gadgets. I still notice some still do deep discharge for their mobile phone's batteries and a few weeks later complain their battery went dead. There are still other battery types I din't cover because I don't have enough time :P. Anyway thanks for dropping by!

Dolly Sandy said...

awesome work,The charge of a conventional car batteries is actually
12.6V . Depending on the electrolyte solution, charges difference.