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Switcher Hangout The place for switchers to discuss their new machines, and how to work with OS X. General support can be had here for newbie stuff, like "How do I restart my new iMac?" :)

G4 Battery

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Is there an optimal way to charge the Powerbook G4 battery? Specifically, is it best to run it down to almost 0% and then charge it fully, or can I just regularly charge it from various levels of battery life remaining.

I'm also curious to know what happens when the battery dies, if anything.
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Newer Powerbook's battery is a 'Lithium-Ion' or 'Lithium-Polymer' type. Mean thery have no memory effect unlike the older Nickel Metal-Hydrates (NiMH) and Nickel Cadmium (NiCd). Normally they should last 12-24 months, after which the battery's chemistry will be worn out and a replacement will be required.

Battery Facts (Q&A):


When do you charge a lithium ion battery? Do you wait until it's very low like around 20% or is it good to start charging the battery when the voltage drops? How do you maintain a good healthy lithium ion battery?


Unlike nickel-cadmium and nickel-metal hydride rechargeable batteries, lithium-ion (li-ion) rechargeable batteries have no memory effect, therefore, it is not necessary to fully discharge your battery before recharging. Actually, li-ion batteries will generally last longer if you do not completely discharge them before recharging. For example, if you regularly recharge a li-ion battery only after discharging it completely (known as "100% Depth of Discharge"), you can generally expect to obtain between 300 and 500 charge-discharge cycles. However, if you recharge the battery after only a partial discharge, e.g., 50%, you can expect to achieve over 500 charge-discharge cycles; even more if you use a lower depth of discharge, such as 20%. Therefore, you can effectively recharge li-ion batteries even if they have only been discharged for a short time.

To maintain a healthy battery, follow the device manufacturer's charging recommendations, and do not expose the battery to temperatures above 60 degrees C (140 degrees F).

Polymer Charging


We plan to use constant voltage - constant current to charge a Lithium Polymer battery:
1. What is the maximum current charge allowed? 1C, 1/2C or what?
2. Can we charge a Lithium Polymer battery EXACTLY like a Lithium Ion battery?


At 08/16/2001 10:09 AM we wrote - The maximum charge current allowed is the C Rate of the individual cell (1C). The recommended charge current is the C/2 rate (0.5C).

You can charge a Lithium Polymer battery exactly like a Lithium Ion battery providing the above charging rates are used. Please refer to our Safety Precautions Guide for detailed information on charging.

Lithium ion and polymer charging recommendations


I am trying to get the correct information regarding the use of my battery in mobile phones and computers. At the store, when we buy a new phone, they suggest to fully charge the lithium-ion/Polymer battery for at least 24 hours, then discharge completely until the device powers off itself, and than repeat this operation two more times. In an article I've read, they mention that the lithium battery life would be affected if discharging completely before charging.

So, what is the best way to keep my lithium-ion/Polymer battery in the best condition so it provides good performance and lasts long?


We recommend fully charging your battery before using it the first time. 24 hours is not necessary, as your charger and battery circuitry will automatically stop charging the battery when it's fully charged, generally in 3 to 6 hours. Unlike nickel-cadmium and nickel-metal hydride rechargeable batteries, li-ion and polymer rechargeable batteries have no memory effect, therefore, it is not necessary to fully discharge your battery before recharging.

Li-ion and polymer cells and batteries will generally last longer (more charge/discharge cycles) if you do not completely discharge them before recharging for the following reasons:

The shelf life of a lithium ion cell is a function of the self discharge, temperature and state of charge (SOC) conditions imposed upon the cell. As the storage temperature and SOC increase, the resultant capacity upon discharge decreases and the impedance of the cell increases. The shelf life is almost cut in half by holding the cell at 100% SOC at temperatures between 30C and 60C as opposed to 50% SOC at the same temperature range. The effect is not as pronounced at room temperature, with the shelf life roughly 75% at a 100% SOC condition as opposed to 50% at elevated temperatures.

Float charges can harm lithium ion chemistry and are not recommended.


Other Facts

Which are better, NiCd batteries or NiMH batteries?[/b]

For most electronic devices it is better to use NiMH batteries than NiCd batteries.* NiCd batteries use Cadmium, a highly toxic heavy metal, that can damage the environment if not disposed of properly. (They should be recycled not discarded).* NiMH batteries usually have a higher capacity than NiCd batteries of the same size.* Some people argue that NiCd batteries deliver faster discharge rates than NiMH batteries.* While this may be true under certain circumstances, the difference is not relevant when considering power sources for electronic devices like digital cameras or portable music players. (If you are choosing a battery to drive a high torque power screwdriver, then NiCds can outperform NiMH).* NiMH batteries require more sophisticated chargers than those typically used for NiCd batteries.* But smart chargers designed especially for NiMH batteries are now readily available.

MH and NiCd batteries self discharge at a MUCH faster rate than alkaline batteries.* In fact, at "room temperature" (about 70 degrees F) NiMH and NiCD batteries will self discharge a few percent PER DAY.* Storing them at lower temperatures will slow their self discharge rate dramatically.* NiMH batteries stored at freezing will retain over 90% of their charge for* full month. So it might make sense to store them in a freezer.* If you do, it's best to bring them back to room temperature before using them. Even if you don't freeze your NiMH batteries after charging them, you should store them in a cool place to minimize their self discharge.
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