Rechargeable Battery Care and Maintenance Guide

There are basically three types of rechargeable Panasonic power tool batteries available for use with consumer electronic products: nickel cadmium (Ni-Cad), Nickel-Metal Hydride (NiMH) and Lithium Ion (Li-Ion). I will discuss the advantages, disadvantages and ways to improve battery performance for each of these three types of rechargeable batteries.

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NI-CAD Batteries
Ni-Cad batteries are probably the most commonly known type of rechargeable batteries in use today. These batteries have a good capacity and maintain a stable voltage throughout their discharge cycle. The stable discharge voltage allows electronic devices, using Ni-Cad batteries, to operate throughout almost the entire discharge cycle. Another advantage to Ni-Cad batteries is that they have a reasonable shelf life between charges. The main drawback to Ni-Cad batteries is the “memory” effect. Another factor that plagues Ni-Cad batteries is the limited number of recharge cycles before the batteries must be replaced. Ni-Cad batteries will usually require replacement every 1-2 years.

Ni-Cad battery memory effect is generally described as the battery operating for a shorter and shorter period of time as the battery gets older. The reason for this is that most people user their Ni-Cad battery operated devices and then promptly place the device into the charger. Over time Ni-Cad batteries develop crystals in the unused portions of the battery material which prohibit the chemical reaction that produces electricity. If you only use your Ni-Cad battery for 30 minutes before placing it back on the charger, over time, your battery will only be able to operate for a maximum of 30 minutes (hence the term memory effect).

There are two simple steps that you can do minimize Ni-Cad battery memory effect. First, always use your Ni-Cad battery operated device until the battery is completely drained. This will minimize crystal build-up and extend your battery’s useful life. Another way to increase your Ni-Cad battery’s useful life is by performing a deep discharge cycle about once a month. A deep discharge cycle is achieved by operating your Ni-Cad powered device until the device completely stops operating. Performing these simple steps should ensure that you achieve maximum life out of your Ni-Cad Hitachi power tool battery.

Ni-MH Batteries
Ni-MH batteries are a newer technology of rechargeable batteries. They have the same advantages as Ni-Cad batteries but they don’t suffer from the memory effect. They also have a longer useful life cycle; about 3-4 years before requiring replacement. The main drawback to Ni-MH batteries is that they have a fairly high discharge rate while in storage. For instance, if you fully charge a Ni-MH battery and then leave it unattended for about a week, it will lose about 20% of its charge.

To avoid this problem, it is advisable to keep your Ni-MH batteries in the charger when they aren’t in use. Because they don’t suffer from the memory effect, keeping them on the charger won’t do any harm. NiMH batteries are more expensive than Ni-Cad batteries, but they will last a lot longer. In the long run NiMH batteries turn out to provide better value.

Li-Ion Batteries
The newest category of commercially available rechargeable batteries are the Li-Ion power tool batteries for AEG. These batteries have all the advantages of Ni-Cad and NiMH batteries plus they have a longer useful life than either of these two types of rechargeable batteries. The main disadvantage to Li-Ion batteries is that they lose about 10% of their useable capacity each year due to chemical breakdown within the cells. There is nothing that can be done to prevent this condition..

Li-Ion batteries have a typical useful life of between 300-500 discharge cycles or about 4-5 years. You can maximize the useful life of your Li-Ion batteries by keeping them on the charger during use (e.g. laptop computer) or keeping them on the charger when not in use. Because Li-Ion batteries are “smart” batteries they cannot be overcharged.

Because Li-Ion battery life is dependent on the number of discharge cycles, anything you can do to minimize the number of discharge cycles will, in effect, increase the battery’s useful life.

Here’s a Li-Ion battery maintenance tip; Li-Ion batteries should be conditioned about once a month. Most Li-Ion batteries have a fuel gauge on the battery (i.e. the LEDs on one side of the battery with a test button) and the electronic device (usually a laptop computer) also has monitoring software to manage the battery power. The accuracy of a Li-Ion battery’s self-monitoring circuitry degrades after about a month of use. If you notice that your battery’s fuel gauge or your device’s operating time estimate is way off, then you probably need to condition your battery.

To calibrate (or condition) your Li-Ion battery, fully charge your batteries (let them charge overnight even if they appear to have a full charge) then operate your device until it shuts down. Recharge your batteries and you should notice an improvement in the accuracy of the operating time prediction.

Here’s a Summary of What You Need to Know About Rechargeable Batteries

Ni-Cad Battery

PRO: Steady Voltage Throughout Discharge Cycle, Good Shelf Life
CON: Suffer from “Memory Effect”
TIP: To minimize memory effect, always operate your Ni-Cad batteries until fully depleted. Completely discharge Ni-Cad batteries about once-a-month
NiMH Battery

PRO: Steady Voltage Throughout Discharge Cycle, no “Memory Effect”
CON: Shelf Discharge Rate Higher Than Ni-Cad Batteries
TIP: Keep NiMH batteries on charger when not in use.
Li-Ion Battery

PRO: Steady Voltage Throughout Discharge Cycle, No Memory Effect, Better Shelf Life Than NiMH Batteries
CON: Lose About 10% Useful Capacity Each Year
TIP: Minimize battery cycles by keeping Li-Ion battery operated devices on charger when available. Condition Li-Ion batteries about once-a-month to keep them calibrated.
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