Everything You Never Wanted to Know About Batteries
Here's a primer about batteries.
Read this and you should know more about batteries than anyone else you know.

NiCad
Nickel Cadmium batteries, better known as NiCad’s are the cheapest and most durable rechargeable batteries we will discuss. They offer a pretty good power-to-weight ratio and maintain a constant voltage output, meaning they maintain the same voltage output until almost completely discharged then they'll suddenly drop. They also perform well under rugged conditions like cold.

With a shelf life as much as five years while still able to hold a charge. NiCad's will need replacing far less frequently than other rechargeable batteries.

Discharging NiCad's completely/too deeply, over and over can damage them. They should be used until almost complete discharge is reached, then recharged.

Memory Myth:
NiCad batteries have always been related to the "memory effect". The memory effect goes like this:
Precisely repeated charging to full without overcharging, then discharging to a point not completely discharged. results in the battery remembering this shortened charge/discharge cycle and thinks this is actually a full cycle.

Memory Myth Reality:
The fact is there is no "memory effect". What can happen and is mistaken for the "memory effect" is called a voltage depression. If a NiCad battery is repeatedly OVER charged, crystals can form on the cell plates damaging the battery and resembling the "memory effect". Exercising the battery once a month by Discharging to almost full discharge then recharge fully without overcharging can eliminate these crystals thus eliminating the voltage depression.

At room temperature a new NiCad battery loses about 10% of its capacity in the first 24 hours after removing from the charger. The self discharge rate settles to about 10 to 20% per month after that.

Advantages:
* Lowest cost
* Rugged, Excellent load performance, even at cold temperatures
* Longevity, up to five years
* Can be stored for long periods (Although may hold lesser charge)
* Easy to recharge after prolonged storage

Disadvantages:
* Susceptible to Voltage depression from overcharging
* Damaging effects from repeated deep discharge
* Contains toxic metals
* Fairly high self discharge rate
* High maintenance-Exercise once every month, (full discharge, full charge)




NiMH
Nickel Metal Hydride batteries are similar to Nickel Cadmium but without the environmentally unfriendly metal cadmium making a more "environment friendly" battery has a much higher capacity than NiCad's, about 30% higher. NiMH batteries suffer far less from "Voltage Depression" or inappropriately known as the "memory effect" discussed earlier. Exercising the battery once every 3 months should keep this problem at bay.

However, the "self discharge" rate of Nickel Metal Hydride batteries are significantly higher than that of a NiCad battery at about 30% per month, even more in hotter climates.



NiMH batteries are not as rugged as NiCad's and have a shorter life span of 2 to 3 years compared with NiCad's at up to 5 years. Plus high ambient temperatures can greatly reduce their life span.

Advantages:
*No toxic metals
*Higher capacity than NiCad (30%)
*Minimal Voltage Depression susceptibility

Disadvantages:
* Limited life span (2 to 3 years)
* High self discharge rate
* High temperatures shorten life span
* Some maintenance-Exercise once every 3 months, (full discharge, full recharge)




Li_Ion
Lithium-ion batteries have a high energy density, meaning, a smaller lighter battery can store more energy than Nicad or NiMH.

Lithium-ion is a low maintenance battery. There is no so-called memory and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge rate is less than half compared to nickel-cadmium. At 5% in the first 24 hours after charging, then only 1 to 2% a month thereafter. Lithium-ion cells have much less toxic waste, causing little harm when disposed. But always recycle your rechargeable batteries.

Despite its overall advantages, lithium-ion has its drawbacks. It is fragile and requires a protection circuit which is built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge. This alone makes Lithium-ion fairly expensive to manufacture, therefore more costly to consumers.

Aging is a concern with most lithium-ion batteries and manufacturers don't readily offer this information. Some capacity deterioration is noticeable after one year, whether the battery is in use or not and the battery can fail after two or three years, offering the shortest life span of the battery chemistries covered.

Manufacturers are constantly improving lithium-ion and life span may increase in future chemistries/versions.

Storage in a cool place can slow the aging process. Manufacturers recommend storage temperatures of 15°C (59°F). In addition, the battery should be partially charged during storage. 40% charge or more.

Advantages:
* High energy density - (potential for yet higher capacities).
* Relatively low self-discharge - (self-discharge is less than half that of nickel-based batteries).
* Low Maintenance - Virtually no voltage depression Limitations (periodic exercising not necessary)

Disadvantages:
* Fragile, Requires protection circuit to maintain voltage and current within safe limits.
* Subject to aging, even if not in use - storing the battery in a cool place and at 40% charge reduces the aging effect.
* Expensive to manufacture - (about 40 percent higher in cost than nickel-cadmium.)

Whew! that was a lot on information, but now you know.