Generally used Lithium ion battery

Portable cordless power tools like laptop, cell phone, camera, mp3 device and so on are very common to everyone nowadays, so the need for rechargeable battery grown substantially recently. Almost all of our rechargeable batteries for those mentioned devices have replaced by lithium ion batteries.
Lithium-ion batteries have high energy density, lighter, can handle recharge/discharge cycles, low charge losses per month(around 5% per month of its charge only.)Lithium-ion battery packs are expensive, to make yours to last longer, here are some things to keep in mind:

• Lithium ion chemistry prefers partial discharge to deep discharge, so it's best to avoid taking the battery all the way down to zero. Do not use up all the charge stored in the battery Since lithium-ion chemistry does not have a "memory", you do not harm the battery pack with a partial discharge. If the voltage of a lithium-ion cell drops below a certain level, it's ruined. Unlike Nickel-cadmium battery, they have no memory effect, which means that you do not have to completely discharge them before recharging.

"Memory Effect:
This is when the battery is continually recharged before it has discharged more than 50 percent of its power, causing it to essentially "forget" that it could fully discharge to begin with. Therefore, the battery can no longer store as much as its actual power capacity. Battery life shortened."

• Lithium-ion batteries age. They only last two to three years, even if they are sitting on a shelf unused. So do not "avoid using" the battery with the thought that the battery pack will last five years. It won't. If you are buying a new battery pack, you want to make sure it really is new. If it has been sitting on a shelf in the store for a year, it won't last very long, because it degrade as soon as they leave factory. Manufacturing dates are important.
• Avoid heat, which degrades the batteries. Lithium ion extremely sensitive to high temperatures. Heat causes lithium-ion battery packs to degrade much faster than they normally would.

Article source: How Lithium Ion Works

Preserving Our Rechargeable Battery

Batteries come in many varieties, from lead acid, to nickel-cadmium, nickel metal hydride and lithium ion.
Every battery has its own Charge Storing Life Time, there's no battery, rechargeable or otherwise, will last forever. All batteries suffer from aging cells and the longer they are used, the less charge capacity they ultimately will have. Rechargeable batteries are still a great way to save money and reduce waste.
Recharging time is shortened sequentially from more than 10 hours to less than one hour.

First thing we are going to consider is "Rate of charge".
Rate of charge : quantity of electrical current is allowed into battery by your charger.
To preserve batteries' charge capacity, a good charger is needed to avoid over charge. Overcharging may occur when batteries charger has high charging rate. The quicker the rate of charge, the more chance there is of over charging, which can ruin a battery's chance of holding its charge. To avoid over charge, it's depend on ability to dissipate the charging current once maximum power has been reached. Most chargers have built-in voltage regulators do this, allowing you to safely leave your cell phone or computer plugged in overnight.

One common problem in nickel-cadmium rechargeable batteries is something known as the memory effect. This is when the battery is continually recharged before it has discharged more than 50 percent of its power, causing it to essentially forget that it could fully discharge to begin with. Memory effect is caused by the formation of hard-to-dissolve cadmium crystals deep within the battery. Cadmium crystals are an unavoidable by-product of discharge; the trick is to keep them small enough to be reformed as cadmium during the charging process. When a battery is not fully discharged, the crystals deep within the battery are not affected by the influx of electrical current, so they are not reformed as cadmium and can grow into the troublesome larger cadmium crystals. The battery will still function normally, but is maxed out at 50 percent. The memory effect can be avoided by fully cycling the battery once every two to three weeks by allowing it to discharge completely, and then fully recharge.
Article source: How Stuff Works


My case of swellen battery
This happened I left my phone charged while using it as a internet connection access point for my laptop at work.
I kept doing it for weeks, and the battery size was getting bigger than its original size.

And so the battery was recharged over again every once the power went one level lower than 'fully charged'(100%), and get it fully charged. This process repeated all over again until it became very hot, and swollen slowly until it's noticeable by my sense of touch, and it went more serious till my phone's back cover can never close/clip back well again.

In short, it's a lesson for me, and note for everyone else:
In order to preserve your electronic device's battery, good to avoid using it at recharging.
Best(but it's still a hearsay) recharging way is to get your device recharged at it fully turned off, it's condition where battery getting charges at lowest 'stress'.

Swollen battery 

View from side of the battery

SDHC is SD flash memory card?

You might have heard about Secure Digital High Capacity (SDHC) flash memory, do you know the differences between this SDHC and Secure Digital(SD) card?
Of course they do have big differences between them.
A card reader might not be able to read SDHC while work well for SD card, but it's already a past, many devices have become SDHC compatible nowadays. However, older SD compatible devices(example: digital camera) don't normally support SDHC card, so check the devices' memory card compatibility first before purchasing SDHC card.
The picture, show a SDHC card with 4GB capacity and the 4 within a circle implying it's class speed rating.
High capacity of SDHC is in the range of 4GB to 64GB or maybe higher in the future.
What is Class Speed Rating?
This is what developer can choose which data-writing speed specify to a card, so a garanteed minimum data transfer rate is fixed.
There are 3 classes, which is Class 2, Class 4 and Class 6.

For more detail, you can download a pdf file from here.