[EVO 4G General] z28marols1:
This is taken out of wikipedia under lithium ion batteries.

Charging procedure

Stage 1: Apply charging current until the voltage limit per cell is reached.

Stage 2: Apply maximum voltage per cell limit until the current declines below 3% of rated charge current.

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

The charge time is about three to five hours, depending on the charger used. Generally, cell phone batteries can be charged at 1C and laptop-types at 0.8C, where C is the current that would discharge the battery in one hour. Charging is usually stopped when the current goes below 0.03C but it can be left indefinitely depending on desired charging time. Some fast chargers skip stage 2 and claim the battery is ready at 70% charge. Laptop battery chargers sometimes gamble, and try to charge up to 4.35 V then disconnects the battery. This helps to compensate for the battery's internal resistance and charges up to 100% in short time.

Top-off charging is recommended when voltage goes below 4.05 V/cell

Lithium-ion cells are charged with 4.2 ± 0.05 V/cell, except for military long-life cells where 3.92 V is used for extending battery life. Most protection circuits cut off if either 4.3 V or 90 °C is reached. If the voltage drops below 2.50 V per cell, the battery protection circuit may also render it unchargeable with regular charging equipment. Most battery protection circuits stop at 2.7–3.0 V per cell.

For safety reasons it is recommended the battery be kept at the manufacturer's stated voltage and current ratings during both charge and discharge cycles.

Disadvantages

Cell life

Charging forms deposits inside the electrolyte that inhibit ion transport. Over time, the cell's capacity diminishes. The increase in internal resistance reduces the cell's ability to deliver current. This problem is more pronounced in high-current applications. The decrease means that older batteries do not charge as much as new ones (charging time required decreases proportionally).

High charge levels and elevated temperatures (whether from charging or ambient air) hasten capacity loss. Charging heat is caused by the carbon anode (typically replaced with lithium titanate which drastically reduces damage from charging, including expansion and other factors).[36]

A Standard (Cobalt) Li-Ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively. In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.

Safety requirements

If overheated or overcharged Li-ion batteries may suffer thermal runaway and cell rupture. In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell, in which case recharging would be unsafe. To reduce these risks, Lithium-ion battery packs contain fail-safe circuity that shuts down the battery when its voltage is outside the safe range of 3–4.2 V per cell. When stored for long periods the small current draw of the protection circuitry itself may drain the battery below its shut down voltage; normal chargers are then ineffective. Many types of lithium-ion cell cannot be charged safely below 0°C.

In short, the higher the voltage in the cells for extended periods of time increases not only irreversible damage to the cells ability to hold a charge but also the possibility of catastrophic failure of the cells which could lead to damage to the device as well as personal injury.

We talk about modifications we do all the time that can damage our devices. However messing with the battery is the only thing that can actually hurt us. Overclocking the CPU will only shorten the life of the CPU and upon failure it just stops working. It cannot and will not explode.

Please, all of you, pay attention to the cautions from the manufacturers about the batteries before messing with them. Its all fun and games till someones phone explodes!