| Q1.What should be known about assembling battery packs? |
| 1. Shocks, high temperature or contacts of sharp-edge components should not be allowed in battery pack assembling process.
2. Soldering directly to polymer tabs is not recommended. When you solder directly to the polymer tabs, it is necessary to ensure not to apply too high welding temperature and too long welding time, to guarantee that the temperature transmited to the cells is lower than 80℃. Temperature above 80℃ may cause damage to the polymer cells and degrade their performances.
3. In case that the battery packs are fixed by ultrasonic welding, it is necessary to ensure not to apply too much ultrasonic welding power to thepolymer cell and electronic circuits such as PCM. Otherwise, itmay cause serious damage to the cells and electronic circuit. |
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| Q2. What are the diferences betwee high C-rate and low C-rate lithium? |
| polymer (Li-Po) batteries.
In general, the diferences lie in the materials made of the positive & negative terminals, the area density design, the electrolyte ingredient, the septum data and the density of inside pieces. |
| Q3. How is a Li-Po battery made? |
| When a Li-Po battery is made, five main aspects should be considered carefully: (1). Battery Pack should have suficient strength, so that the polymer battery inside could be efectively protected from mechanical shocks; (2). The polymer cell should be fixedto the battery pack onits large surface area - no cell movement in the battery packshould be allowed; (3). No sharp edge components should be inside the packcontaining the polymer battery, and meanwhile, suficient insulation layer between wiring and the cell should be used to maintain multiple safety protection; (4). Ultrasonic welding is recommended for polymer tab connection to obtain low-resistance, high-reliability and light-weight properties;(5). Polymer packs shouldbe designed carefully so that no shear force is applied, and also, no heat is generated even when leakage ocurs for mishaps. PCM from electrolyte leakage should be isolated as perfectly as posible, and narrow distance between bare circuit patterns should be avoided. |
| Q4. How to Charge li-Po battery? |
| 1. Charging Current: Charging current should be less than the maximum charging current listed in specifications. Charging with higher current than recommended may cause serious damage to cell performance and safety features,leading to heat generation or leakage. 2. Charging Voltage: Charging should be performed at a voltage less thanthat listed in specifications (4.20V/cell). Charging at above 4.25V-the absolute maximum voltage, must be strictly prohibited.The chargers used should have this voltage limitation function. Charging with higher voltage than specified is very dangerous, which may cause serious damage to the cell performance and safety features, leading
to heat generation or leakage. 3. Charging Temperature: The cells should be charged within a range of temperatures listed in the specifications. Always let the batteries cool down to ambient temperature before charging. 4. Prohibition of Reverse Charging: Do not reverse the positive(+) and negative(-) terminals. Otherwise, the batery pack wil be reverse-charged and abnormal chemical reactions may ocur. Ecesively high current may flow during recharging, possibly leading to damage, overheating, smoke emission, bursting and/or ignition.
5. Use specific Li-Po charger only. DO NOT use a Ni-MH or Ni-Cd charger. It is your responsibility solely to ensure that the charger you purchased works properly.
6. Never charge batteries unattended. Always monitor charging process to assure batteries are being charged properly. Always charge the batteries in an isolated and safe area away from any flammable or/and combustible materials. |
| Q5. Why do we need formation process? |
| Organic solvents easily decompose on the negative electrodes during charging, leading to battery swelling, drop of cell capacity, and unsafety caused by activereaction. The purpose of the formation process is to form a solid layer called the solid electrolyte interphase (SEl), which is electrically insulating yet provides significant ionic conductivity. This interphase prevents further decomposition of the electrolyte after the second charging. |
| Q6. Why do Li-Po batteries bloat/swell? |
The Li-Po batteries may bloat or swell due to the following reason:
1. Overcharging:Normally, the maximum charge voltage is 4.2V for RC batteries. If the batteries were overcharged beyond 4.4V, electrolytic oxidation process would happen, which generates mass gas leading to battery swelling.
2. Overheat:When discharging in high temperature or high C rate, the temperature of the inner part of the battery can be even higher, which gasify the electrolyte and results in swelling.
3. Shot-circuit.:If short circuit happened, the cell voltage would drop very fast and the electrolyte would be reactive to generate gases, leading to battery swelling.
4, Sealing:If sealed without proper processing, the battery cell would have water and air in, so that the electrolyte would be reactive to generate gases, leading to battery swelling. |
