Monthly Archives: April 2017

lipo battery pack construction

LiPo is a short way of saying Lithium Polymer batteries, Lipo batteries are packaged generally in prismatic pouch made of some plastic polymers. These batteries are known for their exceptional “boost discharge capabilities”. Lithium polymer batteries are labeled nnC where nn is a number. For example a 1000mAH Lipo battery with 50C label is capable of supplying 50 Amperes of current for a fixed time. Lipo is lighter in weight and hence is more energy dense than Lithium Ion batteries. You will find these batteries in toys where weight is a constraint e.g. flying toys for kids, toy quad-copters, heli, airplanes etc. But what is the basic construction of a LiPo battery? The lipo battery construction is as follows:

lipo battery pack construction

Anode: aluminum foil current collector. Metal oxide active material (NMC, NCA, LCO, LFP). Binder (PVDF – Polyvinyladine Fluoride). Conductive carbon (Acetylene black, Vulcan , graphite )

Cathode: copper current collector. Graphite active material. Binder (PVDF, or CMC/SBR — carboxymethyl cellulose and styrene butadiene rubber). Conductive carbon.

Separator: polypropylene film, ionically conductive but electrically insulating, e.g. Celgard

Electrolyte: carbonate solvents including ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC). Lithium salt, eg lithium hexafluorophosphate (LiPF6)

Pouch material: aluminum with polymer coating.

Tabs: aluminum cathode tab, nickel anode tab

Construction: double sided anode and cathode sheets are stacked and wrapped in separator, sometimes in Z-fold pattern. Anode and cathode Electrode stack tabs are ultrasonically welded together, placing them in series. Anode and cathode tabs are further welded to external tabs (Al or Ni, see above). Welded stack is packaged in 3-side sealed pouch, filled with electrolyte, then 4th side is sealed in vacuum pouch step.

How to safety discharge batteries

The batteries make our life more convenient, as the electric power, we should use them safety. Last week, we talk about how to charge lipo battery, from the article you have learned charge lipo battery is not easy thing, we should take more carefully. Today, we will give you some advises about how to discharge batteries.

1. Don’t discharge Batteries at amperage rates higher than specified on Batteries’ labels.

2. Don’t allow the temperature of Batteries to exceed 140°F during discharge. Adequate cooling for Batteries is required, especially when discharging at or near maximum rates.

3. Don’t discharge Batteries to voltage below which they are rated by the manufacturer when measured under load (connected to the vehicle or a charger capable of discharge). Batteries discharged to a voltage lower than the lowest approved voltage may be damaged, resulting in loss of performance and potential fire when Batteries are charged.

4. Don’t discharge battery to a level below 3V per cell under load.

For Tattu series batteries which are used for Unmanned Aircraft System, The recommended cut off voltage is 3.5V per cell.

5.Don’t leave battery unattended during the discharging process. During the discharging process, user should monitor the process constantly and react to potential problem that may occur.

6. In case of emergency, discontinue the process immediately, disconnect the battery, place it in a safe area, and observe it for approximately one hour. This may cause the battery to leak and the reaction with air may cause the chemicals to ignite, resulting in a fire. A safe area should be outside of any building or vehicle and away from any combustible materials. A battery can still ignite even after one hour.

7. User need to check the conditions of the battery before use it or discharge it. Stop using it if user found the cells are not balanced or cells are puffing or weeping.

And finally, don’t over discharge the battery, over discharge the battery maybe let the battery damage or fire, so please take more carefully to discharge batteries