Safety protection solutions for e-bike battery pack

The safety of lithium batteries for electric bicycles is a key concern of the industry. Judging from the fire situation of electric bicycles, most fires are caused by battery thermal runaway. There are two main reasons.

One is the internal quality problems of the battery cells, including dust, lithium dendrites, metal impurities and burrs, which pierce the diaphragm and cause internal short circuits in the battery cells, eventually causing thermal runaway of the battery pack.

The second is thermal runaway induced by factors such as battery pack assembly process and use environment, such as external high temperature, overcharge and overdischarge, external high current short circuit, charger mismatch, protection board failure, etc., resulting in damage to the internal structure of the battery cell. Causes an internal short circuit, causing thermal runaway of the battery pack.

The above two reasons also explain the importance of quality testing. It is not advisable to only produce battery packs without performing process and finished product quality testing.

Battery cell cycle life tester, battery pack charge and discharge test system, battery pack performance tester and battery pack PCB tester are all essential.

Solving the problem of battery safety for electric bicycles is a systematic and meticulous work that requires efforts in many areas such as battery cells, battery pack assembly processes and usage methods.

Among them, battery cells are undoubtedly the core and most fundamental part of battery safety.

The safety protection of lithium battery cells can be designed and manufactured from the aspects of diaphragm safety, positive electrode safety, electrolyte safety, cap safety structure and process safety control.

The safety protection solution of the diaphragm: The diaphragm is an important barrier between the positive and negative plates inside the battery cell. A high-safety diaphragm must be selected, which should have the characteristics of heat resistance, flame retardancy and high puncture strength.

Positive electrode safety protection solution: Choose positive electrode materials with stable structure, long cycle life, low heat release, and low risk of overcharging lithium. For example, lithium iron phosphate materials are not easy to release oxygen molecules when decomposed, and will not have a spontaneous combustion effect.

Electrolyte safety protection solution: As the flammable part of lithium batteries, electrolyte protection can be divided into three stages: the electrolyte overcharge prevention additive cyclohexylbenzene (CHB), trimethyl phosphate (TMP), and all-solid electrolyte.

Cap safety structure: three-layer protection of PTC protection, circuit breaker protection and blasting pressure relief protection, such as the use of a positive temperature coefficient thermistor, used in the battery to protect against overcurrent (about 7A), and temperature (about 90°C) Protective effects.

Process safety control guarantee: including automatic feeding and batching system, automatic extrusion coating, automatic film production and winding, automatic Korean assembly line, 10,000-class dust-free workshop, process demagnetization and dust removal, etc., to create a product manufacturing guarantee system.