The use of chemical batteries is becoming more widespread, and the application of these components will result in a better and less expensive protection for the battery pack.
A, NiCD battery: NiCD batteries with low impedance and stable chemical properties are not as sensitive to overcurrent as NiMH and Li-ION batteries. However, due to low losses, the application is still extensive. However, in short-circuit or over-current conditions, their low internal resistance causes higher currents to pass. Often the cause of failure of these batteries is overcurrent, not overheating, and products that are applied by any battery material are suitable.
B, NiMH battery: NiMH battery has higher energy density than NiCD battery. These batteries are more susceptible to degradation when over 90C. It is more suitable to protect the battery with VTP or LTP than SRP/LR4 material. According to the design method of the battery, both the SRP and the LR4 can protect the battery, but the thermal conductivity is stronger when using LTP and VTP.
C, Li-ION battery: Among all chemical batteries, Li-ION battery has the highest energy density and the most sensitive chemical properties. Circuit protection is required for use and charging. The commonly used protection device is an integrated circuit, but this is not the safest because the integrated circuit itself may also cause a short circuit or its CMOS startup failure makes the protection device unsafe.
When it exceeds 90C, the Li-ION battery will also begin to degrade. Since the voltage of this battery is the largest, the circuit protection requirements are more stringent. Although LTP, SRP and other series have been used in the battery early, VTP is the most suitable PTC component. For large-capacity Li-ION batteries, the LR4 series has shorter operating time and is more suitable than the SRP series.
1), problems and analysis: NICD, NiMH, Li-ION are commonly used in special protection circuits for mobile phones and computers. The causes of these battery pack failures are usually: accidental short circuit of the positive and negative terminals; the charger can not stop charging the fully charged battery; use the wrong charger or the polarity of the battery. The PTC chip series is mounted in series in each unit of the battery pack to provide overcurrent and overtemperature protection to the circuit.
2) Protection requirements: In the event of a fault, the voltage of the mobile phone can reach 16V, the voltage of the computer can reach 24V; the current can reach 100 amps. In the overcharge condition, the battery pack needs to be over-temperature protected. The NiCD battery cannot exceed 120C, and the NiMH and Li-ION batteries cannot exceed 90C.
3), PTC self-recovery fuse selection: LTP, VTP and LR4 are commonly used in mobile phones and cordless phones, SRP, LTP and LR4 series with high holding current are often used in desktop and laptop computers.
For NiMH battery packs, VTP, LTP materials allow designers to increase thermal conductivity protection. Patches and VTP series for some special applications can be used in AAA battery cells.
Summary: Because of the low cost, low impedance, maximum energy density, and low price of chemical batteries, they are widely used in production and life. In many applications, it has been found that excessive current will always cause problems such as chemical battery explosion and overheating.
Engineers have analyzed the customer application failures and found that the use of self-recovering fuses as chemical battery fuses can effectively prevent overheating caused by chemical battery overcurrent, so engineers designed the characteristics of self-recovering fuses and chemical battery applications. A professional chemical battery over-current protection Solution to solve customer's use problems.
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