How to calculate the protection current of the lithium battery protection board

It's not easy for you to calculate, there are no parameters needed (the most important thing is that there are no reward points), each lithium battery protection board configuration is different, different configurations, the protection current is not the same.

First of all, you need to understand IC chips.

High-precision voltage detection and control circuit) is the short-circuit detection voltage of what is V, and the second thing to know is MOSFET (field effect transistor.

The internal resistance is how many ohms.

For example, the detection voltage of the IC is U, and the internal resistance R of the MOSFET is ohm, i=U R=, so the protection current is, that is, when the instantaneous current is reached, the short-circuit protection will be carried out.

At present, the mainstream of lithium batteries in the market is two types of batteries, lithium iron phosphate batteries and ternary batteries. The material system of lithium iron phosphate battery and ternary battery is different, lithium iron phosphate is a voltage platform, the cycle life is more than 2000 times, the ternary battery is a voltage platform, the cycle life depends on different manufacturers, different models and processes, some can do 500 cycles, some can do more than 1000 cycles. The high-temperature performance of lithium iron batteries is good, and the low-temperature performance of ternary batteries is good.

In terms of safety, iron and lithium are better. Choose a ternary battery and assemble it into a 48V battery pack, you need 13 strings to use a ternary battery, the nominal voltage will be a little higher, and the number of strings assembled into a battery pack will be a little less. Choose lithium iron phosphate battery to assemble into a 48V battery pack, using lithium iron phosphate battery requires 16 strings, the nominal voltage value is only, and more batteries are needed in series to increase the voltage.

There are many people who think that my battery is 48V20Ah and I need to use a 20A protection board, and mine is 48V80Ah and I need to use an 80A protection board, etc., and I choose a protection board based on the size of the capacity, which is completely wrong. It is recommended to confirm the specific parameters of the protection board from the direction of the power of the product, voltage requirements, and various functions.

It may be that the internal resistance of the MOS transistor is too large, resulting in an increase in voltage drop, if there is a diode in series in the middle, the voltage drop will definitely occur, and there may be bad parts on the protection board, resulting in inaccurate sampling and the output will be affected.

When the battery is charged so that the voltage exceeds the set value VC (the specific overcharge protection voltage depends on the IC), VD1 flips to make COUT low, T1 cuts off, and charging stops. When the battery voltage falls back to VCR (the specific overcharge protection recovery voltage depends on the IC), COUT becomes high, T1 turn-on charging continues, and VCR must be less than VC by a fixed value to prevent frequent jumps.

Lithium battery protection board precautions.

The taboo of using lithium batteries in series is that the self-discharge of the battery is seriously unbalanced. As long as everyone is the same, it doesn't matter, the problem is that this state is an acutely unstable state, the self-discharge of a good battery is very small, the self-discharge of a bad battery is very large, and the state of self-discharge is not small and not small, and the state is generally from good to bad, and this process is unstable.

Therefore, it is necessary to screen out the batteries with large self-discharge, and only leave the battery with small self-discharge (generally the self-discharge of qualified products is small, and the manufacturer has measured it, and the problem is that many unqualified products flow into the market).

1. It depends on how big your output current is, the larger the current, the greater the voltage drop.

Second, it may be that the internal resistance of the MOS tube is too large, resulting in an increase in pressure drop.

3. If there are diodes in series in the middle, there will definitely be a voltage drop.

Fourth, there may be bad parts on the protection board, resulting in inaccurate sampling, and the output will be affected.

48V 40A lithium battery, can not use 30A protection board output current is too small, to use a special lithium battery 48V80A ant protection board.

The protection board needs to be selected according to the motor power and battery pack voltage, and the main choice is the same battery type (ternary or iron-lithium cannot be mixed), working voltage (there are 13 strings of ternary lithium batteries 14 strings (usually 13 strings, but 14 strings are not a lot), 15 strings of iron and lithium (common 16 strings)), rated current.

At the moment when the electric vehicle starts, its working current will be more than twice the rated current of the motor, the protection board needs to meet this condition, the common 48V motor has 350W, 500W, and the special has a greater power, the 350W motor working current is 7A, and the protection plate needs to meet the rated 15A, and the 500W motor working current is 10A.

The protection board needs to meet 25A (its speed is fast, the starting current is also large, and the current of the protection board is relatively large). The output current of the protection board is large, the internal resistance is a little lower, and the cost is acceptable.

Ternary 48V13 string 15A protection board is the most common, because there are many disassembly boards on the market, as long as a few yuan, like a 30Ah lithium battery, it is best to find a regular current of more than 25A. 16 strings of iron and lithium are common, usually less second-hand, ** relatively high, 30A current is more than 70 for ordinary disassembly, and the ant board with Bluetooth can monitor the battery voltage is 200.

48V60Ah lithium battery, 20A or 25A protection board is best used on electric vehicles, and 10A protection board is used for power supply.

Hello, I'm glad to answer this question for you, in order to protect the life of the lithium-ion battery pack, it is recommended that the battery charging voltage should not exceed at any time, that is, the protection voltage of the lithium-ion battery protection board is not higher, the equalization voltage is recommended, and the battery discharge protection voltage is generally above.

The charger recommends that the maximum voltage is the number of strings, the larger the self-discharge, the longer the equalization time, and the cells with excessive self-discharge are already difficult to equalize and should be removed. Therefore, when choosing a lithium-ion battery protection board, try to choose an overvoltage protection board and a balanced one for left and right starting. I hope my answer will help you!

Ask how it counts.

Thank you for your question! I thought it was 20a.

Ask a good question. Won't 40A be bad for the battery.

The continuous discharge current is the maximum current that the battery can work safely at this current for a long time.

The maximum discharge current is the maximum temporary current allowed by the equipment, and the working time varies with the setting of the protection board. Generally, the continuous discharge current cannot be exceeded for continuous work.

The continuous current can be discharged for a long time without damaging the control board, and the maximum current is also called the limited current that cannot work at the maximum current for a long time or will burn out the control board.

The upper limit of the charging cut-off voltage of a single-string lithium iron phosphate cell is , and the charging cut-off current is.

The voltage platform is close.

48 strings*, in order to ensure the service life of the battery, the recommended charging cut-off voltage is 54V.

The discharge cut-off voltage of a single string is, so the discharge cut-off voltage of the 48V module is 15 strings*, which is conservative to 38V.

Because it is a module, considering the voltage imbalance of a single string, it is necessary to add a single string voltage detection, and when one of the strings is lower, it is recommended to cut off the output.

The above is a personal opinion.

The protection voltage of the lithium battery protection board is not adjustable.

The lithium battery protection board is a charge and discharge protection for the series lithium battery pack; When fully charged, the voltage difference between each single battery can be guaranteed to be less than the set value (generally 20mV), so as to realize the uniform charging of each single battery in the battery pack, which effectively improves the charging effect under the series charging mode.

At the same time, the over-voltage, under-voltage, over-current, short circuit and over-temperature states of each single battery in the battery pack are detected to protect and prolong the service life of the battery; The under-voltage protection enables each single cell to avoid damage to the battery due to over-discharge when it is discharged.

Wraparound. There are two main parts of the finished lithium battery, the lithium battery cell and the protection plate, and the lithium battery cell is mainly composed of positive plate, separator, negative plate and electrolyte group.

Positive plates, separators, negative plates are wound or stacked, packaged, filled with electrolyte, and made into cells after packaging, the role of lithium battery protection plate is not known to many people, lithium battery protection board, as the name suggests, is used to protect lithium batteries, the role of lithium battery protection board is to protect the battery is not discharged, not charged, not current, and there is output short circuit protection.