What are the technical points and precautions for replacing lead-acid batteries with lithium batteries for electric vehicles?

　　The battery on a battery car can be understood as a mobile and dischargeable power supply. The power supply is ultimately used for other loads such as motors and light bulbs on the car. The power supply pays attention to parameters such as voltage, current and capacity. As long as the voltage is relatively close, it will not exceed Depending on the rated voltage of the load on the car, you can change the lead-acid battery to a lithium battery. The larger the capacity, the longer the mileage.

　　The battery on a battery car can be understood as a mobile and dischargeable power supply. The power supply is ultimately used for other loads such as motors and light bulbs on the car. The power supply pays attention to parameters such as voltage, current and capacity. As long as the voltage is relatively close, it will not exceed Depending on the rated voltage of the load on the car, you can change the lead-acid battery to a lithium battery. The larger the capacity, the longer the mileage.

　　1. When refitting, you must consider the issue of volume and space. With the same capacity, the volume of lithium batteries is only half that of lead-acid batteries, so it can definitely be installed. However, you must pay attention to some shape and packaging issues. After all, the space in the car may not be the same as that of lead-acid batteries. The battery is oriented in exactly one direction, so you need to consider fixing it reliably to prevent it from falling due to vibration. And if economic conditions permit, of course it is hoped that the capacity of the modified lithium battery will be as large as possible. Therefore, it is necessary to make full use of the space and choose batteries with reasonable shapes for layout. If you replace it with the same capacity, because there is a lot of remaining space, you need to find something to fill the extra space when replacing it to prevent the lithium battery from shaking and falling off when driving.

　　2. When disassembling the battery, although the battery output has two positive and negative wires, which is very simple, you should also remove them one by one, wrap the exposed wire lugs with tape, and then mark the ± mark, so that when you install it back, it will be correct. Connect the positive and negative terminals one by one to avoid connecting the positive and negative terminals in reverse when you are confused at work, or inadvertently short-circuiting the positive and negative terminals of the positive and negative batteries, causing safety problems.

　　3. When purchasing lithium batteries, it is best to ask the merchant to match the same or similar plug terminals. If the plug shapes are different, some may require re-crimping the wire lugs or welding, or even converting wires. Be sure to pay attention to the current size when choosing. To match the specifications, it is best to put a DC multimeter and re-measure the voltage when wiring to avoid inverting the positive and negative. Remember, the positive and negative poles must be placed separately, and do not perform operations such as grounding the negative pole.

　　4. If you replace the battery and increase the size of the motor and controller, you must consider whether the main circuit line should also be thickened. You can check the electrician's manual to see how many square meters of wire can pass how many amps of current. If the original car If the line is thinner, it will also leave safety hazards, and the efficiency and power effects will be compromised.

　　5. When converting lead-acid batteries to lithium batteries, the charger must be changed to a dedicated one for lithium batteries. Lead-acid batteries have large internal resistance. Generally, the output voltage of the charger is higher, and many have pulse charging functions, which may cause the lithium battery to be charged. It will be overcharged because it is protected by a protective board. When charging, the output voltage of the charger will be set abnormally, and the lagging cells may not be fully charged, causing damage. If the protective plate happens to be broken, such high-voltage charging may easily cause an explosion.

　　6. If possible, you can consider changing the undervoltage and overvoltage protection ranges of the controller. The lead-acid battery cell is 2 volts, and 6 of them form a 12 volt battery. The lower discharge limit is generally controlled to be above 10.8 volts. The nominal voltage of a ternary lithium battery cell is 3.7 volts. The actual voltage of three cells connected in series is only 11.1 volts, but the lower discharge limit can reach 9 volts. If four batteries are connected in series, the lower discharge limit is 12 volts. If you continue to use lead-acid The threshold protection voltage of the battery will cause part of the power to not be effectively released, reducing the advantages of lithium batteries. The first step is to open the four-corner screws of the battery and carefully open the upper cover. You can see that there are four 12V lead-acid batteries inside.

　　In the second step, after remembering the battery wiring clearly, use a soldering iron to remove the wires from the battery. Pay attention to prevent the battery from short-circuiting during operation.

　　The third step is to take out all the old batteries and put the lithium battery in. When installing the battery, there are some small plastic protrusions inside that separate the original lead-acid battery. This must be removed, otherwise the new battery will be worn out in the future.

　　Step 4: Connect the terminals on the battery and wrap them with electrical tape.

　　However, it should be noted that when the original lead-acid battery is replaced with a lithium battery, the voltage must be consistent with the original vehicle battery, the capacity can be increased, and the battery life can be longer. Even with the same capacity, lithium batteries have longer range and life. Secondly, it should be noted that the original charger cannot charge lithium batteries, and a special charger needs to be purchased separately or customized.

　　Of course, some people will also ask whether the controller and motor need to be replaced? When replacing the lithium battery, as long as the voltage is the same, it is a good thing to have a larger capacity. The capacity of an electric vehicle can be increased at will, as long as the voltage remains unchanged, the motor and controller will have little effect. Of course, there is also a problem. If there is a problem with the quality of the lithium battery itself, it is likely to burn out the controller.

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