Working principle of charger:
The batteries used in our electric scooters and electric wheelchairs are usually 24V DC, so its charger is a 24V charger, that is to change the household 220V AC into DC above 24V and below 30V (usually the full charge voltage of lead-acid battery is about 27V, and the full charge voltage of lithium battery is about 30V), Then this involves converting alternating current into direct current, and then charging the battery by pulse. It is like pumping water from the "underground" and then sending it to our home through the "pipeline". There is a "conversion" process in the middle.
How electric energy is converted:
This conversion process is a seemingly simple but actually very complex process. Firstly, 220V AC enters the "rectifier filter" circuit after passing through a fuse, rectifying 220V AC into about 300V DC, which is stored in a "warehouse" (capacitor), and then a "gate" (MOS tube is also called switch tube) is established in this place, Then set up a "management department" (charging management chip). At this time, the "charging management department" can control the switch of the "gate" to supply power to the following "substation (coil transformer)". The transformer reduces the 300V DC through the electromagnetic induction of the coil and enters two different "pipelines", and one pipeline enters the "charging station" The electricity is supplied to the battery, and a pipe returns a small part of the electricity to the "management" so that they can continue to discharge through the gate. This is the simple working principle of a charger. I don't know if you understand it!
The conversion process generates heat:
Above, we have made an analysis and analogy of this transformation process. This process runs at a very fast speed in our chargers. This speed can reach tens of thousands of times per second at the highest. Then the fast switching of the "gate" will bring a lot of heat. Another part of the heat is the working heat of magnetic induction coils and electronic components, In order to protect the "gate" from being burned out, we need to heat it. There are probably two ways of heat dissipation, one is fan heat dissipation, and the other is aluminum sheet heat dissipation. The latter is relatively expensive and is widely used in precision electrical appliances, such as TV sets, computers, electromechanical equipment, etc.
How to dissipate heat:
That's what we focus on today. The heat dissipation methods of the charger are generally divided into two types: one is the built-in small fan, which is equipped with vents at both ends of the charger to let the air flow away the heat through the rotation of the fan, and the other is the heat dissipation through the aluminum sheet and shell. This method is also called closed charger, and the aluminum sheet is wrapped around the circuit board, Then the shell is wrapped with aluminum fins, so that the heat is transferred to the shell, and then the heat is radiated into the air through the shell. These are the two heat dissipation methods of common chargers.
Which is better:
Since there are these two ways of heat dissipation, someone will ask which is better? This can only be said to have its own advantages and disadvantages. This can only be distinguished according to the use environment. The cooling mode of the fan is relatively intuitive, the cost is low, the manufacturing requirements for the circuit board are not high, and the cooling efficiency is not very high. It is easy to cause circuit failure due to water and moisture, which is relatively easy to be damaged! Because of its simple manufacture and low cost, it is widely used in the charger of ordinary electric vehicles. The closed charger with shell heat dissipation has relatively high cost and high manufacturing requirements for the circuit board. The heat dissipation efficiency is slightly higher than that of the fan, but it is not intuitive. The shell temperature is relatively high during operation. Because this design can well isolate the corrosion of moisture on the circuit board and shield electromagnetic waves, it is widely used in the power supply of electrical appliances and mobile phone chargers.
Power conversion:
Another problem that we are more concerned about is the calculation of charger power. Here we take the charger of our scooter and mobile phone as an example to make a conversion. Our commonly used charger is 24V, and the charging current is 2a to 3a. According to the formula: P = UI 24 * 2 = 48W, 24 * 3 = 72W, let's take a look at the power of mobile phone charger. Now many mobile phones are equipped with fast charging head. This fast charging charger can output three different voltages of 5V, 9V and 10V, and the maximum charging current can reach about 4a. According to the formula: P = UI, we can calculate 10V * 4A = 40W, This is a 40W fast charging head. Take Huawei mobile phones as an example, you can see the word "40W" on the charging head.
question answering:
Through the above analysis of the working principle and heat dissipation mode of the charger, we can intuitively answer the questions fed back by users. Our scooter or wheelchair charger has two heat dissipation modes, fan type and closed aluminum plate type, and the closed type is more efficient and reliable; The power of our charger is only equivalent to the power of the fast charging head of a mobile phone. The working temperature in summer is almost the same as that of the mobile phone charger. The power supply appliances will pass the safety test when they are designed and manufactured. Compared with the temperature, humidity and water inflow, they pose a greater threat to the safety of the appliances and are more likely to cause potential safety hazards. Please charge in strict accordance with safety specifications, improve risk awareness, and do not modify the charging line and charger of the original vehicle without permission.
