If possible, use a battery or device with a higher voltage than your 18650 lithium battery (preferably). Note that a single section should not exceed 5V, and it is best to limit the current. Charge and unplug your 18650 lithium battery to see if it can start. If so, it can be loaded and unloaded normally. If not, it may be broken. I hope this helps you.
We all know that if the battery voltage is too low, the car will not start and catch fire, so what should we do if the battery voltage is too low ? What is the normal battery voltage?
Method 1: When starting the vehicle, listen carefully to see if the engine makes a “hmm” sound. If so, the vehicle battery is dead. The way to deal with this situation is simple: just charge the car battery in time.
Method 2 : Another situation is that the car battery is broken. At this point, you can test the car battery and generator at the same time to see if they can work properly. If the car battery or alternator is found to be defective, they should be replaced promptly.
Method 3: If the car shows that the battery voltage is too low, but the car can ignite normally, then the problem is not serious and the car owner can fix it. 'ignore.
In addition, in daily use, try to avoid turning on the lights or listening to the radio for a long time when the engine is off when parking for a long time, you should also turn off unnecessary items; electrical equipment (interior and exterior lighting, audio and navigation, etc.) power supply. ).
The battery voltage of our family cars is essentiallyof 12 volts, but if you measure it, you will find that the battery voltage is often higher than 12 volts when the engine is off, and the voltage measured when the engine is idling will be higher. In fact, this is not a battery problem, but a normal phenomenon. This would be a problem if the voltage measured with the engine off was 12 volts or less.
Some people here may have questions: The voltage listed on the battery is 12 volts. Why is the actual voltage higher than 12 volts? In principle, this is determined by the properties of the lead-acid battery, or it can be said that it is determined by the chemical reaction properties of the lead-acid battery itself. Generally, the batteries we use convert chemical energy into electrical energy. The voltage generated by this chemical reaction is determined and cannot be modified.
For example, the essence of the releaserge of a lead-acid battery is the flow of electrons generated by the reaction of lead and dilute sulfuric acid. The maximum voltage generated by this chemical reaction is only 2.4 volts, which fluctuates. depending on the intensity of the chemical reaction, roughly around 2 volts. Therefore, in order to obtain a higher voltage, we need to build several chemical reaction units of lead and diluted sulfuric acid inside the battery and connect them in series to increase the voltage. Each reaction unit is called a monomer and the voltage produced is called monomer voltage. The cell voltage is only related to the principle of chemical reaction and has nothing to do with the size of the battery. Even if you build a lead-acid battery as large as a house, if it contains only one reaction unit, its voltage will still be 2 volts.
The voltage of lead-acid batteries is 1.5 to 2.4 volts and the median value de 2 volts is called nominal voltage. Therefore, there are actually 6 lead-acid batteries working together inside the vehicle's lead-acid battery. When connected in series, a voltage of 12 volts can be obtained. When the battery is fully charged, releaseThe chemical reaction is violent during electricity. The maximum cell voltage is 2.4 volts and 6 cells connected in series is 14.4 volts. The chemical cutoff voltage is 1.5 volts, so when the battery voltage approaches 9 volts, it means the battery is about to die. In other words, although the nominal voltage of the vehicle battery is 12 volts, the actual voltage is between 9 and 14.4 volts. The higher the voltage in this range, the greater the power.
There are also lithium batteries used in our daily lives. Depending on the power level, the battery cell voltagelithium is 2.75 to 4.2 volts and the nominal voltage is 3.7 volts. It can be seen that the voltage of lithium batteries used in daily life is basically a multiple of 3.7. For example, many drone batteries have three batteries connected in series, so their nominal voltage is 11.1 volts, but the actual measured full-charge voltage is higher than 12 volts. There are also lithium batteries for balance cars with a nominal voltage of 36 V, but in fact the full charge voltage is higher than 40 V.
For lead-acid batteries, the voltage of Ideal single charge should be 2.7 volts, which means the voltage generated by the car's alternator should reach 16.2 volts to fully charge the battery. However, considering the voltage resistance of electrical devices in cars, the maximum generator voltage is limited to 14.5 volts. Therefore, in theory, ifthe car battery is charged only by the generator, it will never reach a truly fully charged state. However, compared to the working state of a car battery, this is sufficient.
From the above we can deduce common sense:
1. When the engine is off, it is normal for the battery voltage to be above 12 volts. The higher the voltage, the more powerful the battery. If the battery voltage is often around 12 volts or even lower than 12 volts when your car is turned off, this means that the battery's performance has decreased and you may consider replacing it.
2. The output voltage of the car generator is constant and can charge the battery even at idle speed, but the charging efficiency is not as high as at high speed.
3. There is no need to deliberately charge the battery during daily use, as the battery does notcould not be fully charged by the generator voltage alone. If you really want to fully charge the battery, you can consider using a charger (as you can see in the picture above, when charging a 12 volt battery, the charging voltage is 16, 6 volts, which once again proves that the car generator cannot fully charge the battery).
4. If possible, you can use a special charger to charge the battery every 1-2 months, which can extend the life of the battery. Don't worry if you don't meet the requirements. As long as you don't discharge too much during daily use, it can be used for several years.
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