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Series lithium battery:Series battery PACK lithium battery is a common phenomenon in the process of assembly, this paper introduces a series of lithium battery protection circuit, series lithium battery charge equalization method, IC series lithium battery lithium battery can be balanced, parallel? The difference between series lithium batteries and parallel connection is the series of lithium batteries.
I. equalization principle of series lithium batteries:
1, the series lithium battery in the electric vehicle to provide power for the automotive high-power lithium battery group, in order to ensure the capacity of the entire battery pack, the battery equalization management is necessary.
2, the series lithium battery market battery management IC of all kinds provides a voltage balance management function, users only need to connect the components can be achieved, but unfortunately, most batteries are used in power management IC way to achieve the balance between each cell / shunt resistor. This is acceptable for small power battery packs, such as laptops, handheld devices, or batteries for electric bikes. But for the Bai'an battery, the power consumed in vain is wasted, but also for the electric vehicle to promote "environmental / energy", how much is also justified.
3, tandem lithium batteries in lead-acid battery era, for the battery pack balance has appeared in a variety of ways. The following is mainly aimed at lithium batteries, introduces several feasible equalization methods.
4, series lithium battery resistance shunt, energy consumption: this way is the most common and the simplest way on the market. The protective panels for lithium batteries on the 09 year electric bicycle show, including the protective panels for electric cars, are implemented in a resistance manner. The reason is simple: easy to implement, no better way. In fact, it is also the least expensive way.
The series lithium battery circuit is as follows:
4, the principle of series lithium battery voltage controller circuit is very simple, real-time monitoring of the battery, if it is found that a section of the voltage is too high, and reached equilibrium opening conditions, the corresponding battery switch will open, then the resistance of the corresponding battery will have power flow. If at the time of the Suzhou PACK lithium battery manufacturers will charge the battery, then the current flowing through the battery will be reduced, the battery charging rate, the final voltage with other battery of the same; if the time is in the discharge or idle, then the battery power will be consumed in the corresponding resistor, the final voltage drop, and achieve the same other battery level. Of course, the equilibrium condition can be set by itself, or it can set the equalization function only when charging.
Two. What are the advantages of lithium batteries in series?
1, lithium battery has the biggest advantages: low cost, simple structure, easy to implement.
2, tandem lithium batteries for small companies without R & D capabilities, this is also the only way to exist.
3, the series of lithium batteries is also obvious disadvantages: a waste of energy, heat, and the balance of efficiency is low, because resistance energy consumption will take time, in high power battery pack, which also had to consider. In fact, now many large companies do electric sprayer lithium batteries will use the method of series of lithium batteries, but like some international class companies have achieved a balanced way more advanced, the energy use efficiency is higher, faster way to balance.
Three 、 equalization charging method of series lithium battery:
1, the series of lithium ion battery equalization method of lithium battery is now the most widely used the most simple, of course, other equalization method has always existed, but because of the large capacity lithium battery has been extended, but many manufacturers do not have the strength to the product of these technologies, so the lithium market is very rare, fortunately, battery manufacturers have PACK one kind of active balancing integrated into special IC, although the use of CPU can also be achieved, but the reliability of the software and hardware such as after all, the product will become simple.
2. When the V3 is higher than V2, the IC pin connected by the P3S terminal outputs PWM. At PWM OFF, the Q1 is connected, and the V3 loops through the Q1 and the inductor (as shown in the red line). When the power of V3 is consumed, the inductor current rises and the energy is stored in the inductor. At PWM ON, the Q1 is cut off. At this point, the V2 is connected to the freewheeling circuit through the diode and inductor in the Q2 (as shown in the blue line). At this point, the current stored in the inductor drops and the energy shifts to V2. So far, the process of energy transfer from V3 to V2 is completed, knowing that the PWM is closed when the voltage is equal.
3, series lithium batteries for the PWM frequency, duty cycle, the choice of the capacity of the inductor, the three are interrelated. The recommended frequency of IC for Ti is 200kHz, which can reduce inductance and reduce cost.
4. The number of PWM needed for series lithium batteries is 2 x (n-1), and N is the number of batteries. Relatively or more. And the energy transfer can only be transferred from one battery to the battery adjacent to it. If the number of batteries is large, the control algorithm is quite complex, and the key issue is the cost.
5, series lithium battery, if use bq78PL114+BQ76PL102, can manage 8 batteries at most. If the electric car needs 80 knots, then 10 batteries are needed to manage them, so the cost is increased. So this IC should be for handheld devices, lithium batteries, 12.8V lithium batteries, or laptop batteries, or electric bicycle batteries more appropriate.
Four. What are the differences between series lithium batteries and parallel lithium batteries?
1, the series lithium battery, its voltage is the sum of the voltage of each sub battery, the output power (that is, after the series of electricity) is related to the weakest capacity of a single battery.
2, parallel battery voltage is the maximum value of each sub battery voltage, the output power is N times of the weakest battery sub battery (N is the number of sub batteries).
3, because no matter in series, or parallel output power battery and the battery in the battery to some weak, so the battery selection recency and nearly the same performance may be in the battery, or the performance of the battery group Henan PACK battery factory to do the good (or new) batteries to battery work is weak, thus reducing the battery performance, battery life is bad the best child.
Look at the site map and learn more about the series of lithium battery protection circuit diagrams.