Devices for energy storage for dynamic current of the battery are: the lead-acid batteries, nickel-hydride batteries, metal and lithium-ion batteries.

Span of lead acid batteries contain toxic substances like lead, and high energy density is low, charge and discharge and short life, the refractory waste and other shortcomings, has been largely eliminated by future systems energy storage [1].

Ni-MH batteries are alkaline batteries, due to tension monomer is relatively low, and there is “memory effect” on a regular basis the large-scale dumping is necessary, which greatly increased the tasks of system power management . Secondly, its also self-discharge rate (10% ~ 15%) of defects [2-3].

In comparison with other batteries, lithium-ion IBM ThinkPad T40 battery with high power density (800W/Kg), single high-voltage (average voltage of 3.6 V), does not pollute the environment, self-rate discharge is low (about 3% ~ 5%), there is no “memory effect” and other characteristics, is an ideal battery power [4], it has been widely used in mobile power , hybrid cars, the switchgear and low voltage devices in standby power, such as space flight, the device energy storage.

An internal force of the lithium-circuit fault protection

Monomer average voltage of lithium battery is only 3.6 V, the discharge current also certain requirements. To improve the current system and level of tension, in some occasions, generally use parallel dynamic series after the formation of high-current, high voltage Li-ion battery as the energy systems. As the voltage is very sensitive to lithium batteries, batteries are generally increased when using a certain protection circuit. View the most dynamic of the internal circuitry of lithium battery protection was found, its protection circuit is fairly simple, usually only over / under voltage / over current / short circuit protection. In normal use, this hp F4486B battery can be normal in a short time of loading and unloading. However, the inclusion of the protection circuit with lithium batteries used in systems for hybrid electric vehicles are going through a phase of high current discharge and charge, we found the maximum voltage between monomers and lower voltages serious inconsistency: Yes monomer other batteries in charging the battery voltage is always under normal conditions, because its threshold voltage has reached the maximum protection of recharge channels are closed, resulting in the total pressure on the entire energy system can not pre-determined requirements, another set of monomer battery voltage is still within the normal discharge conditions, because of its voltage reaches the lower threshold voltage is closed to protect discharge channel, causing the entire energy system can not be fully discharged. These two phenomena have seriously affected the performance of energy systems for monitoring the equalization of the toshiba PA3383U-1BRS battery is to solve the above-mentioned phenomenon of the most effective approach.

2 Improved Lithium Battery Protection Circuit Principle

A balanced circuit is the first man to reach the hardware circuit, which may limit the battery voltage of the monomer or monomer between the coherence between the minimum voltage to effectively protect the battery charge voltage and lower the ceiling voltage discharge , from a fundamental to reduce the impact of the battery on the system to improve battery performance and extended to battery life. It includes the balance and balance of both types of circuit to its name suggests, they were the maximum protection of the battery voltage and the voltage limit of the battery.

In this paper, two sets of vehicle design hybrid electric power system: Series 3 Li-ion battery system protection (maximum voltage of 12.75V, the average discharge voltage of 10.8 V) and channel 10 system lithium apple M8403 battery protection (maximum voltage of 42.5V, the average discharge voltage 36V), discharge current, 10A and 40A respectively. System principle illustrated in Figure 1, which is in its protective circuit basis (over / under voltage / temperature / over current / short circuit protection) based joins the upper and lower balance circuit.

2.1 EQ TL431

TL431 is a three-terminal shunt tube regulator, its basic features can be found in reference [5] This article, based on the characteristics of their designs on the balance of the circuit shown in Figure 2. Adjust R1, R2, R3 resistance when the voltage exceeds a set value when they opened TL431, through the resistor R * Power consumption of energy to reduce battery voltage to reach a fixed point (equilibrium point). With the internal electric vehicles and electric vehicles equipped with a balanced circuit experimental results when the balance to be 4.20V, the resistance values are: R1 = 68kΩ, R2 = 100kΩ, R3 = 4.3kΩ.

The balance of the next circuit based on TL431 as shown in Figure 3. When the switch is off, because of optocoupler 817 is not opened before the class to optocoupler circuit also unable to work after school, the work of the BATCL50L battery in a state of normal discharge; When closed, the Post optocoupler optocoupler stage with the opening of the first class one after another opened, the circuit through the resistor R18 to reduce energy consumption and protect the chips sent until the voltage battery is low to protect the chip to force the battery voltage is stable at its low voltage limit Vmin, to achieve the objective and balanced.

From this principle of a balanced circuit can be seen that the current balance of the circuit can not exceed the upper limit of protection TL431 current (70mA or so). Capacity constraints due to a balanced, high-current charge and discharge can be applied between the circuit. To increase the balance of the circuit without compromising the ability of TL431, the TL431 can be used in parallel.

2.2 Parallel equalizer TL431

TL431 shunt and balanced the circuit shown in Figure 4. The principle is similar to Figure 3, only through parallel TL431 for the balanced expansion of current targets. Found in the actual production, as TL431 has a small difference between doing two average balance of power is not entirely consistent. To reduce the occurrence of these phenomena, the general screening methods to improve the TL431 for these circuits, which probably increased the workload of production.

2.3 Improving the equalizer TL431

To improve the balance of the capacity of the circuit, while reducing the workload of the TL431 output filter, this article using the 8550 design of an improved balance of the circuit of power transistor as shown in Figure 5. Once the extra power when TL431 will open, 8550 launch of a PN junction due to handle pressure and opening resistors consumes IBM ThinkPad T41 battery power until the battery voltage on the equilibrium point. Once balanced, the figure would be light-emitting light-emitting diode has played the role of operational instructions. By adjusting the set R1, R2, R3 resistance, they can set the balance point of the upper spring. Figure R1, R2, R3 resistance is relatively large, after the close of the TL431 little effect on the equilibrium point can be ignored. And the balanced circuit is also shown in Figure 5, only a change of R1, R2, R3 corresponding resistance.

3 Experimental results

The compositions of these functions with a string of 10 Office of Protection of lithium batteries a 400W DC motor driven experiments and found that all protective plates in a lithium battery when the total pressure of about 42.5V charging off tube protection against surges on the ground, pressure or almost total 29.2V for the discharge out of the market when the protection of the tube voltage, protecting the plate with a battery pack lithium in the testing stage for overcurrent detected: discharge current of 39A or more, the protective panels were made over-current protection, temperature of 109 ° C when the switch in the off-discharge circuit, the effective protection of the market of the discharge tube. The above data indicate that the circuit is essentially achieved the over / under voltage / over current / over-temperature protection, the basic requirements.

After a long round-trip charge-discharge test, collect relevant data, drawings, can be achieved without a balanced circuit waveforms comparing the experimental data are: the balance of the circuit of a hp PP2182D battery lithium and lithium 2 upper limit of the variation in battery voltage, such as that shown in Figure 6 and Figure 7, the ultimate balance of protection of lithium batteries 3 times the upper limit of battery voltage changes as shown in Figure 8, and balanced with the protection of batteries and lithium batteries 4 of 5 threshold voltage to change the battery of Figure 9 and Figure 10 shows the non-balanced circuit with 6 cells Lithium minimum voltage of the battery as shown in Figure 11. Figure 1, the points of all curves measured for the first time the limit of the battery (bottom) voltage, curve 2 points for long term running of the toshiba PA3395U-1BRS battery measured upper limit (lower) the voltage value.

On the accession of a balanced circuit the maximum voltage of the battery is maintained at an equilibrium point of 4.22V and 4.18V or more, effective protection of the upper limit of the battery voltage, non circuit to balance the maximum voltage of the battery which seems random, by virtue of membership of a balanced circuit the battery voltage level is maintained below the equilibrium point around 2.91V, the effective protection of the lower end of the battery voltage, non-balanced circuit limits the voltage of the battery which seems chaotic, badly damaging the battery life of the nature of coherence and the.

This departure from the practice of engineering, the dynamic nature of lithium batteries in a phase of high flow discharge occurred after the upper and lower limits of the phenomenon of unequal tension is proposed based on the balance of the circuit TL431, and lithium-depth study of a balanced circuit. Practical results show that the design and balanced on the balance circuit and the circuit not only ensures high speed of discharge of the battery after the battery requirements of consistency, but also effectively protect the battery voltage the upper and lower limits for the further study of high battery performance energy storage systems and hybrid systems for electric vehicles has laid a solid foundation.