Rechargeable lithium-ion battery equalization Space Techniques (part 1)
Lithium-ion storage device of energy for development of the probe is the third generation storage device probe energy. It has a light weight, small volume, no memory effect, the benefits of temperature adaptation in width, the main use of nickel-cadmium batteries, replacing the nickel-hydrogen batteries. Lithium-ion batteries for the ratio of the weight of aerospace may be 90 ~ 110Wh/kg, compared to 45 ~ 60Wh/kg NiMH battery indicators have obvious advantages. However, the electrochemical properties of lithium-ion battery charging process requirements must be strictly controlled, therefore, to design a special charging circuit management to control the spacecraft charge lithium-ion batteries. Dell TD347 Dell U4873 Dell D5318
The key technology of lithium-ion
Li-ion replacement battery Ni-Cd, Ni-MH battery can be applied to a simple plug and play “approach, because the lithium-ion and nickel-cadmium, nickel-hydrogen batteries have one of biggest differences: overcharging lithium-ion is strictly prohibited. Therefore, we must combine the characteristics of the circuit design of new lithium-ion battery management. Lithium-ion battery management circuit of Battery critical point (with Ni-Cd, Ni-MH battery charge management circuit main difference) are mainly two aspects: the burden and load equalization.
In engineering applications, the battery cell lithium-ion batteries in parallel from a single monomer or composition of the battery module in the battery must be serial, consider the process of recharging the battery or monomer imbalance battery module, and over time, these imbalances will become increasingly serious, serious impact on battery life and reliability, thus equalizing charge is the key technology of lithium-ion battery. Dell HD438 Dell Y9943 Dell FK890
A constant current - constant voltage (cone) Charge Control Model
The use of nickel-cadmium, nickel-hydrogen satellite battery power system, essentially using constant current charging mode, when reached VT curve, power electronics, pressure, third mode control electrode to stop charging when the control point, completion of a load. control lithium-ion battery is not suitable for the use of these methods because they do not warrant charges the rechargeable lithium-ion is still limited to the final pressure within prescribed limits, even if the voltage final charge is guaranteed, in general, immediately after the pressure reaches the final charge stops charging, the rechargeable lithium-ion batteries to reach the final after fracturing still need to add capacity by 30%. Years from lithium-ion battery development for the constant current - constant voltage control load is the most common and most suitable for the load control method. In this mode, the first battery charger lithium-ion battery for constant charging current when the battery voltage increases gradually, when the battery voltage reaches the value set for constant voltage when the load current decreases approximately exponentially, so that kind of pricing model for load control, also known as the cone. Dell GK479 Dell NF343 Dell PC764
Two load-balanced technology
The space should be used with the balance of the lithium-ion battery charging technology, this view has been fully recognized at home and abroad. Technology equalizing charge primarily to address long-term single cell lithium-ion battery charge polarization phenomenon in electrochemical properties, so that the merits of a balanced load takes time, money and labor ie the work can be effectively audit.
Rechargeable lithium-ion balancing civilian products in the attention and has not been applied because of the multi-cell single section is rarely applied in series, reliability, life does not ask. The lithium-ion batteries in electric vehicle system, the series of sessions over single cell, have adopted a balanced load technology, generally used for control and SCM systems on a single battery practice shunt resistor control a single battery charge. This approach control complex, inefficient, heat consumption Tai balanced long early Yizhi aerospace production scenario this method, and now foreign technical staff working Tantaogengjia ideal. Dell GW240 Dell RN873 Dell Y6142
Importance of the equalizing charge is to make lithium-ion batteries maintain a voltage difference only in the expected range, thus ensuring the life of every cell in the satellite is not subjected to excessive stress at the impact and damage. Without a balanced load control, with the increase in the charge-discharge cycle, the cell voltage gradually unique differentiation.
In general, only lithium-ion battery charging voltage is 50mV away is perfectly acceptable. We believe that the main cause is through the efficacy of a single battery charge, the self-discharge rate different. On the other hand, a single cell in the circuit for measuring the current consumption should also seriously consider the impact, sometimes measuring circuit power consumption has reached the magnitude of the battery self-discharge current. life of the lithium-ion experiment, and some technical staff to accommodate the battery first or the last series alone is often the first damage, often caused by consumption as measured circuit. Dell Studio 1435 battery Dell Studio 1436 battery
Load control circuit
A load control bypass
Light through the diode array of solar charge directly to the lithium-ion battery charging, the battery is in charge of each cell are the branch circuit. When a single cell voltage reaches the set value, the bypass load started turning the power transistor, shunt some of the load current to maintain the voltage of the single cell is a constant in a narrow range. Identify the characteristics of the battery charge current decreases (approximately exponentially) until the end of illumination. This pricing method can not guarantee that any equalization battery single charge, but a bypass circuit of higher power, the load current is difficult to measure.
2 Split Load Control
single cell through the various check the battery voltage sampling circuit, respectively, after removing the single cell or a maximum gate voltage, the circuit for signal conversion from the reference signal of error signal The error signal in the circuit shunt regulator, the control group of lithium-ion battery The only tension. Either the battery voltage reaches a set value, the battery charge current decreases on average. Using a switching regulator shunts the constant monomer charge, the charging current is pulsed in order to use the lithium-ion battery need to control the group can adapt to changes in current load. Dell Studio 15 battery Dell Studio 17 battery
Main Error Amplifier (MEA) sampling signal bus voltage, causing the error signal sent to the shunt. It is, shunt regulator, along with a bus voltage of the battery and single control voltage of the battery.
Paragraph 3 Charge Control
Comparison of single cell from an inspection of the single cell voltage sampling circuit, any one of the single cell voltage exceeds a given value, or the door will produce a transient voltage signal, the circuitry to disconnect throughout the prosecution case locked, which makes the load current drops to third, where once again the signal voltage to generate a second charge to turn the table, until the last turn off the load range. When the load pulse or in the shadow of the coming period, the circuit generates unlock unlock signal circuit load control can make the process of the next refill. Clearly, when the constant voltage, the load current is not similar to exponential, but ladder-type step decreasing. dell latitude d830 battery Dell Studio 14 battery