1、原 文Title：RAPID CHARGE SYSTEM FOR LEAD-ACID BATTERY OF SOLAR ENERGY STREET LIGHT BASED ON SINGLE-CHIP MICROCOMPUTER1. IntroductionOur country is very rich in solar energy resources and the utilization of solar energy heat is one of the technologies that are of the highest commercial degree and the mo
2、st universal application in new and renewable energy resources. Under the initiative of building saving society, the solar energy electro-optic illumination is our countrys realistic choice under the existing national condition and it reduces the expenditures of municipal administration on street la
3、mp to a certain extent. Especially in the newly-built urban road section and remote border district that has difficulty in using electricity, it is of the strongest promotion and is taken seriously by Finance department; it is honored as the 21st centurys green project.2. The basic theory of battery
4、 chargingIn the mid-1960s, American scientist Mas has done the massive experimental study to the charging-up process of ringent accumulator cell, and proposed acceptable charging curve taken by the accumulator by the lowest gas efficiency for premise, the curve function is i = I 0 e . The experiment
5、 indicated that if the charging current changes according to this curve,it may reduce the duration of charging greatly, and has not affect on batterys capacity and its life, thus it had established research direction to the method of the fast charging. is called the curve the best charge pattern in
6、principle.It May see that the initial charging current is very big from the Mas curve, but weakens very quickly. The primary cause is that it comes into being the phenomenon of polarization during the process of charging. The phenomenon of polarization is refers to that the interior the sealed accum
7、ulator has produced the oxygen and the hydrogen during its process of charging, when the oxygen cannot be absorbed promptly, then it piles up on the positive plate, enlarge the pressure of the interior of battery, the batterys temperature rises, reduces positive plates area simultaneously, performan
8、ce by the increase of interior resistance. The polarization can affect the speed and the quality of charging, and even reduce the life of accumulator. Therefore, its important to develop fast charge system of battery whose performance is fine and movement is reliable. By Not affecting the service li
9、fe of accumulator as far as possible for premise, it hoped that it can fill the battery capacity sufficiently adopting the biggest charging current in a short time,and the battery neither produces too much gases nor causes the interior hyperpyrexia during the process.3. Solar street light systemIn t
10、he solar streetlight system, accumulators charging source is from the solar cell, the change of climate and the users excessive using electricity are very easy to cause the accumulator over-discharge, and therefore the normal works guarantee rate of the solar streetlight is lower than the situation
11、of alternating current by far. If the Lead-acid battery is in the state of over-discharge during use process, then the accumulators life will reduce greatly. Otherwise, if the accumulator cell has been in the use process floats the charge or the shallow discharge condition, then accumulator cells se
12、rvice life will lengthen greatly, even lengthen one more time. Therefore, the function of the charging and discharging control system is obvious in the streetlight system merely relies on the solar cell for the battery charging, its performance has decided accumulators performance, systems reliabili
13、ty and systems cost directly.3.1 pulse charging methodThe theoretical base of pulse fast charge method is by superimposing certain frequency, width and high negative pulse or midway stops for a short time during the charge, makes the lead ion participates in the response produce Pb by dissolving PbS
14、04 and PbO2 with enough time and enhances its density, also makes the procreant H+ and HS04- ion put aside with enough time from the surface of electrode. Its synthetical effect is to reduce the polarization of the accumulators concentration, permit to enlarge the charging current, reduce the chargi
15、ng time.Because the phenomenon of polarization is often not obvious during the initial period of charging ,it may adopt big electric current 0.81 time of rated capacity to carry on the constant-current charge, makes the accumulator charging attain to the 50%60% rated capacity in a short time. Stop t
16、o charge when the single standard voltage of accumulator rises to 2.4V, the water starts to decompose and micro air emits (about is 25 milliseconds). In order to eliminate the electric charge accumulation of the electrochemistry polarization and the gas which forms in the pore of pole plate, after s
17、topping sufficiently, Making the accumulator through one big current pulse whose direction is opposite to charge by discharging after stopping charging, then stops (about 40 milliseconds) charging again, the depth of pulse is 1.53 times of charging current, the pulse width is 1501000 microseconds. T
18、he later charging-up process follows this cyclic until sufficiently. This may make the speed of polarization reduce obviously, thus solves the problem of accumulators life influenced by fast-charge.3.2 master controller P87LPC767The control loop still consumes accumulators energy after control circu
19、it cutting off loads return route and therefore the control loop must reduce the electronic component to reduce the power lost as far as possible. Stemming from this intention, this electric circuit takes micro controller P87LPC767 of PHILIPS as CPU. This micro controller suits for many situations r
20、equesting high density, low cost, particularly its power loss is only 0.44mA1.7mA when it works round 100kHz4MHz, the supply voltage is 3.3V, thats very suitable for power supply system of accumulator.P87LPC767 takes P1.7 (Fzs) and P1.6 (PWM) as the grid control signal of MOSFET, then controls its b
21、reak over condition, guarantees the steady operation of circuit. This controllers load is streetlight, therefore it is of function of control, that is to say when theres sunlight,VG2 cuts off; when the ray is insufficient in the night or rainy day,VG2 break over to supply streetlight. The solar cell
22、 arrays output voltage drops obviously because of insufficient ray, therefore it can judge the situation of ray by measuring output voltage decomposed, taking it as the criterion for break over and a closure of VG2.3.3 MOSFET actuations and protectionMOSFET is the control component of voltage and it
23、s of merits of high operating frequency, cheap and so on. This system has selected IRF230 of IR Corporation. Systems operating frequency is 30 kHz, if the frequency is high, it may make smaller, thus reduces overall systems volume greatly, and then saves weight.MOSFET VT3 is the discharge switch of
24、battery in the system, when the lead-acid battery discharges, from the point of view of protecting accumulator, when the accumulators voltage is smaller than over-discharge voltage, VT3 cuts off to cut off the loop between the accumulator and the load, carries on “over-discharge protection”, avoids
25、the battery over-discharge, damages the accumulator. When the solar cell array supplies power again, only when the accumulators voltage rises to the floating voltage again, then VT3 break over again, connects loop of load. This method is when the breakdown appears, grid signal removed in 2s rapidly,
26、 this system has chosen EXB481 as MOSFET driver. EXB841 is mixed IC, it can drive to 600V IGBT as high as 400A and1200V IGBT as high as 300A. Because of the delay of driving circuit signal is less than 1s, the mixed IC is suitable for on-off operation as high as about 40KHZ.3.4 experimental result a
27、nalysisIt carries on the experiment adopting the way of traditional constant flow - constant pressure charge way , changing current by stages and present discharge pulse charge way for charging the battery in the solar energy streetlight, experimental result as shown in Table 1:Table 1 experimental
28、comparison of charged way compared to the traditional constant flow constant pressure charge way , the charge re acceptance increased 6.64%,accumulators exotherm reduced 3.6%. The belt discharges the pulse charge with discharging is of the shortest duration of charging, the exotherm is high, but all
29、 is in accepted scope. All things considered, the belt discharges the pulse charge with discharging is better way of charging. The extra characteristics that displayed in the test system by the pulse charge way with discharging is given below: 1. The capacity of accumulator increased fast, the charg
30、e can eliminate the polarization, made the chemical reaction be full, therefore accumulators capacity increased. At the same time, the new accumulator neednt to discharge after initial charge which saved the electrical energy and brought convenience for use. 2. The effect of getting rid of sulfurati
31、on is remarkable. General method of getting rid of sulfuration is both time-consuming and troublesome, however the method of charging with discharge pulse only needs 45 hours, and the effect is all right.4.conclusion The charge system controlled by microcomputer is of characteristics: the volume is
32、small, the weight is light, the control loop is simple, the reliability is higher and so on, and therefore time is favored. The manipulative system of streetlight charge adopted microcomputer technology, it took the solar cell as power in the article, the hardware has been simple, the duration of charging was short, the cost was low, the efficiency and the reliability had been enhanced. It both had guaranteed the solar cell array was at the best functional mode,and made the accumulator be at the correct charging and discharging condition like this, meanwhile it could use the electrical energy
