Voltage charging

If the charging process continues after all the lead sulphate has been used up, then the charging voltage rises. Hydrogen is liberated from the lead electrode, and oxygen is liberated from the lead dioxide electrode. The accumulator is then said to be gassing . 

The use of a reactor in series with the ctipacitors w ill reduce the harmonic effects in a power network, as well as their effect on other circuits in the vicinity, such as a telecommunication network (see also Section 23.1 1 and Example 23.4). The choice of reactance should be such that it W ill provide the required detuning by resonating below the required harmonic, to provide a least impedance path for that harmonic and filter it out from the circuit. The basic idea of a filter circuit is to make it respond to the current of one frequency and reject all other frequency components. At power frequency, the circuit should act as a capacitive load and improve the p.f. of the system. For the fifth harmonic, for instance, it should resonate below X 50 Hz for a 50 Hz system, say at around 200-220 Hz, to avoid excessive charging voltages w hich may lead to... 

Charge and discharge current densities were in the range of 0,15-1,0 mA/cm2, the final charge voltage of the model of the cell was 4,18-4,20 V. 

Figure 5.8 Log-log plots of the depletion time and time for the surface potential to decay to its half-value fj/2 versus charging voltage Vq for an amorphous Se Te 13 wt% photoreceptor film of thickness 70 pm (from Ref. [8]). The inset shows the dependence of the depletion time on the Te content (from Ref. [9]).

If a complete cell is charged to, e.g., 4.1 V, then the potential Z carbon of the fully lithiated negative electrode will be about 0.1 V vs. Li/Li+. Therefore, the potential Eoxiie of the fully charged positive electrode in this example will be 4.2 V vs. Li/Li+. Needless to say that this trivial relationship must be remembered when data for half cells (vs. metallic lithium) are compared to the data for complete cells. An important consequence of this trivial relationship is the potential excursion of the counterelectrode in the case of an anomalous behavior of the carbon electrode (and vice versa). Imagine that, in the previous example the potential of the carbon would shift to 0.3 V vs. Li/Li+ due to a malfunction of the carbon electrode. If the end-of-charge voltage of the complete cell would be the same, namely 4.1V, then the potential of the positive electrode would be 4.4 V vs. Li/Li+. In such a case, the safety of the entire cell could be compromised. 

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