Available online at www.sciencedirect.com Journal of Power Sources 177 (2008) 217–225 Studies of the pulse charge of lead-acid batteries for PV applications Part I. Factors influencing the mechanism of the pulse charge of the positive plate A. Kirchev ∗ , M. Perrin, E. Lemaire, F. Karoui, F. Mattera Commissariat de l’Energie Atomique, Institut National de l’Energie Solaire, INES-RDI, Parc Technologique de Savoie Technolac, 50 Avenue du Lac L´ eman, 73377 Le Bourget du Lac Cedex, France Received 30 July 2007; received in revised form 28 September 2007; accepted 27 October 2007 Available online 17 November 2007 Abstract The mechanism of the positive plate charge in pulse regime was studied in model lead-acid cells with one positive and two negative plates (8 Ah each) and Ag/Ag 2 SO 4 reference electrodes. The results showed that the evolution of the electrode potential is much slower on the positive plate than on the negative plate. Regardless of this fact, the calculated capacitive current of charge and self-discharge of the electrochemical double layer (EDL) during the “ON” and “OFF” half-periods of the pulse current square waves is comparable with the charge current amplitude. The result is due to the high values of the EDL on the surface of the lead dioxide active material. The influence of different factors like state of charge, state of health, pulse frequency, current amplitude and open circuit stay before the polarization was discussed. The previously determined optimal frequency of 1Hz was associated with a maximum in the average double layer current on frequency dependence. The average double layer current is also maximal at SOC between 75 and 100%. The exchange of the constant current polarization with pulse polarization does not change substantially the mechanism and the overvoltage of the oxygen evolution reaction on the positive plate. The mechanism of the self-discharge of the EDL was also estimated analyzing long-time PPP transients (up to 2 h). It was found that when the PPP is lower than 1.2 V the preferred mechanism of EDL self-discharge is by coupling with the lead sulphate oxidation reaction. At higher values of PPP the EDL self-discharge happens via oxygen evolution. The high faradic efficiency of the pulse charge is due to the chemical oxidation of the Pb(II) ions by the O atoms and OH radicals formed at the oxygen evolution both during the “ON” and “OFF” periods. © 2007 Elsevier B.V. All rights reserved. Keywords: Lead acid; Pulse charge; Electrochemical double layer; Oxygen evolution 1. Introduction One of the most severe problems of the lead-acid batter- ies operating in solar energy storage applications is the lack of charge due to the intermittent current from the photovoltaic (PV) module. The insufficient charge results often in hard sul- phation of the positive plate [1], when the cells are flooded, and sulphation of both plates, when the cells are valve-regulated [2]. Recently a new charge strategy was proposed to overcome the ∗ Corresponding author at: CEA-INES, Laboratory of Solar Systems, 50 Avenue du Lac L´ eman, INES-RDI BP 332, 73377 Le Bourget du Lac, France. Tel.: +33 4 79 44 45 49; fax: +33 4 79 68 80 49. E-mail address: angel.kirchev@cea.fr (A. Kirchev). insufficient charge of the lead-acid batteries for PV-storage [3]. The strategy consists of two-step charge algorithm—the first step is galvanostatic until a certain cell voltage limit is reached and the second step is pulse-current (or interrupted-current) charge for a fixed amount of time. It was found that the application of the pulse-current step in this algorithm reduces substantially the quantity of the residual PbSO 4 at the end of the charge. In the literature, the first studies concerning the pulse charge of lead-acid battery are directed towards its application for rapid charge of traction cells for electric vehicles [4–6]. The results show that the rate of the charge can be accelerated substantially down to 30–60 min for the full charge of an empty battery with- out substantial loss of energy. More recent studies show other advantages of the rapid pulse charge: it can be used to over- come negative phenomena limiting the exploitation period of 0378-7753/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2007.10.095