EP1562049-A1  MATTERA F ET AL: "Characterisation of photovoltaic batteries using radio element detection: the influence and consequences of the electrolyte stratification" JOURNAL OF POWER SOURCES, ELSEVIER SEQUOIA S.A. LAUSANNE, CH, Bd. 113, Nr. 2, 27. Januar 2003 (2003-01-27), Seiten 400-407, XP004402936 ISSN: 0378-7753;  DESMETTRE D ET AL: "EXPERIMENTAL STUDY OF STRATIFICATION OF ELECTROLYTE IN LEAD/ACID BATTERIES USED FOR SOLAR ENERGY" 2ND WORLD CONFERENCE ON PHOTOVOLTAIC SOLAR ENERGY CONVERSION. / 15TH EUROPEAN PV SOLAR ENERGY CONFERENCE. / 27TH US IEEE PHOTOVOLTAICSSPECIALISTS CONFERENCE. / 10TH ASIA/PACIFIC PV SCIENCE AND ENGINEERINGCONFERENCE. VIENNA, AUSTRIA, JULY 6 - 10, 1998, Bd. VOL. 2, 6. Juli 1998 (1998-07-06), Seiten 2135-2138, XP001138150 ISBN: 92-828-5419-1;  DESMETTRE D ET AL: "EXPERIMENTAL STUDY OF STRATIFICATION OF ELECTROLYTE IN LEADACID BATTERIES USED FOR SOLAR ENERGY" 2ND WORLD CONFERENCE ON PHOTOVOLTAIC SOLAR ENERGY CONVERSION. 15TH EUROPEAN PV SOLAR ENERGY CONFERENCE. 27TH US IEEE PHOTOVOLTAICSSPECIALISTS CONFERENCE. 10TH ASIAPACIFIC PV SCIENCE AND ENGINEERINGCONFERENCE. VIENNA, AUSTRIA, JULY 6 - 10, 1998, Bd. VOL. 2, 6. Juli 1998 (1998-07-06), Seiten 2135-2138, XP001138150 ISBN: 92-828-5419-1EP1562049-B1  DESMETTRE D ET AL: "EXPERIMENTAL STUDY OF STRATIFICATION OF ELECTROLYTE IN LEAD/ACID BATTERIES USED FOR SOLAR ENERGY" 2ND WORLD CONFERENCE ON PHOTOVOLTAIC SOLAR ENERGY CONVERSION. / 15TH EUROPEAN PV SOLAR ENERGY CONFERENCE. / 27TH US IEEE PHOTOVOLTAICSSPECIALISTS CONFERENCE. / 10TH ASIA/PACIFIC PV SCIENCE AND ENGINEERINGCONFERENCE. VIENNA, AUSTRIA, JULY 6 - 10, 1998, Bd. VOL. 2, 6. Juli 1998 (1998-07-06), Seiten 2135-2138, XP001138150 ISBN: 92-828-5419-1;  MATTERA F ET AL: "Characterisation of photovoltaic batteries using radio element detection: the influence and consequences of the electrolyte stratification" JOURNAL OF POWER SOURCES, ELSEVIER SEQUOIA S.A. LAUSANNE, CH, Bd. 113, Nr. 2, 27. Januar 2003 (2003-01-27), Seiten 400-407, XP004402936 ISSN: 0378-7753