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New battery charge control for PV systems


The target of the presented project is to improve the life of lead-acid batteries.
The battery manufacters of lead-acid open batteries give a life of S to 10 years for "special solar" types (and sometimes more). These figures are generally used in the expected cost of solar systems.
The on-site experiences show that the effective obtained life of these batteries is not the expected values: very often the real battery life is lower, and often more than two times lower.
Why the observed life of batteries is not the expected ? It is not a question of manufacturing: the manufacturers have now an enough large experience in this field (thick plates, value of gravity, value of max voltage required...). It is, for us, due to the max charge quality of the batteries used in PV generators.
The proposed research wants to develop a new regulation concept which uses as basic information, the gasing of lead-acid open batteries instead of the voltage, which is not, in fact, a good indication of the battery state of charge (it depends of charging current age of the battery, temperature !). Gasing of battery is an absolute an chemical phenomena (charging current, age, temperature...): when gasing appears (with homogene gravity electrolyte!. the battery is surely charged.
- Gasing appears when the battery is charged, whatever the "environment" parameters of the battery.
- Proposed gasing detection (already tested on a model in a laboratory) is simple and reliable: storage of gas in a small receptacle installed in the electrolyte with electrodes inside: when gas has filled the receptacle, the electrodes are in gas and not in electrolyte and the electric resistance between these electrodes become infinite instead of zero, giving an information to the "outside" world of the battery (the receptacle has a small calibrated hole to evacuate slowly the gas).
- The use of this binary information can be taken into account in a "PV regulator" which decides when the battery is charged, for example if "we can count x electrodes-drying for each battery element of the set within y minutes".
- The use of this binary information can also be used to check the good health of battery elements, for example if "the time to count x electrodes-drying of one element is y times greater than the average time for the set of the battery".
The different phases of this research will be:
- Studies of variation of the operating conditions
- Reactivation of the laboratory model, validation of observed results
- Study, design and development of pre-industrial sensors
- Development of mathematical model for the overcharge process
- Tests of the prototypes of gassing detection systems
- Study, design and development of pre-industrial regulators
- Tests of pre-industrial prototypes in laboratory, comparison with classic controllers
- On site tests of pre-industrial prototypes

Funding Scheme

CSC - Cost-sharing contracts


Comité Scientifique et Technique des Industries Climatiques
Domaine De Saint Paul
78470 Saint-rémy-lès-chevreuse

Participants (4)

Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
22,Avenida Complutense
28040 Tabernas
Hyperion Energy Systems Ltd.
Main Street
120 Watergrasshill
Oldham France SA
Rue Alexandre Fleming
62033 Arras
15,Rue Carnot
91170 Viry Chatillon