Charge balancing system for a power battery comprising a predefined number of modules connected in series, a module comprising at least two accumulator stages, an accumulator stage comprising at least one accumulator, characterized in that said system comprises: - a plurality of insulated converters (107, 121) mounted in parallel, respectively connected on the one hand to a predefined number of associated accumulator stages, and on the other hand to a low-voltage network supplying power to electrical auxiliaries (A1, A2, A3, An) of a motor vehicle, with no auxiliary battery, including: • a plurality of first one-way converters respectively connected on the one hand to the terminals of a module, and on the other hand to the low-voltage network, and • a plurality of second one-way converters respectively connected on the one hand to the low-voltage network and on the other hand to the terminals of the accumulator stages of said module, and - a control unit for said converters (107, 121) configured to: • control at least one first converter so as to bring the predefined number of associated modules to a nominal voltage level, and to control a transfer of energy in a first direction from the power battery to said low-voltage network via said first converters, and to • control at least one second converter so as to bring said associated accumulator stages of a module to a nominal voltage level, and to control a transfer of energy in a second direction from said low-voltage network to the power battery via said at least one second converter, and in that - the first one-way converters are configured to supply power to the low-voltage network supplying power to electrical auxiliaries (A1, A2, A3, An) with no auxiliary battery and to balance the state of charge of the modules, and the second one-way converters are configured to balance the state of charge of the stages within the modules, and in that - the first one-way converters and the second one-way converters are configured to transfer powers of different orders of magnitude, the first one-way converters being configured to transfer a greater power than the second one-way converters. - a plurality of insulated converters (107, 121) mounted in parallel, respectively connected on the one hand to a predefined number of associated accumulator stages, and on the other hand to a low-voltage network supplying power to electrical auxiliaries (A1, A2, A3, An) of a motor vehicle, with no auxiliary battery, including: • a plurality of first one-way converters respectively connected on the one hand to the terminals of a module, and on the other hand to the low-voltage network, and • a plurality of second one-way converters respectively connected on the one hand to the low-voltage network and on the other hand to the terminals of the accumulator stages of said module, and • a plurality of first one-way converters respectively connected on the one hand to the terminals of a module, and on the other hand to the low-voltage network, and • a plurality of second one-way converters respectively connected on the one hand to the low-voltage network and on the other hand to the terminals of the accumulator stages of said module, and - a control unit for said converters (107, 121) configured to: • control at least one first converter so as to bring the predefined number of associated modules to a nominal voltage level, and to control a transfer of energy in a first direction from the power battery to said low-voltage network via said first converters, and to • control at least one second converter so as to bring said associated accumulator stages of a module to a nominal voltage level, and to control a transfer of energy in a second direction from said low-voltage network to the power battery via said at least one second converter, and in that • control at least one first converter so as to bring the predefined number of associated modules to a nominal voltage level, and to control a transfer of energy in a first direction from the power battery to said low-voltage network via said first converters, and to • control at least one second converter so as to bring said associated accumulator stages of a module to a nominal voltage level, and to control a transfer of energy in a second direction from said low-voltage network to the power battery via said at least one second converter, and in that - the first one-way converters are configured to supply power to the low-voltage network supplying power to electrical auxiliaries (A1, A2, A3, An) with no auxiliary battery and to balance the state of charge of the modules, and the second one-way converters are configured to balance the state of charge of the stages within the modules, and in that - the first one-way converters and the second one-way converters are configured to transfer powers of different orders of magnitude, the first one-way converters being configured to transfer a greater power than the second one-way converters.