A thermal device comprising: - at least one thermal means dissipating thermal energy, in operation, the thermal means comprising cells of an electric storage battery, - means for thermally managing the thermal means, comprising an enclosure having a volume in which a heat-absorbing substance is disposed for exchanging heat with said thermal means, in a nominal operating situation, the substance being a suitable latent heat storage element to absorb by phase change a quantity of heat dissipated by the thermal means, and - a channeling (21,31; 23,28) between the volume of the enclosure and the outside environment, characterized in that: - said channeling defines a discharge (21, 31; 23, 28) allowing, in an abnormal overheating situation of the thermal means, that at least a part of said substance is evacuated towards said outside environment further away from the thermal means than said volume, then at least a part of said substance in a gaseous phase, and, - the enclosure comprises two walls (33a,33b) face to face, maintaining a distance between them to store the substance 15, and at least one of the following characteristics is realized: - the boiling temperature of the substance is comprised between 70°C and 130°C, within 10°C, - the said latent heat storage element is encapsulated in a fluid that vaporizes between 75 and 150°C, - the said latent heat storage element has a melting temperature between 15°C and 50°C and a boiling temperature between 75 and 150°C, - the said latent heat storage element is totally liquid below 70°C, within 10°C, and suitable to gradually change, by boiling, from a liquid to a gas state between 70°C and 130°C, within 10°C, - the said heat-absorbing substance is water or a water based mixture. - at least one thermal means dissipating thermal energy, in operation, the thermal means comprising cells of an electric storage battery, - means for thermally managing the thermal means, comprising an enclosure having a volume in which a heat-absorbing substance is disposed for exchanging heat with said thermal means, in a nominal operating situation, the substance being a suitable latent heat storage element to absorb by phase change a quantity of heat dissipated by the thermal means, and - a channeling (21,31; 23,28) between the volume of the enclosure and the outside environment, - said channeling defines a discharge (21, 31; 23, 28) allowing, in an abnormal overheating situation of the thermal means, that at least a part of said substance is evacuated towards said outside environment further away from the thermal means than said volume, then at least a part of said substance in a gaseous phase, and, - the enclosure comprises two walls (33a,33b) face to face, maintaining a distance between them to store the substance 15, and at least one of the following characteristics is realized: - the boiling temperature of the substance is comprised between 70°C and 130°C, within 10°C, - the said latent heat storage element is encapsulated in a fluid that vaporizes between 75 and 150°C, - the said latent heat storage element has a melting temperature between 15°C and 50°C and a boiling temperature between 75 and 150°C, - the said latent heat storage element is totally liquid below 70°C, within 10°C, and suitable to gradually change, by boiling, from a liquid to a gas state between 70°C and 130°C, within 10°C, - the said heat-absorbing substance is water or a water based mixture. - the boiling temperature of the substance is comprised between 70°C and 130°C, within 10°C, - the said latent heat storage element is encapsulated in a fluid that vaporizes between 75 and 150°C, - the said latent heat storage element has a melting temperature between 15°C and 50°C and a boiling temperature between 75 and 150°C, - the said latent heat storage element is totally liquid below 70°C, within 10°C, and suitable to gradually change, by boiling, from a liquid to a gas state between 70°C and 130°C, within 10°C, - the said heat-absorbing substance is water or a water based mixture.