Method for diagnosing a set of accumulator batteries distributed in a fleet of motor vehicles, said motor vehicles each comprising an electric traction motor supplied with current by one of said accumulator batteries and a communication system designed to communicate with a remote server, characterized in that it comprises: a) a step of transmission, by the communication system of each motor vehicle, of at least one value (ΔU i, ΔU i-1) of at least one diagnostic parameter (ΔU) of the accumulator battery associated with said motor vehicle, b) a step of reception, by the remote server, of the values (ΔU i, ΔU i-1) transmitted in step a); c) a step of statistical calculation of a reference value (ΔU ref, α ref), on the basis of the values (ΔU i, ΔU i-1) received in step b), d) a step of diagnosing the accumulator batteries, taking into account the values (ΔU i, ΔU i-1) received in step b) and the reference value (ΔU ref, α ref) calculated in step c), the method being characterized in that: - in step a), the communication system of each motor vehicle transmits two successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of the accumulator battery associated with said motor vehicle, - in step b), the successive values (ΔU i, ΔU i-1) transmitted in step a) are received, - in step c), said reference value (α ref) is calculated on the basis of the differences between the successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of each accumulator battery, and - in step d), an item of data relating to the differences between the two successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of each accumulator battery is compared with the reference value (α ref) calculated in step c), and a second diagnosis of each accumulator battery is deduced on the basis of the result of this comparison, an accumulator battery being considered to be faulty if the first and second diagnoses indicate a fault with the accumulator battery. a) a step of transmission, by the communication system of each motor vehicle, of at least one value (ΔU i, ΔU i-1) of at least one diagnostic parameter (ΔU) of the accumulator battery associated with said motor vehicle, b) a step of reception, by the remote server, of the values (ΔU i, ΔU i-1) transmitted in step a); c) a step of statistical calculation of a reference value (ΔU ref, α ref), on the basis of the values (ΔU i, ΔU i-1) received in step b), d) a step of diagnosing the accumulator batteries, taking into account the values (ΔU i, ΔU i-1) received in step b) and the reference value (ΔU ref, α ref) calculated in step c), - in step a), the communication system of each motor vehicle transmits two successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of the accumulator battery associated with said motor vehicle, - in step b), the successive values (ΔU i, ΔU i-1) transmitted in step a) are received, - in step c), said reference value (α ref) is calculated on the basis of the differences between the successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of each accumulator battery, and - in step d), an item of data relating to the differences between the two successive values (ΔU i, ΔU i-1) of each diagnostic parameter (ΔU) of each accumulator battery is compared with the reference value (α ref) calculated in step c), and a second diagnosis of each accumulator battery is deduced on the basis of the result of this comparison, an accumulator battery being considered to be faulty if the first and second diagnoses indicate a fault with the accumulator battery.