Had the same problem. "Fully" charged, gives up the ghost after a short journey. After brief research, it seems to be a general problem with these models. Battery must specifically not be too empty or too full, some upgrade to other batteries.

After initiating a return, we were told that "experience has shown" that the repair/replacement costs more and we therefore promptly received a credit note with the instruction to dispose of the faulty product correctly.

It wasn't the battery but the two vehicles...

Meanwhile we have 4 of these vehicles at home, none of them work, always the same, plug in the battery and the charger lights up permanently green...
According to Carrera battery defective...
Great... :-(

Unfortunately I cannot help as I have given it away.