battery problem 2402 model 115 T330L RWD 07 plate

[pepperpot]

Evening gents,
had problems starting in the last couple of weeks. If i leave the sat nav plugged in the van almost stalls on turn over.
i have two batteries under the drivers seat, do the both need changing? (had this van just over 3 years, dont think batteries have been changed before)
cheers
graham

[ake]

Yes, batteries are probably original and due for replacement, they are nearly eight years old!