Highly suggest you buy a Foxwell BT 100 pro 12v battery analyzer..
Pretty cheap, I am thinking $30 bucks or so on Amazon. It tells you everything you want to know, dead cells, conditions etc.
I use it on my boat, truck, jeep toad etc. and coach batteries.
This is A LOT easier than taking them to AutoZone to be analyzed...OR trusting someone trying to sell you new batteries.