I recently bought two 200ah 12v long tubular batteries, they were manufactured in sept. 2021 so I thought they needed a little charge to balance.
So I charged them individually with a 12v charger until they both rested on 13.80v
I connected them on series to the mppt solar controller and to an inverter.
The solar charge controller was charging them on 29v, in the evening I measured their voltage individually and the results are in the image 
