Dear BBForks!
Thank you for your answer which is exactly what I was waiting for! And thank you also to all the persons who take time to answer to this post!

Best regards.

I'm assuming you're purchasing a new truck with a choice of batteries? Variables, such as working enviroment, physical size of truck, shift work, etc need to be explored in order to give an accurate answer.

Lifts are designed around an 8 hr shift. Installing a larger A/H battery than needed may mean that the lift needs a charge right in the middle of a shift. If this becomes the norm- overcharging the battery may become prevolent- shortening the life of the battery.

I think that the time spent investigating the advantages of different A/H batteries would be better spent developing a effective charging system that works around the 8-8-8 system.
In smaller operations with limited lifts, the 8-8-8 system is very difficult to follow. Unless a system is in place & followed, overcharging the battery becomes the norm & battery life deminishes greatly.

Some new trucks can be had with different size / AH batteries, on certain reach trucks going for the larger AH battery can have an effect on the overall length of the truck.
Something to think about if aisle width is tight when you spec a truck.
If you look on BT forklifts it gives a MINIMUM & MAXIMUM battery weight on the data plate that the truck is rated for.

The original battery should have a plate or stickewr on the side wit make and model etc. That might be a good starting point. But there is no guarantee it is the original battery.

Dear Leon_W,
Thank you for this prompt answer!
I still have not purchased the truck, and want to order the most suitable battery.

If you are planning to fit a smaller A/H battery than the original you might have to fit some ballast. The truck will have been spec'd with a specific size (A/H) and weight (to act as counterbalance) you need to check manufactures spec. You would get more work time out of a higher A/H battery.