Thank you all for your support

I often make the point that it is -watts- (current) that are what is required to do work (move things), and can be compared to horsepower.
watts are volts X amps.
When voltage drops, amps increase to get the same watts to do the same work.
I have for a very long time now, heard and expected the higher voltage batteries to become more common in America, like they are in Europe, but in the USA, the economy has slowed down the "turn over" of trucks, (keeping older units repaired rather than trade up to newer technology trucks). I [for sure] fully agree with Swoop, that a lead acid battery system is the most "cost effective" for most operations.

in a multi-shift operation the ideal application is one battery per shift.
this way you would have one battery in the truck
one battery charging
one battery in 'cool down' stage (which should be ready to use when other battery is charging)

it will be a constant rotation

having a battery delivery system in place will help make changing the batteries out alot easier.
This system would consist of a battery station with capability to move the batteries in and out of a roller tray at the station and on and off the lift truck which would have a battery removal tray option in it's battery compartment.
There is also the option to have an overhead lifting device such as a hoist on a I beam that can traverse across the battery station to a loading/unloading zone where the battery can be changed out.
I have also seen attachments that can be mounted to a palletjack that will allow battery removal and installation.

There are different types of battery handling systems out on the market that can accommodate what you would need.

As for what voltage battery to use? The most common is 36V or 48V with the 36v being more common. (in some cases depending on that type and model lift you get it may be 24V.

72v systems are not common any more and batteries would have to be special ordered in most cases.
In some new trucks like linde and jungheinrich i have seen 80v systems coming out for the past couple years. Most of these 80v trucks we sold a hydrogen cell battery pack was bought and installed on these trucks but i'm sure regular batteries (lead acid) or sealed maintenance free type batteries can be obtained as well.
In either case for the above mentioned they will require regular maintenance and for a hydrogen cell system you will have to depend on a licensed trained tech specifically to maintain those.

In my opinion as a seasoned lifttruck tech for the past 30yrs i would say that the lead acid type battery would be the most practical and cost effective way to go.

the sealed maintenance free batteries could also be an option but they do cost more and do require a special charger but do not require hardly any maintenance.

The hydrogen cell battery system is environmentally friendly but is very expensive and maintenance is also very costly.

You really need to determine exactly what you want before making any decisions.

When considering a double/triple shift operation the simple answer is one battery per truck will not suffice. To identify the most efficent truck you need to get the KW/h rating for each truck and establish the highest capacity battery available for each machine i.e. the Ah rating of the battery. With these figures you can calculate the theoretical maximum hours useage for each machine. However, you also need to consider the application for each machine. For example a truck which uses the lift hydraulics more per hour than another machine will draw more power from the battery than a machine that is just being driven.
If you want to minimise running cost and eliminate the need for battery changing then you should investigate fuel cells. The intial capital cost will be higher as will the implementation.

Well... plenty of issues to be clarified.

- what trucks (brand, type, capacity etc...)?
- what application (loads, surfaces, real working hours/day, etc...)?

Anyway, you must remember, that:
Bigger voltage doesn't mean bigger capacity.

The traction and hydraulics motors for 80V usually have more power so they can climb up on bigger slopes, but paralelly it doesn't mean that 80V works works much longer than 48V.

80V are 20-40% more expensive than 48V.

Usually 80V are used for the trucks with bigger capacity (see your application).

In my opinion, you should consider the fact, that the fleet should taylored for all application aspects, not only the working time.