Here is an interesting article published by MEHDA. themhedajournal.org/2011/07/22/breaking-down-the-power-options/

I recall the big oil shortage of the early 70's & waiting in long lines and hopefully would be able to buy 10 gallon of gasoline. The promoters of electric powered vehicles lifts saw this as the demise of ICE powered products. Granted over time the the class I electric products saw a small and steady increase in the percent of all units sold. This growth came at the expense of the Class IV cushion tire products up to the 7- 8000 lb. lift capacity. But the Class V ICE pneumatic tire products % of all sold remain fairly stable.

While battery technology has "some what" changed over the years the lead acid battery still remains the primary seller for use in industrial fork lifts. New technology in batteries & charging system is being market & tested but the price tag still remains a significant obstacle.

Just my 2.5 cents worth & I have been out of the business since 2007 after 41 years.