Swoop has described the BDI and code display unit clearly, but from what has been stated I would agree that the battery needs thoroughly testing as in my experience the capacity can be reduced dramatically after a couple of years use and especially if a lot of opportunist charging has taken place, also the battery sending circuit on these trucks can give some problems and one of the weak spots can be the key switch assy which in my opinion is weak on these trucks in that they don't conduct the full voltage when worn also the line contractors can Be prone to voltage drop. So the main cables from the battery need checking for voltage drop back to the power unit to see where the voltage drop is occurring.

Regards Titus