battery for PERC 6/i in T7400 ?

I have an old T7400 with a PERC 6i card.
At startup this message appears during PERC 6/i initialisation:
"Your batter is either charging, bad or missing and you have VDs configured..."

I'm assuming a new battery is needed. Or is there some other action that is better (recharge somehow?)
If a new part is necessary, What is the DELL part number for the battery?

I can see part number 405-10780 but it's compatibility list does not mention T7400. Is this the correct part number to use for the battery in a PERC 6/i in a T7400?