EVery time I had a problem battery it was an Exide...
I've been looking at one of those for the Imperial.
It just so happens that we replaced one at work. I saw it in the core pile and the date on the battery was March 2016. I pulled it and took it home. If I can get it to take a charge I'll bring my old battery in as a core.
It had 11.7 volts on it when I put the intelligent charger on it last night. The battery went up to 13.1 volts before I took it off the charger and was at 13.0 when I left this morning.
I'll check it when I get home to see if it's still holding 13 volts.