battery

[White Lightning]

Hello everyone, I am a new member to the forum as I am a new owner to a 1963 C336 N480WL (hence "White Lightning"). The previous owner unfortunately is suffering dementia so I am not able to ascertain the reason to the following question...
This aircraft has TWO battery boxes (one on the pilot side - factory location, and another on the co-pilot side - above the fuel filter) and the positive & negative battery cables have been wired in series so I am "assuming" that there were 2 12v batteries (since no battery was in either box nor do these boxes allow a 24v battery to fit yet the dimensions fit a 12v battery).
Anyone ever heard that Cessna did a 2x12v from factory option? Any excellent reason to have it this way (I don't like the idea or expense of buying 2 batteries nor the issues caused with potentially imbalanced batteries/charging)?

I would appreciate the collective thoughts and wisdom from this group!

p.s. Having owned many aircraft since 1990s, I have enjoyed amazing results from Concorde batteries vs the Gill counterpart. It gets even better when you choose to utilize the specific BatteryMinder made for Concorde!