It's been decades since I had a traitorous spy in Trojan engineering.
It depends on the thickness of the positive plates and the density of the paste. You can ask Trojan a question that may or may not raise their "PROPRIETARY INFO!" hackles.
ARE THE SAME PLATES USED IN THE T-105 AND T-1275?"
A phone call to Sata Fe Springs, CA. is inexpensive.
If they answer the question with "No" then the 1275 plates are going to be slightly thicker.
Ultra-high density plate paste is extremely expensive. I do not know this guaranteed but I can only assume Trojan reserves the high-priced-spread for the industrial battery line. The dollar per amp hour and calculated by weight is a clue to what an industrial battery consists of, material wise.
But this is quibbling the point...
The 1275 is a different animal than the 31
More antimony and denser plates make re-learning trends & tendencies a must.
The voltage/gassing point will be different as will float voltage value.
Charge acceptance will be different a whole new world.
Learn to fine-tune float voltage. Exactly enough watts to not allow gravity to degrade over time.
All flooded batteries tend to have a weak sister cell. Find it right off the bat.
