They sure look like calcium calcium telecommunications batteries. Find out. C/C batteries are designed for low maintenance very seldom used, with a recommended discharge level of 80% remaining. Discharge C/C batteries to 50% regularly and you are going to discover an entirely new meaning for the phrase "I blew it"
This is assuming the batteries really are Calcium/Calcium. I wouldn't touch a used C/C battery even if they cost $20.00 each.
If they are lead antimony at least 5% antimony then they could deserve a hard look.
JMHO