My batteries are almost 5 years old now. Unfortunately in the past year we had severe grid electricity outage so my batteries have been exhausted by multiple deep cycles of discharge. My system uses a 24 Sunlight 2v - RES 8 SOPzS 1380 batteries. What I am facing now is that voltage drops dramatically as batteries reach 60-65% (drops below 44v). I am wondering if there is something I can do to try to extend their battery life to try for at least 1 year or 2 years. Thanks!