Science Buddies: "Ask an Expert"

I have a solar project having 500w capacity, i use some old batteries(120 ah, 60ah) for it. At start they were giving good performance but now i feel that batteries are draining earlier then before, i tested battery voltage and other aspects but found them ok. what could be other reasons of early drainage?

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This could be memory effect of rechargeable batteries. You can identify what kind of batteries they are and try out some methods to restore the charging capacity.