Charged batteries should read around 12.6 volts after an hours rest from charging . — Should not drop off . — Bad cell in battery 1 would be my call . — 9 year old charger ……. ??? — Best course of action is as stated above — Fully charge batteries / let rest one hour / load test all . — Replace as needed , along with the charger . — Just my humble opinion after 46 years of automotive repair . — Hoss