Battery alchemy?

Trickle charging won’t do it.

You need to buy a good quality charger that will DESULFATE the battery. Read @DFX 340 Duster ’s post again. You are getting a low reading for that cell, because it’s sulfated. Desulfating it will help, but it will never return back to full amperage. I desulfate my batteries any time I rotate my tires, keeps em happy