I bought a new Zeus 12v 7 aH battery a few weeks ago from the bait shop for $29 how much was it at F&F? I hooked it up to my marcum charger and it said the new battery was already at 90% so I just took it out and used it. After that I guess it depends what type of charger you have. The old charger that I have from a old Aqua-vu was a 12.5 volt dc output .500 mA and they say charge it twice as long as you use it. So if I use it for 4 hours charge it for 8. I think the only way to check the charge is with a volt meter, fully charged it should have about 13 volts after you let it sit a while after the charge.