Originally Posted by Too Tall
I assume once voltage reaches 12.7 (off the charger) that's a full charge?
.. 12.7V is NOT full if the batteries are connected to the coach and less than 24 hours has passed since you last charged or used them. THIS assumption is what kills batteries. This is why you need a true battery monitor.
12.7 could quitel literally mean a battery half full if because the surface charge (not real) put on the battery by charging takes 24 hours at rest to dissapate. Rather inconvenient if you boondock. LOL
Absent a real battery monitor the ONLY way to know when you are 100% when you stop charging is using a hydrometer and testing at least a few cells in each battery.... pain in the ass but accurate. Read the link to avoid the pitfalls in mesurement that are possible & simple to avoid.
Using the Battery Hydrometer
You will definitely be surprised and how many HOURS it will be before you get a full charge. But if you are short term boondocking ( less than a week) you don't necessarily have to get all the way to 100% as long as you don't fall below 50% and can cycle between 50 and 80-90% until you can get home and plug in for an overnight charge to 100%. (This is only for wet cells....agms' are much more sensitive about needing a full charge.)