Originally Posted by firsthere
When we got home I checked them, unplugged from the truck for a couple hours and they were at 12.81v. All my batteries are new so probably best case. (the original AC Delco's lasted 11 years.) The 04 came set up for the trailering and since it's a Duramax two batteries and high output alternator.
Based on voltage it sounds like they were still warm from charging... actually 12.7 volts is considered 100%; best bet (if you can) check for a full charge is via hydrometer; you should see 1.265 SG (based on typical flooded) because I would think (based on my experiences) unless the batteries were above 3/4 at the start (12.4 volts or 1.225 SG) it should have taken longer than a couple of hours to reach "happy". I've had several trucks / trailers and charged while driving without much success, some miserably under achievers; before I knew much about the process. Granted, battery theory is so complicated, me saying I know anything is a stretch. I try to learn something everyday and hopefully not always the hard way! I do enjoy the conversation.
I think we sometimes fail to consider what is right for a camper that lives off the grid and one that only has to travel a few hours from one plug in to another is different; and the cost effectiveness of one solution doesn't fit all. One thing that's for sure is that if you don't take care of your batteries, you will be constantly helping the battery makers bottom line.
Here's what seems like a decent tutorial on charging.