You need more posts to have the avatar. My girls are still young- 3 years and 10 months. It's a big enough PITA to wrestle a struggling, overly tired, whiny **** 3 year old in now... I can't imagine doing it with the truck 4" higher.

 

If a battery has been fully discharged, it will oftentimes sulfate to the point where the plates will be shorted and I've seen this happen to relatively new batteries. At best, the battery will retain a charge for a short period of time but will discharge itself. Usually, they'll get to the point where they won't even take a charge. The best thing you can do is to disconnect the batteries and check the voltage at the posts on each one. If it's less than 12 volts, it's probably low. Place it on a battery charger and the charger should show a load. If it doesn't, then the battery is probably bad. You can also get an inexpensive tester at the auto parts store that will test the specific gravity of the electrolye in each cell. Typically, a discharged battery will show low specific gravity in all cells but it will be similar in each cell or show a slight taper in specific gravity from one end to another. If one cell is much lower than the rest, then that cell has probably sulfated and the battery is essentially shorting itself out internally.

Also, if your batteries are really low, charge them with an external battery charger, don't rely on the alternator(s) to do the job. You risk overloading the alternator and can damage it and then you'll end up with two problems.

Once your batteries are charged, install them in the vehicle (be sure your posts and clamps are clean and tight) and then check the voltage at one of the batteries (they're wired in parallel so one battery is all you need to check) before starting the vehicle. If it's fresh off the charger, it will probably show a voltage above 12 volts. Just note the voltage and then start the vehicle. With a slightly fast idle, you should see the voltage increase at the posts to about 13.4 - 14.2 volts and this will be a basic test to show that your alternator is at least putting out some charging voltage.

I hope this helps!