Is it possible to finish a load with this high voltage?

If you already have the rotten egg smell, you have a bad battery, I personally would not top it off, but would change them and check the charging system. Batteries can and do blow up, if it is hot and smelling it will not take a lot to get a boom out of it.

 

Wrench was just telling me at PM this morning one of there trucks started to BLAZE due to bad batteries. It's being towed in, he hasn't seen it yet, dude got it out with his extinguisher.

 

The smell is hydrogen sulfide gasses.

If your smelling that odor, your batteries are toast.
Replace all of them, then have the start/charge system tested.

 

And do not inspect them without full safety gear, a explosion can be had and acid will be everywhere.

 

Was there a poultry company nearby? I once slept next to a dairy. The smell woke me up out of a dead sleep in the middle of the night.

 

Sometimes the rotton egg smell is really just the smell of the truck stop

 

May need to replace the alternator as well. Now or soon.

 

If the truck was running that is alternator output and 14.3 to 14.7 is normal. With the key on and engine OFF that is battery voltage.