Dead batteries

[Ed Shankle]

Hi all electrical engineer, I've got a mystery. My 2 6 volt and 1 12 volt batts all passed hydrometor test and showed 12.5 volts yesterday. Put them in my car last night, brought them to the boat today and installed the 6 volt ones first. Nothing, volt meter on panel showed nothing. Checked with my multimeter, nothing.
Tried the hydrometer and passed, fully charged
Checked the 12 volt batt sitting on thr cabin floor with multimeter. Nothing. 
Thoughts, before I go off and buy new ones?
Thanks

[Ron Hill]

Ed : I'd have your hydrometer checked before I did anything.

With the batteries installed does the engine start OK? and the rest of the electrical equipment act OK?

A few thoughts

[Ed Shankle]

Ron, no as I mentioned, nothing works, volt meter on electric panel doesn't budge either. I'm getting new batteries. I'm more interested in how batteries can look good via hydrometer and multimeter one day and the next day be dead.

[scgunner]

Ed,

How old are the batteries? I'd take them to an auto parts store and have them load tested, at least the 12 volt. I usually use my batteries for about 3 years then replace them.

[waughoo]

As scgunner noted, the load test would be critical to finding out if they are any good.  A battery can take a charge and register a good resting voltage, but once a load is placed on it, fall flat on its face.  I am a bit curious how they were showing 12v the night before, but became dead flat by morning.