This has 12 volts. Volts alone means absolutely nothing.

 

Mine did the same thing (Odyssey pc680). I connected it to a trickle charger and it didn't work. I had a local Les Schwab hook it up to one of their more powerful chargers and it still didn't work despite showing fully charged. I ended up biting the bullet and bought a new one that works perfectly. The place where I bought the new battery mentioned that these smaller ones are very powerful but are a black hole when it comes to charging.

Looking back, the old battery was giving subtle clues before it finally dying on me. Radio presets kept resetting and whiny long starts on cold mornings.