….sounds just like mine. Put a charger on it says charged, but no grunt to turn the bike over..
the top of the odyssey unclips, then there's 6 small rubber cups over the 6mm or so holes. I had previously got a big car AGM to come back to life by adding just 40ml to each cell till the bare plates disappeared as the matting swelled up and shrunk back adding over the course of an hour till the plates were out of sight permanently. That one's still going 4 years on.
The odyssey took shed loads, you can't see in, so I used a small syringe expecting to get maybe 20 to 30 ml per cell, till it was just damp (not slopping about in a puddle). Yet some took over 120ml and still wanted more a few hours later, no wonder it wasn't doing much. It then takes a few days on charge to settle back to normal. The car one actually seemed to improve with time and it sits abused as feed for an old halogen worklamp for working on my bike. Last charged mid summer, after more than 10 hours use feeding a 50w bulb, (when writing up the odyssey experience on a different forum) 2 weeks later in the middle of this winder having been around 0C for a week I went to measure, it was still happy at 12.9v
The odyssey it currently at 12.8v saying "strong" on my oxford charger
