My battery was flat and will not turn the engine over, I am now charging it, but just noticed none of the cells are bubbling.

Should they all be bubbling away during charging or not?

Yes, shouldn't be a problem.

Stu

When the battery is fully charged they should all start to bubble --- one cell bubbling on a battery that failled to start a car would make me suspect a problem ---- ie dead cell (aka gassing or shorted cell)

Charge the battery for a decent period, let it sit for a few hours, check the voltage with no load on should be at least 12.4 volts 12.8 is better .

Fit it to the car and measure the voltage when you try and start the car. It should normally should 9 to 11 volts when cranking if it drops to 6 volts when cranking or if it drops to 6 volts then slowy rises to 8 to 9volts then you have a battey with a dead cell.