What would you expect the voltage of a healthy battery to be?

Had it in mind that a normal 12 volt battery should be around 13.2 when charged but not under load ...

Battery on my motor is measures 12.4 (charged, no load) that seems bit low ...

Anyone measured theirs by any chance? Stornoway Grey GS ... What a fine motor ... but not any more ... ... psst look at my gallery!
Company cars ... a thing of the past - May 2013.

Battery voltage won't necessarily represent battery health, often a dying battery can still show a fairly good voltage level. You really need to know the battery internal resistance which is normally how workshop battery test systems work. 58 HSE, auto, lago grey, tints. Mine and my dogs Storm and Sky
TT Quattro, black. Ers.
AC Cobra rep in build. Ars.

It will depend how long since the battery was last on charge, i.e. engine running. From about 13.4 volts immediately after coming off charge it will decay down to its passive level which will never be its "no load" level as the long as it is connected to a car, because current will always be being drawn by the car systems. 12.4 volts if it is after a couple of hours off charge sounds OK to me.
Easiest way to check a batteries health, without a fancy tester, is to check its voltage with a decent load, ie headlights, on but no engine running. The voltage will drop to, maybe, 11.? volts and should stay fairly constant for the few minutes of the test (0.1 or 0.2 volts drop would be OK). A poor battery will drop voltage quickly, by 1 or 2 volts, and may even boil a cell, so keep an eye on it - nasty stuff that acid! Don`t drive faster than your angel can fly!

The reason I firswt asked the question was because I'd suffered a flat battery, for no obvious reason. Nothing was left on and car was only left overnight. Started easy enough after using a starter pack.

Now, this afternoon just suffered a second flat battery, car standing for less than 24 hours and again nothing left on, but failed to start. I left the car stand a few minutes then metered the battery, down at 11.3 volts ....

Again it started with a started pack connected. Voltage once running is a healthy 14.4 - 14.6 @ 1500 rpm no no load. This drops to 14.2 with all the lights on, then down to 13.7 with the heated rear screen turned on.

So charging system seems OK, looks like its new battery time ...

Cant't decide whether to take it to the dealer only to be told 'everything looks OK' or wait for next fail to start and call LR Assist. Has anyone had a battery replaced by LR Assist? Stornoway Grey GS ... What a fine motor ... but not any more ... ... psst look at my gallery!
Company cars ... a thing of the past - May 2013.

Similar to yourseld Avtur, we had suffered a number of flat battery instances for no known reason. At this point the car was only 6 months old and took it to the mechanics and asked them to check battery condition and charging circuit, only to be told all was fine and that we must have been driving too many short stop/start trips. A week later we travelled 1930kms in two days only to experience once again another flat battery. LR Assist contacted the local mechanic for that area who diagnosed within minutes, with the aid of a hydrometer, that the fault was indeed the battery, low specific gravity in one of the cells. The battery was replaced under warranty and 8 months later still going strong and have not been subjected to any further flat battery issues.