Alkaline's typically have 1.5v of voltage and rechargeable's have 1.2v. Voltage on its own does not tell you how much charge (Juice or mAh) remain in a cell - the only way to accurately determine this today is to discharge the cell, like the MAHA C-9000 does in the Refresh/Analyze or Breakin cycles.
Alkalines tend to hold voltage near 1.5v and then suddenly drop off whereas rechargeables will drop-off gradually.
BTW, you should always keep your cells together in sets of two or four, depending on your use and make sure whatever charger you use, it is capable of doing single cell charges.
hmm i could have sworn it was the otherway round, rechargeables keep the power then suddenly drop and alkies start dropping power as they are used, straight away.
Also my eneloops are showing 1.4v and 1.47v instantaneous battery voltage
I would keep cells together, but i have devices that need 1, 2, 3 and 4 batteries.
I was basing my thoughts on this post by Flash Havoc on the YN-622-c's which I mis-interupted voltage drop for starting voltage levels:http://flashhavoc.com/yn622c_review/
(near the end):
"...like many TTL triggers the YN-622C are sensitive to battery voltage, that is why we use good alkaline when possible (Energizer/Duracell) and not rechargeable. That is because alkaline have a considerably higher voltage to start with, the rechargeable NiMH are already close to the YN-622 cut off voltage when fully charged."
All my Eneloops are routinely in the 1.4 to 1.147 range - this is normal.
Most of my sets runs flashes or triggers is sets of two or four. For single cell use like mice and remotes I tend to use different sets of Eneloops or Duraloops and this is where a charger such as the MAHA C-9000 charges single cells. Cheaper chargers will charge in pairs or worst four cells at the same time - all the cells will get the same amount of charge whether they are full or not.