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There is even more news about DELL. Even after replacing the battery with another one ORIGINAL, by their own technician (all the job cost 400 eur including new keyboard and touchpad, damaged by the swollen battery), after only 12 months the new battery is BULGING AGAIN!

Have written to Dell tens of email and they are completely SILENT. This is a serious danger for all the airflight in the world!

This issue is still as relevant this year. With Samsung and Panasonic recalls showing potential for battery fires from Li ion batteries are real. Dell on the other hand have chosen to keep quiet their own manufacturing problem on their Dell XPS models. Those laptops have a higher than average chance of batteries expanding within their casing leading to situations where consumers see their laptop cases distorting and  their trackpads lifting away. The worrying issue is that Dell are choosing to ignore this citing warranty expiration as a valid reason to walk away from their safety responsibilities. One example can be seen at www.mod-gadget.com/dell-xps-laptops-widely-suffering-from-swollen-battery/ . Another example at https://twitter.com/ViralKiller1/status/891650973789290496
There are plenty more on both the web and twitter..

Indeed, battery cells of macbook pro retina have same voltage, I checked it (but only at one charge level). I had theory that the individual battery packs have voltage, as the 3 elements (each 2cells parallel) connected in series because they have different shape
off: 3963,3962,3963 mV (total 11900 mV)
on (18.5W CPU load, 24W total ~ 2.1A in pmset -g rawlog): 3830,3838,3824mV (total 11500 mV)
~ 200 mΩ (60 mΩ per element, each element has  2 parallely conncted cells)

It seems despite different shape , they have same capacity, becaouse they have nearly same voltate.

To dasheddisc,

Most available Li-po batteries are the same as that of the most common Li-ion batteries.  3.7V indicated/nominal voltages and 4.2V 100% charged.  There are 3.6V/4.1V varieties back in the day and supposedly there are higher max charge voltage varieties that feature new chemistry, but I have never seen these.

A Fluke meter is what I use to measure any Li-ion/Li-po battery. I remember that a smart-charging circuit designed to never overcharge lithium-based batteries is also mandatory in almost all of the world. I think one can easily engineer that smart-charging circuit to have a hysteresis and shut down until the battery has depleted to about <95% charge before the charging circuit kicks in.  You can just as easily program the charging circuit to stop charging at a voltage of 4.13V.  You lose may be <10% of the total battery capacity in exchange for about 3 times the total charge-discharge cycles.  That engineering trade-off is one that is worth making.  You can easily make up the capacity loss by slightly enlarging the battery dimensions, tuning the firmware/drivers/OS and using more power-efficient components. 

I have also seen designs that locates the battery at the coolest places of the laptop (again, Macbooks come to mind) or at the worst locations (e.g., MSI Apache/Pro laptops, where the battery is near the hottest parts next to the rear hinge along the heatpipes), so there is definitely a thermal factor in laptop design that plays a big role in the longevity and capacity of these batteries. 

Macbook with Magsafe: if you block central pin of the Magsafe 2 adapter (with thin-adhesive tape) it changes the macbook & adapter behaviour:
- restricts adapter output form 85W to 60W ( so you may experience  battery discharing even when plugged in more often [it may happen even when plugged without 3rd pin blocked, becaause the CPU may  eat more than 90W! and 7W for LCD and others])
- inhibits charging (to keep battery level on desired value)
- pmset -ac identifies the adapter as Unidentified.

But I do not know about the battery topology (Macbook Retina Pro), it has Li-Pol  rectangular cells (3 symmetrical pairs). Do all battery cells have same voltage in any particular battery State Of Charge  ?  I measured it  long time ago (i there are 4 contacts  indicating three individual voltages in parallel).

I think from measurements, not all phone/laptop makers define 100% charge as the maximal 4.2V / cell for lithium-ion batteries.  I would imagine that most manufacturers would be smart enough to choose a voltage between 4.2V to 4.1V per cell to maximize charge-depletion cycles.  You can double or triple the effective battery cycles by choosing a voltage closer to 4.1V / cell.  I think that Lenovo and Dell's user threshold settings on the batteries are already integrated into the firmware of other brands, but are not user-controllable.  On Macbooks, for example, I have noticed that leaving the Macbook plugged in at all times does not result in any wear of the battery, so that the firmware must be switching between the battery and the AC on its own without user intervention.  The actual recorded cycle counts are also way above typical lithium-ion designs, which implies that the batteries are intelligently managed and peak battery voltage of 4.2V / cell is unlikely to have been ever used.