Where does it always say this? The wrap doesn’t have any ratings on it.
Ignore this paragraph…
If this is something the vendors are showing then, as always, take their ratings with a grain of salt. AFAIK, the P42A is still rated at 4000mAh (minimum) with a “max discharging current rating” of 45A. Vendors are probably using 4200mAh because they think the “42” in the model number means all of the cells will reach 4200mAh. They all have reached over 4100mAh in my testing but not 4200mAh.
I just received a copy of the latest datasheet and it does list the typical capacity as 4200mAh.
45A is not the continuous discharge rating of the cell though! Molicel rates their cells for the applications their big customers buy the cells for…power tools, vacuum cleaners, etc. The 45A rating is “non-continuous” and use of these cells at rates that high is limited by the max temp rating of the cell of 85°C with a recommended cutoff of 75°C to avoid shorter cycle life.
Any use at 45A though, even less, accelerates the aging of the cell. This is noted in the datasheet. It doesn’t run very efficiently at such high power levels anyway,
I estimated the true continuous current rating (which can be used for directly comparing one cell to another) at about 25A. It was set there for safety, performance, and cycle life reasons. Many go above that rating and many stay below it. It all depends on our priorities.