Molicel/NPE P42A Lithium-Ion Cell Review

Molicel/NPE P42A Lithium-Ion Cell Review

The Molicel/NPE P42A is a Lithium-Ion cell with a massive current capability – up to 45 amps! The capacity is around 4200mAh. Read on!

Official Specs

Here’s a link to the Molicel/NPE P42A Lithium-Ion Cell product page.


These cells start at $12.99.  Volume discounts start with the third cell, and get better from there!  Buy them at [only at]!

Short Review

These seem like good cells, with nice performance.  My A and B cells seemed to perform ever so slightly different only high discharge.  The full capability of these cells won’t be needed in most flashlights that could use them, but using a 45A cell at lower currents just means better performance in general!

Long Review


These cells ship in a plastic flip-top box.

Build Quality

The positive terminal is a 3-prong type.



I’ve tried to keep the scales similar, so over time the charts will be generally comparable.

Discharge tests




“Bounce back” is what the cell voltage does when the cell rests after a discharge. After heavy discharge rates, the cell voltage bounces back higher when discharge is stopped.  This corresponds to a discharge amount of less energy and does mean that there’s energy left in the cell.  So if I selected the cell with the highest bounce back voltage (ie the cell that was discharged at the highest current), then discharged it to 2.8V at 0.2A, I’d still find that there was a lot of energy still in the cell.

Here is why I think it is so interesting about “Bounce.”  A poorly performing cell will bounce back higher after high discharges.  That’s because the IR is higher, and because the cell performs much worse under high loads.  So a good-performing cell will bounce back much less because it’s much more capable of high discharge.  At high discharge on a capable cell, more of the energy makes its way out of the cell!  Hence less bounce.

I more or less figured this out on my own, so I welcome discourse about this topic.  Until I hear it’s wrong, I propose this as a new metric for cell quality!

Charge Test


Power, Constant

Internal Resistance

Most often (read: always), internal resistance is mentioned as a spot value.  In truth, the IR changes over time.  Due to cell age and cell heat among other things.  A graph of IR is interesting because it can show, for example, when a cell begins to “die” – at which point the remaining energy will be “harder” to extract.  This is when the IR spikes.  In the graph below, that’s around 750-800mAh.  These graphs are also useful for determining if a cell would be good for a hot-rod flashlight, for example.


This is a good cell.  Low internal resistance, good temperature performance at high currents, and moderately high capacity for having such a high current capability…


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4 thoughts on “Molicel/NPE P42A Lithium-Ion Cell Review”

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  4. Thanks for this good paper. The point I wanna ask is what the IR in ohms for “A” cell. What does this mean. For example what is IR 0.2 vs 20. Can you reply?

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