This is the new battery size that is slightly larger than 18650 cells. This cell is a high current cell with moderate capacity.
The two cells tracks perfectly and can easily deliver the rated current.
But the batteries get warm when delivering high current.
At maximum rated current they are up to 81°C
In this discharge the battery is in free air, i.e. it has better cooling.
Conclusion
This battery is a very good battery and one of the best high current cell I have tested to date. At lower current there is no reason to use this cell (Instead use the NCR20700B cell), only when the current is above 10A is this cell interesting.
Notes and links
My test stations is only equipped to handle up to 30A, this means higher current must be done on other equipment.
Yes, but this cell it not far behind. I am not going to do a 50A test
I doubt it.
What I will probably need soon* is a 4 terminal rig that can do more than 40A without melting.
*I hope soon is some time away. I can fairly easy do up to 90A current draw, but I have no good idea how to make a 4 terminal battery holder to handle that (I do not have a lathe).
There is definitely being generated a lot of heat, but I do not really know if it is the holder or the battery.
The inner pin do not generate any heat, the current is virtually zero.
The battery gets hot and probably faster than my thermo sensor can follow.
The contact surface between battery and holder may also generate heat, just 1 milliohm would be 2.5 watt
The outer part may also heat at 50A, I do not now how much resistance it has.
The wire connection at the back may generate some heat.
The cable is getting warm, I uses 2.5mm2 (13 awg) (It is a bit thin for 50A).
Give the fixed position metal holder an insulating material coating, let's say a PTFE coating (rock bottom electrical conductivity, by the way). This way you can replace the plastic holder pieces with some sort of metal crafted ones, completely eliminating this problem.
Mmm, better coat both side metal holding parts, fixed and movable. Adds insulating safety while not excessively enhancing the holder's heatsinking ability, it would definitively impact cell temperature measurements otherwise (lots of cooling!).
The inner pin is used to measure voltage directly on the battery terminal, that is the idea with 4 terminal connections. Any voltage drop in the connection and wires do not affect the result.