Introduction
I recently got my hands on a couple of LG INR21700-M58T, and since nobody tested those unicorn-batteries before, I figured I’d grab my old RC charger (Junsi 106b+), check whether it is accurate with my Fluke DMM (turns out, it is) and have it log some discharge curves. And since I was already at it, I decided to continue with other cells I had at hand.
My test setup is limited to approx. 4A with LiIon cells (20W max), so I could only test lower loads - but to be honest, lower loads are what matters for me, personally. I am a fan of sustained performance in flashlights, and short super bright turbo boosts do not really matter much for me. So here we are, 21700 cells tested at 4A, 2A, 1A and 0.5A.
Test setup and methodology
As mentioned, I am using a Junsi 106b+ as a charger/datalogger. It makes use of 4 wire measurement, where the cell voltage is determined through 2 separate leads connected to the balancer port, instead of using the main wires for higher accuracy. These are soldered to the battery holder as close to the cell contact as possible. Sadly I can not contact the cell directly, so expect some voltage drop to still be present across the cell-to-holder contacts.
The cells are charged to 4.2 V, then the charger is set to wait for 10 minutes before beginning discharge down to 3.2 V.
The Junsi takes a timestamped datapoint for cell voltage and current every 2 seconds. These are logged, and then used to compute capacity and energy in a second step, when the graphs are drawn with R.
Results
LG INR21700-M58T
Samsung INR21700-50S
EVE INR21700-50E
Sofirn 21700 flat top (5000 mAh, from LT1s)
Conclusion
I hope these measurements have any value for the community. I do not have the high quality measuring equipment or access to as many cells as others, for example Mooch (I picked 3.2 V as an end of discharge, so my energy results would be comparable to Mooch’s “E-score”). I just had fun measuring, and decided to just put my results out there. Maybe they are interesting to someone.
If you have any comments or suggestions on how to improve, go ahead. My main uncertainty is, whether or not I should discharge the cells lower, as Anduril seems to enter LVP only around 3.0 V, or stick to my current 3.2 V end of discharge. Are there any metrics I am currently not publishing but you’d be interested in seeing?
Scheduled cells
This section lists cells I have access to, and plan to measure in the upcoming days/weeks. I will update the start post accoringly when a new cell drops.
- NA
Not scheduled cells
This section lists cells I have access to, but no current plans to measure (for example, due to a lack of a matching cell holder). If people mention that they are interested in a particular cell, I can try and figure out a way to add it to the queue.
- Keepower UH1835P (1200 mAh 18350)
- Vapcell M11v2 (1100 mAh 18350)
- Unknown Sofirn 18350 1100 mAh (included with SC13)
- Unknown Lumintop 14500 920 mAh with USB-C
- Unknown Wurkkos 14500 900 mAh (included with HD10, possibly TS10v2)
- DLG INR14500-095
