To perform electrical discharge tests, I use a programmable load and an Arduino DAQ circuit that records temperature and voltage information.

I also tear down batteries before and after the failure test to assess their construction quality and get the 18650 cell manufacturing information when available.

Then I use this information to score the batteries relative to each other on honesty, durability, capacity, power, and safety.

And last I assign an S/A/B/C/F tier score based on their category ratings and my assessment.

[Insert test bench photo]
[caption, centered] You can see the ITECH8516C+ programmable load connected to a battery via a dismantled DeWalt Drill handle (so that the electrical contacts are OEM). Additionally the Arduino circuit logs temperature and voltage. Temperature comes from thermocouple probes that I Kapton-tape directly to the cells, and voltage comes from the V_sense contacts on the battery.

Honesty:
A measurement of how much the seller is lying about their pack capacity. If capacity is the same or greater than their listing, 5 bars. Otherwise their score is reduced in proportion to the lie.

Durability:
A measurement of physical build quality and electrical durability under strenuous use.
1/2 of the score comes from the teardown: is the electrical routing robust? Are the tool contacts flimsy and prone to failure? Are there red flags?
1/2 the score comes from how many cycles of the High-Power Cycling Test the battery survived, relative to the rest of the batteries tested.

Capacity:
The measured batteries are partitioned into 4 equal-width bins based on their capacity in Wh. Scores of 2, 3, 4, and 5 bars are assigned based on how they compare to the other batteries.

No batteries with abysmal / unusable capacity have been tested yet.

Power:
A score that reflects whether the battery can be used to run circular saws, chainsaws, etc. The peak-sustained-power reported from the failure test, and the number of cycles from the High-Power Cycling Test, are used. Batteries that cannot achieve 800W output in the failure test or survive <= 5 cycles in the High-Power Cycling Test are given 0.5 bars: 800W output is required for high-power tools.

Safety:
Hand-scored, I look for a few details in determining pack safety:
 - Sketchy 18650 cells: unlabeled, aftermarket, or recycled cells get bad scores in safety
 - Smoke during the High-Power Cycling Test: under normal use, packs should shut off (based on their thermistor values) before they start smoking. If a pack started melting or smoking during the cycling test, or a cell vents, that's a red flag
 - Bad electrical construction: if I deem the pack is at risk of shorting, melting something internally, or behaving unexpectedly, it scores lower
 - Presence of engineered safety features: Waitley has a reliable high-current fuse, which is a nice touch not present in other batteries, and distinguishes 4.5 vs 5 bar ratings