Some people take vacations. I test batteries
The shipment came in and the cells were in good condition. Amazingly, they are 8.2 mm thick instead of the requested 9 mm and weigh in at 120 g each. If they check out at 5000 mAh they would store an impressive 154 Wh/kg. Impressive given the high C-rating they come with. The missing 0.8 mm will have to be padded out with cardboard, or for the more thermal-management inclined, aluminium heatsinks
My test rig is a 2s2p kit terminated using the screw terminals. They can take the current almost as good as a soldered pack and are easy to pull apart again.
I started off with a ~1 C discharge test for capacity. Basically a bunch of nichrome wires wound on a peg board. I normally use this load for cycle-testing, but it gives good numbers through the ammeter function on my DMM.
This gives a full 10 Ah (2p) and equates to 158 Wh/kg. Winning
Next up, a 5.5 C discharge test.
The load has shifted to a coil of galvanised wire plunged in a bucket of water. The loads are around 50 amps, measured with a current clamp.
So far so good.
10 C - this is about 100 amps through the test rig. My current clamp is the only tool for the job.
So even at 10 C the cells are able to deliver all of the Ah claimed and the sag is at about 3.7 V.
Okay, 20 C - this is a 200 amp continuous load through a 2s2p battery. What kind of load would be appropriate?
Why did it stop at 7 Ah?
I think we have hit the limit of continuous testing. For 10 second bursts, we can easily get 400 amps or so, but continuous high drain tests are pretty unusual in the real world.
Still, I'm satisfied these cells are as good as the current 40 C cells I use in Voltron, and they pack more energy per gram than before.
So who wants batteries?