Very expensive shipping to New Zealand via USPS is the only option available right now. There was a cheaper option until some idiot tried to import a gun.
As you can see on the below graph that 20A is too high
There’s too much voltage drop on the 20A to be of much use. Sofirn don’t give a data sheet with a max temp so I didn’t want to risk it. 20A reached 70 degrees.
This test on the Samsung 25R shows that the 30A is too high and it’s similar to the 20A curve of the Sofirn. I’m kind of new to judging discharge curves but it looks too high.
EDIT: I don’t know why I can’t link that page but select and search via google and it’ll come up
I always though maximum discharge rates where based on temperature. Cells tend to vary in max temp with some at 70°C and some at 80°C. If it did not exceed 70, then it might be fine at 20A continous. I'm not familiar enough with discharge curves to know what's considered usable or not usable.
HKJ's links uses spaces which require the advanced post editor to post them.
Yeah, at 25A you can see it sag and then as it heats up the voltage rises back up. That and the big loss of capacity says 25A continous is not so good. I’m surprised the temperature didn’t go higher.
I know HKJ is on this forum, I wonder what he would think of these discharge curves.
I have noticed that Mooch and HKJ don’t always agree on the Continous Discharge Rate of the same cell so it makes sense that it is somewhat subjective.
I think I would say the Sofirn HD cell is not good for 25A continous due to it’s big loss of capacity and the dip and recover in voltage.
Maybe 20A CDR is more accurate, but still not quite as good as the Liitokala black or cyan 5000mah (which is 20A CDR).
It’s definitely better than the Sofirn non-HD battery, though. I don’t think anyone has done discharge tests on it like above, but it’s reduced lumens tells me they are not high current at all.
Some of that capacity would be resistance/heat though so it’s not what’s actually gone into the battery. I’ve had an Ultrafire 18650 show 7000mAh while charging lol. Chargers that measure mAh are useful but a discharge test is needed to determine exactly what the true amount is.
FWIW - I just got two Sofirn light kits with their own branded batteries. One was a 21700 and the other an 18650. First thing, I rand them through a normal test cycle in a Zanflare analyzing charger. Both tested well past100mah over their ratings.
Just eye-balling that discharge curve, it looks like at least 15 watts of heat would be generated inside the cell when draining at 20 amps. I’m surprised it only reached 70C. It might get hotter if it was inside a sealed flashlight.
I have nothing against Sofirn batteries. They seem to be decent cells, but not for high-drain lights. I use one of their 18650 cells in an old Niwalker light, but it’s probably only drawing about 3 amps. Sofirn lists it as a high-discharge battery, but it’s certainly not. Neither does it meet their 3000mAh capacity. At around 2800mAh, it’s not bad. Good cell for a 1000 lumen light, but not much more.
There’s certainly better options out there but they are decent as a bundled cell.
The Sofirn 3000mAh 18650 black matches the Sanyo NCR18650GA up to 10A. I’m not sure what you tested but these ones were 2987mAh at 0.2C that’s pretty decent. The Sanyo NCR18650GA is rated at 3500mAh but only achieves 3300mAh