sig 3 backup battery?

Cool. That's good to know, since you can't send Li-ion batteries only via mail these days... You can ship it inside device.

The weight is the simplest way to tell a high quality battery from a phony in my opinion. A lot of 18650 either have limited electrolytic inside them, or actually have a cheaper smaller battery inside the larger casing. Those batteries tend to weigh much less.

However, now that people are catching on to this, I wouldn't be surprised to see the fake sellers adding sand or something internally to bring the weight up.

The best way of course is to charge the battery to full potential and then discharge it measuring the current flow while under load.

I use a Tenergy TB6-B discharger for this purpose. There are others out there made for this exact purpose, but I got mine on sale for around $45 last year. I actually had an iMaxB6 before that worked fine until one day it didn't. But it was far less expensive...though not as comprehensive in features. Anyone who rebuilds battery packs...these are a must have...though if you are just trying to discharge a battery then probably a simple 10-20 watt resistor can handle he current load without excessive heat...but you would want to monitor the voltage and not have it drop below 3V to prevent permanently damaging the battery where it won't recharge again.

That's why I buy my cells from a trusted local seller who actually tests all the cells to see which are good.

As he also tests for vape and torch users he tests at diff current draw so graphs them nicely so we can see what mAh they actually have and what current delivery they handle for users who need that

John

Yeah, we can thank the vape shops for the increased demand on 18650s for sure!