Came here to say this. Be careful @Hoodini those cheap ass chinese batteries are well, cheap for a reason. you’ll be lucky if they are 1000mah.
If you must use them, get yourself a charger that has the ability to capacity test. It’ll drain them with a known mah, then recharge them and tell you final capacity. (Sucks it only does this with one slot, but if you do 1 out of every 10 you’ll have a good sample rate.
Charger like this:
http://a.co/5BjvEe8 KINDEN 18650 Smart Battery Charger Universal Intelligent 4 Slot Automatic LCD Display for Li-ion LiFePO4 Ni-MH Ni-Cd AA AAA C 26650 18350 17670 RCR123 Fire Prevention Material
As an added plus for you, it will run off 12v