18650 cutoff voltage?

[adski]

I have been using some old vtc4's in my 2s series mod, I have been getting the low battery screen when my batteries are reading 3.7v each and 3.10ish under load. I assume that both batteries can be discharged a fair bit more than this. Most battery tests I have looked at discharge each cell to 2.5volts. Will setting each cell cutoff to 2.75v give me a safe longer run time? So that the low battery screen comes on when the batteries sag under load below 2.75v? Thanks in advance

[VapingBad]

IIRC the hard limit is 3.0 V, but as I'm sure you know newer batteries will do better.

[turbocad6]

also your battery contacts can make a HUGE difference here. when a battery shows 3.7v at rest and hits a battery warning when vaping it is most likely less than great connections, unless of course the batteries are just crap

[James]

Google for LiPo discharge curves, or the discharge curve for your particular battery to see what will happen.

You will see that capacity does not advance much at all once you are in the 3V range - at that point a LiPo battery is essentially drained. Weak Battery will move horizontally along that curve to lower C levels until it finds what the battery can sustain at its current state of charge, allowing you to use all the capacity available at lower C levels.

You can see on these curves that the 10C line will end at a lower capacity than 5C, which ends at a lower level than 1C, etc. When the battery is really low, it simply can't do 50W, and a few puffs later, can't do 40, 30, etc. But we have it give you what the battery can stably give. Letting the battery fall even further before reducing the current demanded of it won't help.

Without the Weak Battery feature (it's not just a warning message), you see the capacity falls off a cliff on those discharge curves? You'd be done already. Unless your battery connections have a ton of resistance, lowering it is unlikely to buy you more than a percent or two.

[adski]

Thanks peeps, they were just abused old batteries. I'm now using 2 x LG mj1's they are rated 10amp constant (not sure on the pulse rating) I'm only using a tank around 40 watts so am not pushing them. I have left the cut off at 3.09v. They are around 25Wh and last for absolutely ages, getting nearly double the vape time I was getting on 1300mAh 3s.