Battery Safety and Mechanical Mods

[xXToYeDXx]

I just got my first mechanical mod and rda. For anyone interested I got a Stingray X Black Copper mechanical mod and a Kryptonite 454 Big Block. Both authentic as in *Not clones*.

I've searched for an answer to this question and I can't find any. The most I get is a vague "You'll feel it drop" which doesn't help when I'm trying to remain as safe as I possibly can be. This is a subjective thing and so it might still feel strong enough to me at 3.2 volts (depending on the resistance of my atty) which may not be safe to fire at that voltage.

I purchased 2 Sony VTC4 18650 30 Amp batteries and I'm checking the output voltage on my multi meter frequently.

What I want to know is this: At what point should I take the battery out to charge it? At what voltage output is the battery no longer safe to fire, or risks of battery damage begins to be unsafe? I want numbers. There has to be a definitive point where it becomes unsafe, it can't just be "when you feel it drop". So far I've been putting the batteries on the charger when they hit about 3.7 Volts, but that means I only get about 20-30 of vape time per charge cycle. Is this normal or should I be getting more time out of each cycle? Should I be using the battery more before charging it? Maybe when it hits 3.6 volts? 3.5?

My atty build is a .5 Ohm dual coil

 

[Ryedan]

I've searched for an answer to this question and I can't find any. The most I get is a vague "You'll feel it drop" which doesn't help when I'm trying to remain as safe as I possibly can be. This is a subjective thing and so it might still feel strong enough to me at 3.2 volts (depending on the resistance of my atty) which may not be safe to fire at that voltage.

I've been using mechanical mods for a couple of years now. Getting to know what the battery voltage is in use has become fairly second nature to me for familiar setups. One of my favorite vapes is a Cyclone RDA with known air holes on a Reo Grand with dual coils at ~0.45 Ω using rayon wicks. When I first started using that setup I checked battery voltage often to get to know how it vaped at different voltages. I can almost always now tell when I should check the voltage or just change the battery. What complicates this a bit is that the vape changes with new wicks and a clean coil, but I know that now and compensate for it. The vape also changes if I build at slightly lower or higher ohms but again, I know that now and compensate for it.

I purchased 2 Sony VTC4 18650 30 Amp batteries and I'm checking the output voltage on my multi meter frequently.

What I want to know is this: At what point should I take the battery out to charge it? At what voltage output is the battery no longer safe to fire, or risks of battery damage begins to be unsafe? I want numbers. There has to be a definitive point where it becomes unsafe, it can't just be "when you feel it drop". So far I've been putting the batteries on the charger when they hit about 3.7 Volts, but that means I only get about 20-30 of vape time per charge cycle. Is this normal or should I be getting more time out of each cycle? Should I be using the battery more before charging it? Maybe when it hits 3.6 volts? 3.5?

My atty build is a .5 Ohm dual coil

The Sony VTC series batteries are rated for 2.5 volts minimum which I understand means under load. I don't remember where I got the 'under load' initially so I Googled it quickly now and found this thread on CPF. I realize that information is not conclusive, but you can do more research yourself if you feel like it or maybe someone who has more knowledge than I do will chime in here.

IMO there is no set voltage under which battery degradation definitively starts. Batteries degrade when used (or even are just stored) even if we are very easy on them. It is more a situation where degradation happens faster the lower you discharge your batteries, the more amps you draw, the quicker you charge them, the higher you charge them in voltage, the higher the temperature you run them at and the higher the temps you store them at. I'm sure there are a few more variables that I've missed

I have taken a couple of my VTC3 and VTC4 batteries down to ~2.5V (no load) and had no issues with them. I realized I had done that when I took them out and recharged them immediately. The longer they stay at low charge the more damage happens to them. Do this too often to them and they become prone to internal shorts which can lead to venting with flame which can be considered exploding if it is 'enthusiastic' enough. A mod with insufficient venting will also be much more dangerous at lower levels of battery energy release than one with good venting.

Yes, I'm sure that at some point of undercharge (or some other abuse) batteries can be considered damaged, but it is a grey area and 'damaged' is not to my knowledge defined well enough to make the concept anything more than a judgement call until they get really bad.

My typical atty resistance is also around 0.5 Ω like yours and at that resistance I can vape around 5 ml of juice by the time my batteries go from 4.2V to 3.7 - 3.6V, no load. I'm using middle age VTC3, VTC4 and new LG HE2 and Samsung 25R batteries. That means I go though a bit more than one battery a day if I don't vape much that day or two batts if I vape a lot one day. If you are getting around 20-30 minutes of vape time IMO you are either vaping all the time, your atty resistance is way less than what you think it is, or your batteries are worn out.

The last thing I would like to point out is that these batteries go from 4.2V to 4.1V in a few hits at 0.5 Ω. They run between 3.9-3.6V for significantly longer. Once they get down to around 3.2V they go down really fast again. Trying to 'catch' a battery in a mechanical mod at say 3.2V or less is IMO not a good idea.

 

[ScottChensoda]

In general, the '0' series of Li-ion batteries have a discharge cut-off level of 2.5v which is set by the manufacturer by means of internal circuitry contained within the cell. The idea being that if you discharge the cell below this level it will descend into 'sleep' or 'hibernation' mode thereby protecting both the cell and the user from damage. Recovering a cell from sleep mode can be achieved if your charger has the ability to apply a trickle charge of a maximum of 250ma.

What is far more important is ensuring your charger does not charge beyond 4.2v. Each time you charge between 4.2 and 4.5v you are decreasing the over all life cycle of the cell, while exceeding 4.25v dramatically increases the risk of irreparable damage or even thermal runaway.

To answer your specific points, man with tongue twisting name:

Though technically you are safe to vape down to 2.5v the reality of it is, that much sooner than that, you will reach the point where your battery will just not have the gonads to generate power to the coil in order to give you a satisfying vape. Hence the oft used expression 'when you feel it drop'. As has been said, this point varies due to coil ohmage, internal battery resistance, mod resistance and battery age.

Charging at 3.7v sounds about right to me with a 0.5ohm coil and while frequent checking of battery levels is a good thing, I would be mindful not to develop an angst over it. Hopefully, any fears you may have had have been somewhat allayed. Carry on vaping.