18650 Sony VTC4

[sasaeel]

Im vaping on copper mech mod and mutation x V3 rda @ 0.2ohm dual coil, i noticed that my top cap contact pin(copper) gets warm while vaping, same on my battery's top, the steelish color area gets warm.
So, they get bit warm for hand, not even noticeable, but when i touch em with my lips, i can feel they are bit warm, copper contact pin on top cap is almost hot on my lips.
Is that normal? battery aint getting hot, just the top part.

 

[Nickstive]

It's pretty normal for the contact pin to get warm, especially when you're rocking dual sub ohm coils. It's drawing large amounts of power from the battery and any time there's energy transfer, there's heat. The coils themselves are also probably contributing to the heat you're experiencing. As long as the battery isn't venting though, you should be alright.

 

[sasaeel]

Yeah, no venting, thats good but is that normal too that battery gets warm from top at the steelish color part?

 

[Darth Omerta]

Sounds normal enough, as long as the battery isnt getting extremely hot in any place. Im assuming your battery goes in your mech with the positive side pointed at the tank. This is where the energy transfer occurs. When energy is transferred a small amount of heat is to be expected, but if it does not cool quickly enough or it over heats then you might have a potentially dangerous situation on your hands.

Out of curiosity, what mech and what tank are you using and what is the resistance of your coils.

Edit: somehow missed the rda and ohms in the original post. My bad. I use mechs exclusively and i agree that even though the math works out for vaping .2 ohms i think that its better to be safe and ive never fired my rda below .4, my usual is .5

 

[Boden]

I would not go below 0.5ohm with that battery. Below 0.5 go with a dual battery series box mod.

 

[Cacique]

.5 ohms on a VTC4 leaves 72% headroom according to Steamengine, .2 leaves 30% haedroom. IMO you're good at .2, but I wouldn't go anything past that. Whatever battery you use, you want to leave some headroom in there. You can use Steam Engine to see how much your build puts on the battery. I believe it's recommended to have around 30-50% headroom.

 

[Boden]

.5 ohms on a VTC4 leaves 72% headroom according to Steamengine, .2 leaves 30% haedroom. IMO you're good at .2, but I wouldn't go anything past that. Whatever battery you use, you want to leave some headroom in there. You can use Steam Engine to see how much your build puts on the battery. I believe it's recommended to have around 30-50% headroom.

0.2 ohms at 4V is a 20A draw the vtc4 is a 20A continuous draw battery. (30A 0.2 second pulse rating)

40% headroom would be 0.4ohms

 

[Cacique]

To my understanding VTC4s are 30A. They're advertised as such and while I've seen many people say they're 20, it was my understanding that was incorrect. Hopefully someone else with the info will pop in. Steam Engine also shows them as 30A batteries.

 

[Boden]

They do have a 30A pulse rating. These cells are made for running motors. When a motor starts up it needs a short burst of energy to get it started. When engineers spec a battery for a cordless drill they go by the pulse draw of the motor. That is why the cells we use are labeled the way they are. The continuous draw rating is around half the pulse rating. A bit higher when they are new and lower as they age. That is why old cells heat up more than new ones. As they age the internal resistance goes up, lowering the available output.

Edit: After some research I found that the 30A rating is correct in a device with protection circuits. I think derating the battery for use in a mech is advisable.

US18650VTC4 SPEC(1).pdf - Google Drive

 

[Darth Omerta]

I don't know if I agree with derating a battery's specs based on use in a mech vs regulated mod. One can be safe and give themselves more headroom based on the type of mod they choose but that doesn't change the specs. The battery has a 30A max continuous discharge regardless of the gear in which it is used. It has always been my understanding that mechs cant regulate how much is drawn and therefore do EXACTLY what the battery is capable of doing. That said, one should also be aware of volt drop on whichever mech they are using lest they end up demanding more from the battery than what its able to do.

My apologies if my understanding is incorrect. I am still relatively new to the finer details of battery ratings and safety which is why i tend to stay .5+ on my builds until im using regulated.

 

[Boden]

I don't know if I agree with derating a battery's specs based on use in a mech vs regulated mod. One can be safe and give themselves more headroom based on the type of mod they choose but that doesn't change the specs. The battery has a 30A max continuous discharge regardless of the gear in which it is used.

The 30A spec is under very specific conditions. Ecigs do not meet most of those, even the ones with protection.

It has always been my understanding that mechs cant regulate how much is drawn and therefore do EXACTLY what the battery is capable of doing.

The resistance of the device plus the resistance of the coil dictate how much energy is drawn from the battery.

That said, one should also be aware of volt drop on whichever mech they are using lest they end up demanding more from the battery than what its able to do.

The "volt drop" ie internal resistance of the mech-mod adds to the total resistance seen by the battery. The higher the total resistance the less energy the battery is able to transfer through the system.

My apologies if my understanding is incorrect. I am still relatively new to the finer details of battery ratings and safety which is why i tend to stay .5+ on my builds until im using regulated.

Good idea

 

[Mooch]

In my testing, being posted soon, the VTC4 can be used at 30A but like any other cell at those very high current levels, it runs damn hot...about 92°C. This will shorten cycle life and reduces the safety margin betwen its operating temp and the point at which it will vent. At 20A it runs at the same temp as a 25R, about 75°C. Up to 25A there are cells that will last longer when used for vaping, like the 25R.

But...

When used continuously the VTC4 runs at a lower temperature at 25A (and higher) than every other cell except the HB6 (haven't tested the VTC3 yet though). This is important if you are running a build that draws 30A and the mod autofires or a mech's button gets pressed in your pocket.

Sooo...yes it's a 30A cell but running it that hot is not advisable. Based on temperatures and cycle life, it's a 20A cell that's outperformed by other 20A cells. Above 20A, if you must do that, it's probably your best choice.

 

[Darth Omerta]

Very thorough. I dont mind being wrong when i can be shown exactly where im wrong. Thank you!

Also: big thanks to Mooch! Look forward to seeing your tests! Worked well for me in the past!