Hey forum, just wanted to know about safety on my current build on my setup. I'm running a dual Clapton coil which ohms out at about .14. I'm using a stingray x clone with Sony vtc4's. So I am pulling 30 amps on this battery which it is rated for. Is it bad to keep on running the battery at the max continuos amp limit. I'm wondering whether I should rebuild it and go with something at a higher ohm like a .2 or .3.
Amp limits
- Thread starter Horizon Vapes
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Yes, absolutely. I 100% recommend rebuilding at a higher resistance.
You want to give yourself "headroom". As your battery gets older, its C rating and CDR actually decrease slightly. That 30A may not be 30A in a couple months. Among other things, most ohm readers aren't particularly accurate with sub-ohm readings. Even expensive Fluke DMM's are pretty sketchy reading below .2 ohms. You have no headroom if your build is actually a .13, and at these low resistances it makes a huge difference.
(All at 4.2V, obviously, a freshly charged 18650):
.3 ohms = 14A
.22 ohms = 20A
.15 ohms = 30A
.1 ohms = 42A (no battery can safely run this)
0 ohms = dead short (battery goes into thermal runaway, you have a bad time).
If you want to be safe, rebuild no lower than .3 ohms.
ETA:
And don't even get me started on all the sketchiness of the validity of battery tests/re-wraps/etc., because really that's a whole other tirade for a whole other time. Keep it below 20A and you'll be riding a wave of safety. The safety wave, brah.
You want to give yourself "headroom". As your battery gets older, its C rating and CDR actually decrease slightly. That 30A may not be 30A in a couple months. Among other things, most ohm readers aren't particularly accurate with sub-ohm readings. Even expensive Fluke DMM's are pretty sketchy reading below .2 ohms. You have no headroom if your build is actually a .13, and at these low resistances it makes a huge difference.
(All at 4.2V, obviously, a freshly charged 18650):
.3 ohms = 14A
.22 ohms = 20A
.15 ohms = 30A
.1 ohms = 42A (no battery can safely run this)
0 ohms = dead short (battery goes into thermal runaway, you have a bad time).
If you want to be safe, rebuild no lower than .3 ohms.
ETA:
And don't even get me started on all the sketchiness of the validity of battery tests/re-wraps/etc., because really that's a whole other tirade for a whole other time. Keep it below 20A and you'll be riding a wave of safety. The safety wave, brah.
Yes. I'm an electrician and our code book says you should ever tax a circuit for more than 80% of it's maximun limits. It seem like a good safety rule for battery safety as well. Cuz, you know, it's electricity too. 
I think around .2 is your safe zone.
I think around .2 is your safe zone.
+1. Please rebuild that a skosh higher. I use VTC4s as well, and I won't take them higher than 27 amps, for a 10% safety margin, and I am actually more comfortable at 25.Twenty-five actually figures .168 but, as noted above, without a dedicated milliohm meter-- calibrated-- you're shaving your safety margin very thin. Also as has been said, the batteries deteriorate over time and with charging. I never build anything less than a .2 reading on my dinky little $15 screw-in-the-atty ohm meter, and I breathe better at .3.
I don't believe Sony has officially published the amp limits for their batteries. In fact, the company doesn't like the fact that vapers are using their batteries for vaping, period. They are being produced only for OEC power tools which have their own protection circuitry. The fact that Sony VTC batteries are available at all to vapers is due to some of them leaking out into the public domain.
The Sony VTC4 batteries are believed to be 30 amp continuous batteries.
You are putting a lot of faith into a cheap ohm reader in being precisely accurate to the tenth/hundreth of an ohm. Always tend to err on the side of safety when you make your builds by allowing some safety head room.
Everyone is free to set their own parameters, and I can only say what mine are.
I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 30A batteries, that would be 15A. The Ohm's Law Calculator tells me that a .28 ohm build is as low as I would want to use.
The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the battery's c rating (amp limit). So down the road, a 30A battery may only be a 15A battery.
The batteries we have can be quite safe if you use the correct batteries and do not abuse them beyond their recommended amp limit. Most battery incidents result from user error or wrong calculations, or ignoring safe battery practices.
Exceeding a battery's amp limit can cause it to go into thermal runaway. A battery venting in thermal runaway will release extremely hot gas, toxic chemicals, and possibly flames. Once this chemical reaction begins, there is no stopping it. The gas can build up inside a mod, and if there is inadequate venting the mod becomes a little pipe bomb.
There Was a Vape Blast at Vape Blast
The Sony VTC4 batteries are believed to be 30 amp continuous batteries.
You are putting a lot of faith into a cheap ohm reader in being precisely accurate to the tenth/hundreth of an ohm. Always tend to err on the side of safety when you make your builds by allowing some safety head room.
Everyone is free to set their own parameters, and I can only say what mine are.
I try to never exceed 50% of the CDR (continuous discharge rating) of a fully charged battery (4.2v). So with a 30A batteries, that would be 15A. The Ohm's Law Calculator tells me that a .28 ohm build is as low as I would want to use.
The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades so does the battery's c rating (amp limit). So down the road, a 30A battery may only be a 15A battery.
The batteries we have can be quite safe if you use the correct batteries and do not abuse them beyond their recommended amp limit. Most battery incidents result from user error or wrong calculations, or ignoring safe battery practices.
Exceeding a battery's amp limit can cause it to go into thermal runaway. A battery venting in thermal runaway will release extremely hot gas, toxic chemicals, and possibly flames. Once this chemical reaction begins, there is no stopping it. The gas can build up inside a mod, and if there is inadequate venting the mod becomes a little pipe bomb.
There Was a Vape Blast at Vape Blast
I always recommend keeping it above .2 it just isn't worth the risk to go that low on an unregulated device. The difference in cloud production is minimal and even though you may be safe I don't like any bet where losing costs me my fingers.
Alright thanks for the help guys! Gonna rebuild it today. What's your favorite build that reads around a .3 or so. Was just gonna go with either a 26 gauge or 24 gauge 5 wrap.
I keep it simple, twisted 26 gauge dual coil, 6-7 wraps I'm not sure what size my wraps are, I use a small screwdriver. It usually comes out between .25 and .4
On the vtc4 stay below 15 amps. The 30A spec is for sub-second (0.2 second) energy draw such as would happen when a motor is starting up. The continuous rating is generally half the pulse rating.
I keep my builds as simple as possible. K.I.S.S. (keep it simple, stupid)
I keep my builds at 0.5 ohm or higher; dual coil 28 gauge 3 mm diameter (for easier wicking). Doing both spaced and microcoils.
At 20A continuous the VTC4 has the same max temperature as the 25R, about 75°C. The VTC4 can easily be used continuously at 20A.
Above 20A, as with every other cell I've tested, the VTC4 gets too hot to ensure a decent cycle life for the cell. But the VTC4 still runs cooler than just about any other cell above 20A. At 30A the cell almost reaches 100°C, which is a ridiculously high level to operate a cell at, but it's still low enough to provide a bit of safety margin against venting.
...continuing my previous reply...
I do agree though that operating the VTC4 at 15A or below is a good idea for long cell life. But, this is good advice for any cell. Vapers use cells so far beyond what these cells were ever designed for that it still amazes me. The ratings I give in my testing reflect that and are limited by safety concerns instead of cell life. Use 50% of the continuous rating and the cell will last for at least a couple of years (assuming proper charging and storage practices).
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