C rating, amp limits, and you
This is a guest post written by Morandir835, an e-cig enthusiast, admin on the Vapor4Life forum, and a regular on their ECF sub forum.
I’ve covered this topic a few times on the forum, but never here on the blog. Before the latest additions of the OMG line, it wasn’t something that really needed to be covered. Every battery has three ratings, nominal voltage (in the case of lithium cobalt and lithium manganese 3.7v), milliamp hour (mAh or milliamps per hour), and c rating. Most people are somewhat familiar with the first two, but not the last (c rating).
Every PV (personal vaporizer) with an integrated controller (which covers every vaporizer Vapor4Life sells except the OMG All Day) also has its own built-in amperage limit. This limit is separate from the battery (batt) or cell used inside the PV, and usually lower than the maximum output of the battery or cell used in the PV itself.
There is a heavily used saying that it’s not the voltage that kills you, but the amperage. This proves true with batteries, especially lithium based ones. I have never heard of any catastrophic failure from a battery running in usable voltage range (as in 4.2v-3.2v) failing from a .1 amp current draw on it. 3+ amps though is a completely different story. This is where the c rating and amp limits of the battery/PV come into play.
This is the maximum sustained (not burst) output of a battery. It requires only knowing the mAh rating of the battery and its value to calculate. Here is an example using a few different batteries:
Battery A- 1600mAh, 15C= 24 amps
Battery B- 2800mAh, 2C= 5.6 amps
Battery C- 3100mAh, 2C= 6.2 amps.
On protected lithium batts there is a built-in protection circuit that shuts the battery down if you try to go over that limit. With unprotected batteries there is nothing to stop them on the physical level of the battery itself from going over that amperage limit, which can lead to cell failure. This is why you should never use an unprotected cell inside a PV that doesn’t have its own built layers of protection. I will use two Vapor4Life mods as an example. The OMG All Day has no built-in controller, only a hot spring to help prevent battery failure. This mod should only use protected cells. The V4L Handle however has thermal shut off, amp limit, short-circuit protection, and reverse battery detection. This mod can use unprotected batts because of these layers. Never use a lithium cobalt unprotected cell though, there is a reason these ship with a protection circuit. Use the “safe” chemistry lithium manganese cells only if you’re going unprotected (high drain cells). These batteries have high sustained amperage limits for the 18650 size ranging from 10a-30a, far above that of lithium cobalt.
Having already brushed up on this, I will now explain it. Every electronic device has an amperage limit. The outlets in your house, the batteries you use, the USB port on your computer, USB adapter, etc. This dictates how high of a current you can run. This limit works with the cell’s amp limit on PVs. It’s lower than the actual maximum output on the batteries themselves. The V4L Handle is a good example of this. The battery that ships with it is rated for 5.6a maximum output, the unit itself has a 4 amp range limit (3.5-4a, with most being around 3.7-3.8a). This is done so you don’t push the battery to its maximum output. Even if you put a battery rated for 24 amps in it, it won’t change what the amp limit of the PV itself.
How does this affect the vaper?
Dual coil cartomizers need a lot of amperage to run, especially the 1.5ohm rated variety. This is why even with the V4L Handle you can’t push them to 6v if you set it to that. It will supply it the maximum voltage it can within its amp limit. With passthroughs (PT) it’s not the PT that controls the power, but the source of power itself. To run a 1.5ohm dual coil carto at 5v (that’s voltage standard on USB ports, which is why it runs at 5v) you need at least 3.33a of power. Currently, there is no USB adapter on the market from anyone I’ve seen rated for that kind of output. This is why people are having issues using the 1.5ohm dual coil cartos on the PT. The best cartomizers to use on a PT are single coil 3ohm cartomizers (sold as tank replacement cartos) or CoolCarts.
I hope this was helpful. If you have any questions please feel free to contact me through the V4L Forum, ECF, or e-mail.
Contact Morandir835 via e-mail at Morandir835@hotmail.com or through his page on ECF at http://www.e-cigarette-forum.com/forum/members/51087/morandir835.html
“Even Though I Nothing Learned, With Strength I Burned.” €“ Emperor