Ohm's 101

[rep1977]

I am new to vaping and I have no clue what to look for in terms of ohm's.
Can someone please break this down for me? I currently have a KR808D1 stick battery.
I just ordered an adapter (808 to 510) along with a Boge17 tank. I'm just worried I might damage my battery if the ohm's aren't what they should be for my battery.

 

[DaveP]

Ohms law is a series of equations that calculate voltage, power in watts, current flow in amps, and the resistance and voltage necessary to achieve various end results.

You can think of voltage being analogous to water pressure in a hose and amperage (current flow) to be equal to the volume of flow in a water hose. The hose itself presents resistance to that flow. Smaller hoses create more resistance to water flow and larger hoses present lower resistance to flow.

So, the higher the resistance the slower the flow and vice versa.

In ecig terms, a lower resistance coil presents more resistance to battery voltage flow and that creates more voltage drop across that resistance, which results in greater heat through the coil and a hotter vape. Raising the voltage across the same resistance accomplishes the same result. In a flashlight, higher voltage or lower resistance in the coil in the bulb results in brighter light.

Here's a calculator along with formulas to show you how voltage, resistance, current, and amperage interact.

Ohm's Law Calculator | V=IxR

 

[rep1977]

Thanks you DaveP! Will I damage my battery if the wrong ohm resistance is being used?

 

[DaveP]

Thanks you DaveP! Will I damage my battery if the wrong ohm resistance is being used?

If you use a mod that employs electronic circuitry that limits the load on the battery, no. A mechanical mod that uses only the battery connected to an atomizer (like a flashlight) will allow you to overload the circuit and produce extreme loads on the battery with very low resistance coils.

Li-ion batteries can overheat and go into what's called thermal runaway. Once the battery heat reaches a certain point, the electrolyte heats, expands, and spews through vent holes. A protected battery contains a circuit that opens like a circuit breaker before that point. So, if you use Li-ion batts, make sure they are protected batteries.

A safer choice is to use LiMn (lithium Manganese) IMR batteries. These can absorb huge overloads on the order of up to 10 amps for short periods without failure. IMR batts employ no circuit protection because it's not needed. Still, you want to use a mod that employs electronic sensing and limiting in the circuitry contained in the ecig mod itself. You can never be too safe with something you use near your face!

To read more about batteries go to Basic to Advanced Battery Information from Battery University.

 

[rep1977]

Great info. Thanks again DaveP!!!

 

[darkhood]

http://www.e-cigarette-forum.com/forum/general-e-smoking-discussion/378914-suggestions-newbies.html

 

[subversive]

Don't use low resistance ( less than 2.4 ohms or so ) on a stick battery unless you don't mind early battery failure. They can decrease the lifespan of 650 mah eGo-types as well. They also suck more power, meaning your batteries will need to be charged a bit more often. If you decide to go the LR route anyway, it's important to keep the coils/carto filler/etc wet so they don't burn.

The point of low resistance is that it simulates higher voltage vaping on a standard PV. I have used 1.7-2.0 ohms on batteries not meant for low-resistance because I enjoy it, but it's definitely not good for the batteries. At the same time, using an atomizer that is rated much above 2.4 ohms is not very satisfying on a standard battery.

 

[DaveP]

I recommend using a good heavy duty variable voltage mod with 2.5 to 3 ohm coils as opposed to lower voltage on the 1.5 and 2 ohm coils. Keeping the voltage closer to the native voltage of a cell results in lower heat dissipation and longer cell life. Most regulators discard the unused power as they raise or lower the output voltage drawn from the source battery. You still create heat either in the battery or in the regulator circuitry (or both).

3.5 volts with a 2 ohm coil produces 6 watts of vaping power. 4.25v on a 3 ohm coil produces the same 6 watts. To get the 8 watts that some people like, a 2 ohm atty has to be run at 4 volts. That requires a regulated kick circuit, so they go down to 1.5 ohms and lower to vape at 3.4v or 3.7v. Then, you begin to exceed the 2.5 amp limits of eGo type batteries and shorten the effective life of the batteries.

All of that is better accomplished by using a mod that uses 18650 batteries and a good kick/boost regulator circuit that can produce 3.5 amps or so. Money spent at the outset results in more vaping satisfaction and a larger assortment of atomizers that will work. You either spend it a little at a time on various lower priced mods or once on a really good one.

 

[jeffd]

here is a good thread regarding kr808 that I searched. remember the sites search feature is your friend!!
http://www.e-cigarette-forum.com/fo...earching-best-method-use-kr808-batteries.html

I too use and love my 808 stuff along with my larger ego setups. I find there is a place for small cigalike stuff depending where you are and what your doing. hth, cheers

 

[DanFromRioRancho]

This chart is helpful

https://s3.amazonaws.com/data.tumblr.com/tumblr_m9dkanCt0I1qc8949o2_1280.png

 

[SteveW]

I made this spreadsheet yesterday:

http://www.e-cigarette-forum.com/forum/new-members-forum/379396-ohms-law-calculator-excel.html

The sweet spot for vaping is generally considered to be between 6 & 8 watts. If you plug target wattages into this, it will give you applicable voltages. If you have a variable voltage mod then you can use something like this. Your other option is a mod that has variable wattage like the Vamo. It seems complicated but is really fairly simple whichever way you go. I have variable voltage (Provari) and love it.

 

[GloryVaprs]

Great thread, and very useful info!

Here is something I ran across a while back from discount vapers.


Battery/Voltage----------------------Single Coil---------Dual Coil
510, 901, 808 ------------------------2.0 - 2.5 ohm-----NO!
eGo Batteries-------------------------2.0 - 2.5 ohms----1.5-1.7 ohms
3.7v (Go-go, Larger eGo, Riva)-----1.7 to 3.2 ohms---1.5-1.7 ohms
5v (Variable Voltage)----------------2.5 to 3.2 ohms---2 ohms
6v (Variable Voltage)----------------3.2 ohms and up--2.5 ohms
7v (Variable Voltage)----------------4.5 to 5 ohms------3 ohms

 

[DanFromRioRancho]

One cautionary note should you decide to push the envelope on resistance: some batteries have constant voltage, some have a narrow range of voltages over the course of the cycle, others have a large range of voltages over the course of the cycle.

As an example, the JoyeTech eGo has a constant 3.3v while the eGo clones often run "hot" off the charger and then decline i.e. the SmokTech eGo-K starts at 4.2v then declines to 3.1 over the course the cycle. I would not be surprised if there were similar profiles amongst KR8's.

Might be worth your time to check the vendor/manufacturer websites for your specific battery to ensure that your choice of resistance "works" at the extremes of the operating voltages.

 

[DanFromRioRancho]

Thought I should expand on the previous message. Most KR808's are rated at 3.7v (don't know about yours).

With a 2ohm resistance, you would get ~7 watts at 3.7v. But if the fresh-off-the-charger top-end voltage was 4.2v, you would get ~9watts which would burn your juice at a minimun, possibly fry the atomizer.

With a 2.4ohm resistance, you would get ~6watts at 3.7v. But if the end-of-cycle low-end voltage was 3.1, you would get ~4watts and not be producing much (if any) vapor before the battery was actually discharged.

 

[SteveW]

Thought I should expand on the previous message. Most KR808's are rated at 3.7v (don't know about yours).

With a 2ohm resistance, you would get ~7 watts at 3.7v. But if the fresh-off-the-charger top-end voltage was 4.2v, you would get ~9watts which would burn your juice at a minimun, possibly fry the atomizer.

With a 2.4ohm resistance, you would get ~6watts at 3.7v. But if the end-of-cycle low-end voltage was 3.1, you would get ~4watts and not be producing much (if any) vapor before the battery was actually discharged.

Hence the beauty of variable voltage mods. To be honest, it would drive nuts if I had to take these factors into consideration all the time. I am too old, too lazy and too cranky these days

 

[Jeff Young]

Glad i read this thread great info

 

[Natedogg1026]

I use 2.8's on my Twist at 4.8V's. Makes my caranilla taste like heaven. Yuuuuuuuuuuuuuuummmm.

 

[DanFromRioRancho]

I am too old, too lazy and too cranky these days

Amen, Brother! I suspect that I have blue jeans that are older than a lot of the folks here.

But, he does have KR808's.

Until he upgrades (if ever), he needs to take these things into account. If he doesn't, he'll be posting here in a week or so asking why his atomizers are only lasting 2 days and why his juices start tasting like crap halfway through the discharge cycle.

 

[SteveW]

I use 2.8's on my Twist at 4.8V's. Makes my caranilla taste like heaven. Yuuuuuuuuuuuuuuummmm.

Using my calculator, that is just over 8 watts (8.2) - right at the top end of the butter zone!

 

[DanFromRioRancho]

Using my calculator, that is just over 8 watts (8.2) - right at the top end of the butter zone!

Just for giggles, Steve, go back to my first post in this thread (#10) and open the chart