New to RBA/RDA Voltage/Amp - Ohm Question

[JakeM]

Hey all quick question for those of you with a bit more experience in the rba world. I'm finally making the jump to rebuildables and am trying to get as much info from youtube/threads as possible but filtering the nonsense from legitimate advise is harder than I thought it'd be.
So I may have jumped the gun and ordered 2 EFEST purple 20A 3.7V 3100Mah batteries and 100ft of 28g kanthal wire. A friend of mine thinks I may have ordered a battery too strong, but from what I'm reading I may be alright if I keep the Ohms around 1.0.

What resistance range should I target?

Thanks

 

[Bunnykiller]

your friend needs to learn a bit more about batteries...
what you have will work fine in the 1.0+ ohm range
try going for 1.5 to be safe untill you learn more about sub ohm coils

 

[Bunnykiller]

and Welcome to ECF

 

[p7willm]

There is no too strong. The 20 A says the battery can do 20 amps, not that it has to do 20 amps. It will produce up to 20 amps and above that you may have problems, fire, venting, battery damage, etc. I use 30 amp sonys in all my mods, even some regulated ones that will not go over 4 amps.

Use an ohm's law calculator and see that a freshly charged battery, at 4.2 volts, will draw 4.2 amps. Well within the 20 amps available from the efests. I try, and succeed, to keep my draw under 80% if the battery. The ohms law calculator will be your friend. Use it when you build a coil and check the voltage before you fire it.

This assumes a mechanical mod. If the mod is regulated then it will have a maximum input that it will not go above.

The type of atty has a great effect on the kind of vapor produced and different vapers like different kinds of vapor. The Juice also will effect the vape. You have to find the coil that you like. 1 ohm is a fine place to start. Try it with 1.4 and see if you like it better. Depending on which one you prefer go higher or lower, always check your ohms before you fire and keep within your batteries 20 amps and be careful.

If, like some, you can not tell the difference then go for the coil with the lowest amps and vape longer.

It's a journey and you may find you are happier not building. That's up to you.

 

[Despraci]

The battery you ordered is just fine at 1ohm. If you decide to start cloud chasing .3 ohm I would recommend sony VTC5 or efest purple 35amp. Now you didn't say if you were using a mech mod, if so I always recommend the two batteries I mentioned for safety reasons. If your using a vw mod like a DNA30 then the battery you choose will be acceptable.

You friend needs to learn about batteries. No such thing as a "too strong" when they are all 3.7v. There is only safe and unsafe Batteries when it comes to vaping. This is were you need to understand ohms law and your equipment.

Welcome, and I sense a disturbance in the force... As if somebody will soon link Baditude's battery guides.

 

[BShady]

As others have stated, the 20A rating of your batteries is the ceiling (maximum) discharge current. Depending on who mfg'd your cells, that may be a peak rating or continuous. If you're using an APV (usually don't like less than 1.2-1.5 ohms) or mod that can handle it, you can get down to about .3-.5 ohms without destroying anything (generally).

Your battery can then theoretically discharge up to 20A max at any given time, and has a total capacity of 3100mAh - which means you can have it discharge 3.1A for one hour before it's discharged. Generally the capacity in mAh is the deciding factor that determines the physical size of a cell or battery, and the discharge rate is dependent upon the quality of the components and mfging. Also, just because a cell can discharge at 20A doesn't mean it's gonna throw 20A every time you hit the switch.

The easiest way to figure out how much power (watts) / current (amps) / voltage you're using is the power formula and Ohm's Law:
Power Formula: V x A = P
Where V is volts, A is amps, and P is watts.
Ohm's Law: V = A x R
Where V is volts, A is amps, and R is ohms. A simple way to visualize Ohm's Law is:
V
A R

Thus, you can multiply A and R to get V as above, or divide V by A to get R, or divide V by R to get A. This relationship predicts certain behaviors, such as:
If V is constant, any increase in R will decrease A.
If A is constant, any increase in R will increase V.
If R is constant, any increase in either A or V will also increase the other of A or V.

So, to use your battery, if your cell is at an operating V of 4.0 and you have installed a 0.5ohm coil, your battery will be sending 8A of current through it. If you use a 1ohm coil, it would be 4A, and so on. If you use a VW unit, you can calculate that at 10W, your cell will discharge between 2.381A and 2.778A with the cell V decreasing from 4.2V to 3.6V (which is the normal range for Li-Ion and LiPo cells). This sounds weird at first, but makes sense when you keep Ohm's Law in mind - as voltage decreases, amperage must increase proportionately in order to keep the overall power output at the same 10W level. If your wattage is fixed at 10W and you have a 0.5ohm coil, your amperage will be about 2.23A and your voltage about 4.48V.

Using these simple formulas and the technical specs for your wire, you can always determine what will be safe and what probably isn't.
Any other questions, post here or PM me and I'll be glad to help if I can.

Hope this helps,
Bill

 

[JakeM]

As others have stated, the 20A rating of your batteries is the ceiling (maximum) discharge current. Depending on who mfg'd your cells, that may be a peak rating or continuous. If you're using an APV (usually don't like less than 1.2-1.5 ohms) or mod that can handle it, you can get down to about .3-.5 ohms without destroying anything (generally).

Your battery can then theoretically discharge up to 20A max at any given time, and has a total capacity of 3100mAh - which means you can have it discharge 3.1A for one hour before it's discharged. Generally the capacity in mAh is the deciding factor that determines the physical size of a cell or battery, and the discharge rate is dependent upon the quality of the components and mfging. Also, just because a cell can discharge at 20A doesn't mean it's gonna throw 20A every time you hit the switch.

The easiest way to figure out how much power (watts) / current (amps) / voltage you're using is the power formula and Ohm's Law:
Power Formula: V x A = P
Where V is volts, A is amps, and P is watts.
Ohm's Law: V = A x R
Where V is volts, A is amps, and R is ohms. A simple way to visualize Ohm's Law is:
V
A R

Thus, you can multiply A and R to get V as above, or divide V by A to get R, or divide V by R to get A. This relationship predicts certain behaviors, such as:
If V is constant, any increase in R will decrease A.
If A is constant, any increase in R will increase V.
If R is constant, any increase in either A or V will also increase the other of A or V.

So, to use your battery, if your cell is at an operating V of 4.0 and you have installed a 0.5ohm coil, your battery will be sending 8A of current through it. If you use a 1ohm coil, it would be 4A, and so on. If you use a VW unit, you can calculate that at 10W, your cell will discharge between 2.381A and 2.778A with the cell V decreasing from 4.2V to 3.6V (which is the normal range for Li-Ion and LiPo cells). This sounds weird at first, but makes sense when you keep Ohm's Law in mind - as voltage decreases, amperage must increase proportionately in order to keep the overall power output at the same 10W level. If your wattage is fixed at 10W and you have a 0.5ohm coil, your amperage will be about 2.23A and your voltage about 4.48V.

Using these simple formulas and the technical specs for your wire, you can always determine what will be safe and what probably isn't.
Any other questions, post here or PM me and I'll be glad to help if I can.

Hope this helps,
Bill

It does help, great feedback thank you guys. As far as the mod goes its a smok magneto not a VW/VV. I lost my evic last week, hence the move forward to rba's. It helped me convince my wife I "needed" to buy the rest of the parts to get started. Now I need an ohm meter, and some practice wrapping coils and I think I'll be good to go.

 

[JakeM]

The battery you ordered is just fine at 1ohm. If you decide to start cloud chasing .3 ohm I would recommend sony VTC5 or efest purple 35amp. Now you didn't say if you were using a mech mod, if so I always recommend the two batteries I mentioned for safety reasons. If your using a vw mod like a DNA30 then the battery you choose will be acceptable.

You friend needs to learn about batteries. No such thing as a "too strong" when they are all 3.7v. There is only safe and unsafe Batteries when it comes to vaping. This is were you need to understand ohms law and your equipment.

Welcome, and I sense a disturbance in the force... As if somebody will soon link Baditude's battery guides.

Yeah I wish I woulda known the Amp rating was just a max output, I'd of gotten the 35A efest.

 

[rc3po]

It does help, great feedback thank you guys. As far as the mod goes its a smok magneto not a VW/VV. I lost my evic last week, hence the move forward to rba's. It helped me convince my wife I "needed" to buy the rest of the parts to get started. Now I need an ohm meter, and some practice wrapping coils and I think I'll be good to go.

If you have Win8, there is a good little app called "Ohms Law" that will make it a lot easier for you.

 

[KenD]

Yeah I wish I woulda known the Amp rating was just a max output, I'd of gotten the 35A efest.

Please note that the 35a Efest actually has a 20 amp max continuous discharge, not 35. It's a rewrapped LG he2. Great battery, but note the amp limit.

Sent from my GT-I9100 using Tapatalk

 

[dice57]

You should be fine, but Efest tends to overstate their batteries stats. They'll usually advertise the pulse amp rating rather than the continuous amp ratting. But they are not a bad batt to use.

Till you get competent on your builds and knowledge of batts and ohms law, would stick around the 1.5 ohm range. Still get a decent vape and not working batts to hard. 28 is a good versatile wire to start with.

I use 30 amp continuous batts and higher. Like as big as amp buffer I can get, plus having more useable power.

 

[JakeM]

BShady,

I know now that the 20Amp rating is "max" output now but how do I find out what the actual output is? I'm not really seeing it on their site but perhaps its because I'm not sure what I'm looking at :/ I know I'm a bit ignorant here just bare with me. Maybe you guys will see something I didn't.
efestpower. com /Product /1908425029 (take the spaces out I cant post links yet)
Just so I'm clear on this I take the actual Amp output and punch that into the Ohms Law Calc?

 

[JakeM]

You should be fine, but Efest tends to overstate their batteries stats. They'll usually advertise the pulse amp rating rather than the continuous amp ratting. But they are not a bad batt to use.

Till you get competent on your builds and knowledge of batts and ohms law, would stick around the 1.5 ohm range. Still get a decent vape and not working batts to hard. 28 is a good versatile wire to start with.

I use 30 amp continuous batts and higher. Like as big as amp buffer I can get, plus having more useable power.

OK so it can be done then, I'm not finding many youtube video's of >1. Ohm coil builds using 28g, I guess its cause it isn't much to brag about. I was just trying to get a feel for how many wraps I should go for (I know it can vary depending on how tight your making em too)

 

[Baditude]

I know now that the 20Amp rating is "max" output now but how do I find out what the actual output is? I'm not really seeing it on their site but perhaps its because I'm not sure what I'm looking at :/ I know I'm a bit ignorant here just bare with me. Maybe you guys will see something I didn't.
efestpower. com /Product /1908425029 (take the spaces out I cant post links yet)
Just so I'm clear on this I take the actual Amp output and punch that into the Ohms Law Calc?

A battery's output (in a mechanical mod) is always going to be ~3.5 - 4.2 volts~.

Finding a battery's amp limit can be challenging. Not all manufacturers or vendors list it, may list it in a confusing way, or confuse the continuous rate with a pulse/peak rate (Efest 35 amp batteries only being a 20 amp continuous battery). The industry standard is to use the battery's continuous discharge rate in amps.

I literally spent weeks researching & accumulating the amp ratings of the batteries we use in mods and made the following list. There were conflicting specifications from various sources, so I always used the most conservative spec for safety reasons. PBusardo was sent my list, he double-checked the specs from his sources, and now uses my list on his website. PBusardo's Battery Information Guide

Battery Basics for Mods: IMR or Protected ICR? <-- contains a current list of amp ratings for batteries (continuous discharge rate).




When using the Ohm's Law Calculator to calculate the battery amp draw of a coil in a RBA, always use 4.2 volts as the voltage (a fully charged battery's voltage).

Type in your coil's measured resistance and 4.2 for the voltage. Click calculate. The "current" will be the amperage the coil will pull from the battery. You should never pull more amps than the continuous discharge rate in amps for that battery, and you should allow for some safe headroom on top of that.

Ohm's Law for Dummies

 

[Necrotic]

With the Efest 20 amp you can build a coil all the way down to 0.21 ohms and it should be within "safe" for the battery... at .21 ohms you will be pulling exactly 20 amps off of the battery.

 

[dice57]

With the Efest 20 amp you can build a coil all the way down to 0.21 ohms and it should be within "safe" for the battery... at .21 ohms you will be pulling exactly 20 amps off of the battery.

Umm, will agree can go, but safely go??? Not so sure. That's like running your car at redline all the time. Can you do it? Sure you can, is it safe? well, in the short term yeah, but in the long term, well, batt is going to be used as hard as possible, putting stress and wear on it, and most likely using it's life up quicker.

Also since you are on the edge of the amp limit, what would happen if one has an accidental continuous fire? Will the batt handle the demand and just die as it runs out of volts, or can it maybe vent, and cause some damage.??

It's never a good idea to push anything to it's max limit all the time. a 0.2 ohm build I would be more comfortable using at least a 30 amp batt, gives one some additional safe buffer amp zone. and yeah, I do have builds that dip below the 0.20 homage.



Vape long and Prosper.!!!

 

[619BigHouseCollective]

Ohms law is the business, there is a app on the smart phone market called vapors toolbox, has a lot of calculators specifically for vapes

 

[K_Tech]

What resistance range should I target?

I can't say what YOU will like, but if you're just starting out, I think you should try out a few different coil configurations in the 0.8 to 1.4 (or so) range. Once you get the hang of wrapping and wicking microcoils, I think you'll be pleased by the results in that range.