Use of RDA on a regulated device

[Tonikallinn]

I have a Drag 157w box mod, which is a dual 18650 box mod. I want to start building but i am not sure what Ohms are safe for my batteries. I have both 2 VTC4s (2100 Mah 23Amp rated by mooch) and Samsung 30Qs (3000Mah 20Amp rated by mooch) and was wondering what minimum ohms are safe for each. I would really prefer to use the 30Qs as they're higher Mah, and then use the VTC4s on my mech with a resistance that i know is safe for a battery in a mech . How do Ohms work on a regulated dual battery mod???

[Walt]

Pretty much anything you like  with that mod and those batteries.  If the build is to low in resistance the mod will tell you so.  

A regulated mod uses a DC to DC converter which to a great degree isolates the batteries from the resistance of the coil.  I think it's easiest to think of with the converter in the middle of the supply side with the batteries and the demand side with the coil.  On the demand side the mod will adjust the voltage to whatever is necessary to achieve the power setting you have chosen.  On the supply side the voltage is whatever the two batteries are putting out in series.  The amperage demanded on the supply side is simply the chosen power setting in watts divided by the voltage the batteries are achieving with a bit of loss due to the converter.  

Here is an example:

You are using a 0.15Ω coil and you have the mod set to 150 Watts.  For this example I'm going to be generous and say that the converter is 95% efficient.  You are now asking the supply or battery side to provide 157 Watts.  You have been vaping for a bit and your batteries are not achieving 3.5V each.  In series they are providing 7V.  157Watts/7V = 22.4A that the batteries must provide.  That 22.4 amps must run through both batteries as they are in series so each battery should have a CDR or continuous discharge rate of at least 22.4A.  What will your mod do if you are only using batteries that provide 18A?  Depends on the mod.  Some will throttle down the voltage on the demand side and provide less power than what you are asking for.  Some mods will tell you that you have insufficient power available for the setting.  Some mods will ignore the condition as the manufacturer has specified the use of 35A batteries which btw we all know do not exist.  So what happens if the condition is ignored?  If you are vaping every 30 seconds on new batteries you will probably not notice a difference.  If you are chain vaping like crazy on an older set of batteries, well, I don't know.  The potential for a problem exists.  

From everything I have read and heard, the VooPoo has a decent chipset.  It should provide adequate protection.  It is however always good to understand what is going on in a mod and not just use any old battery expecting the mod to compensate.  

[Tonikallinn]

6 minutes ago, Walt said:

Pretty much anything you like  with that mod and those batteries.  If the build is to low in resistance the mod will tell you so.  

A regulated mod uses a DC to DC converter which to a great degree isolates the batteries from the resistance of the coil.  I think it's easiest to think of with the converter in the middle of the supply side with the batteries and the demand side with the coil.  On the demand side the mod will adjust the voltage to whatever is necessary to achieve the power setting you have chosen.  On the supply side the voltage is whatever the two batteries are putting out in series.  The amperage demanded on the supply side is simply the chosen power setting in watts divided by the voltage the batteries are achieving with a bit of loss due to the converter.  

Here is an example:

You are using a 0.15Ω coil and you have the mod set to 150 Watts.  For this example I'm going to be generous and say that the converter is 95% efficient.  You are now asking the supply or battery side to provide 157 Watts.  You have been vaping for a bit and your batteries are not achieving 3.5V each.  In series they are providing 7V.  157Watts/7V = 22.4A that the batteries must provide.  That 22.4 amps must run through both batteries as they are in series so each battery should have a CDR or continuous discharge rate of at least 22.4A.  What will your mod do if you are only using batteries that provide 18A?  Depends on the mod.  Some will throttle down the voltage on the demand side and provide less power than what you are asking for.  Some mods will tell you that you have insufficient power available for the setting.  Some mods will ignore the condition as the manufacturer has specified the use of 35A batteries which btw we all know do not exist.  So what happens if the condition is ignored?  If you are vaping every 30 seconds on new batteries you will probably not notice a difference.  If you are chain vaping like crazy on an older set of batteries, well, I don't know.  The potential for a problem exists.  

From everything I have read and heard, the VooPoo has a decent chipset.  It should provide adequate protection.  It is however always good to understand what is going on in a mod and not just use any old battery expecting the mod to compensate.  

So let's say i have a build that's .186. The recommended wattage seems to be about 50-100w (100w probably being too hot to vape). I do 109.5/7.2 as the nominal voltage is 3.6. Which equals  15.2Amps. Im good to go? Does that mean that at max each battery is providing 15.2Amps? On the samsung 30Qs which are 20Amp continous? And the converted is actually EXACTLY 95 percent

And do you not really need headroom for a regulated device because of their safety features?

[Walt]

31 minutes ago, Tonikallinn said:

So let's say i have a build that's .186. The recommended wattage seems to be about 50-100w (100w probably being too hot to vape). I do 109.5/7.2 as the nominal voltage is 3.6. Which equals  15.2Amps. Im good to go? Does that mean that at max each battery is providing 15.2Amps? On the samsung 30Qs which are 20Amp continous? And the converted is actually EXACTLY 95 percent

And do you not really need headroom for a regulated device because of their safety features?

Each battery would be providing half of the required amperage in terms of mah but the full amperage is running through both batteries.   Think of it as a single, two cell battery providing 7.2V @ 15.2A.  And yes, you are good to go!  

[Tonikallinn]

35 minutes ago, Walt said:

Each battery would be providing half of the required amperage in terms of mah but the full amperage is running through both batteries.   Think of it as a single, two cell battery providing 7.2V @ 15.2A.  And yes, you are good to go!  

Thank you very much!

[krix66]

The box(or a website you can order it from) generally have an ohm limit rating. If you can find it on directvapor.com and read the description it will tell you your ohm limits

Sent from my LGL52VL using Vapor Talk Forum mobile app

[Tonikallinn]

2 minutes ago, krix66 said:

The box(or a website you can order it from) generally have an ohm limit rating. If you can find it on directvapor.com and read the description it will tell you your ohm limits

Sent from my LGL52VL using Vapor Talk Forum mobile app
 

Mine goes to .05 and i don't think i will ever be going that far down....my batteries don't allow it anyways and i can't find batteries here that go above 20-23A

[Walt]

If you're interested in electricity/electronics, you can get a much more realistic impression of what these devices will and can do if you double check the marketing claims with your own calculations.  A good example are the mods that will allow the device to fire down to .05Ω in temp control.  Some of those mods cap the wattage available setting far below the max power of the mod when in TC.  Some appear to be relying on the fact that the available wattage setting will only be applied for a very short period of time at the beginning of the vape and that the power needed to sustain vaping temperatures available in TC is greatly diminished.  There are some manufacturers that just plain worry me.  They say to use some unobtainable battery that will supply 35A continuous.  Looking at safety in terms of statistics only, it is very rare to see a regulated mod having a catastrophic failure, That's good news obviously but I'm just not satisfied with that form of analysis.  I'm guess I'm probably kinda "down the middle" at least to some extent.  I do believe at some point technical minutia becomes meaningless.  Carrying resistance measurements to six significant digits is picking the white stuff out of chicken ****.  But the difference between .1Ω and .05Ω is double the amperage applied.  Point being if you are working around .75Ω, a .05Ω difference is not going to be significant.  If you are working around .1Ω it's a totally different story.