Ohms law and dual coils

[Alehuta]

Hey guys, new around here but have a question regarding the use of ohms law when it comes to dual coils. I found a similar thread but it didn't really help, as it was centered around battery life, not keeping your batteries from exploding...

I recently got a dual coil kit that's powered by two 18650s (using Samsung 25r rated for 25A). The two pre-built coils that came with this were both 0.6 ohm, so 0.3 ohm total resistance. My device (an iJoy RTDA) is variable wattage. With the original coils, I was using 80W, which was either 11A or 16A depending whether I calculated it as the single coil resistance or dual. Didn't care too much since I was satisfied at 80W and either way I cut it, I was well below the amp rating of these batteries.

I picked up some 0.25 ohm coils, when installed, the built-in ohm meter reads 0.14 ohm. Now I need to know which number to go off of for calculations to determine if I'm in a safe place, whether the calculation should be single coil resistance or total resistance?

Electricity isn't my strongest field, but I'd imagine it should be calculated off a single coil's resistance since that's the highest resistance in the circuit, resulting in the highest amperage drawn off the batteries? I'd just like to be sure one way or another. Any info is appreciated.
Thanks

 

[Eskie]

If you're using a VW mod, Ohms law doesn't apply. The board does all the work of assuring sufficient current is delivered based on the wattage you selected. Your Samsung 25R batteries are excellent and rated 20A. Unless you want to get all math like, the simple rule is a 20A battery is good for about 60W and staying under the CDR. So a one battery mod with that battery will run fine to 60W, a two battery mod 120W. So in your case, with a dual battery mod, you can run the build up to 120W. The resistance, single, dual, or even more coils doesn't matter so long as the total resistance is within the specs of the board. Most boards are good down to 0.1 ohm these days. If you ever need to run a single battery mod over 60W get something with a higher CDR than 20A. Here's a list of battery guru Mooch's recommended batteries and trustworthy suppliers to help you select a model

It probably needs some updating with some recent new Samsung models out now. You can read Mooch's reviews in the battery section under VW mods on the forum.

 

[Alehuta]

If you're using a VW mod, Ohms law doesn't apply. The board does all the work of assuring sufficient current is delivered based on the wattage you selected. Your Samsung 25R batteries are excellent and rated 20A. Unless you want to get all math like, the simple rule is a 20A battery is good for about 60W and stating under the CDR. So a one battery mod with that battery will run fine to 60W, a two battery mod 120W. If you need to run a single battery mod over 60W get something with a higher CDR than 20A. Here's a list of battery guru Mooch's recommended batteries and trustworthy suppliers to help you select a model
View attachment 760509

It probably needs some updating with some recent new Samsung models out now. You can read Mooch's reviews in the battery section under VW mods on the forum.

Ah, so the number of batteries effects that as well? Like I said, electricity has never been my strongest suit! So using two Samsung 25r, I should be safe up to 120W regardless of amperage seeing as it's a regulated device?

 

[uthinkofsomething]

Yep, no need to freak out about ohms law on your mod. If you find you want more than 120 watts or ryn your mod close to 120 all the time, you may want higher amp batteries like vtc5a or some of the 30 amp cdr batts that are out there.

 

[Alehuta]

Yep, no need to freak out about ohms law on your mod. If you find you want more than 120 watts or ryn your mod close to 120 all the time, you may want higher amp batteries like vtc5a or some of the 30 amp cdr batts that are out there.

Awesome, thanks a ton. Just pumped it up to 90 and 100 to try. Much better flavor and I'd be satisfied sitting in that range.

 

[Zaryk]

The amps you are seeing on the screen of the device is what the board (circuit board) is putting to the coils, not what the board is drawing from the batteries. Basically, the board has components on it that will amplify the amps that it draws from the battery to power the coils. So this makes ohms law not really apply to regulated mods (mods that you can adjust the power output on). You really only need to worry about ohms law with unregulated mods. Just follow what @Eskie recommended, 60w per battery for 20a batteries.

 

[Eskie]

Ah, so the number of batteries effects that as well? Like I said, electricity has never been my strongest suit! So using two Samsung 25r, I should be safe up to 120W regardless of amperage seeing as it's a regulated device?

Yup the battery count matters. Most dual or more battery regulated mods are set up in series. So 2 4.2V batteries will give you a max of 8.4V. But unlike a mech in which you use the higher 4.2V for your calculation as that is the greatest drain on amperage, you use the regulated board cutoff which is usually around 3.2V for the greatest drain. Being in series is what allows you to draw a higher current from your batteries.

I would also advise you to ignore that Amp display value on the mod screen. That represents what the board is sending to the tank, not what it's drawing from the batteries. I think it causes more confusion than being of any real benefit to the user.

Edit: oops @Zaryk just said that.

 

[Alehuta]

Yup the battery count matters. Most dual or more battery regulated mods are set up in series. So 2 4.2V batteries will give you a max of 8.4V. But unlike a mech in which you use the higher 4.2V for your calculation as that is the greatest drain on amperage, you use the regulated board cutoff which is usually around 3.2V for the greatest drain. Being in series is what allows you to draw a higher current from your batteries.

I would also advise you to ignore that Amp display value on the mod screen. That represents what the board is sending to the tank, not what it's drawing from the batteries. I think it causes more confusion than being of any real benefit to the user.

Mine displays the bolts opposed to amps. But yep, was confusing. For a little while it was "oh.no they're 4.2v batteries and it's showing 4.3v oh no" but then realized current is amps, not volts, so that was moot anyway

 

[Asbestos4004]

FYI ... higher resistance equals LESS amps required and lower resistance equals MORE amps required.
Those who've already posted are correct that with your current mod, you'll be ok. But if you ever wind up with a mech, base your calculations on dual coil....not single .

 

[Eskie]

FYI ... higher resistance equals LESS amps required and lower resistance equals MORE amps required.
Those who've already posted are correct that with your current mod, you'll be ok. But if you ever wind up with a mech, base your calculations on dual coil....not single .

And Ohms law does apply with a mech so you will need to do the math as their won't be any logic circuit in there to bail you out. And multi-battery mechs open up another layer of complexity.

So just enjoy your current vape and step away from the calculator.

 

[sonicbomb]

Calculating battery current draw for a regulated mod | E-Cigarette Forum

 

[Baditude]

WATTAGE PER SINGLE BATTERY on REGULATED MOD:
(Wattage doubles when using 2 batteries; triples when using 3 batteries)
(based on the amp rating of the battery used and the wattage setting used by the vaper)

Up to 45W:

Samsung 18650 30Q, 3000 mah 15 amp CDR

Sony 18650VTC6 3000mAh 15 amp CDR

Up to 60W:

LG 18650HG2 3000mah 20 amp CDR

LG 18650HE4 2500 mah 20 amp CDR

Samsung 18650-25R, 2500 mah 20 amp CDR

Sanyo UR18650NSX, 2500 mah 20 amp CDR

Sony 18650VTC5, 2600 mah 20 amp CDR

Sony 18650VTC4, 2100 mah 23 amp CDR

​

Up to 75W:

LG 18650 HD4 2100 mah 25 amp CDR

LG 18650 HD2 2000 mah 25 amp CDR

Samsung 18650-24S, 2500 mah 25 amp CDR

Sony 18650VTC5A, 2500 mah 25 amp CDR

Up to 90W:

LG18650HB6 1500mah 30 amp CDR

LG18650HB2 1500mAh 30 amp CDR

LG18650HB4 1500mAh 30 amp CDR

Samsung 18650-20S 2000mah 30 amp CDR

Are you using a single, dual, or triple battery regulated mod? In the interests of keeping things simple:

-If you use a good quality 15 amp CDR battery like the Samsung 30Q or Sony VTC6, then you are good up to 45 watts per battery; 90 watts using two; 135 watts for three batteries.

-If you use a good quality 20 amp CDR battery like the LG HG2 or Samsung 25R then you are good for 60 watts per battery. If using a 2-battery regulated mod, you're good for 120 watts as you have two batteries. If you are using a 3-battery mod, you're good for 180.

-If you use a single 25 amp CDR battery like the Sony VTC5A, then you are good for 75 watts per battery, 150 watts for two batteries, and 225 watts with three.

-If you use a single 30 amp CDR battery like the LG HB6 you are good up to 90 watts; with a pair of 30 amp CDR batteries you could safely do 180 watts.

​

When using a mechanical mod, use Ohm's Law: Explain it to the Dumb Noob: Ohm's Law Calculations for a Mechanical Mod

 

[BrotherBob]

Mine displays the bolts opposed to amps. But yep, was confusing. For a little while it was "oh.no they're 4.2v batteries and it's showing 4.3v oh no" but then realized current is amps, not volts, so that was moot anyway

Welcome and glad you joined.
Happy to hear you have it all under control.