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How to determine the Resistance (Ohms) your Mod/Battery/RDA/RBA can handle

(NOTE: This is information we've found online and just consolidated into a couple pages for ease of use, and while we at TKO Vapor, it's affiliates, parent company, and any/all persons and entities associated with us believe them to be accurate, we are not responsible for any misuse, damage, injury, etc resulting from the use of this information.)

So, you want to build your own RBA/RDA, but you're not sure what your configuration can handle? Here's where you find out!

 

Before we get to the calculator, here's a quick explaination on how Ohm's work, based upon volts and amps used.

Ohms Law

So, the max Voltage output from the battery you're using pushes the Amps through your atomizer. The Ohms resistance level is what you're building within your RDA/RBA when you are building your coils/wicks. This calculator will allow you to plug in your Current (Amps) and Voltage (volts) and will give you the minimum allowable Ohms that your build can be, and will still give you a fully working build! You should be able to determine your Amps and Volts from your battery/mod configuration.

Not sure what your battery amps, C rating, etc is? See below for a chart of many of the current Mech Mod batteries available!


Power rating for rechargeable batteries

The critical factor for ecig APV use is the C rating (discharge current) in amps. The minimum possible value for safe and effective ecig use is 1 amp (= 1000mA) although ideally it needs to be higher. The ideal rating is 2.5 amps (2000mA) or better as a conventional atomizer usually draws 1A to 2.5A .

Battery amp Limits

These ratings are general guidelines taken from information on the internet and NOT all from the manufacturers.

 

Battery name and mah Continuous Discharge Amps Maximum Discharge Amps C Rating Safe Ohm to run
         
AW IMR        
AW 14500 600 mah 4.8 amp 6 amp 8c 0.9 ohm
AW 16340 550 mah 4.4 amps 5.5 amp 8c 1 ohm
AW 18350  700 mah 6.4 amp 7 amp 8c 0.7 ohm
AW 18490  1100 mah 8.8 amp 11 amp 8c 0.5 ohm
AW 18650 1600 mah 16 amp 24 amp 15c 0.3 ohm
AW 18650 2000 mah 7.5 amp 10 amp 5c 0.5 ohm
         
Efest IMR        
Efest 10440 350 mah 1.4 amp 3 amp 8c 3 ohm
Efest 14500 700 mah 5.6 amp 7 amp 8c 0.8 ohm
Efest 16340 700 mah 5.6 amp 7 amp 8c 0.8 ohm
Efest 18350 800 mah 6.4 amp 8 amp 8c 0.7 ohm
Efest 18490 1100 mah 8.8 amp 11 amp 8c 0.5 ohm
Efest 18650 1600 mah 20 amp 30 amp 18.75c 0.3 ohm
Efest 18650 2000 mah 15 amp 20 amp 8c 0.4 ohm
Efest 18650 2250 mah 18 amp 20 amp 8c 0.5 ohm
Efest 26500 3000 mah 20 amp 30 amp 6.5c 0.5 ohm
Efest 26650 3000 mah 20 amp 30 amp 6.5c 0.5 ohm
         
EH IMR        
EH 14500 600 mah 4.8 amp 6 amp 8c 0.9 ohm
EH 15270 400 mah 3.2 amp 4 amp 8c 1.4 ohm
EH 18350 800 mah 6.4 amp 8 amp 8c 0.7 ohm
EH 18500 1100 mah 8.8 amp 11 amp 8c 0.5 ohm
EH 18650 2000 mah 16 amp 20 amp 8c 0.4 ohm
EH 18650 NP 1600 mah 20 amp 30 amp 18.75 c 0.3 ohm
         
MNKE IMR        
MNKE 18650 20 amp 30 amp 18.75c 0.3 ohm
MNKE 26650 20 amp 30 amp (60 amp pulse) 18.75c 0.3 ohm
         
Samsung ICR INR        
Samsung ICR18650-22P 2200 mah 5 amp 10 amp 4.5c 0.9 ohm
Samsung ICR18650- 30A 3000 mah 2.4 amp 5.9 amp 1c 1.5 ohm
Samsung INR18650-20R 2000 mah 7.5 amp 15 amp 7c 0.6 ohm
         
Sony        
Sony US18650v3 2150 mah 5 amp 10 amp 4.5c 0.9 ohm
Sony US18650VTC3 1600 mah 15 amp 30 amp 18.75c 0.3 ohm
Sony US18650VTC4 2100 mah 15 amp 30 amp 14c 0.3 ohm
Sony US18650VTC5 2600 mah 15 amp 30 amp 11.5c 0.3 ohm
         
Trustfire IMR        
Trustfire 14500 700 mah 2 amp 4 amp 2c 2.2 ohm
Trustfire 16340 700 mah 2 amp 4 amp 2c 2.2 ohm
Trustfire 18350 800 mah 4 amp 6.4 amp 5c 1.1 ohm
Trustfire 18500 1300 maah 6.5 amp 8.5 amp 5c 0.7 ohm
Trustfire 18650 1500 mah 7.5 amp 10 amp 5c 0.6 ohm
         
Panasonic        
NCR18650B 18650 3 amp 4 amp 1.1c 1.5 ohm
NCR18650PF 18650 5 amp 10 amp 3.4c 0.9 ohm
NCR18650PD 18650 5 amp 10 amp 3.4 c 0.9 ohm
NCR18650 18650 2.7 amps 5.5 amps .5 c 1.6 ohm
any other protected 18650 3 amp 4 amp   1.5ohm
any unprotected 18650 5 amp 10 amp   0.9 ohm
         
Orbtronic        
sx22 18650 22 amp 29 amp 11 c 0.3 ohm

 

Chart of C ratings vs size

These ratings are general guidelines taken from information on the internet and NOT all from the manufacturers.

1C or less for some Li-FePo4
Assume 1C for generic Li-ion unless otherwise noted
1.5C for ultra/sure/trust/-fire Li-ion
2C for AW ICR (Li-ion)
3C for BDL 10440 IMR (Li-Mn)
5C for BDL 14500 IMR (Li-Mn)
8C for AW 14500 and 16340 IMR (Li-Mn)
10C for AW 18650 IMR (1600mAh) (Li-Mn)
10C for AW Li-FePo4

Max drain rate in amps is C in mAh / 1000 x C rating

Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply a load of 8 times the capacity).
Therefore the max discharge current in amps is: 600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
= 4800 / 1000
= 4.8 amps

This shows it has enough beef to safely and effectively run an atomizer - which some 14500's don't. In other words it is less likely to go into thermal runaway if there is an internal fault in the battery, is overcharged, and is then used to power a device that draws a relatively high current such as an atomizer; and it will not suffer from excessive voltage drop when powering the atty.

Useful formulas

Amp draw = voltage / resistance

Example: a 5 volt APV is used with a 2.5 ohm atomizer - what current is drawn?
5 / 2.5 = 2
The battery must supply 2 amps.

Power used by atomizer in Watts = volts x amps, or volts x volts / resistance

Example: a 5 volt APV delivers 2 amps to the 2.5 ohm atty - what power is used?
5 x 2 = 10
The atty uses 10 watts
or
5 x 5 / 2.5 = 10 watts