How to divide volts/amps/watts with a multi-battery mod

[AMOB79]

Hi all:

Just trying to understand how amperage and voltage and wattage works with a 3-battery mod. I have a Wismec RX GEN3 with 3 Sony VTC5A batteries. I’m currently running at 70 watts, which is just under 20 amps at 3.65 volts. Do I divide these numbers by 3 to see what each battery is providing? Is my logic sound? Or are all three batteries providing the numbers I see on my display? Help me understand this please. Thank you!

 

[Coastal Cowboy]

Not hard. Divide the wattage by the number of batteries and divide by 3. This gives you a rough approximation of how many amps will be required from each cell. You should make sure your batteries are capable of delivering what's demanded by the device.

Using what I'm gonna call the @BoogaWu Rule--only buy batteries made by companies that make good televisions and only buy from a reputable source.

 

[Topwater Elvis]

To add to what Coastal Cowboy said---> Calculating battery current draw for a regulated mod | E-Cigarette Forum

 

[AMOB79]

Great article. Thanks for the replies. So if I’m understanding correctly, I’m using a 0.19 ohm build at 70watts. According to the Ohms Law calculator, this is drawing just over 19 amps. Is each battery providing 19 amps, or is each battery providing one third of the total 19 amps? Sorry, just trying to educate myself for battery safety. And by the way, Mooch rated each VTC5A battery at a continuous 25amp rating, so I am definitely in the safe zone.

 

[MJCSD]

Hello and welcome to ecf

 

[Topwater Elvis]

The link provided explains it in terms easier to understand than I can.

When using a regulated power device resistance is irrelevant as long as it is within the devices operating range.

The cells provide power to the 'chip' (input).
The 'chip' powers the delivery device (output).
All decent power device have input & output amp limits.

Just before & at the power devices low voltage cutoff battery amp demand will be highest.

The vtc5A (must be A) will support up to 75w per cell.

As cells are used & age they lose capacity, the harder they're pushed the faster degradation take place.

 

[AzPlumber]

Great article. Thanks for the replies. So if I’m understanding correctly, I’m using a 0.19 ohm build at 70watts. According to the Ohms Law calculator, this is drawing just over 19 amps. Is each battery providing 19 amps, or is each battery providing one third of the total 19 amps? Sorry, just trying to educate myself for battery safety. And by the way, Mooch rated each VTC5A battery at a continuous 25amp rating, so I am definitely in the safe zone.

Resistance and ohms law only applies to mechanical mods. Read the link @Topwater Elvis supplied for an explanation on how to calculate amps per battery for a regulated device.

To add to what Coastal Cowboy said---> Calculating battery current draw for a regulated mod | E-Cigarette Forum

 

[BoogaWu]

Not hard. Divide the wattage by the number of batteries and divide by 3. This gives you a rough approximation of how many amps will be required from each cell. You should make sure your batteries are capable of delivering what's demanded by the device.

Using what I'm gonna call the @BoogaWu Rule--only buy batteries made by companies that make good televisions and only buy from a reputable source.

No need to quote me one that one, it's something I picked up along the way.
And yes, calculating safe watts on a regulated device is basically watts/3v/# of batteries. The 3v can vary a bit depending on the device, but most devices shut off at 3.3v and figure 10 percent loss to the mod, so 3 volts per battery at shutoff for safety.
So, 180/3v is 60 amps total, 3 batteries gives you 20 amps per battery.

 

[sgobots]

Not hard. Divide the wattage by the number of batteries and divide by 3. This gives you a rough approximation of how many amps will be required from each cell. You should make sure your batteries are capable of delivering what's demanded by the device.

Using what I'm gonna call the @BoogaWu Rule--only buy batteries made by companies that make good televisions and only buy from a reputable source.

I like that rule!!!

 

[Skunk!]

On regulated devices I personally like to use higher resistance on lower guage creating more surface area on the coil. Low resistance coils work well for mechanicals because you have a fixed 3.7v. Thus the only way to create wattage is through low ohms at the coil. A 20 guage .3 or .4 wouldnt work too well on a mech mod, but I find it perfect on a regulated device which allow you to simply turn up the watts.

 

[sonicbomb]

For both regulated and unregulated, minimum mass and maximum surface area is the way to go.
The thinner the wire you use, the greater the surface area is in relation to its mass and therefore how much power is required to heat it up. If you have two lengths of wire with one twice the thickness of the other, the thicker wire will have twice the surface area but four times the mass.

On an unregulated device this is more difficult as you have a fixed voltage and amp draw dictated by the resistance of the coil. This can be mitigated by using multiple parallel strands of thin wire to keep the resistance sufficiently low to generate the wattage you want.

On a regulated device you could use coils that are high mass and low resistance and just over power it with wattage.
But using a low mass coil but with lots of surface area and a subsequently higher resistance will be far more efficient. That means more vapor at a lower temperature and longer battery life.

Understanding the relationship between power and coil resistance | E-Cigarette Forum

https://www.e-cigarette-forum.com/blog-entry/understanding-battery-capability-capacity.7995
https://www.e-cigarette-forum.com/b...nship-between-power-and-coil-resistance.7753/

 

[suprtrkr]

In general, the answer to the basic question-- how much is each cell stressed in any given situation-- is dependent on how the cells are wired together. Assuming all three cells are identical-- always use identical cells in a multiple battery configuration-- wiring them in parallel, where all three negative poles are connected together, as are all three positive poles, the battery pack will provide the same voltage as any single cell, and 3x the amperage or current capacity. Wired in series-- the cells are nose to tail, with the connections made between positive and negative poles on different cells-- the battery pack provides 3x the voltage of any single cell, and the amperage of only one.

That doesn't mean a lot to you in the current application: in your RX GEN3, the cells are in series, but the actual draw on the batteries is controlled by the mod's board. That value is the native current required to fire the coil, plus the I²R losses on both the board and in the mod's current path itself. Think of it as two separate circuits: in one circuit the batteries power the board, and in the other the board powers the coil.

Bottom line: with 3 VTC5As in your machine, you are well within the capacity of the cells at 70 watts, regardless of coil value. This is because your three cell pack is actually providing a 20+A current capacity at 11.1V (nominal), not 3.7V. The controlling derivative of Ohm's Law here is Amps=Watts/Volts, so at 70 watts you're looking at 70/11.1 = 6.3Amps (ignoring losses), or well within the cell capacity.

Welcome to the board, and vape on...

 

[AMOB79]

You guys are awesome. Thanks so much.

 

[Bunnykiller]

its the same as trying to figure out how many HP each cylinder of a car engine is producing...

 

[Baditude]

To keep things as simple as possible:

• Coil resistance is relevant only with a mechanical mod.
• Coil resistance is irrelevant with a regulated mod.
• Choose the battery for a regulated mod based upon the wattage setting that you will be vaping at. Just because you have a 200 watt mod doesn't mean you will be vaping at 200 watts, right?

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, your 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 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 assuming the mod cuts off when the batteries reach 3.4 volts.

WATTAGE PER SINGLE BATTERY:

20W-45W:

Samsung 18650 30Q, 3000 mah 15/20 amp CDR
Sony 18650VTC6 3000mAh 15/20 amp CDR​

20W-60W:

LG 18650HG2 2000mah 20 amp CDR
LG 18650HE2 2500 mah 20 amp CDR
Samsung 18650-25R, 2500 mah 20 amp CDR
Sony 18650VTC5, 2600 mah 20 amp CDR
Sony 18650VTC4, 2100 mah 23 amp CDR
AW 18650 3000 mah 20 amp CDR​

30W - 75W:

LG 18650 HD4 2100 mah 25 amp CDR
LG 18650 HD2 2000 mah 25 amp CDR
Sony 18650VTC5A, 2500 mah 25 amp CDR​

60W - 90W:

LG18650HB6 1500mah 30 amp CDR
LG18650HB2 1500mAh 30 amp CDR
LG18650HB4 1500mAh 30 amp CDR​

 

[Topwater Elvis]

@Baditude
The LG HD2 2000mah & LG HD4 2100mah are both 25a CDR cells also...

The Sony vtc 6 should read 18650 not 18659.

 

[Baditude]

@Baditude
The LG HD2 2000mah & LG HD4 2100mah are both 25a CDR cells also...

The Sony vtc 6 should read 18650 not 18659.

Thanks Topwater. Changes made.