Need a refresher on Battery safety in series/parallel reg. Box mods.

[Mrez]

So I need to bone up a bit on the above. With recent testing done by Mooch on the Vtc5's basically being 20A continuous I was to reevaluate my builds for my incoming Snowwolf 200W mod. I've got both a pair of 25rs and VTC5's to put in it. I don't expect to hit the 200W mark, but I am not sure how to use Ohms law when you have a dual battery scenario in parallel or series.

So I know with a single battery, mech mod, 20Amp, my lowest build (assuming no battery sag/voltage drop, etc...trying to keep it simple and safe) is about .25 ohm. That gives me 16.8 amp, and roughly 70ish watts. Realistically I know I'm not getting the full 4.2 v out of the battery, but .25 ohm has always been my lowest build.

What changes when you add a second battery in a regulated mod? Messing around with Steam-engine, if i plug in .25 ohm, and 4.2 volts, but jump the wattage to 100, then I hit 20 amps, and 5 V. Is that my upper range for this type of mod? What happens in terms of safety if i drop my resistance down to .2? To much for a 20Amp pair to handle in a regulated device?

 

[State O' Flux]

Dual series doubles voltage. Dual parallel doubles the potential wattage / amperage... at the output.
Wattage (for the purposes of calculating SE heat flux values) will be the result of desired net resistance and voltage... in the case of a dual parallel, will still be 4.2V.

The OL derived wattage doesn't care about your wire gauge or coils in parallel count... just the net resistance and battery voltage.
Heat flux does care about the wire gauge (AKA wire surface area & mass), coils in parallel count and net resistance, and is directly affected by them, both together and independently.

Your priorities are surface area and heat flux. The latter is a known or desired value, the former is where you shoot for the greatest value... without leaving your desired heat flux range, or having an excess of heat capacity or leg power loss.

 

[Mrez]

Thank you Flux...I'm not sure I understood all of that. I understood from previous discussions, that on something like a dual battery in parallel mechanical box mod, I could essentially double the amps of the battery when planning my builds. So using 25r's I could plan for having 40 amps to work within. What I am not sure of is how a regulated chip effects this, or a regulated chip with the batteries in series. If the batteries are in series, my voltage available increases, but the amps remain the same? So I plan my builds based around 20 amps?

Real world application is for dual clapton's coming in between .2-.25. Any higher, and they don't seem to work on mechs, the ramp up time is to slow to be useful. I have to fine tune the build a bit (was using nichrome cores with a 30 gauge kanthal outter wrap), but I should have my 34 gauge nichrome outter wire this week, which should help with my ramp time. The atty's will be used for both mech and regulated box mod. Just not sure what my target should be.

 

[ddarlington24]

Alot of technical info there I try to keep it pretty simple as far as parallel goes it's like tie-ing 2 batteries together the voltage stays the same while increasing capacity /Mah while doubling the raw amps achievable - I personally favor this method.

Series doubles the voltage so instead of 4.2 it's now 8.4v while the capacity hasn't changed from a single 18650 (25r 2500Mah) within a series . The only real issue with series is using identical batteries and you can't miss match them.

And then theirs the issue of balance charging / if you run a series charge them outside of your device keep them labeled so you can identify them not to mix them up.

 

[edyle]

So I need to bone up a bit on the above. With recent testing done by Mooch on the Vtc5's basically being 20A continuous I was to reevaluate my builds for my incoming Snowwolf 200W mod. I've got both a pair of 25rs and VTC5's to put in it. I don't expect to hit the 200W mark, but I am not sure how to use Ohms law when you have a dual battery scenario in parallel or series.

So I know with a single battery, mech mod, 20Amp, my lowest build (assuming no battery sag/voltage drop, etc...trying to keep it simple and safe) is about .25 ohm. That gives me 16.8 amp, and roughly 70ish watts. Realistically I know I'm not getting the full 4.2 v out of the battery, but .25 ohm has always been my lowest build.

What changes when you add a second battery in a regulated mod? Messing around with Steam-engine, if i plug in .25 ohm, and 4.2 volts, but jump the wattage to 100, then I hit 20 amps, and 5 V. Is that my upper range for this type of mod? What happens in terms of safety if i drop my resistance down to .2? To much for a 20Amp pair to handle in a regulated device?

One way of looking at it simply, is just figure out how much power you want from each battery.

If you decide you don't want to draw more than 20 amps from the battery, and assuming the mod will allow the batteries to drop down to 3 volts each,
watts = volts x amps = 3 x 20 = 60 watts per battery.

so build coils that won't need more than 120 watts

 

[Mrez]

Alot of technical info there I try to keep it pretty simple as far as parallel goes it's like tie-ing 2 batteries together the voltage stays the same while increasing capacity /Mah while doubling the raw amps achievable - I personally favor this method.

Series doubles the voltage so instead of 4.2 it's now 8.4v while the capacity hasn't changed from a single 18650 (25r 2500Mah) within a series . The only real issue with series is using identical batteries and you can't miss match them.

And then theirs the issue of balance charging / if you run a series charge them outside of your device keep them labeled so you can identify them not to mix them up.

I think my device runs in series to achieve a higher voltage. What is the practicable upshot of doubling the voltage if I'm essentially still limited in amps? And what is the battery drain like when you have them in series? Is the load pulled evenly from both?