ohms law and box mod wattage

[astronomicals]

If I understand it correctly, on a VV "boost only" mod, your resistance is what will determine your minimum wattage.

The ipv Mini2 has a minimum wattage of 5 watts, but, it cant put out a voltage below the batterys present max. Right?

So on a full charge of 4.2 volts the ipv can only achieve 5 watts if i build a coil with a resistance of about 3.5 ohms. Also, with my setup of a 0.8 ohm coil I can only really go as low as ~22watts, when the battery is full [even if i set it to 5 watts].

Is this all correct? This is how a boost only chip performs, right? I think im missing something.

 

[Slurp812]

I have a DNA 30 clone, and it does seem to do this. The battery is never at 4.2 under load. Maybe like 3.9, but accurate regulation begins at 4.0 volts.

 

[bwh79]

Is this all correct? This is how a boost only chip performs, right? I think im missing something.

Sort of. The IPV Mini, however, can switch between DC-DC and PWM modes. In DC (direct current) mode it can't fire below the battery's native voltage, but in PWM (pulse-width modulation) mode, it can simulate step-down by switching the current on and off really fast (about 30 times/second, with the amount of "on" to "off" time dependent on your setting) so that the the voltage "looks" like less than the battery's charge level when averaged over time. Each individual pulse is still at full battery voltage, though. At settings higher than the battery voltage, PWM ceases to be necessary and you get the same flat DC signal in either mode.

 

[TyPie]

Sort of. The IPV Mini, however, can switch between DC-DC and PWM modes. In DC (direct current) mode it can't fire below the battery's native voltage, but in PWM (pulse-width modulation) mode, it can simulate step-down by switching the current on and off really fast (about 30 times/second, with the amount of "on" to "off" time dependent on your setting) so that the the voltage "looks" like less than the battery's charge level when averaged over time. Each individual pulse is still at full battery voltage, though. At settings higher than the battery voltage, PWM ceases to be necessary and you get the same flat DC signal in either mode.

Very good explanation I think......this is how I understand it (but I sure can't express it as well as you...)

 

[astronomicals]

Thanks for the detailed reply. Does the IPV Mini2 have PWM as well. If set to DC would my calculations have been [close to] correct?

 

[bwh79]

Thanks for the detailed reply. Does the IPV Mini2 have PWM as well. If set to DC would my calculations have been [close to] correct?

The numbers look good, yeah (presuming the ideal case of 4.2v and zero sag, which is not usually the reality.) I actually don't know if the v2 has the same mode-switching or not but it's easy enough to check: on the v1 you press the fire and + buttons at the same time to enter PWM mode, fire and - together for DC-DC.