Build optimization for Battery Life of single battery mods

[GeorgeS]

Greetings, I'm always in search of my "Holy Grail" where in my tank+battery run out at about the same time.

Seriously though, there are many things we can do to EXTEND battery run time with our builds. A few 'givens' are:
- larger mass requires more time or power to heat up but also holds that heat longer
- higher power drains a battery quicker than lower power
- stepping a battery voltage UP (Boost) is vastly LESS EFFICIENT then stepping a voltage down (Buck)
- the room temp resistance of a coil determines the cold voltage for the power selected
- the vaping temp (assumed here @ 400F) resistance of a coil determines the voltage for the power selected

Given that the batteries that we use generally have a 3.2V to 4.2V range (being dead to fully charged) the MIDDLE can be considered @ 3.7V.

The concept here is that we are going to optimize the resistance of our coil so that at our desired power setting our mod is ether:
- outputting <= 3.2V at all times
- outputting <=3.7V at all times
- outputting <=3.7V at least 1/2 of the time

I'll start with a chart I made with a fixed Wattage of 35W and a selection of coils made with NIFE used in TC mode:

From the above chart a coil resistance of >= 0.4ohms would be borderline battery run time at room temperature. However <=0.35 or even <=0.25 Ohms require even less voltage over the discharge curve of the battery.

At 30W we have even more justification for building <=0.25 ohms:

At 25W:

And again at 20W:

As the charts show, depending on the coil resistance and target power level we can optimize for greater/longer run time on battery with the coil resistance so that our mod does not have to 'boost' or step up the battery voltage.



g.

 

[englishmick]

Interesting numbers, thanks.

I did hit that holy grail spot with my wife's gear. She has Lemo's running in TC. By chance the batteries do run out at the same time as the juice, which is convenient. I only do hers when she dumps them on my desk so I can fill and change the battery at the same time.

 

[GeorgeS]

Interesting numbers, thanks.

I did hit that holy grail spot with my wife's gear. She has Lemo's running in TC. By chance the batteries do run out at the same time as the juice, which is convenient. I only do hers when she dumps them on my desk so I can fill and change the battery at the same time.

Good Job!

Personally if I'm going to 'fiddle' with a Mod, I'd rather take care of BOTH at the same time rather than refill and then very soon after swap batteries or swap batteries and then shortly afterwards do a refill. I prefer to have them in 'sync'.

Given the charts I calculated above my thinking is that for a given 'target wattage' I wish to use a 'target cold resistance' for the best battery life. So while picking '3.2v' as my target firing voltage I get:

35W - <= 0.3Ohms
30W - <= 0.35Ohms
25W - <= 0.4Ohms
20W - <= 0.5Ohms

So onto Steamengine to find which AWG's and # of wraps are going to hit a given cold resistance.



g.