scootervapes
Member For 4 Years
In a regulated device, wattage set the same, how would battery life vary between a .1 ohm coil and say a .5 ohm coil?
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Battery life at different ohms?
- Thread starter scootervapes
- Start date
Ok, say you're running that .1 ohm coil at 50 watts, your current draw would be 22.36 amps at 2.36 volts the same wattage using a .5 ohm coil would be 10 amps at 5 volts. So with the .5 ohm coil, your battery life would be about twice as long.
Here's a link to a good Ohm's Law calculator: http://www.sengpielaudio.com/calculator-ohm.htm
Here's a link to a good Ohm's Law calculator: http://www.sengpielaudio.com/calculator-ohm.htm
scootervapes
Member For 4 Years
I've got a good calculator, wasn't sure if higher amp draw or higher voltage draw would kill the battery quicker. I'm alright with electricity, usually I just read about something when I need to know something and learn a few things,...for once I just didn't care that much, and thought someone else would know without the effort.
SAME wattage, SAME battery life.
Lets look at this for a second.
Battery current does not equal coil current. There are always 2 sides to the equation in a regulated mod.
Battery current does not equal coil current. There are always 2 sides to the equation in a regulated mod.
Hey, no problem.I don't mean to be an asshat, but I am intimately familiar with the math involved. I only wish to help other understand.
OK, ill do it again. Lets of course simplify this for our example. Lets just say the regulator circuit is very efficient, and always only uses ~5 watts when you press the button. 50 watts is a pretty good amount of power from a 20 amp cell, so we will use 3.8 volts for the battery side of things. As the battery drains, we need more current to maintain 55 watts output, so the strain on the battery increases as voltage goes down. The opposite of a mech mod. OK, so we want 50 watts at our coil. We need 55 watts total from our battery. Here its important to remember the atty resistance has noting to do with this calculation. 55 divided by our 3.8 volts is ~14.5 amps we are using from the battery. To the battery this looks like a .26 ohm load regardless of whats on the other side of the regulator. On the atty side of the regulator, your calculations hold true. Current is traded for voltage in the 0.5 ohm coil. Voltage is traded for current on the 0.1 ohm coil. The regulator does this. Roughly speaking it works like a transformer with AC voltage. I also need to add that these are average voltage/current numbers. The regulator works by taking very large current pulses from the battery. In the case here, where the average battery current is ~14 amps, the current spikes are likely around 30 amps!
As mentioned, if the device is regulated then the coil resistance does not affect battery life if you keep the watts constant, because the current the battery sees shouldn't change by any significant margin assuming the circuits are doing their job properly.
However, running higher currents will wear out a battery quicker. So if you're either regulated and you turn up the watts, or if you're unregulated and you drop the resistance, then the battery will wear out quicker. This accelerates when you start getting near the max discharge spec of the battery, or if you allow the battery to get hot. Obviously if you're using a 25R, rated at 20A, and you're running it at 3A, then going to 4A won't make any significant difference. But if you're at 15 and you go to 20 then that will make a significant difference.
However, running higher currents will wear out a battery quicker. So if you're either regulated and you turn up the watts, or if you're unregulated and you drop the resistance, then the battery will wear out quicker. This accelerates when you start getting near the max discharge spec of the battery, or if you allow the battery to get hot. Obviously if you're using a 25R, rated at 20A, and you're running it at 3A, then going to 4A won't make any significant difference. But if you're at 15 and you go to 20 then that will make a significant difference.
NemesisVaper
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Have some posts been removed from this thread? Seems like there are some missing.
Good info above. Since I learned more about regulated devices from people here (Inc Slurp- ta m8!) I've tested it out. Indeed the cells last the exact same time at 0.2 and 0.8 ohm at 50W.
At 0.2 on a mech a battery doesn't last me long at all. I've not built on a mech above 0.3 for a long time. Guess I'd need to change wire. 24awg at 0.8 would be pretty weak compared to what I'm used to.
Good info above. Since I learned more about regulated devices from people here (Inc Slurp- ta m8!) I've tested it out. Indeed the cells last the exact same time at 0.2 and 0.8 ohm at 50W.
At 0.2 on a mech a battery doesn't last me long at all. I've not built on a mech above 0.3 for a long time. Guess I'd need to change wire. 24awg at 0.8 would be pretty weak compared to what I'm used to.
None that I'm aware of.
NemesisVaper
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Just me being tired mate. Night shift etc. Got chance to read it properly now.