What is voltage drop? Is it the difference between what the battery had in it and fires at in a mech??
Noob question: voltage drop??
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My understanding is the difference in the voltage of a fresh battery at around 4.2 volts, until it stops making vapor around 3.4 volts.
Yes. It's the difference between the voltage of the battery fired with no load and under load.
A freshly charged battery should show between 4.1v and 4.2v. When you put an atty on, and fire it, the higher the volts the lower the drop.
IMO, anything over 3.7v is decent for voltage drop. The higher the volts the better.
Also, the resistance of the coil will affect how much drop.
Hope that helps
Yes Curmudgeon... that helps tremendously. Anxiously awaiting my k100 and doing my research. .. wanted to make sure I get good use from my mm and diligently check ALL the variables. .. THANK YOU
Need to make sure everybody involved is talking the same language. Electronics guys refer to the difference between the battery levels as no-load and loaded voltage. Voltage drop is the amount of voltage that is lost in wiring and connections. Even though textbooks assume that wires and contacts have no resistance, they do. Resistance causes voltage to be dropped when current passes through it. If a battery measures 4.2V and then measures 4.1V under load, it could be the load dragging it down, or it could be bad contacts causing 1V to be "dropped" as it passes through the circuit.
Oh, oh pick me!
You will have to excuse me if I muddy things up a little but we "Electronics guys" are usually not good teachers.
Yes, there are two main things involved here with each of those having multiple causes themselves.
1. Internal resistance of the battery (cell) itself which can vary quite a bit from battery xyz to battery abc and will also vary with the load put on it, age, and temperature. Batteries are not the perfect voltage sources we often think of them as being and all will have this "internal resistance". In example, an AW IMR18350 had 0.066 ohms internal resistance at 3 amp load when I tested it. This "drop" is seldom thought about except by "Electronics guy".
2. The resistance of the circuit (mod) itself. Every component and connection that we use will have resistance. The battery spring and connection to battery and mod housing or wire, the connection at the other end of the battery, the switch, etc. etc. and they add up. In example, a Hero Hybrid I have tested at 0.066 ohms at 3 amps load. (coincidence it was the same as the battery)
0.066 ohms doesn't sound like much, but it is responsible for 0.2 volts lost with a 3 amp load. Volts = Amperage times Resistance (E=I X R) so 3 amps times .066 ohms equals 0.2 volts (rounded) that was lost in heat etc. inside the battery and another 0.2 volts lost from heat etc. in the mod itself for a total of 0.4 volts "drop" from 4 volts unloaded battery voltage to 3.6 volts at the coil under load (button pressed and vaping).
So 1/10 th of the voltage was being "dropped".
Just as important however 1/10 th of the amperage was also "lost".
How can that be?
Because 3.6 volts was applied to the coil, less amperage was flowing through it than would have been at 4 volts.
Amperage equals voltage divided by resistance (I = E / R)
So 1/10th less voltage equals 1/10th less amperage.
We call the total power lost the I squared R losses.
In a DC circuit Power equals Amperage squared times Resistance (P = I squared X R)
So since 10% of the amperage was "lost" 20% of the power was "lost" from those 2 little 0.066 ohm losses!
To go a different route, Power equals Voltage times Amperage (P=E X I).
So 10% less voltage times 10% less amperage results in 20% less power again!
Lets example this one more direction just in case there are still doubts.
Power equals Voltage squared divided by Resistance (P=E squared / R)
So 10% less voltage means 20% less power this route also!
BTW
Because of this relationship, doubling the voltage at the same power level will quarter the losses (Close but not quite in the real world due to other factors) and 4X voltage at the same power level will be 1/16th the loss, 10X will be 1/100th the loss, well you can see the trend.
This is why we bump up voltage at the power station and then bump it back down later to lower those losses during transmission.
Good explanation, Mundy; however, when dealing with high school kids and non-techie people, I tend to err on the side of over-simplification before I break out the math. It's amazing how scared 16-18 year old kids are of basic math.
Good thing Kirchhoff isn't around and on this forum. 8-o
I might have had to dust of my old circuit analysis textbook.
They disassembled (pun intended) the System 370 years ago but I still have my trusty slide rule handy.
Geek fun aside, my father gave up teaching advanced college accounting long ago because he was having to teach the students the per-requisite math.
I hope not, but wouldn't put it past them. That's about the age I started sneaking smokes out of my parents' packs.
No, I taught high-school electronics for 13 years...glad that is done with. The state dept. of education finally did away with it because of dwindling enrollment across the state -- students wouldn't take the classes because of the math and problem-solving. I felt like Mundy's dad...it was very annoying to have to teach 11th-grade students how to do basic pre-Algebra and variable substitution just to be able to do Ohm's Law. AC was a nightmare - basic Trig with little or no coverage of rotational/vector stuff that you really need to understand. Impedance and reactance were also difficult. Only about 5% of my students could deal with thinking at that level. Either the students are learning less, or I was getting fewer of the "good" students, or both.
No, I taught high-school electronics for 13 years...glad that is done with. The state dept. of education finally did away with it because of dwindling enrollment across the state -- students wouldn't take the classes because of the math and problem-solving. I felt like Mundy's dad...it was very annoying to have to teach 11th-grade students how to do basic pre-Algebra and variable substitution just to be able to do Ohm's Law. AC was a nightmare - basic Trig with little or no coverage of rotational/vector stuff that you really need to understand. Impedance and reactance were also difficult. Only about 5% of my students could deal with thinking at that level. Either the students are learning less, or I was getting fewer of the "good" students, or both.
Nail on head.
DC wasn't that tough, but A/C was a booger due to all the formulas I was having to remember.
Until I understood the vector relationships I was only filling in numbers in formulas.
Had a 12th grade vo-tech teacher that was an old school WW2 electronics technician that didn't allow those new fangled calculators and made us do everything on a slide rule.
You have to understand the vector relationships with a slide rule or you are lost.
It hit me like a ton of bricks one day and after my epiphany it all made sense and the world was right again.
Impedance and reactance are simple if you understand the vector relationships.
Only had to remember a handful of equations and the vector relationships and I could come up with any of the A/C equations needed.
Filters, impedance transformations, and resonate tanks suddenly were such a simple thing I wondered how I managed to trudge through all that without understanding.
Yeah, there's usually an "Aha!" moment when you can see that something clicked in their heads. Unfortunately, that didn't happen often or early enough. I'm with you - learn the fundamentals and derive the formulas you need. Forgot all that memorization nonsense. I worked as an engineering tech for a while designing EMI/RFI filters, so I had a real crash-course in the "interesting" bits of AC. Turns out that the books are mostly wrong once you get to working in that area - lots of black magic. I still remember a power-line filter that would not have the proper insertion loss I needed at a particular range of frequencies. After re-designing, re-building, re-testing multiple times, a senior engineer (former military aviation tech/engineer) comes over and says, "See that disc cap going to ground? Try moving that ground leg 180 degrees and re-solder it." I mean, how do you learn that kind of stuff?! Of course it worked...
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