@fernand: So much to respond to here...
Due to the overwhelming success of the original iStick (20W), there are now a number of very small, very powerful regulated mods. ELeaf has added three more to the iStick line (the 10W mini, the 30W I just received, and a 50W that is shipping to vendors this week from China). There is the Defender you just received, which from all I've heard so far, uses the same chip as the iStick 20W, but has a different physical design, and
perhaps a slightly higher capacity battery. The IPV Mini was recently released (that's the one you asked about that has five memory positions), as was one whose name escapes me at the moment that purports to have temperature control (ala the evolv DNA40). Note that the one whose name escapes me has not shipped yet, so no one has tested it yet. None of the new contenders goes lower in power/voltage though, they're all fighting to have
more in the top end. More importantly, none of the new mini mods are as small and hand friendly as the iStick line, with the exception of the Defender you just got (which also has some advantages, such as the reversable eGo/510 connector). All of the rest of them, so far, are larger enough that they just don't provide the same experience. They don't fit the hand or the pocket as well. I enjoy the way my iStick 20W and 30W feel (wisecracks allowed). None of this would matter if the iSticks didn't work well; they all do. The 10W mini, which I picked up for a friend, is tiny, a delight to use, and way better than the VV Spinner it replaced!
If it makes you feel any better, after using the new iStick 30W for a day, there are only two things about it that I prefer to the old one. (1) It's not PWM (Pulse Width Modulated) anymore, and is calibrated in rms volts instead of mean volts. (Check out
Todd's review, just posted. Phil Busardo's review will have the most technical detail, but he hasn't reviewed the iStick 30W yet). This means I can get a "real" 5 Watts out of it, rather than the 7.5W or so that's the true minimum for the 20W version. Most people are concerned with the top end, not the bottom end, but both you and I are not most people.
With about half of the different concentrates I use, I prefer (true rms) 5W-6W for the attys I use. 7W-8W is just a
little more than I like, requiring me to take two second hits instead of the five second hits I prefer.
(Talk about first world problems). That's actually the reason I got the 30W version; I'm perfectly happy with the 20W version other than I wished it went a little lower. (2) I do like the locking voltage/wattage buttons, but only because I now set the power to above the minimum on the 30W version. I always ran my 20W version at the minimum, so I just pushed the down button before I fired it, and if for some reason the power had been accidentally set higher, it would just go back to the minimum. I would NOT have purchased the 30W version just for the button lock (or the floating 510 pin or the SS 510 connector).
Here are some charts I made for myself when I got the iStick 20W, note that there are
both voltage and wattage limits on both ends, and coil resistance plays a part in this. Also (most importantly to our less-is-better quest here), note also that the voltages/wattages in the chart below are based on mean voltage, not rms voltage. That means that all the numbers below are higher than we're used to, especially in the low end. As I mentioned previously, that means that when my 2.2Ω coil is shown as drawing 5 watts, it's really drawing between 7.5W and 8.0W. It also means that if I happened to use one of my 3.0Ω attys (I have a few, but I don't prefer them), I could set it to 3W (mean) and get a real (rms) 6W into it.
Eleaf IStick 20W Absolute Limits
1Ω - 3Ω coils
3v - 5.5v
3w - 20w
1.0Ω Coil (9w-20w)
3.0v = 9w = 3a
4.5v = 20w = 4.5a
1.5Ω Coil (6w-20w)
3.0v = 6w = 2a
5.5v = 20w = 3.7a
1.8Ω Coil (5w-17w)
3.0v = 5w = 1.7a
5.5v = 17w = 3a
2.0Ω Coil (4.5w-15w)
3.0v = 4.5w = 1.5a
5.5v = 15w = 2.75a
2.2Ω Coil (4w-13w)
3.0v = 4w = 1.4a
5.5v = 13w = 2.5a
2.5Ω Coil (3.6w-12w)
3.0v = 3.6w = 1.2a
5.5v = 12w = 2.2a
3.0Ω Coil (3w-10w)
3.0v = 3w = 1a
5.5v = 10w = 1.8a
I can provide you graphs of mean vs: rms for different resistance coils, if you like, but it gets even more complicated, due to the circuitry in the 20W version. The mean vs: rms curves are different when the battery is less than 2/3 full. Longer duration of the "on" pulse in the duty cycle when the input (battery) voltage is lower means that the difference between mean and rms gets smaller. Your half charged battery will be displaying more accurate (closer to rms) readings. Hopefully you're not too medicated when reading all of this; it's confusing enough as-is.
As far as testing the health of a battery, the best way is to charge it fully and discharge it fully while monitoring the voltage, current, and capacity.
If you're talking about eGo type batteries and other mods that have built in non-removable batteries, it's pretty much impossible to measure their discharge capacity (as you don't have access to the battery itself, and most mods have a timeout, which would make for a horrible few hours of pressing the button every 10 seconds). So with mods where you don't have access to the actual battery, the way to judge is to measure how much energy you put into the battery when charging it from empty to full. You can use one of those $10 USB gizmos I mentioned a few messages ago to do this. Run your eGo down until it stops firing your atty, then charge it up to full and read how many mAh you put into the battery. It should be about the same number that the battery is rated for (e.g., a 650mAh eGo twist should take about 650mAh to recharge it). The reason it's about the same, rather than more, is because even though the charging process isn't 100% efficient (meaning you would think you'd have to put more than 650mAh into a 650mAh rated battery), you aren't discharging the battery down to 2.5V before the eGo electronics shut you down, more like 3.2V, and battery manufacturers rate capacity down to 2.5V.
If you want to test, e.g., 18650 batteries, the best way to check is with an intelligent battery charger. I use sophisticated RC chargers which will allow me to charge and discharge multiple batteries while keeping a record of the whole process, including how much capacity the battery has and how much it takes to charge it back up. One of the chargers I use displays numerically on the charger itself and also hooks up to my computer to provide graphs and the like. The other one has a built in OLED screen that displays multi-color graphs natively. I don't have one, or know the particulars of, the Nitecore you have, but if it can discharge as well as charge, and can tell you how many mAh are used when charging and discharging, you can use it to evaluate your batteries.
As far as your Nightcore not charging a really dead battery while your "cheap" charger would, that depends on both the design of the charger and if the battery has a protection circuit board. It sounds like the Nitecore doesn't have a mode to deal with totally dead batteries. You have to slowly pulse the battery, watch for its voltage to suddenly increase, and keep a very close eye on its internal resistance. Once the battery gets above a certain voltage (maybe 2V?), the charger can do its normal thing. Pulsing a totally dead lithium battery is dangerous though, and any lithium battery that's been allowed to discharge to zero is likely to suck big time even if you can resurrect it.
The only complaint is that at 2.5 ohms, the Defender can't put out less than 5 watts or 3.5 volts, which is more than my Provari at 3.3 volts, so for someone looking for the promised "1 to 8 volts", the spec is not completely honest, if not misleading.
That's interesting. I just put a 2.2Ω and a 2.9Ω atty on my iStick 20W and the 2.2Ω atty reads 3.0V/4.0W and the 2.9Ω atty reads 3.0V/3.1W. On my new iStick 30W, the 2.2Ω atty reads 3.3V/5W and the 2.9Ω atty reads 3.8V/5W. So maybe the chip in your Defender is NOT the same as the one in the iStick 20W! Note that you can't exceed
any of the upper or lower voltage OR wattage ratings. The iStick 30W has different limits from the iStick 20W (beyond just the additional 10W available with the iStick 30W). Note that it has lower limits for both voltage and wattage. (But remember also that the 20W is mean volts and the 30W is rms volts and in reality the 30W actually can put out less than the 20W does!).
iStick 20W..........iStick 30W
1Ω - 3Ω coils......0.4Ω - 5.0Ω coils
3v - 5.5v...........2V - 8V
3W - 20W..........5W - 30W
You are correct that there is no way your Defender can actually go to 1V without exceeding either the wattage or resistance limits. 1V delivering 5W requires a load of 0.2Ω, which is below the lower limit for its resistance.
I wish it came with a 1 amp USB charger. I wish it had the lock feature.
I deliberately ordered my iStick 30W "naked". No eGo adapter, no USB cable, no charger. I have a zillion of those, don't need any more, and it saved me $3
Whew, that was a long one!