John

No, but that might be related if you were. What are the cold resistances of the coils you are switching between? Mis-detecting and toasting kanthal is easier to do, toasting nickel is harder, so hopefully we can get to the bottom of whatever is going on quickly. Whe it fries the coil, what is it showing as the detected resistance?

Are you ohm locked?

Ah ha. Here's the confusion. The load you're measuring isn't resistive. Burden voltage doesn't enter into it to measure the current accuracy of our charge sensor/display. Microamps or not. So I think we're on the same page now. Test away.

The "burden" of the shunt resistance as you call it will certainly depress the output voltage getting through the cable, but as you're trying to correlate current to current, I'd think that your meter is already compensating for any nanoamps lost through the measurement circuit. In terms of running a test to see if it will blow ports, that's totally valid. Attached to a data port, it is programmed to draw only 500 mA. What you want to try is using a "charge only" cable as those pretend to be a charger regardless of what the host device actually is. But absolutely, beat on it and report back what you get.

Current law, not law of potentials (voltage law) USB power delivery is a safe zone box. For a standard USB port, the box extends from 4.5v to 5.5v and from 0mA to 500mA. Outside the box the device should limit current to move back into the box. Realistically ports are built with enough output resistance that they typically droop to the minimum of the spec at the maximum current, but that is a designed behaviour, as it is the cheapest way to protect against short circuits. The heat generated in the wires is a function only of the current flowing through the wires and the resistance of the wire. I squared R, voltage doesn't enter into it. But I think I see what you're getting at. You want to see if our USB current measurement is accurate. If you have a good ammeter, just strip the VBus line out of a sacrificial cable and run it in series through your ammeter. The voltage supplied to the DNA 200 will be a little lower due to sense resistor loss inside your meter, but the current has only one path, so the current read by the meter will be exactly the current drawn and sensed by the 200.

Milliamps is milliamps, voltage losses don't change it. https://en.wikipedia.org/wiki/Kirchhoff's_circuit_laws So I'm not entirely clear what you mean by "shunt losses nulled." The DNA 200 and all responsible USB devices will limit current if the port can't hold voltage, but that doesn't change the 500 mA spec. There isn't a way to force charge display, but you can put charge parameters on the main display if you're interested.

Do you have the powered hub connected to a PC? We've tested with amazon brand, sentry, ukonnect, pluggable, and a variety of generics. USB spec for a high power device is 500 milliamps (5 unit loads), and we tell the computer we will be drawing that much. If the hub can't supply that much or if other things are plugged into the same hub and it can't power all of them it could decline to connect. http://www.ti.com/lit/an/slyt118/slyt118.pdf if you don't care to slog through the actual USB docs. Where do you get a value of 420 ma from? The DNA 200 will in all cases limit current draw to keep the voltage at the port above 4.45 volts, so it won't overdraw or brown out a computer port regardless. If you want to do that test, simply purchase one of the moronic "charge only" USB cables that have d+ shorted to d- to emulate a charger. I thought I had one that wasn't working for a second, but windows was just taking its time installing the hub.

That's probably not a bad rule of thumb, all things considered.

And make sure you don't overheat the tab and break the pouch seal, or the battery will puff after a few cycles.

Absolutely. If you click "record" it will save all the graphed data as a CSV file that you can open in Excel or similar. Being able to walk back graphically isn't a bad idea either, but the recording capability is there now.

http://batteryuniversity.com/learn/article/bu_808b_what_causes_li_ion_to_die and others on the site are good reading. It is important to note that C ratings are based on the nominal capacity, not the measured capacity at that discharge rate or lifespan, but cycling cells to death certainly happens faster at higher discharge powers, so it is still a good discussion to have.

Sure, but it isn't that simple. Where did the capacity go, and more importantly, what side effects did that loss of capacity have? I am certainly not saying don't have extra margin. I'm just saying that an "add 20%" rule of thumb is too simplistic, because as the capacity decreases, the proper c rating changes as well. Not always intuitively. Also, it isn't unusual to see an identical cell rates as 20c from one place, 30c by another and 50c by a third. Or have a manufacturer understate capacity to inflate the C rating.

9 volts and 23 amps is 207 watts, which is the output power plus the board losses. Where do you get a different number? Edit: I see what you did there. That's a valid concern (battery ampacity at end of life) but that will vary from cell design to cell design. Not as straightforward as adding 20% The board, wiring, solder joints, fuses and the like, plus the pack in any condition need to be able to do 23.

You will be fine. We have run these in plenty of nonmetallic enclosures, as well as without any enclosure at all. Do make sure you run the case analyzer, though, as your mod's thermal properties will not match the aluminum reference design.

The USB pads are surface mount. The mechanical mounts for the connector are through hole slots.

We haven't had difficulty with powered hubs here, what brand and model is causing you trouble? The device won't violate USB spec if it sees data lines, so that isn't a great worry.

Are you planning on vaping near 200 watts? 20 is a bit light, but it is silicone insulated, so unless you're a serious cloud chaser, I wouldn't worry about it too much. You're more likely to damage the cells replacing it than you are likely to damage the wire using it. A reasonable alternative would be to splice in heavier gauge wire as soon as it comes out of the pack.

Yup, the resistor got knocked off. You can see the divot in the solder where it used to be. It is a 100 ohm resistor. Without it, it can't read the cell. You could send it to us and we'll put one back on. Or if you got it from protovapor and they want to set up a return, that's no trouble either.

Vapingbad, we're adding a full battery analyzer in the next version. It calculates the capacity and builds the full discharge curve for a battery automatically. Not a bad idea for measuring mod resistance. That might be easier than doing the same in atomizer analyzer, writing it down and typing it.

Could be, but the balancers get tested explicitly during the final functional test, so to ship out they were reading properly at some point. Pictures of the board would probably clear it up.

Use a multimeter to measure the cells with the pack not connected to the board. Disconnect the tap and the power leds. Measure the hole pack voltage, and the the voltage on each cell and report back. If it is reading below 8v, it will immediately power the board off when you disconnect USB and aren't holding the fire button down. The turnigy batteries aren't horrible if you get a good one, but the QC is pretty suspect. I've gotten packs with dead cells, packs with cells installed backwards... etc Alternatively, you could have the balancer leads shorting. An exuberant soldering job on the connector could cause this, or it might be mounted such that one of the solder tails of the balancer leads is able to short to case. Blowing fuses should be singularly rare, so there's probably a short circuit going on somewhere for it to happen. If none of that, post a high resolution image of the front and back of your board and maybe we'll be able to see some assembly error there. One way or another we'll get you going, so don't sweat it too much.

Sure, you could run a 3s2p pack. You'd need to make sure both batteries are in the same condition (perferably new) and are fully charged before you pair them. Parallel the main output leads and parallel the tap connectors. Or buy an off the shelf pack built 3s2p, which the manufacturer will have done all of that when they were building the pack in the first place. In power supply mode (or with a three resistor tap divider) it will run off a car battery if you're REALLY thinking big.

Either do a full charge cycle, unplug and replug the battery, wait through a refinement cycle (about an hour) or use Escribe and set a charge estimate in device monitor.

I would probably massacre a USB micro B extension rather than trying to run wires (appropriately twisted and shielded) individually to a connector. If it was me

You can fire into .01, but it will current limit to 25 watts output with kanthal, or maybe 50 watts once a nickel coil has heated up (and somewhere in between for things in between like twisted nickel/kanthal and titanium) Also you'd really need to nail your mod and tank resistance readings to temperature control properly down that low, so it is a touch impractical to use a coil that low. Possible, but not great results.