A funny thing happened to my Snow Wolf 200W...

[suprtrkr]

I dunno if this is normal, and a search isn't showing anything, so I thought I'd post. I don't carry my SW around with me, preferring "Ol' Reliable"-- a Nemi with the 350 tube-- in the car, but I was vaping my SW when I came home for lunch yesterday. I had run the batteries down near the bottom when I was ready to head back out of the house, but not so flat I was getting the battery low message. Preferring not to charge them when out of the house, I didn't replace them before leaving with the spare set. I am not sure, but I think I forgot to do the 5-click turn off thing before leaving. Actually, I thought nothing of it, if you leave it sit for a while it does it by itself. When I got back, the batteries were so dead flat it wouldn't light the screen at all when I pushed the fire button to 5-click it back on and have a vape. I changed the batts and the mod worked just fine. I put the batteries on the charger-- Xtar VC4-- and the left battery (in the mod) was depleted down to the bottom of the IMR range, and the right one was so far gone the range popped down into the 1-2 volt range and stayed there a few seconds until the machine figured out what kind of battery it had, then popped back up into IMR range. Both batteries charged well and fully, the right one taking only 14 mAh more than the left, well within the normal range for these batteries (VTC4s) and this mod. A check with the voltmeter (my good Fluke) showed them at 4.2 volts, dead on. AFAIK, I have done no damage, and the batteries are fine, although they are still out of rotation and I haven't actually tried them since, the spare set not yet having been vaped dry. The lesson I took was, if you don't turn the mod off with the 5-click routine, there's still a mA, or maybe uA, maintenance current and it will flatten low batteries in just 6 or 8 hours. FWIW, and YMMV.

 

[edyle]

something to keep in mind;
2 18650 lithium batteries in series:
operating voltage: about 6 volts to 8.4 volts
2.5 + 3.5 = 6
So if the cutoff voltage is 6 volts, it is possible that 1 battery has gone all the way down to 2.5 and the other is still ok at 3.5

Would be usefull if future mod designs were able to show you the condition of each battery independently.

 

[suprtrkr]

something to keep in mind;
2 18650 lithium batteries in series:
operating voltage: about 6 volts to 8.4 volts
2.5 + 3.5 = 6
So if the cutoff voltage is 6 volts, it is possible that 1 battery has gone all the way down to 2.5 and the other is still ok at 3.5

Would be usefull if future mod designs were able to show you the condition of each battery independently.

I agree entirely. However, I don't think that's the case here, given there was only 14mAh difference in the recharging of the pair. Surely that would not be enough capacity to drop operating voltage an entire volt? @Mooch 's bench tests don't show voltage drop anywhere near that steep. But I agree in general: it would be very nice indeed if batteries went series on the board, so the mod could watch them independently. And on a similar note, ah, how often have I blessed a good charger...

 

[Mooch]

One thing the tests I do here don't show is that every cell has a different capacity. This can significantly increase the rate of voltage drop of one cell vs. another when you're at very low states-of-charge.

For empty cells the change in voltage can be so severe that for even tiny capacity changes one cell could drop significantly lower than the other even with just a 14mAh difference. I may have misunderstood you but you can see that starting to happen in my test graphs as the cell gets near 2.8V. By the time it gets to 2.0V-2.5V the curve is vertical and plummets for essentially zero additional mAh drawn out.

The lower capacity cell could have discharged further than the other and then was discharged to a volt or so by the SW's standby current draw. When recharged you would only see that 14mAh difference, which really means nothing unless you're at very low voltages.

That one cell might be damaged now and could result in a decent voltage imbalance between the two cells during discharge. You're charging outside of the mod so the imbalance gets "erased" every time you charge but I would keep an eye on the charger starting voltages for a bit. If you see it getting lower each time you charge that cell, or you need to charge more often, then you might have to replace the cells.

 

[Mooch]

something to keep in mind;
2 18650 lithium batteries in series:
operating voltage: about 6 volts to 8.4 volts
2.5 + 3.5 = 6
So if the cutoff voltage is 6 volts, it is possible that 1 battery has gone all the way down to 2.5 and the other is still ok at 3.5

Would be usefull if future mod designs were able to show you the condition of each battery independently.

I agree. The DNA200 is a good start but, IIRC, it only shows individual voltages if you're using the PC software?
A screen could even just split the inside of existing battery bar icon down the center, into two columns. No need to take up more space. For the low battery warning text they could easily say Lo Batt1 and/or Lo Batt2. No need to rewrite tons of code. They would need to monitor both cells though. And that Texas Instruments BMS chip in the DNA200, with its supporting components, is pretty expensive.

 

[suprtrkr]

One thing the tests I do here don't show is that every cell has a different capacity. This can significantly increase the rate of voltage drop of one cell vs. another when you're at very low states-of-charge.

For empty cells the change in voltage can be so severe that for even tiny capacity changes one cell could drop significantly lower than the other even with just a 14mAh difference. I may have misunderstood you but you can see that starting to happen in my test graphs as the cell gets near 2.8V. By the time it gets to 2.0V-2.5V the curve is vertical and plummets for essentially zero additional mAh drawn out.

The lower capacity cell could have discharged further than the other and then was discharged to a volt or so by the SW's standby current draw. When recharged you would only see that 14mAh difference, which really means nothing unless you're at very low voltages.

That one cell might be damaged now and could result in a decent voltage imbalance between the two cells during discharge. You're charging outside of the mod so the imbalance gets "erased" every time you charge but I would keep an eye on the charger starting voltages for a bit. If you see it getting lower each time you charge that cell, or you need to charge more often, then you might have to replace the cells.

Ok, then I am wrong. Thanks, Mooch. I will watch it. I have them marked separately-- I bought two pairs to marry for this mod and they're marked 1a, 1b, 2a, 2b-- so I can.

 

[Mooch]

Ok, then I am wrong. Thanks, Mooch. I will watch it. I have them marked separately-- I bought two pairs to marry for this mod and they're marked 1a, 1b, 2a, 2b-- so I can.

Glad you have a good charger! Makes finding out stuff that could cause problems so much easier for us vapers. A decent charger with voltage readout, along with great batteries, should be (almost) be bought before the mod is!

 

[suprtrkr]

Glad you have a good charger! Makes finding out stuff that could cause problems so much easier for us vapers. A decent charger with voltage readout, along with great batteries, should be (almost) be bought before the mod is!

I am glad, believe. It was one of your posts, some time ago, that convinced me of the need. I started with a Efest SODA, which is adequate and a good charger-- I still have it for backup-- but it doesn't have the readout and one fine day, when the cash and desire accumulated, I bought the VC4. I am truly astonished at the difference it makes. It still charges the same batteries to the same voltage, but I now know a *lot* more about my batteries, and the life they can be expected to exhibit, than I ever did before. I work very hard at getting the n00bs to take care of their batteries, you will have noticed. Why, just marking them so they can be reversed in position each time you throw them in the mod is a big help and can extend their life. They're expensive, and dangerous when mishandled, so taking care of them is both common sense and a good idea.

 

[Stinkytofus]

Xtar vp2, charge it at the lowest setting, least heat