Due to a couple of incidents of the popular Smok Stick V8 and X8 mods catching fire while charging I decided to check if there was anything I could see in a teardown that might indicate a possible cause.
Smok Stick X8 page: https://www.smoktech.com/kit/stick-x8
Smok Stick V8 page: https://www.smoktech.com/kit/stick-v8
Teardown photos: https://imgur.com/a/i1doD
A total of eleven units were cycled five times each and then disassembled and checked. The X8’s and V8’s I had were identical internally.
Bottom line…my testing and the disassembly/inspection was inconclusive. I didn’t see any obvious issues in any of the units I checked and all of them worked properly.
This does NOT mean that every Smok X8 and V8 is unconditionally “safe”!
This also does NOT mean “user error” caused the fires!
We can’t come to any conclusions from my teardown other than I had no issues with the ones I looked at.
I also received one of the units that caught fire during charging, along with the charger that was used. The device was completely charred internally. There was nothing left to inspect other than ashes. The Samsung 5V/1A USB charger block that was being used was still functioning normally, outputting a bit over 5.0V. No conclusions could be made regarding the cause of this device’s failure.
I’d like to thank Eva Campbell for donating three new X8’s, Lynda Abshear for donating two new V8’s and one of the burned V8’s, and All Day Vapes for donating three new X8’s and three new V8’s. Thank you!
Here is what I did for each unit:
– Cycled it three times using a Apple iPad USB charger (5.2V/2.4A) and then 0.13 ohm and 0.4 ohm coils for discharging until the unit would no longer fire. All of the units charged without incident and without getting more than warm externally (near the circuit board).
– The USB cable that shipped with one of the units was used for each charge and handled quite roughly every time it was inserted. I made sure to insert it “upside-down” first every time to try to replicate some of wear & tear it might see during use.
– Cycled it twice using the same coils as before but with a power supply to set the charging voltage to 4.5V to simulate a low quality, i.e., low voltage, USB charging block. All of the units charged without incident and without getting more than warm (near the circuit board).
– Disassembled and inspected it for missing padding or insulators, battery damage during assembly, inconsistent or low quality circuit board soldering, sloppy wiring runs, signs of overheating, missing mounting hardware, inconsistent soldering, etc.
My observations:
– Unit to unit assembly consistency was good except that two of the units had the circuit board soldered to the screw posts instead of using screws.
– Green vegetable grocery bag tape was used to hold the black negative wire from the battery to the circuit board. I guess it was an inexpensive option?
– The black negative wire going up the side of the battery was a very small gauge wire and got hot when about 23A was flowing through it with a freshly charged battery and a 0.13 ohm coil. No damage to the wire’s insulation or side of the battery was seen in any unit though.
– Charging current was 0.65A-0.70A for all the units.
– There was foam padding on the bottom and soft rubber padding on the top of the battery. These would help protect the battery from damage if the mod was dropped but I do not know how these would hold up after lots of drops over time.
– The end/side “flaps” of the pouch cell were very tightly folded against the cell so it all fit in the tube but no damage was seen in any of the cells when I removed the padding and the insulators and unfolded the flaps.
Conclusion:
Since we don’t know what the cause of the failures were I strongly recommend that charging ANY mod should always be done on a non-flammable surface with someone nearby the entire time in case something goes wrong.
Since these kits are sold to newer vapers I’d like to see a decent USB charging block included. It would add minimal cost and prevent the use of low quality chargers.
One of the two 1A USB charging blocks I received with the burnt out unit, but was not being used when the unit caught fire, outputted only 3.90V and less than 0.5A when used. That is about 3.7V to the battery once it passes through the USB cable and the circuit board. This results in a battery that is not fully charged and it could possibly cause problems with the unit’s electronics as this is much lower than the 4.40V minimum voltage for USB these units might be expecting.
I don’t know if low charging voltages, and low quality USB chargers, are a problem or not but including a charger with the unit would make them more “all-in-one” kits and help limit the use of crappy chargers.
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