MrDJ
Legend
- Joined
- Apr 4, 2015
- Messages
- 23,643
posted on AAEC by sriker42
From Mooch :
SAFETY ALERT: Nitecore SC2 charger overheating and failure
I am giving this charger a Do Not Buy recommendation. I was recently asked to help out with the investigation into the possible cause(s) of an accident involving a Nitecore SC2 charger and two cells from a major manufacturer.
18650batterystore sent me a new Nitecore SC2 to test and this unit failed in only three days of fairly heavy use. Luckily I was standing right next to the unit when I smelled something burning. It was then that I noticed that the charger’s display was blinking the eight-LED error “code” for both channels. I quickly unplugged the unit.
I do not know if the unit would have caused the cells to also fail if I wasn’t there to unplug it. Up until then the unit always smelled like “hot electronics” due to how hot it runs.
We do not know what caused the failure involving the other SC2 charger and the two cells yet. The charger was fairly new and both cells were new and were from a major manufacturer and purchased from a reliable vendor. Both cells ended up going into thermal runaway.
A teardown of the SC2 charger I tested showed that one component (a resistor) on a circuit board had blistered from excessive heat and another had failed completely, cracking into two pieces and actually melting the solder connecting it to the circuit board. There seems to be signs of excessive heat in other areas of the board too.
There is a small heat sink located on the other side of that circuit board, near the resistors, but since there’s almost no place for the heat to go the heat sink ends up getting “heat soaked” and becomes useless. This allows the temperature of the circuit board near those failed resistors to rise a LOT.
The high “local” temperatures near these failed resistors means they can’t handle the same amount of power as when their environment is at room temperature and the charger’s design needs to take that into account. Too often this is overlooked by engineers designing a product and could be the cause for these failures.
Or, Nitecore perhaps just decided that 2x2A charging isn’t done very often and that their resistors would last long enough?
In my opinion, if a charger automatically selects 2x2A charging then it should be able to charge as many times times as you want each day without failure. If there are components that get too hot for that then Nitecore should have added a temperature sensor near the overheating components so the charge can be stopped or the charge current lowered if necessary.
For the testing I charged two 2500mAh or 3000mAh 18650 cells at 2A each (the setting the charger picked automatically) seven to ten times each day. This is about 3-4 weeks of charger usage for a vaper charging once a day.
The charger’s outside temperature ranged from 75°C-85°C. This is ridiculously high, too hot to touch. The circuit board temperatures ranged from 90°C to over 100°C. The temperatures of certain components were much higher.
This is unacceptably hot. The high temperature of the bottom of the charger case actually warped the plastic matting on my test bench. Heat is an enemy of electronic components and the hotter a device runs the shorter, on average, its life is.
With all the chargers available to us there is no reason to take risks with our batteries. I recommend not buying this charger. If you already own one I cannot make any recommendations on whether it is “safer” to use it a lower charge current setting or with just one battery. I haven’t tested this Nitecore SC2 charger at lower current settings or with just one battery since the unit I had failed on its first round of tests.
If you are using this charger I strongly urge you to only charge on a non-flammable surface and to always remain nearby and awake.
Thank you 18650batterystore for sending me that unit for testing!
NOTE:
I do not have any charger recommendations I can make yet.
I cannot say if any other Nitecore chargers also have this problem yet.
From Mooch :
SAFETY ALERT: Nitecore SC2 charger overheating and failure
I am giving this charger a Do Not Buy recommendation. I was recently asked to help out with the investigation into the possible cause(s) of an accident involving a Nitecore SC2 charger and two cells from a major manufacturer.
18650batterystore sent me a new Nitecore SC2 to test and this unit failed in only three days of fairly heavy use. Luckily I was standing right next to the unit when I smelled something burning. It was then that I noticed that the charger’s display was blinking the eight-LED error “code” for both channels. I quickly unplugged the unit.
I do not know if the unit would have caused the cells to also fail if I wasn’t there to unplug it. Up until then the unit always smelled like “hot electronics” due to how hot it runs.
We do not know what caused the failure involving the other SC2 charger and the two cells yet. The charger was fairly new and both cells were new and were from a major manufacturer and purchased from a reliable vendor. Both cells ended up going into thermal runaway.
A teardown of the SC2 charger I tested showed that one component (a resistor) on a circuit board had blistered from excessive heat and another had failed completely, cracking into two pieces and actually melting the solder connecting it to the circuit board. There seems to be signs of excessive heat in other areas of the board too.
There is a small heat sink located on the other side of that circuit board, near the resistors, but since there’s almost no place for the heat to go the heat sink ends up getting “heat soaked” and becomes useless. This allows the temperature of the circuit board near those failed resistors to rise a LOT.
The high “local” temperatures near these failed resistors means they can’t handle the same amount of power as when their environment is at room temperature and the charger’s design needs to take that into account. Too often this is overlooked by engineers designing a product and could be the cause for these failures.
Or, Nitecore perhaps just decided that 2x2A charging isn’t done very often and that their resistors would last long enough?
In my opinion, if a charger automatically selects 2x2A charging then it should be able to charge as many times times as you want each day without failure. If there are components that get too hot for that then Nitecore should have added a temperature sensor near the overheating components so the charge can be stopped or the charge current lowered if necessary.
For the testing I charged two 2500mAh or 3000mAh 18650 cells at 2A each (the setting the charger picked automatically) seven to ten times each day. This is about 3-4 weeks of charger usage for a vaper charging once a day.
The charger’s outside temperature ranged from 75°C-85°C. This is ridiculously high, too hot to touch. The circuit board temperatures ranged from 90°C to over 100°C. The temperatures of certain components were much higher.
This is unacceptably hot. The high temperature of the bottom of the charger case actually warped the plastic matting on my test bench. Heat is an enemy of electronic components and the hotter a device runs the shorter, on average, its life is.
With all the chargers available to us there is no reason to take risks with our batteries. I recommend not buying this charger. If you already own one I cannot make any recommendations on whether it is “safer” to use it a lower charge current setting or with just one battery. I haven’t tested this Nitecore SC2 charger at lower current settings or with just one battery since the unit I had failed on its first round of tests.
If you are using this charger I strongly urge you to only charge on a non-flammable surface and to always remain nearby and awake.
Thank you 18650batterystore for sending me that unit for testing!
NOTE:
I do not have any charger recommendations I can make yet.
I cannot say if any other Nitecore chargers also have this problem yet.
