Don, on your RCSNE website, you mention that these MTO batteries have a "next generation battery Protection Circuit Module (board). Can you describe it and how it works?
What sort of magic does it preform?
Hi Steve, it is all about safety. Do you remember reading Kevin Strong description of a lithium battery commits suicide when the pack gets shorted or when the red and black wires accidentally touch.
Well we have eliminated that problem for you and me. Using an MTO battery pack it will be protected during a short and will recover after you fix the shorted wires. Pretty neat.
Thanks for asking, Don
Does that protect the batteries when charging in parallel?
Industrial, Commercial and Retail batteries internationally are provided with PCM’s that meet the requirements under the auspice of IEC SAFETY recommendations for travel and use for at least five years or better.
So far as I know and have realized, PCM’s incorporate EXTERNAL short circuit protection. A self resetting device known as a PTC provides short circuit protection by creating HIGH resistance when copious amounts of current are rendered and later when the short is removed the PTC drops back into LOW on resistance monitoring.
The “Suicide” comment alluded to above is derived from INTERNAL failure modes leading to a short. PCM’s have little to no effect and accordingly offer no protection under said circumstances.
A resettable fuse opens in the event of elevated temperatures around 195*F.
Sleep mode opens the circuit when you run the battery down below the preset voltage safety level, typically a multiplier of 2.2V per cell.
Michael
Steve:
PTC means “Positive Temperature Coefficient”… PTC is not really a device but a description of an attribute of a device.
You probably have a resistor that has a PTC… like the orange PolySwitches we had on our Aristo equipment… too much current it heats up (Positive Temperature), and the Coefficient of resistance increases.
The term “thermistor” is often applied, a THERMalresISTOR … (cute huh?) https://en.wikipedia.org/wiki/Thermistor
(so a short circuit, lots of current, makes heat, the device increases in resistance and limits the flow of current).
Note these gadgets normally do not completely cut the flow of current, just reduce it to a safer level… some current has to flow to keep it hot enough to limit the current.
You can also have a thermal circuit breaker, but those are to sense heat from the cells, not really current. These are normally touching one of the cells. (but the problem is that if a different cell shorts and heats up, it takes a while for that heat to migrate to where the sensor is)
Thermal cutouts are normally good for a sustained high current condition, either caused by too heavy discharge or too heavy charge.
Again not really good for “suicide”, where one cell goes bad, often reduces to a short circuit or reversed polarity, thus way too much current flowing through it and a lot of heat… and a lot of heat in lithium batteries normally results in fire.
Reading Don’s post, his “suicide” seems to be that the pack won’t function after a short, probably tripped the protection PCB.
So I’m in line with Michael, he’s got more expertise than I have in batteries (and I have been using and learning for a long time), but would not mind hearing about MTO’s PCB since it’s not mentioned anywhere on their web site. I have a hard time comprehending how 2 packs can work with each other if their magic PCB’s are not connected and communicating though.
Greg