When lithium batteries catch fire: How overcharging can do bad things to Li-ion cells
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange answerers link it as a quick visual proof that charging a Li-ion cell without proper charger and protection circuitry can set it on fire.
Recommended by 0 people across 0 different months, 2020 to 2021.
What it is
A short EEWorld Online clip showing what happens when a lithium-ion cell is overcharged, ending in venting, smoke and fire. It is a brief demonstration meant to illustrate the failure mode rather than a deep technical explanation.
What people said
Cites Jim Fischer · 2020-03 · Electrical Engineering Stack Exchange · on “Will this LM317 Circuit work for my application?”
I agree with @mkeith's comment to monitor the voltage (relative to ground) at the LM317's power input pin when the fan is attached to the LM317's output pin, and the fan is running. If at all possible use an oscilloscope, not a multimeter, to perform this voltage measurement. (NB: If you don't have an oscilloscope, use a multimeter to measure this voltage.) If the measured voltage at the LM317's input is at or below $$ 11.5\,\mathrm{V} + V_{DO} \approx 11.5\,\mathrm{V} + 2\,\mathrm{V} = 13.5\,\mathrm{V} $$ where \$V_{DO}\$ is the LM317's dropout voltage specification (obtained from the LM317's datasheet), then you know the 19 VDC power source cannot deliver enough power (voltage and current)
Cites Marcus Müller · 2020-04 · Electrical Engineering Stack Exchange · on “Can I solder 5V USB to a tablet battery connector?”
That won't work. You need a charger and safety circuit between whatever voltage supply you use (no matter whether it's 5V from USB or 4V from somewhere else) and your battery. Your tablet has a lithium battery. You can't charge a Lithium Battery with constant voltage; it will catch fire [this video] . Hence, you need the charger integrated in your tablet, or another Lithium battery charging circuit that matches the properties of that battery. Conclusion: Replace the microUSB connector.
Cites user16324 · 2021-09 · Electrical Engineering Stack Exchange · on “Can current flow from positive to positive in real life”
As you say, when the battery voltages are different, yes, current will flow and the circuit can be said to "work". HOWEVER be aware that current flowing into the lower voltage battery will charge it. So, this circuit (whatever else it does) is a battery charger. Now if that's what you intended ... great. However, if the lower voltage battery is not rechargeable, or already fully charged, you will damage it [this video] , and some types of battery don't like that [LINK] .