To what temperature can a power bank safely reach?

Question

Electronics

Hello. I received 2 boxes for a power bank with a board from Ali, such here, for 8 batteries https://ru.aliexpress.com/item/Dual-USB-8x18650-DI... I inserted
8 chocolates into it (original LG HG2) and the plate started heating up wildly, the white one began to stink of burning, the black one just warmed up .. I didn’t wait long, after 10-20 seconds I took out the batteries. How normal is this, what operating temperature can it be? The plates are heated, to which the contacts of the batteries are suitable. Unfortunately, I don't have a temperature gauge, but I got a slight burn with a bubble on my finger when I touched the plate near the board.
These are high-quality batteries, they are unlikely to explode, but I'm afraid that the valve will work and they'll just be scrapped later. I would not want to kill batteries for 2500 rubles with a power bank for 300 rubles)
And, yes, this is without load, I did not try to charge anything, I just inserted the batteries. Here, I wrote it down for the Chinese at their request) https://www.youtube.com/watch?v=XYiC2c9_FMY&t=2s

Answer 1

I inserted 8 chocolates into it (original LG HG2) and the plate started to heat up wildly

In fact, it was necessary to start with one battery.
Did you by chance put the batteries in series? And the symptom is very similar to the closure.
The plate is hot, but the batteries?
Check the entire board carefully for "snot" of solder or just balls, after one wash the flux, if any, it can be conductive or ... yes, just wash it off.
In general - such a spring contact and "pimpa" are far from a fountain in terms of the quality of the contact, you can try to get it. Solder the junction of the springs with the plate, tin the part of the springs in contact with the batteries and the protrusions on the other plate.

Answer 2

Are all banks voltage equalized? If some of them are charged, and some are empty, a current of unlimited magnitude will flow between them. This is harmful to both banks and plates.

Answer 3

≈< 60 C°