Seat Toledo 1.9 TDI 110hp AFN & VW T4 2.5 TDI 102hp: Strong Sparks & Flames During Jump-Start

Hello,

I have a literal problem.
I wanted to start my Seat toledo 1.9 tdi 110hp AFN from VW T4 2.5tdi 102hp.
The battery in Seat is 7 years old and only 60ah. I know too little. But I guess with cable boot it doesn't matter.
The battery in the T4 is 85ah.
I connected the cables in the correct order and when connecting the minus to the ground (engine block, gearbox ...), my tolek shoots and sparks terribly. It pounds so much that the hand withdraws by itself. I had a small hole burned in the engine block and the jaws of the cables are perforated in several places.

The day before, I fired the 80ah battery on the VW Bory 1.9tdi cables and everything was fine.

What is the cause of this very strong sparking? Give small flames.
Or is it that the battery in the T4 is too strong for my Tolek?
Please help.

After all, it is normal to connect a source with high current efficiency (and such is a charged battery of the current donor, additionally with a running engine and alternator giving full current at the moment) to a completely discharged battery in your car. At the time of connection, the current flows probably above 100A, so it must spark.

Added after 3 [minutes]:

zen.ste wrote:

when connecting the minus to the mass of my tolek

zen.ste wrote:

There was a small hole in the engine block

And who catches the clamp on the engine block? Clamps are to be connected to the battery. BOTH.

Yeah I know I did it many times and there were sparks but not like that. Now they literally shoot out little flames.

If the minus is supposed to be minus on the battery, why do they write differently everywhere?
Even on the AutoCentrum channel on YT they say that the recipient's minus is not the battery.

zen.ste wrote:

I did it many times and there were sparks but not like that. Now they literally shoot out little flames

Maybe you have a short circuit in the car, e.g. shorted diodes in the alternator. And when you catch the minus frog, not the engine block, grab the steel parts, e.g. by the ear for lifting the engine, or the body, not cast iron.

Added after 2 [minutes]:

zen.ste wrote:

If the minus is supposed to be minus on the battery, why do they write differently everywhere?
Even on the AutoCentrum channel on YT they say that the recipient's minus is not the battery.

Because YT will take everything just like paper.

Wawrzyniec wrote:

And who catches the clamp on the engine block? Clamps are to be connected to the battery. BOTH.

Those who have a bit of oil in their head and know that connecting the frogs to the battery may result in its explosion.
Therefore, some manufacturers have given special holders for borrowing electricity. Especially where the battery is difficult to access.

If the battery is dead, you buy a new one, because a 7-year-old diesel is a long time for scrap, and you will be permanently firing from others? So you don't burn the car and hurt yourself.
I wonder if the engine is on in the other car. Because I have never connected a weak battery (10-11V) to a charged 14.4.
At the beginning, I connect it to a charged battery in the turned off donor's vehicle for several minutes. Only we fire up the donor and after a few minutes of more powerful charging you can try.