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You can power an external device in the car from the cigarette lighter or socket. In the first one there is a contact clamp-bracket made of bimetal - it is she who shoots the cigarette lighter when it is heated, but in the socket, of course, this is not the case. Sockets can be 21.3 or 22.3 mm in diameter, or 29 to 35 mm deep.
Plugs are made under 21 mm, providing their versatility. The length should be selected. But how to guarantee reliable contact? The spring-loaded cap of the central output tends to push the plug out of the socket, and vibration helps him in this. Therefore, some manufacturers made an annular groove on the plug, which is fixed by the same bimetallic plate. If there is such a groove on the tee, it is better to plug it into the cigarette lighter socket.
Two plug designs - with a fixing groove for the cigarette lighter spring (a) and without it (b). You should also pay attention to size L: the smaller it is, the better

Two plug designs - with a fixing groove for the cigarette lighter spring (a) and without it (b). You should also pay attention to size L: the smaller it is, the better. Two plug designs - with a fixing groove for the cigarette lighter spring (a) and without it (b). You should also pay attention to size L: the smaller it is, the better.
HOW TO BE PROTECTED?
In nine out of eleven variants, fuses were installed in the tee plugs - at 5, 8, more often at 10 A. We checked their operability in a reliable way by connecting an automobile heat electric fan for blowing glass, which required 14 A.
The car’s standard socket is usually protected by a 15 A insert - it can withstand this. But the fuses of all the tees had to be outraged, however, only four products did this. In the fifth, there was no fuse at all, instead the power button on the plug burned out.
The Taiwan splitter into two beautiful, wood-like sockets Auto HK twin socket GT-54309W (price 210 rubles) gave out a lot of smoke from the plug, inside of which only a fuse remained intact. The rest is deformed

The Taiwan splitter into two beautiful, wood-like sockets Auto HK twin socket GT-54309W (price 210 rubles) gave out a lot of smoke from the plug, inside of which only a fuse remained intact. The rest is deformed. The Taiwan splitter into two beautiful, wood-like sockets Auto HK twin socket GT-54309W (price 210 rubles) gave out a lot of smoke from the plug, inside of which only a fuse remained intact. The rest is deformed.
Two more products filled the editorial office with smoke and began to melt. One of the fuses managed to burn only at 20 A, another could not be burned. In all cases, the central contact on the plug and the connecting wire were very hot - they saved on copper.
A separate niche is occupied by a domestic product - an extension cord with a thick wire and a pair of “crocodiles” instead of a plug. It, according to the authors, should be connected to where the clamps can grab onto the current-carrying parts. What to protect in this case is not clear.
The extension cord socket can withstand any load, but the on-board network …
The plug with the USB socket of the Chinese tee Multisocket AC 1216 (price 220 rubles) melted at 14 A very clearly. The fuse has remained unscathed

The plug with the USB socket of the Chinese tee Multisocket AC 1216 (price 220 rubles) melted at 14 A very clearly. The fuse has remained unscathed! The plug with the USB socket of the Chinese tee Multisocket AC 1216 (price 220 rubles) melted at 14 A very clearly. The fuse has remained unscathed!
RESPONSIBILITY DOES NOT BEAR
General conclusion: such tees require very careful handling. On the packages it is usually written that "the manufacturer is not responsible for the car." Therefore, first of all, figure out what current the device that you plan to connect through such a splitter consumes. Serviceable navigator, communicator, radar detector tee will not warm up. But if there is any defect, you don’t have to rely on the fuse. And therefore, a simple tip: from time to time, touch the plug of the tee: it is he who overheats first of all from overload.