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mr crispy

1/25 Type 90 tank with a 3 lead battery?

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My brother picked up this RC tank for his son via eBay. It's branded "King King" and he thinks its a Heng Long copy. The weird thing is the battery has a Tamiya type connector but it has 3 cables running out of the nimh or nicad battery. The connector on the tank also has 3 corresponding leads. But the charger he's been supplied with is a normal Tamiya 2 lead socket with one square and one "U" shaped prong. The 3 pin sockets has 1 "U" shaped prong & 2 square prongs. Although the charger will fit into the battery socket, it won't charge the battery. The pics below may help explain better.

6FA1E7FE-6177-41AA-826B-0DF86D8B4975-4187-0000059F1FC48F19.jpg

395CD18B-EBCA-45E2-A8EA-7D1C1CBBD2C0-4187-0000059F2D26C8E9.jpg

Has anyone had experience of these batteries? What does the 3rd lead do and can we charge them with a normal 2 lead charger? Given thr different colours how do we identify the + and - leads?

Any help would be appreciated.

Nic

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Some NiMH packs will have a temp probe along with the +/- leads that is used by chargers to prevent over charging.

The standard for wiring is to have red to + and black to -. Best way to test is to put a volt meter on the thing.

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Yeah a assumed the black was neg and red was positive. The 3rd wire is blue on the battery side but purple on the tank side. Can I just ignore the 3rd wire when charging as long as the + is connected to + on the charger and - to -? The battery has no markings at all but looks like a Nimh AA 7 cell unit so should be 8.4v.

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It's possible that the blue/purple wire might be a 'centre tap' from the battery pack, to provide 4.8 or 6V to the receiver PCB (i.e. a cheap way to avoid having to include a BEC circuit). The only way to find out for sure is to put a voltmeter between the black and blue wires and black and red wires.

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