We have bought a used Toyota Yaris.

Yesterday I allowed my kids to play in the car, and they discharged the battery...
So I went to take it out to charge it up and I found pieces of a copper and copper coil in between the clamps and 'nips' of a battery.

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This is the first time I saw something like this. I am currently in the far North country (Lithuania) could this have anything to do with cold winters (-20 C). The battery is 44B20L (Wet 12V 35Ah) capacity.

Why would one put copper in between battery contacts and clamps?

P.S I might be overthinking this, could be they simply did this to tighter fit the clamps with the battery and used copper since it is a good conductor? Still, this is something I have never seen yet...

  • 4
    Looks homemade..
    – Martin
    Jul 30, 2019 at 11:21

2 Answers 2


I think your guess will be correct. The clamp has probably been over-tightened in the past, has stretched and is no longer giving a good tight connection. The copper will have been added to act as a shim to make a tight connection.

  • 9
    Or, the original battery died and somebody replaced it with the "wrong" type of battery which had smaller diameter terminals.
    – alephzero
    Jul 30, 2019 at 11:28
  • 7
    @alephzero - I've only ever seen two types of automotive battery connectors, and the top mount style is pretty universal. I'm pretty sure Handy is spot on. Jul 30, 2019 at 12:46
  • 1
    It may be worth noting that the terminals are of different sizes (by 1.4 mm in diameter), but modern cars are built so that it is very difficult to impossible to connect the battery when installed the wrong way around.
    – Pavel
    Jul 31, 2019 at 9:48
  • Even the "right" type of battery can have slightly out-of-spec terminal sizes when sourced from certain manufacturers, necessitating this type of thing. Aug 1, 2019 at 14:54

Why copper? Because it is soft without being too plastic and easy to obtain. It is also highly conductive both thermally and electrically.

Why do it? The terminal no longer clamps the post. The post is too small or the clamp is too large. This creates a sleeve. The thread on that bolt may also be stripped or seized. It is very commonly done to just hammer these on, but that may not be possible if it is not on a flying lead.

Some of that looks OEM, and some of that looks "maybe" (is that a hinged cover ?). A fixed terminal would not give anyone a lot of choice when it comes to battery form factor.

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