When I accidentally depleted our car battery, I charged it's battery from the inside outlets, using a 0-30V 0-10A bench power supply device.

The car has 3 outlets. One individual outlet is rated for 10A, while the combined current is rated at 16 A.

I increased the current, but when I approached 8A, there was a smell of hot copper wire. I immediately decreased the current. At 7A, everything worked fine. And the outlets still work as intended. But I am worried, so I am asking here:

  • Is it safe to keep using that outlet?
  • Is there any possible damage?
  • If there is damage, how to locate it?
  • If there is damage, how to repair it safely? (replace the entire wire.)
  • 2
    What voltage did you set the power supply to?
    – Sneftel
    Commented Jun 17, 2019 at 12:07
  • @Sneftel Around 15.5V, to compensate for the cable voltage drop at the high currents. Had I set it to 14V, charging would not go beyond 2 A. A voltmeter at another power outlet showed 14.3V. While the engine is on, the voltage climbs to 14.6V, which means that any voltage that arrived at the car's electronics, is within safe range.
    – neverMind9
    Commented Jun 17, 2019 at 14:24

1 Answer 1


The smell you describe could be a sign of damage, or it could just be your power supply under a heavy load. The damage could be in the charging system, or the car. Your nose is a valuable tool for tracing that smell, as well as a visual inspection:

  • Male charger plug: If you're using a bench power supply you likely hooked up a car charger male plug to it, maybe re-purposed from another device which wasn't rated for that level of power, so my first step would be to inspect that for damage. Smell it: if it fried then it may still be whiffy. Cut it open if you have to in order to eyeball it
  • Charger: Some electrical components like transformers can sometimes smell when they're under a heavier load than usual. That smell may still be lingering, if you stick your nose in air circulation slits you may detect it
  • Car socket or wiring: if neither the plug or the charger was the source of the smell then it could be the socket or the wiring on the car. Again your nose and eyes are the first tools to use, get a good sniff and an eyeball on the socket with a good flashlight. Look for evidence of melting, discoloration, etc. The wiring is a tough one to say as it depends on the placement of the socket and the make/model of the car. If it's built into the dash then getting a look behind it may be possible, or it may be removing the dash! I have a snake cam that hooks up to my phone for that sort of hard to reach place, they are amazingly cheap these days. If damaged, the wiring should show signs of it. If the wiring or the plug is damaged it would need to be replaced

My money is on your bench supply transformer making the smell, most bench supplies rarely have to produce anywhere close to their rated capacity, and when they do the first couple of times some of the chemicals used in their manufacture evaporate. If that's all it is then happy days.

  • That bench power supply is a SMPS. I also own Linear power supplies, but SMPS is better for high currents.
    – neverMind9
    Commented Jun 17, 2019 at 14:26
  • I put 15A banana plug cables directly into the outlets to charge it. No reverse polarity. (I would have done it with a male charger plug, but our eBay order of them has not arrived yet.).
    – neverMind9
    Commented Jun 17, 2019 at 14:28

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