# Car jump-starting and vulnerable electronics

**URL:** https://boards.straightdope.com/t/car-jump-starting-and-vulnerable-electronics/1007654
**Category:** Factual Questions
**Created:** [September 24, 2024, 12:27pm UTC](https://boards.straightdope.com/t/car-jump-starting-and-vulnerable-electronics/1007654 "2024-09-24T12:27:25Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)
#### Post date: [September 24, 2024, 2:09pm UTC](https://boards.straightdope.com/t/car-jump-starting-and-vulnerable-electronics/1007654/4 "2024-09-24T14:09:50Z")

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> [@burpo\_the\_wonder\_mutt](#):
>
> Being a machine elf, you probably already know this: the battery is hooked up as you described to prevent a spark from igniting whatever batt fumes are hovering around, sparing you an acid bath when/if the sucker explodes.

> [@FinsToTheLeft](#):
>
> I was always taught that negative on the dead car was last and that you can connect to the neg terminal on the good battery because a) there is no spark risk since the circuit is not complete and b) discharged batteries give off hydrogen gas which is the explosion risk.

Yeah, the sparks-near-the-dead-battery explosion hazard isn’t the issue I’m thinking of here. Here’s the issue, quoted from that other thread:

> [@How long will my car battery last setting at the airport](https://boards.straightdope.com/t/how-long-will-my-car-battery-last-setting-at-the-airport/1007602/36):
>
> As long as we’re talking about jump starting cars, be sure to check how to jump start your particular car. Don’t just assume you can hook up battery to battery. Some cars should not be jumped by hooking up the batteries directly. Instead, there may be special posts under the hood that should be used when attaching jumper cables. I know some BMWs are like this. If you jump start a BMW from the battery, it may fry some of the computers (learned from personal experience). Instead, they have a special positive post under the hood that can be used with jumper cables.

How does jump-starting via the battery damage onboard computers in certain cars, and how do special jump-start connection points prevent such damage?

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