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The reason I ask is most portable jump starters have short leads that only reach to the battery terminals, and therefore cannot be used.
Technically, I’m not aware of a reason why other than as a safety precaution. AFAIK, it’s done to minimize the chances of a spark near the battery, where there’s the potential existence of explosive gasses.
 

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2021 718 Cayman GTS 4.0
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Not sure about most, but the ones I have used can easily reach a suitable spot on the frame in any car I have experience with. You don't connect to the negative terminal because as Bob said there is a slight risk of explosion and there is no need to - the negative terminal is connected to the chassis which is the ground in this case. Any bare metal will do.
 

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Discussion Starter · #4 ·
Found this.
The issue has to do with the fact that the computer progressively raises the charging voltage to the battery as the battery ages. This is why one has to let the computer know when a new battery is installed, because if not it will apply too high a voltage to the battery reducing the new battery's life span. Connecting the charger directly to the negative terminal bypasses this system and could cause the computer to erroneously overcharge the battery, reducing its lifespan
The reason I ask is most portable jump starters have short leads that only reach to the battery terminals, and therefore cannot be used.
[/QUOT

Also saw something about coulomb counting for auto stop/start on the neg terminal
 

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The safety issue is what used to be said. It still makes sense. I'm not sure of the computer argument. If the negative terminal is connected directly to chassis ground then it shouldn't matter where you connect a charger.
 

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It is also safest to connect both ends of the positive cable first then the negative ends. This is to prevent, a dropped positive end, from accidentally touching the body and causing a wicked short under the right conditions. If a negative cable is dropped and touches the body it does not much matter.
 

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my neighbor used to be one of these types that knew better than everyone else and did things how he wanted over any instructions and believed in jumping cars by connecting positive to positive and neg to neg and running the car to charge the dead battery faster. after damaging several alternators doing that, he started following the directions for jumping cars.
 

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It is also safest to connect both ends of the positive cable first then the negative ends. This is to prevent, a dropped positive end, from accidentally touching the body and causing a wicked short under the right conditions. If a negative cable is dropped and touches the body it does not much matter.
Actually the exact opposite of that.

Connect the ground first. Then you can drop the positive cable anywhere except on the positive battery terminal without creating a circuit with voltage.

If you connect the positive cable to the positive battery post then the negative cable is ready and willing to suck charged-battery-potentional electrons out of anything it touches. And THAT may cause damage if you drop it on something that is grounded that isn't intended to be an unfused battery ground.
 

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All the instructions I ever saw said to connect the positive terminals first.

The safety question was more about disconnecting than dropping. The reason for connecting ground away form the battery is, or at least was, that the disconnect could cause a spark. If the battery had been giving off a cloud of hydrogen a spark could ignite it. So you wanted to be able to disconnect something away for the battery. I never knew anyone who had such an experi
 

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Actually the exact opposite of that.

Connect the ground first. Then you can drop the positive cable anywhere except on the positive battery terminal without creating a circuit with voltage.
It's the opposite . If your negatives are connected, the first clamp of your positive is also connected, then if you drop the already connected positive anywhere (both cars) then you have a short circuit.
 

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For my part, usual point of a jump is for a start. (BAT is by definition out of reach if the frunk is the goal.) Battery defect may be corroded leads or other high resistivity creating issue or ?; after all the BAT is dead for some reason. So, a direct connect to (through) the battery may fail as well. Chassis connect bypasses the defective BAT. Starter doesn't care where the (-) is as long as there is a complete circuit. FWIW, done it both ways numerous times with analogue and digital cars, conventional and zero maintenance batteries and never fried a computer, blew up the BAT, or incurred the wrath of any of the major automotive gods.
 

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From the Good to Know App:

When jump-lead starting, never connect the black negative cable directly to the battery. Always connect the black negative cable to the ground point B (Fig. 36).”

Porsche actually provide a separate ground point on the left side of the car (as viewed from the seat.)

And from further in Good to Know:

Open front luggage compartment lid.

Please see chapter "Emergency unlocking of the luggage compartment lid".

Remove cover in front luggage compartment.

To remove the cover: Please see chapter "Removing and stowing tire sealing compound or tool box".

Connect the red positive cable to the positive terminal A of the flat battery.

Connect the red positive cable to the positive terminal of the donor battery.

Connect the black negative cable to the negative terminal of the donor battery.

Connect the black negative cable to the ground point B.

Never connect the black negative cable directly to the battery.

Let the engine of the donor vehicle run at a higher engine speed.

Start the engine. An attempted start using jumper cables should not last more than 15 seconds.

Then wait for at least one minute.

With engine running: First, disconnect the black negative cable from the ground point B then from the negative terminal on the donor battery.

With engine running: Disconnect the red positive lead from the positive terminal on the donor battery first, then from the positive terminal A on the flat battery.
 

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It's the opposite . If your negatives are connected, the first clamp of your positive is also connected, then if you drop the already connected positive anywhere (both cars) then you have a short circuit.
Wrong thread. My response was in the context of connecting a device (charger, tender, etc.) to a battery.

Your comment is about connecting two batteries together. In your case there are many ways to screw it up once you have any cables near the batteries connected or otherwise.

Notice that the two pictures you posted show two different ways to connect two car batteries together?

One is correct and one will fry things.
 

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Discussion Starter · #16 ·
Yes, I was wondering if there are pitfalls with a portable battery jumper. They look pretty cheap and easy. Just need to keep it charged. So you get to your car and its dead, defcon 1. Then your frunk doesn't open, defcon 2. Nobodies around for a jump defcon 3. You can call AAA if you have cell coverage and wait for someone to arrive, or use a portable jumper if it is charged. The jumper sounds a bit more convenient. It will open the frunk via the fuse box and also jump the battery. If the frunk does not open, defcon 4, and you need a tow. But the tow hook is in the frunk, defcon 5. Seems like a lot could happen.
 

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Wrong thread. My response was in the context of connecting a device (charger, tender, etc.) to a battery.

Your comment is about connecting two batteries together. In your case there are many ways to screw it up once you have any cables near the batteries connected or otherwise.

Notice that the two pictures you posted show two different ways to connect two car batteries together?

One is correct and one will fry things.
I really don't understand your post.
Wrong thread for me or you ? This thread is about jump starts as I understand , that's what i referred to. It's not about just connecting batteries .
It's in the picture and in the YouTube video.

Both the picture and the video states the same , start with the positive cable first (battery to battery) then go with the negative but the negative goes to the depleted car's engine block or predefined negative jump start point.
This is exactly what is the Porsche good to know app states.
 

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As Boxsteiner mentioned, use a jump starter instead of jump starting from a donor vehicle. Only trick to this is having one charged and available when you need it.
 
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