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Discussion Starter #1
I see a lot of videos that tell you to plug your mini booster box into "any" 12V power jack.
AFAICT, the jacks are only ON when you turn the main keyswitch on, except for low-current for charging a phone.

So, can you plug in a booster box and feed 20-30A back into the battery from ANY 12V jack, or just a certain jack?

Otherwise, you need to connect directly to the battery, if you need a boost or jumpcharge.
 

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Any power take-off point in a car is limited by the wire gauge size and the fuse that is matched to it. Why the cig lighter fuse so often blows out when you hook up to it using something that pulls way more current than the wiring will supply.

That idea is garbage, you will likely never find a jack that will pass that much amp and it is WAAAYY over the 30 amp number you mention. Battery boosting amp can easily be 100 amp if not more, you commonly use 250 using a booster box.
 

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Discussion Starter #3
The NOCO Boost Sport GB20 is supposed to deliver up to 400 Amps. It's recommended that you connect it directly to the battery, which is fine, but doesn't answer my question.

Can you recommend a booster box that can plug into the 12V jack?
 

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I see a lot of videos that tell you to plug your mini booster box into "any" 12V power jack.
AFAICT, the jacks are only ON when you turn the main keyswitch on, except for low-current for charging a phone.

So, can you plug in a booster box and feed 20-30A back into the battery from ANY 12V jack, or just a certain jack?

Otherwise, you need to connect directly to the battery, if you need a boost or jumpcharge.
The BCM (Body Control Module) keeps the power port on the console energized for several minutes after you turn the key to the off position.

I have always been a skeptic of these jump starter boxes that plug into the cigarette lighter but I have to admit that this thing works. I wanted my wife to have a way to jump the battery if it went dead and I knew she could not be getting out of the car to open the hood in a bad neighborhood or a high traffic street. I bought this Stanley Simple Start and left it under the seat for emergencies. Sure enough, my battery was getting old and would not crank one morning. I plugged the Stanley into the power port on the console of my MK3. It does not instantly jump the car off-you have to wait for the green light. Sure enough, the car fired up and I headed out to buy a new battery.

So yes, I can confirm that this device worked through the power port on the console which surprised me. No wiring damage and no blown fuses but that may be unique to this device as I would be concerned if I plugged a high amp jump starter into the power port.
 

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12v port for the most part is protected by a 15-amp fuse.
It would need to see more than that to blow it.
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As for these power port boosters, they don’t dump Amps into it. Just higher voltage.
This higher voltage naturally will bleed just enough charge to boost a “weak battery” to the point of starting the car.
Heck, I’ve boost charged a car with a 21v drill battery before.
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But these micro 12v port boosters only cover “weak” batteries. & that’s fine for the majority of these situations. But for the worse situation of an actual “dead-battery”, these boosters fail miserably.
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This is why one must be ready with a real boost pack like the NOCO unit mentioned. These NOCO units are reliable & fairly simple to use, usually it only takes about three minutes to instruct someone on how to use one. I’ve spent more time getting one of my NOCO units out & hooking it up, than actually having a truck start with it.
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Believe me, it’s better to educate your loved ones on how to use a reliable boost box under the hood. Than to have be stuck somewhere they don’t want to be because of a slow & not so good boost box.
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Should you decide on a connect to battery booster, get one that’s “oversized” for the task.
This way it will do the job without issue & have peace of mind it’ll work when needed.
 

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If you haven’t guessed.
I own two NOCO’s a GB70 & a GB150. & I’ve actually started & ran a few vehicles without their battery with ether one.
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My GB150 has done this with a 1978 F150 before. & these trucks have amp hungry starters. These units are brilliantly dependable & are worth the investment.
But that’s just my opinion. Feel free to purchase whichever is your preferred brand.
 

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Discussion Starter #8
My 2017 Focus has just about everything happening automatically.

If you turn on the radio with the keyswitch off, it will turn off after a while- when the battery runs down to some point.
When you turn off the keyswitch, the headlamps turn off, and even if you turn them on manually, they turn off! when the battery runs down to some point...

So... if you just maintain the car, change the battery when it supposedly wears out, charge the battery regularly in the winter, and turn off powered things when you don't need them, you should never need a booster battery- just a set of boost cables- even a set with 12 or 14Gauge wires should be fine.

So I think I will skip the booster battery and use the "old-fashioned" cables, especially since it (the winter spares and 'emergency stuff kit') fits in a handy nylon duffel with the tow strap, torch, gloves, etc. I load it in the boot with a plastic emergency shovel in the fall, and it comes out in the spring.

Having it in the car is more of an emergency kit for some moron that doesn't take car ownership or driving seriously.

Only the tyre pump permanently stays in with the spare tyre.
 

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Good to know you got good old standby cables.

I’ve a collection of emergency items in my vehicles too.
Water, non-perishable food, blankets, med-kit, tools etc. etc.
 

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I'd put the money towards a good battery & a battery tender....
 
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