As several folks have said, bad idea.
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Just another âI donât like your answers, so Iâll keep asking until I get one that I likeâ post. To the OP, use your jump pack without disconnecting the battery. If the alternator is charging and the battery still goes dead replace the battery. If the alternator isnât charging replace the alt. this is not rocket science.
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Slow day. I have no idea what brand I have but itâs in the trunk and never used it. Both of my batteries are new or near new. If one was discharged I would put the battery charger on it and evaluate whether to replace it. But everyone is free to do what they want as long as they arenât being paid for their actions. Bye.
Nothing like a good booter pack. Sorry bad joke. I know what you meant.
Many people are answering questions that were not asked.
It is not that simple, the vehicles charging system operates at a low voltage, it would take 12 hours for the alternator to recharge the battery. To draw that conclusion in haste results in many unnecessary battery and alternator replacements.
I think that we all understood. You donât disconnect the battery to use the jump starter. You put the jump starter on the still-connected cables, and then remove the jump starter once it starts. Why do you think youâd need to disconnect the negative cable to use the jump starter? Thatâs not how jump starting works no matter what.
And additionallyâŠ
- the battery needs to remain in the circuit to absorb voltage irregularities from the alternator. Can the alternator run the stuff in the car without the battery in the circuit? Sure! Until you fry a computer.
- if the battery is âokâ but has just lost charge for some reason, then - if itâs not an emergency - it should go onto a charger. Alternators maintain a battery charge. Asking them to be battery chargers is abuse of the alternator.
- if the battery is just âdeadâ - meaning it wonât accept and/or hold a charge, then you get a new battery. You make sure it is charged, and go on your way.
So, to reiterate - I think that everyone âunderstood the question.â But itâs still a mystery as you why youâd want to try to run a car from a jump pack - except, perhaps, to limp it to a shop or auto parts store.
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1981 Century limited, 3.8 v6
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Thanks
Iâm guessing that was a sedan, not that hatchback?
Was that equipped with all the bells and whistles?
No matter what? If the battery is shorted?
Okay. Letâs say someone has stolen your battery, will your jumpstart battery start and keep the engine running?
Hi Nedved:
This is about picking between your worst options.
If your current battery is shorted and you leave it installed, then after you jump start the car, your alternator (and battery) could easily overheat, resulting in a fried alternator.
If you remove the battery from a running car, as Cigroller noted, there wonât be anything there to absorb the normal voltage spikes that an alternator charging system produces. Without the battery being installed to act as a capacitor to absorb those voltage spikes, you run a very high risk of blowing some electronic circuitry in the car.
As Nevada noted, the module on the jump starter cables will internally disconnect after the engine starts. This is to prevent alternator power from damaging the lithium-ion battery. That essentially means your car is running without any battery connected, subjecting you to the risks noted above.
I used to run cars without batteries connected back in the 70s. They all ran fine most of the time. I would definitely not do it in todayâs cars with the electronics being used.
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Now you are asking a different question. You original question asked
The answer to that question was no.
Now changed to a âwhat ifâ question. Based on Rainflurryâs comment, I give this answer: Maybe.
My question to you, why? If battery was stolen, just replace it.
But then a new question for you, how did the thieves access the battery compartment?
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Sounds like trying to split hairs nowâŠ
If I comment about someone stealing the battery out of a Corvette, it will probably get flagged⊠lol
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I never would try that to find out. As (many) others have said, your 2008 is full of complex and expensive electronics. Why put it at risk?
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As well it should! 
Adulterated excerpt from the movie Unforgiven:
Corvette Bob: The Corvette is akin to royalty. A majesty that precludes the likelihood of adulteration or thievery. If you were to attempt to steal from a Corvette, your hands would shake as though palsied.
Barber: Oh I wouldnât think of stealing from a Corvette sir.
Corvette Bob: Well thatâs a wise policy, a wise policy. But if you did. I can assure you, if you did, that the sight of such automotive royalty would cause you to dismiss all thoughts of theft and you would stand⊠how shall I put it? In awe. Now, a run of the mill car⊠well I meanâŠwhy not?
I got a free used jump pack battery. 12v 18ah. Sla. Been sitting in garage for 2 months. Was 12.7v yesterday. Might be good? I havenât tried to use it yet.
Not something I approve of, but I observed coworkers doing this several times each week: They start the engine, remove the battery and take it to the parts department for exchange. Several minutes later install the new battery while the engine is still running.
This is done so the vehicle owner doesnât complain that the radio station list and the seat position memory has been erased. One in a thousand chance something will go wrong, I donât do it, and it seems to scare a lot of people.
Out of curiosity, why donât they just use one of those memory devices? I confess to knowing little about them, and donât have one. But I thought thatâs what theyâre for?
Didnât have one, didnât want one, didnât careâŠ
Amazed me that the manager didnât stop that practice.
Half of the vehicles arrive with dead batteries, many others require battery disconnect during repair, so memory reset is common with customerâs vehicles.
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Thanks Nevada for that update.
I wonder if charging system spikes are less harsh than they were years ago.
Or if the electronics in the vehicles are designed to withstand a given level of those spikes.
I agree. Itâs not something I would advocate doing.
Thanks.
Iâd expect the main reason is that configuring a memory saver to the battery takes a certain amount of the techâs time, so the tech will make more money that day by not doing it. Works well as long as the customer doesnât complain. Which apparently they mostly donât, so skipping the memory saver a must work well enough for the tech to accept the risk of the possible adverse consequences to the customerâs car .