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Thread: Car battery jumper

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    Default Car battery jumper

    Would a device like this be suitable to run a laptop that has a flat battery, as i can kill two birds with one stone?
    There is a fine line between "Hobby" and "Madness"



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    Yes.
    I have one of those style packs and it will run MY laptop about 4 hours.

    Be aware the ratings on that are totaly and completely Fictitious. It is impossible for a battery that size to have that sort of capacity and discharge.
    You should take a look at the " dealing with some ebay sellers" Thread.

    I have found it VERY difficult to find these that are true to rating. In the few I have had, I have also found the ones with the less Features ( Flashy lights, power readouts etc) to be the best. These things seem to take up room in the pack and leave less space for the battery. An indication of power and capacity is weight. The more they weigh, generally the bigger the battery.

    The MOST you will get out of a normal sized pack of this type is about 4 Ah, maybe 6. There are larger truck types with more capacity and amp output but they are disproportionally more exy. If you want to mainly use a laptop or appy them for portable power, get the plainest type you can get. will be cheaper and probably more bang for the buck.
    The bigger the claims on capacity for these things AND most other Lipo and 18650 type batterys, they cheaper and less capacity they tend to have. Something with a more modest rating will almost always be better than something screaming 10X the capacity/ output.

    I also use mine to power a remote camera for about 9 hours and they are good for running USB devices from or charging them.
    They will also even start Cars!! :0)

    Do your homework on these things. The crap outnumbers the decent one by a factor of about 50.
    The good ones are excellent and having had them for a while, can't do without them now.

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    Indeterminate -- it shows a DC output jack, and it mentions the voltages available, however no mention is made of what current/wattage that DC output is able to provide.

    What are the specs on the laptop's charger/AC adapter?

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    Wotnot,

    I could use a new one of these. How would one go about testing the capacity?
    I have seen chargers that will do this for 18650's but are there any boards or ways you know of one could test these to Check what their capacity was and satisfy and return requirements if Need be for Fleabay?

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    Quote Originally Posted by george65 View Post
    Wotnot,

    I could use a new one of these. How would one go about testing the capacity?
    I have seen chargers that will do this for 18650's but are there any boards or ways you know of one could test these to Check what their capacity was and satisfy and return requirements if Need be for Fleabay?
    Aaiieee!

    All of these things are junk in my book ...at least, the battery based jump starter stuff..I've lost count of how many have turned up on my workbench...actually, there's one there right now...



    That cost the owner $280 new, about 18months ago -- he used it 3 times to jump start his Cub Scout mower ; same result always, puffed and partially shorted lipo pack ..every single time.

    It's a crap design, destined to fail... goes like this -- these jump packs typically have 3 high current lipo cells in them ; at full charge (4.2volt per cell) that gives you 12.6volts at the alligator clamps, and it dumps the current into your battery.

    The problem is, the designed 'storage' voltage for lipo cells is down near 3.65volts (which is why a lot of lipo powered devices come with the "please fully charge before use", they're shipped at lipo storage voltage), which won't give you enough power to crank/start something. So what happens is, people keep these things fully charged, and carry them around in their boot or something until needed --- so essentially they are in 'storage' at full potential... and the cell chemistry starts breaking down (or dendrites form), and when next you go to draw high current out of them...puff puff, fizzle fizzle...usually the cell at the negative end of the 1P3S string. It's a joke ; what you would really need is a jump pack with 1P4S (16.8v full, 14.6v at nominal storage voltage), and you'd stand a reasonable chance of getting some lifetime out of them -- simply put, lipos don't like to be static batteries, they like to be used (charge/discharge cycles)...it is what it is.

    Relative to what unit the OP cited, this means that DC output jack, must be behind a DC-DC buck, and I'll bet it's limited to 2A output...maybe...maybe less.

    Killing two birds with one stone is actually a reasonable notion, because at least then you'd be using/cycling the lipos instead of storing them at full voltage and them dying in result.

    For mine, a better idea is this (as a flat battery starter) -> ..and buying a decent powerbank for powerbank jobs.

    As you stand a very good chance of destroying the lipo cells in these things to test max current output, it's typically destructive testing -- if you just want to verify the actual stated storage capacity of the cells (mW/h), then you can do that easy enough, but it's still not going to matter or give you any clue if the things will go thermonuclear when you start pulling 200A+ out of each cell.

    Of course the quality of the lipo cells themselves matter, but I've seen $120 units thru to $400 jobs all die the same death, for exactly the same reason.

    HTH =)

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    heres a thing on the capacitive starter that wotnot has in his link

    有段者

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    i have 2 of the capacitor type, both dead. electronics......

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    Thanks again guys for the great feed back, have gone the laptop battery replacement route
    There is a fine line between "Hobby" and "Madness"

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    i recently replaced my dell battery with a larger one and a dell external power pack which charges the laptop and has 2 x usb charging ports as well.

    all up over 12hours minimum.

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    I use lifepo4 jumper when needed, has proved reliable. Before that used small sla 12v batt-lasted years.

  • 13-07-20, 09:48 PM


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