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Thread: O.T. Starting A Truck Wih A Cordless Tool Battery

  1. #1
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    Default O.T. Starting A Truck Wih A Cordless Tool Battery

    Was out for a while this morning helping buddy fix some fencing as he has cattle on open range and he needed a hand up there for the repairs. We had it all done in short order and while walking back to the truck we could see that he'd left his headlights on, and they looked dim when we got back to it.
    Turned them off right away and give the battery some time to rest hoping it would come back a bit.

    Click click click, was all we heard when trying to start the truck. No cell service in the draw we were in and it appeared a long walk was going to be in order to get us out of there.

    Just then I thought to myself, sure would be handy to have one of those li-ion jump starters. Also remembered that I had my 18V Milwaukee sawzall with us with almost a full battery. I found some 10ga. wire in buddy's toolbox and thought we've got nothing to loose but a long walk, let's give it a whirl.

    Hooked my battery up to his, waited about 30 seconds to a minute and his truck flashed right up as if nothing had ever gone wrong. Yay!!!

    Always wanted to get one of those jump starters, now I have one.
    Obviously I didn't have a voltmeter with me and it would have been interesting to see what the system voltage was but I doubt very much that it would have been excessive due to the load placed on the little 18V battery from the almost flat 12V battery.
    The truck was a fairly late model unit with all the electronics still happily functional so not sure if we dodged a bullet or not, the VOM would have helped clarify this while jumping.

    Looking up some specs after we got home and I see the M18 battery I was using is rated @ 90whr while a Noco GB40 jump starter is rated @ 24whr. Not sure what their output voltage is though.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  2. #2
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    Not actually surprising, it takes less than 2 AH to start a vehicle even with high current and 15 sec of cranking, which seems like forever if you do it.

    Nice save, and good out of box thinking!

    EDIT: Hardest thing with some of those battery packs is figuring out which unlabeled prong is positive. That can be an issue.
    Last edited by J Tiers; 10-09-2019 at 06:00 PM.
    1601

    Keep eye on ball.
    Hashim Khan

  3. #3
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    May 2006
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    I like it --- I don't think you hurt a thing due to the massive truck battery being a voltage buffer cuz it was down some,,,

    a little thinking can go a long way, reminds me of when this girls vehicle would not start due to a dead battery, and it was parked head first into a place facing downhill and no room to tow her back out - jumpers would not reach, but this was back in the day of steel bumpers,,, so I strip my positive and negative cables into two long single cables (you know how their melded together in the middle) connect the neg to pos and have one long cable - pull my bumper up to contact hers, connect pos to pos under the hoods - wait a few minutes and off she goes...

    sometimes you got to think outside the box.

  4. #4
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    Thats a pretty dangerous thing, putting positive current through a negative cable, at the least you could have set both vehicles on fire or at the worst triggered the melt down of the entire universe.

  5. #5
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    Quote Originally Posted by The Artful Bodger View Post
    Thats a pretty dangerous thing, putting positive current through a negative cable, at the least you could have set both vehicles on fire or at the worst triggered the melt down of the entire universe.
    Ahhh. . . bull-pucky! Sparks, smoke, spattering lead - - maybe. Fire... not unless you want it. Some people never do anything because.... what if? Always a naysayer somewhere.

    As for me, Willy, amazing save! I never would have thought of it. Now, if needed, I will. Thanks.

  6. #6
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    Quote Originally Posted by J Tiers View Post

    EDIT: Hardest thing with some of those battery packs is figuring out which unlabeled prong is positive. That can be an issue.
    This! I also tried to determine this also and am not sure if I ever did. How do you do it? VOM right? What is the reference? The meter. JR
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  7. #7
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    Quote Originally Posted by JRouche View Post
    This! I also tried to determine this also and am not sure if I ever did. How do you do it? VOM right? What is the reference? The meter. JR
    You can often find a valid reading between the outside terminals. If not, check the voltage from 1 to 2, then 1 to 3, then 1 to 4 and so on till you find a voltage close to what you expect


    To figure out polarity... The meter commonly has one probe plugged into a jack labeled "common" or sometimes "com-". This is for the negative. There is another labeled all sorts of things. Often it's labeled "V/OHM/MA". That's the positive lead.

    Put in 20 volt range. connect both probes to the battery terminals. If neg probe is on the negative terminal the voltage will read close to what you expect. If the neg probe is on the positive terminal the voltage will have a minus sign in front of the voltge.

    With an alalog meter the probes are the same. If connected properly the needle will swing across the meter. If reversed, the needle will dive away from the scale, often hitting the stop. If using an analog meter try a scale for a voltage way beyond what you expect to avoid damaging the needle (hitting the stop). For example use 200 volt setting for a 12 volt battery.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

  8. #8
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    Quote Originally Posted by JRouche View Post
    This! I also tried to determine this also and am not sure if I ever did. How do you do it? VOM right? What is the reference? The meter. JR
    IF YOU HAVE THE METER WITH YOU, then no issue.
    1601

    Keep eye on ball.
    Hashim Khan

  9. #9
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    That's a good trick. I'll have to remember it. Slightly off center... Many hybrids use a 12 volt system to run headlights, turn signals and brake boost systems. In Toyotas, the 12 volts is extracted from the 300 volt battery pack. When you start the car, however, the computer that regulates the 200v to 12 volt inverter has to boot off a small 12 volt battery. Once that inverter is running the 12 volt battery is not needed.

    There are instructions for starting your Prius from a 9 volt smoke alarm battery if the 12 volt battery is dead. You hook it up just long enough to get the 12 volt inverter running and then put the 12 volt battery fuse back in so it can charge.
    At the end of the project, there is a profound difference between spare parts and extra parts.

  10. #10
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    Quote Originally Posted by The Artful Bodger View Post
    Thats a pretty dangerous thing, putting positive current through a negative cable, at the least you could have set both vehicles on fire or at the worst triggered the melt down of the entire universe.
    YES! BE CAREFUL! That, according to reliable scientific research, is what led to the Big Bang!

    -js
    There are no stupid questions. But there are lots of stupid answers. This is the internet.

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