Jump start EV with power tool or AA batteries? Possible?

Discussion in 'General' started by Gsbrryprk8, Apr 19, 2020.

  1. Gsbrryprk8

    Gsbrryprk8 Member

    Does anyone know how many amps an EV draws from its 12V battery when starting?

    If I understand correctly, the car uses its 12V battery at starting just to open relays and switches for the traction battery. I don’t see why it would need 300+ Amps to do this, though I’m not an electric engineer.

    I’ve seen Mehdi Sadaghdar’s video where he trickle charges his dead car battery with AAs in series. I’m wondering if, in a pinch, I could actually *start* my Kona with a 12V power tool battery or a bank of 9 1.5V AA batteries in series (13.5V)? They deliver far less current than a dedicated jump starter, but would it be enough?

    Sent from my iPhone using Inside EVs
  2. It would probably work.
    Don't try by disconnecting the battery and putting the AAs in because the car will probably try to charge it, and that could be bad!?
  3. bwilson4web

    bwilson4web Well-Known Member Subscriber

    More than a few Prius are running around with lawn mower batteries. Cheap yet good enough to work.

    Bob Wilson
  4. Gsbrryprk8

    Gsbrryprk8 Member

    If so, it seems like there’d be a (growing) market for a made-for-EV portable jump starter, smaller than the current crop of portable jumpers out there.

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  5. BlueKonaEV

    BlueKonaEV Well-Known Member

    interestedinEV likes this.
  6. interestedinEV

    interestedinEV Well-Known Member

    That SNL. If you are willing to pay for it, you can get full size drivable Bugatti with just single 80 V Battery with a 12 V car battery for steering. :D

    (Spoiler alert, has a top speed of 19 miles, is made of all most completely of Lego bricks and parts, does not have an accelerator, includes 2304 Lego motors, with Lego Gears etc.) They could have packed it with AA batteries and made it work/

    BlueKonaEV likes this.
  7. The Kona needs around 9 amps once settled down. However, if you have a partly-dead 12V battery in the circuit as well, you can add at least 30+ more amps.
    Well, noting that "trickle charging" a 12V battery is a different question, if you are willing to disconnect the "dead" battery you could probably use a small 12V 7Ah lead-acid battery to get the Kona started, then reconnect the dead battery and disconnect the small battery. You would find such a battery in an alarm system or small UPS.
    LDC, 0.25 sec logs over 27 min.PNG
    In the graph the green line, LDC current settles down to just supporting the Kona after it's finished charging the aux battery, about 9 amps.
  8. Gsbrryprk8

    Gsbrryprk8 Member

    Thanks, kiwiME, that’s the kind of info I was looking for. Except that I’m not sure how to interpret it.

    What do you mean it needs 9 Amps once settled down? Is that the draw on the 12v battery after the car is started? I only want to know what it needs from the 12v to start the car. Essentially, what’s the smallest battery I could use to start an EV in a pinch.

    Sent from my iPhone using Inside EVs
  9. bwilson4web

    bwilson4web Well-Known Member Subscriber

    In theory, I would combine ultra-caps with rechargeable batteries and a solar tickle charger. The ultra-caps provide the inrush amp power and run power for the minute or so it takes to get it running. The solar tickle cells build up the power over time to have enough energy for a 'start' into a nearly dead 12V battery. Then drive directly to where you can get a replacement.

    Bob Wilson

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