Lithium Jump Starter Disassembly Is Revealing

High-capacity lithium batteries tend to make everything in life better. No longer must you interact with your fellow human beings if your car battery goes flat in the carpark. You can jump the car yourself, with a compact device that fits in your glovebox. [Big Clive] decided to pull one apart and peek inside, and it’s quite the illuminating experience.

The first thing to note is there is almost no protection at all for the lithium battery inside. The output leads connect the lithium pack inside directly to the car battery, save for some diodes in series to prevent the car’s alternator backcharging the pack. [Clive] demonstrates this by short circuiting the pack, using a copper pipe as a test load to measure the current output. The pack briefly delivers 500 amps before the battery gives up the ghost, with one of the cells swelling up and releasing the magic smoke.

The teardown then continues, with [Clive] gingerly peeling back the layers of insulation around the cells, getting right down to the conductive plates inside. It’s a tough watch, but thankfully nothing explodes and [Clive]’s person remains intact. If you’ve never seen inside a lithium cell before, this is a real treat. The opened pack is even connected to a multimeter and squeezed to show the effect of the physical structure on output.

It would be interesting to compare various brands of jump starter; we imagine some have more protection than others. Regardless, be aware that many on the market won’t save you from yourself. Be careful out there, and consider jumping your car with an even more dangerous method instead (but don’t). Video after the break.


54 thoughts on “Lithium Jump Starter Disassembly Is Revealing

  1. I’ve used(tried) to use something similar once. It blew up in the same moment i turned the key in the ignition to start. Lesson learned! Now i have a lead acid jump starter as backup, and probably will for a very long time.

    1. With PbA batteries, there’s a significant effect that makes the battery act like a capacitor. It holds some “top” charge that turns the engine a few times and then the current dies down. This is something around 1% of the actual capacity of the battery, so you can get away with connecting just about any ~14-15 volt source to the battery to charge it up a little, wait 60 seconds, and then start.

      That’s basically how these jump starters work. They don’t provide much current in and of themselves.

      1. This is what everyone is missing here, the purpose is to get your battery up to cranking capacity, not to be the battery itself. Yes it will provide some support current but the primary Pb battery is supposed to still be primary

  2. BigClive is an idiot. “I wonder what kind of protection there is”. Of course there is none! The lithium cells are say 3Ah and hopefully 40C so can safely handle about 120A. Starting a car is a 200-300A nominal business. So where do you put your current limit? Set the limit at 120A and the car won’t start. Set the limit at 200 and some cars will start. Set the limit at 300A and you don’t get any protection. What’s the use?
    Then implementation. Say your current limit and/or over-discharge circuit has a 2mOhm resistance. You’ll be getting 400mV or 80W of heat in the circuit. Where are you going to leave that waste heat?
    When it’s fully charged, there is about 11V * 3Ah or about 120kJ of energy in the system. If you short circuit that, where is that energy going to go? I’ll tell you the answer: Into heat inside the system. The system will heat up and catch fire.

    Can someone send this guy a fuel tank with petrol. I wonder what he’ll do with that!

    1. 40C? That’s with cheapest drone batteries. Some of them can even do 120C continous current. And starting a car easily falls into “short duration” overcurrent, so I wouldn’t be surprised if you could draw 200C for starting your car. 200C*3Ah is 600A.

      As for being an idiot, he is not, he just didn’t know what kind of currents small lion batteries can nowadays provide. I’m still amazed at what can be done and plan on doing a railgun with them. 1kA was REALLY hard to get several years ago, now you can do it with 2 small batteries instead of large bank of capacitors in car trunk.

      1. LiPOs can supply mad currents. High energy density Li-Ions are still limited to around 5-10 C discharge current. The higher the energy density, the lower the discharge current – hence why Tesla batteries can’t be supercharged in 5 minutes even if you had the power.

    2. BigClive is not an idiot. you are correct on the power analysis. The point here is if this device cannot be made safe (and reliable) it should not be allowed to be sold at all. It will cost more but it’s not hard to implement a relay, thermal measurement and multiple fail safes. But as you can imagine cheaper is better in the eye of the consumers.

      I’ve bought many dangerous things but this one is not getting trough the door.

      1. This might work satisfactorily in one fringe scenario – jumpstarting Electric Vehicles or Hybrids, which usually depend on a smaller 12V lead-acid batt whose only purpose is energizing the contactors & computer electronics to get the HVB->12V DC/DC converter started before you can disconnect. All engine starting happens via high-voltage battery. Dead EVs and HEV/PHEVs are a known thing with some brands (Ford…) due solely to the 12V lead-acid battery, and BTW the EV charge port is dead too (contactors & computers not operating correctly) so you can’t “jump” them with an EV charger.

    3. Other than over current, even these lipos should still have over and under voltage protection lest they go below the safe operating voltage or overcharge and swell like a balloon.

    4. It’s simple. You don’t use a current limit because this device is not an electronic circuit that can be regulated. It is a fixed device that produces 12v and a fixed number of amps. You install a circuit breaker that is designed to trip a bit beyond the rated current output. You have the breaker inside the unit with a reset button on the outside.

    1. Clive’s a qualified electrician. And PROPER qualified too! From back in the day, not the cornflakes-packet qualifications they give out nowadays. Apparently. I only know what I’ve heard Clive ranting about it, but back then you had to apprentice and take proper exams. Now it’s just a dozen silly questions about which way round to put a plug in. Some sort of scam based around the assessment or awarding agency being privatised and now just purely out for money. You pass the qualification as soon as your cheque clears.

  3. I have a set of jump leads. Proper ones. Not bought in a supermarket, or cheapo outlet for $10 but a good set with long cables and thick, good quality clamps and well crimped.
    I’ve used them by asking people for a jump and I’ve helped people out by jumping them.

    I find this an interesting product.
    It seems entirely self serving.
    “I’ll look after myself than asking for help.”
    Is this what people do now?

    Best way to jump a car is with a running car, or a large battery, but ideally a large battery with a motor running and charging it. I dont imagine you get much longevity with one of these. Good luck clearing out an air lock on the fuel line.

    1. -cars in places you can’t get another car
      -avoids damage risk to my $30k electrical network while giving/receiving help to another car in an unknown state
      -rural places require self rescue
      -personal experience shows these packs (mid sized) actually work as well or better than high quality jumpers

    2. In what way is it more self serving than you having your high quality jumper cables?
      It doesn’t stop you from offering assistance to others, it doesn’t demand you taking someone else’s time and potentially risking damage to their vehicles. It also doesn’t stop you from having high quality jumper cables.

    3. The only time I have used my jumpstarters we’re to help other people. Never had to use it on my own car. calling something self-serving seems very narrow-minded and a lack of creativity on how to use a product.

      1. Narrow minded quite possibly.
        I dont see the need to be running around with a spare battery pack with a limited life span and questionable recycling practises.
        Verses a set of jumpers made from steel and copper with a bit of insulation that will last decades (and have done)

        But you know, all for progress.

        1. These things are Lifesavers when you’re out of town. They can fit in a backpack so they can be used on motorcycles, and they can jump start them dozens of times on a charge. I’ve used them for myself or others many many times on dirt bike trips through the desert, because I’m not going to get a jump start when I’m 30 miles from the nearest road.

    4. I have self-made cables, 4 strands of 10ga copper wire for each side, with good clamps on them. along with the “big three” upgrade on my cars I’ve never failed to start anything that had air fuel and spark.

      I use my lion jump box constantly. best spent $35 in my toolkit. no it won’t start a completely dead battery on a 5.7l v8, but in most situations (read: lights work but engine doesn’t turn over) it works great.

    5. Mate, have you met the public? They’re TERRIFIED of each other! Interacting with another human being freaks them right out, spine turns to jelly and eyes fix forward, staring and blinking.

      In London it’s much worse, to the point of paranoia. I think most Londoners would rather be stabbed in a nice private dark alley, than have someone talk to them on the Tube. Is New York as bad, or Mumbai, or Rio, or other big cities around the world?

      Fortunately the Northern English are reasonably friendly and sensible people. Southerners though, if you don’t have a socially acceptable reason from The List to talk to someone, they don’t like it.

      This also seems to tie in with patterns of voting Conservative, for some reason.

  4. Really surprising there haven’t been news reports or recalls of these devices. Most of the times I’ve been involved with jumpstarting, either my own or someone else, usually takes more than one attempt. You hook up the cables, let the dead battery charge a while, then turn the key, with fingers crossed. Sometimes you get lucky, sometimes you wait, and try again. Sometimes it something more than a dead battery, and you eventual give up.

    These glove box jump starters seem to be a one shot deal, but I think most people will keep trying, until completely drained. Just like they did, with their car battery, until it was to dead to give more than a ‘click’. These just seem prime for a fire, least occasionally. Jumper cables are the better gift, since if you need them, you have to find someone willing to help, takes time, little inconvenient and embarrassing. Great motivation to take better care of your car, and not neglect or abuse your battery.

    I guess we won’t have to worry much about these things for too long, since we won’t be using internal combustion, once the ‘Green New Deal’ gets pushed into law, like ObamaCare. Vast majority of us drivers, will be walking, riding bikes, and mass transit, since the demand for electric cars will greatly exceed the supply and capacity to produce them. Even if you could afford one, you’d have to wait a while to get one. Hopefully, there will be generous subsidies, like health care…

    1. >Vast majority of us drivers, will be walking, riding bikes, and mass transit, since the demand for electric cars will greatly exceed the supply and capacity to produce them.

      This results in less emission, more exercise and might eventually force city planners to rethink their car-centric design. :P

    1. Worked great for my 2008 Miata which had a completely dead battery after several months of sitting in a garage. 4cyl 170HP engine so pretty typical of an average car. Had plenty left after three starts as it took me a couple attempts to keep it from stalling out as it needed help holding idle.

    2. A summer or two ago, I helped a young man get his mini-van started.
      It was an older vehicle prone to breakdowns.
      He carried some kind of booster pack in the vehicle.
      It wasn’t able to get it started that day, and jumper cables to my vehicle didn’t work either.
      At least, not until I shaved the insides of his battery connectors with a knife.

    3. Microstart xd-10 300a continuous 600a peak will start a completely dead Ford v10 school bus a couple times on a charge. The Cummins diesels only if they are low. Pretty impressive to me.

  5. Sure, it failed, but at 500 amps. It’s not something you will use for much except a sort-of one-off emergency use.
    I have one for my motorbike, a HP2 Enduro. It doesn’t have the world’s biggest battery, and if it gets drained, say trying to start it. Or else the lights stayed on for a bit, then I know i have this. Very handy in a remote place.

    I took my own apart because I was curious how it could supply so much current.

  6. Uh Uh. Nope!

    You can run the numbers on the battery pack’s A/H rating and talk about protection or lack of all you want.

    All I need to know is that this thing is only about the size of a human hand and yet it holds enough energy to start a car. Clearly this is not something that should be banging around neglected in a car’s glove box or baking in that car on a hot summer’s day.

  7. I just spit my tea at the authors statement:
    “High-capacity lithium batteries tend to make everything in life better. No longer must you interact with your fellow human beings if your car battery goes flat in the carpark. ”

    Life is better if you don’t have to interact with humans! There are times I agree with this fully. Seems the word is getting out.
    This device seems a minor reduction in human interaction, at best, however. There are other more effective way to avoid those nasty creatures.

    Do I need some kind of s tag for this post?

    1. “This device seems a minor reduction in human interaction, at best, however. There are other more effective way to avoid those nasty creatures.”

      Telecommuting, online shopping, VR, not bathing. The problem’s being worked on.

  8. What the heck is wrong with you people claiming that jumping two cars together can cause damage to either of one? NO it won’t if done properly (i.e., do not connect the + to the – and vice-versa, duh!).

    1. in an autospark. I hate to say it’s very common for cars to get trashed when jumpstarting, especially if the battery is absolutely stone dead so internal resistance is high, and they are a bit to keen to try start it before the battery gets some juice. the transient spikes and brown-outs kill ECUs quick fast in a hurry. usually corrupting an eeprom or 2. BMW’s “from”failures on e90s being a classic example

    2. Jumping a car with another car is not a cut and dry procedure that anybody can perform equally well,that’s what the engineer designed the keyed ignition for,if no engineer has put thought into ensuring that any stupid ass can jump a car without damaging it then lost of stupid asses will damage a car doing it

  9. I wonder why I can’t just replace my car battery with two or more motorbike Li-ion 12V packs?
    Plus loads lighter and though expen$ive putting two in parallel should decrease the strain.
    Looks like the cheapest units are about £160 each but less if used, ie from scrappers.
    I can afford a £30 bribe paid in cash to a scrap yard operative!

    1. Because most cars don’t have over voltage or proper charge controllers, and use the Lead Acid battery as a buffer. Overcharge a motorcycle battery sized Li-ion battery, and at a minimum your hood will have a new hole in it, change in the paint quality, or a new flame job. :)

  10. I have a lithium ion jump starter with “BoltPower” circuit board that appears to be dead from sitting on the shelf too long.
    Is there a way to revive it?

  11. I was concerned about protection when I bought my Noco charger. According to the supplied User Documentation it has some sensing circuit that (from my notoriously bad memory) detects the correct connection of a knackered lead-acid battery and only then removes the current limiter. I like that, a lot.

    However . . . I ended up on this blog trying to understand how the charger even manages to supply such a large current through such (subjectively) skinny leads. It took a lot of convincing to persuade me that these small batteries would even turn my 3.0L Diesel engine over, I still don’t see how they do (but they certainly do)

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