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.

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.

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.

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

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.

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.

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.

It can safely handle 120A and a car is normally 200-300? From what you’re saying, the pack is under designed for the usage profile.

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.

That and as demonstrated by HaD, we don’t like being treated like children, so no warnings, or safeties. We like our danger.

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.

If your LEAF is flashing its middle blue light then it’s charging its 12V battery from the traction pack.

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.

It probably happened and nature took its way to eliminate idiots – no new dangerous videos anymore …

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.

-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

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.

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.

Narrow minded quite possibly. Meh. 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)

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.

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.

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…

>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

I have always wondered if these tiny jump starter packs really work. Do they actually work? Can they only work on cars that are just barely dead but don;t work on fully dead batteries?

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.

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.

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.

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.

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.

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

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!).

Well, the tow truck operator managed to ruin the $2400 ECU in my wife’s Subaru when he tried to jump start it…

Yeah. 24V and 12V don’t mix well. It’s been seem numerous times that someone tries that. It goes well on old cars, new ones, not so much.

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

12v Battery Powered Kids Toy Children Car

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!

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. :)

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