Lithium Jump Starter Disassembly Is Revealing

March 1, 2019 by Lewin Day 55 Comments

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.

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Jump Start Your Car With A Drill Battery

August 16, 2018 by Lewin Day 99 Comments

Sometimes, you move to a new city, and things just aren’t going your way. You’re out of cash, out of energy, and thanks to your own foolishness, your car’s battery is dead. You need to jump-start the car, but you’re feeling remarkably antisocial, and you don’t know anyone else in town you can call. What do you do?

It’s not a problem, because you’re a hacker and you have a cordless drill in the back seat of your car. The average drill of today tends to run on a nice 18 volt lithium battery pack. These packs are capable of delivering large amounts of current and can take a lot of abuse. This is where they come in handy.

Typically, when jump starting a car, another working vehicle is pulled into place, and the battery connected in parallel with the dead battery of the disabled vehicle. Ideally, the working vehicle is then started to enable its alternator to provide charge to the whole system to avoid draining its own battery. At this point, the disabled vehicle can be started and its alternator can begin to recharge its own battery. After disconnecting everything, you’re good to go.

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Coin Cell Hacks That Won The Coin Cell Challenge

January 15, 2018 by Mike Szczys 22 Comments

It’s amazing what creative projects show up if you give one simple constraint. In this case, we asked what cool things can be done if powered by one coin cell battery and we had about one hundred answers come back. Today we’re happy to announce the winners of the Coin Cell Challenge.

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Coin Cell Challenge: Jump Starting A Car

December 8, 2017 by Tom Nardi 80 Comments

Clearly a believer in the old adage, “Go Big or Go Home”, [Ted Yapo] has decided to do something that seems impossible at first glance: starting his car with a CR2477 battery. He’s done the math and it looks promising, though it’s yet to be seen if the real world will be as accommodating. At the very least, [Ted] found a video by [ElectroBOOM] claiming to have started a car with a super capacitor, so it isn’t completely without precedent.

Doing some research, [Ted] found it takes approximately 2,000 W to 3,000 W at 14 V to start the average car engine. This is obviously far in excess of what a coin cell can put out instantaneously, but the key is in the surprising amount of potential energy stored in one of these batteries. If the cell is rated for 1000 mAh at 3 V, [Ted] shows the math to find the stored energy in Joules:

According to the video by [ElectroBOOM], he was able to start his car with only 6,527 J, and [Ted] calculates it should only take about 9,000 J on the high side from his research. So as long as he can come up with a boost converter that can charge a capacitor with high enough efficiency, this one should be in the bag.

[Ted] has started putting together some early hardware, and has even posted the source code he’s using on a PIC12LF1571 to drive the converter. He notes the current charge efficiency is around half of what’s needed according to his calculations, but he does mention it was an early test and improvements can be made. Will it start? If it does, this is some awesome Heavy Lifting.

Hand Cranked Generator Charges Supercaps, Starts Car

January 4, 2017 by Dan Maloney 82 Comments

Pity the lowly lead-acid battery. A century of use as the go-to method for storing enough electrons to spin the starter motor of a car engine has endeared it to few. Will newer technology supplant that heavy, toxic, and corrosive black box under your hood? If this supercapacitor boost box is any indication, then we’d say lead-acid’s days are numbered.

To be fair, we’ll bet that number is still pretty big. It takes a lot to displace a tried and true technology, especially for something as optimized as the lead-acid battery. But [lasersaber]’s build shows just how far capacitive storage has come from the days when supercaps were relegated to keeping your PC’s clock running. With six commercial 400F caps and a custom-built balance board, the bank takes a charge from a cheap 24V hand generator. The output is either to a heavy-duty lighter socket or some automotive-style lugs, and the whole thing is housed in a simple box partially constructed using energy stored in the bank. Can the supercaps start a car? Stay tuned after the break for the answer.

Although we’ve seen supercaps replace a motorcycle battery before, we’re a little disappointed that the caps used here only have a 1500-hour life – lead-acid wins that fight hands down. But this one gives us lots of ideas for future builds, and we’re heartened by the fact that the supercaps for this build ring up to less than $70.

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How A Hacker Jump Starts A Car

January 31, 2016 by Dan Maloney 73 Comments

Here’s the Scenario: you need to get somewhere in a hurry. The problem is that your car has a dead battery and won’t turn over. The Obvious solution would be to call a friend for a jump. But is the friendless hacker out of luck in such a situation? Not if you can whip up a quick parts bin jump starter.

Clearly, [Kedar Nimbalkar]’s solution would be practical only under somewhat bizarre circumstances, so we’ll concentrate on what we can learn from it. A spare PC power supply provides the electrons – [Kedar]’s 250W supply pushes 15A at 12 volts, which is a pretty respectable amount of current. The voltage is a little anemic, though, so he pops it up to 14.2 volts with a 150W boost converter cooled with a PC fan. A dual panel meter reads out the voltage and current, but a VOM could substitute in a pinch. About the only thing you might not have on hand is a pair of honking 10A diodes to keep current from creeping back into the boost converter. [Kedar] claims he got enough of a charge back in the battery in five minutes to start his car.

As jump-starting goes, this hack is a bit of a stretch. It’s not the first time we’ve seen a MacGyver’d jump starter, though, and you never know when the principles and hardware behind these hacks will come in handy.

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Who Knew Thinkpad Batteries Require A Jump Start?

August 1, 2011 by Mike Szczys 59 Comments

Lithium battery packs reaching the end of their life usually have a lot of kick left in them. That’s because they’re made up of multiple cells and it only takes the failure of one to bork the entire battery. One of the most interesting examples we’ve heard of this is in the Toyota Prius, but that’s a story for another time. In this case, [Mika] wanted to resurrect the battery from his IBM Thinkpad T40. He identified the offending cell and replaced it, but couldn’t get any juice out of the battery after the repair.

He was measuring 0V on the output, but could measure the cells instead of the control circuitry and was getting over 11V. Clearly, the control circuit wasn’t allowing an output. We completely understand the concept here (think about that really bad press about exploding laptop batteries). It seems there’s a lockout mechanism when the control circuit loses power. [Mika] managed to get past this by shorting voltage into the control circuit, a method he likes in the video after the break to jump starting a car.

We’ve seen similar cell replacement for power tools, like a Dremel or a Makita drill.

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