Turn Off Those Batteries With Their Protection Chip

It should be a feature of every device powered by a lithium-ion battery, that it has a protection chip on board that automatically disconnects it should it go out of its safe voltage range. A chip most often used for this purpose in single-cell applications is the Fortune Semiconductor DW01, and [Oliver] shares a tip for using this chip to power down the battery. The DW01 has a CS, or current sense pin, which if taken high momentarily will put the chip into an off state until the battery is disconnected.

Looking at the DW01 datasheet we can see that this would work, but we can’t help having a few questions. The CS pin is a safety sensor pin, providing over current, short circuit, and reverse polarity detection. It’s the kind of pin one might mess with only when one is absolutely certain it’s not likely to trigger a dangerous fault condition, so a bit of care should be required. However, we can see that leaving its resistor in place and supplying it a momentary logic level through another resistor should work. We’d be interested in the views of any readers with more experience in the world of lithium battery protection on this hack.

Meanwhile, a good read for any reader should be our look last year at lithium-ion safety.

Lessons In Li-Ion Safety

If you came here from an internet search because your battery just blew up and you don’t know how to put out the fire, then use a regular fire extinguisher if it’s plugged in to an outlet, or a fire extinguisher or water if it is not plugged in. Get out if there is a lot of smoke. For everyone else, keep reading.

I recently developed a product that used three 18650 cells. This battery pack had its own overvoltage, undervoltage, and overcurrent protection circuitry. On top of that my design incorporated a PTC fuse, and on top of that I had a current sensing circuit monitored by the microcontroller that controlled the board. When it comes to Li-Ion batteries, you don’t want to mess around. They pack a lot of energy, and if something goes wrong, they can experience thermal runaway, which is another word for blowing up and spreading fire and toxic gasses all over. So how do you take care of them, and what do you do when things go poorly?

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Better Battery Management Through Chemistry

The lead-acid rechargeable battery is a not-quite-modern marvel. Super reliable and easy to use, charging it is just a matter of applying a fixed voltage to it and waiting a while; eventually the battery is charged and stays topped off, and that’s it. Their ease is countered by their size, weight, energy density, and toxic materials.

The lithium battery is the new hotness, but their high energy density means a pretty small package that can get very angry and dangerous when mishandled. Academics have been searching for safer batteries, better charge management systems, and longer lasting battery formulations that can be recharged thousands of times, and a recent publication is generating a lot of excitement about it.

Consider the requirements for a battery cell in an electric car:

  • High energy density (Lots of power stored in a small size)
  • Quick charge ability
  • High discharge ability
  • MANY recharge cycles
  • Low self-discharge
  • Safe

Lithium ion batteries are the best option we have right now, but there are a variety of Li-ion chemistries, and depending on the expected use and balancing and charging, different chemistries can be optimized for different performance characteristics. There’s no perfect battery yet, and conflicting requirements mean that the battery market will likely always have some options.

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Electric Drift Trike Needs Water Cooling

Electric vehicles of all types are quickly hitting the market as people realize how inexpensive they can be to operate compared to traditional modes of transportation. From cars and trucks, to smaller vehicles such as bicycles and even electric boats, there’s a lot to be said for simplicity, ease of use, and efficiency. But sometimes we need a little bit more out of our electric vehicles than the obvious benefits they come with. Enter the electric drift trike, an electric vehicle built solely for the enjoyment of high torque electric motors.

This tricycle is built with some serious power behind it. [austiwawa] constructed his own 48V 18Ah battery with lithium ion cells and initially put a hub motor on the front wheel of the trike. When commenters complained that he could do better, he scrapped the front hub motor for a 1500W brushless water-cooled DC motor driving the rear wheels. To put that in perspective, electric bikes in Europe are typically capped at 250W and in the US at 750W. With that much power available, this trike can do some serious drifting, and has a top speed of nearly 50 kph. [austiwawa] did blow out a large number of motor controllers, but was finally able to obtain a beefier one which could handle the intense power requirements of this tricycle.

Be sure to check out the video below to see the trike being test driven. The build video is also worth a view for the attention to detail and high quality of this build. If you want to build your own but don’t want to build something this menacing, we have also seen electric bikes that are small enough to ride down hallways in various buildings, but still fast enough to retain an appropriate level of danger.

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Non-Newtonian Batteries

Batteries placed in harm’s way need to be protected. A battery placed where a breakdown could endanger a life needs to be protected. Lithium-ion batteries on the bottoms of electric cars are subject to accidental damage and they are bathed in flame-retardant epoxy inside a metal sled. Phone batteries are hidden behind something that will shatter or snap before the battery suffers and warrant inspection. Hoverboard batteries are placed behind cheap plastic, and we have all seen how well that works. Batteries contain chemicals with a high density of energy, so the less exploding they do, the better.

Researchers at Oak Ridge National Laboratory have added a new ingredient to batteries that makes them armored but from the inside. The ingredient is silica spheres so fine it is safe to call it powder. The effect of this dust is that the electrolyte in every battery will harden like cornstarch/water then go right back to being a liquid. This non-Newtonian fluid works on the principal principle of shear-thickening which, in this case, says that the suspension will become harder as shear force is applied. So, batteries get rock hard when struck, then go back to being batteries when it is safe.

Non-Newtonian fluids are much fun, but we’re also happy to see them put to use. The same principle works in special speed bumps to allow safe drivers to continue driving but jolts speeders. Micromachines can swim in non-Newtonian fluids better than water in some cases.

Electric Bike From The Ground Up

Electric vehicles are getting more traction these days, but this trend is rolling towards us in more ways than just passenger vehicles. More and more bikes are being electrified too, since the cost of batteries has come down and people realize that they can get around town easily without having to pay the exorbitant price to own, fuel, and maintain a car. Of course there are turnkey ebikes, but those don’t interest us much around here. This ebike from [Andy] is a master class in how to build your own ebike.

Due to some health issues, [Andy] needed a little bit of assistance from an electric motor on his bike, but found out that the one he wanted wouldn’t fit his current bike quite right. He bought a frame from eBay with the right dimensions and assembled the bike from scratch. Not only that, but when it was time to put the battery together he sourced individual 18650 cells and built a custom battery for the bike. His build goes into great detail on how to do all of these things, so even if you need a lithium battery for another project this build might be worth a read.

If you’ve never been on an electric bike before, they’re a lot of fun to ride. They’re also extremely economical, and a good project too if you’re looking for an excuse to go buy a kit and get to work. You can get creative with the drivetrain too if you’d like to do something out of the box, such as this bike that was powered by AA batteries and a supercapacitor.

Getting The Lead Out Of Lithium Battery Recycling

When that fateful morning comes that your car no longer roars to life with a quick twist of the key, but rather groans its displeasure at the sad state of your ride’s electrical system, your course is clear: you need a new battery. Whether you do it yourself or – perish the thought – farm out the job to someone else, the end result is the same. You get a spanking new lead-acid battery, and the old one is whisked away to be ground up and turned into a new battery in a nearly perfect closed loop system.

Contrast this to what happens to the battery in your laptop when it finally gives up the ghost. Some of us will pop the pack open, find the likely one bad cell, and either fix the pack or repurpose the good cells. But most dead lithium-based battery packs are dropped in the regular trash, or placed in blue recycling bins with the best of intentions but generally end up in the landfill anyway.

Why the difference between lead and lithium batteries? What about these two seemingly similar technologies dictates why one battery can have 98% of its material recycled, while the other is cheaper to just toss? And what are the implications down the road, when battery packs from electric vehicles start to enter the waste stream in bulk?

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