One ESP8266, One Battery, One Year… And Counting.

January 15, 2020 by Jenny List 24 Comments

There are times when a sensor is required that does its job without the need for human attention over a long period, and for those applications a minimal power drain is a must. [Dave Davenport] had an EPS8266-based moisture sensor, and became disappointed in having to replace its AA batteries every few months. With an 18650 Li-ion cell and a bunch of power-saving tricks that time has been extended so far to over a year and still going, so he’s written a blog post detailing how he did it.

Some of his techniques such as turning off the sensor or using a better LDO regulator than the stock Wemos one are straightforward. Others though are unexpected, such as using the memory associated with the on-board RTC to store the WiFi connection info and channel number during sleep. The normal ESP8266 connection sequence involves a network scan, by hanging onto what it found last time the extra time and thus power expended by it can be avoided. Similarly switching from a DHCP lease to a fixed IP address cuts the time the device waits for a lease and thus the time it has to stay awake.

We might not all have ESP8266 moisture sensors to build, but we’re many of us on a quest to sip less power in our projects. Let us help you with a previous sojourn into that arena.

ESP8266 image: connorgoodwolf [CC BY-SA 4.0].

Model S Motor And Volt Battery Go Together Like Peanut Butter And Jelly

January 13, 2020 by Roger Cheng 55 Comments

A common project category on this site is “put a Raspberry Pi in it”. For people who wrench on their cars, a similarly popular project is the “LS Swap”. Over the past few years, the world of electronics and automotive hacking started to converge in the form of electric car conversions, and [Jalopnik] proclaims the electric counterpart to “LS Swap” is to put a Telsa Model S motor and a Chevy Volt battery into a project car.

The General Motors LS engine lineup is popular with petro heads for basically the same reasons Raspberry Pi are popular with the digital minded. They are both compact, very powerful for the money, have a large body of existing projects to learn from, and an equally large ecosystem of accessories to help turn ideas into reality. So if someone desired more power than is practical from a car’s original engine, the obvious next step is to swap it out for an LS.

Things may not be quite as obvious in the electric world, but that’s changing. Tesla Model S and Chevrolet Volt have been produced in volume long enough for components to show up at salvage yards. And while not up to the levels of LS swaps or Pi mods, there’s a decent sized body of knowledge for powerful garage-built electric cars thanks to pioneers like [Jim Belosic] and a budding industry catering to those who want to build their own. While the decision to use Tesla’s powerful motor is fairly obvious, the choice of Volt battery may be surprising. It’s a matter of using the right tool for the job: most of these projects are not concerned about long range offered by Tesla’s battery. A Volt battery pack costs less while still delivering enough peak power, and as it was originally developed to fit into an existing chassis, its smaller size also benefits garage tinkerers fitting it into project cars.

While Pi SBCs and LS engines are likely to dominate their respective fields for the foreseeable future, the quickly growing and evolving world of electric vehicles means this winning combo of today are likely to be replaced by some other combination in the future. But even though the parts may change, the spirit of hacking will not.

[Photo: by Jim Belosic of motor used in his Teslonda project]

Hackaday Podcast 049: Tiny Machine Learning, Basement Battery Bonanza, And Does This Uranium Feel Hot?

January 10, 2020 by Mike Szczys 3 Comments

Hackaday editors Mike Szczys and Elliot Williams sort through all of the hacks to find the most interesting hardware projects you may have missed this week. Did you know you can use machine learning without a neural network? Here’s a project that does that on an ATtiny85. We also wrap our minds around a 3D-printed press brake, look at power-saving features of the ESP32 that make it better on a battery, and discuss the IoT coffee maker hack that’s so good it could be a stock feature. Plus we dive into naturally occurring nuclear reactors and admire the common, yet marvelous, bar code.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

Continue reading “Hackaday Podcast 049: Tiny Machine Learning, Basement Battery Bonanza, And Does This Uranium Feel Hot?” →

Choosing The Right Battery For Your Electric Vehicle Build

January 7, 2020 by Lewin Day 43 Comments

Many a hacker has looked at their scooter, bike, or skateboard, and decided that it would be even better if only it had a motor on it. Setting out to electrify one’s personal transport can be an exciting and productive journey, and one that promises to teach many lessons about mechanical and electronic engineering. Fundamentally, the key to any build is the battery, which has the utmost say in terms of your vehicle’s performance and range. To help out, we’ve prepared a useful guide on selecting the right battery for your needs.

One Chemistry To Rule Them All

Batteries come in all shapes and sizes, and a variety of different chemistries that all have their own unique properties and applications. When it comes to small electric vehicles, it’s desirable to have a battery with a low weight, compact size, plenty of current delivery for quick acceleration, and high capacity for long range.

30 years ago, options were limited to lead acid, nickel cadmium, and nickel metal hydride batteries. These were heavy, with low current output, poor capacity, and incredibly slow charge times. Thankfully, lithium polymer batteries have come along in the meantime and are more capable across the board. Offering huge discharge rates, fast charging, light weight and high capacity, they’re undeniably the ultimate choice for a high performance electric vehicle. They’re also wildly popular, and thus cheap, too!

There are some hangups, however. It’s important to keep all the cells in a pack at the same voltage in order to avoid cells back-charging each other. This can cause damage to the pack, or even explosions or fire. Maintaining the battery voltages to avoid this is called “balancing”. It can be handled in various ways, depending on the exact style of battery you’re using, as we’ll cover later.

Additionally, lithium batteries do not like being over-discharged. As a rule of thumb, it’s a good idea not to let your batteries drop below 3.0 V per cell. Failure to keep this in check can lead to ruining a pack, hurting its maximum capacity and ability to deliver current.

There are thankfully ways around these issues, and which ones you use depends on the battery you choose for your application. Continue reading “Choosing The Right Battery For Your Electric Vehicle Build” →

The Hornsdale Power Reserve And What It Means For Grid Battery Storage

December 16, 2019 by Lewin Day 130 Comments

Renewable energy has long been touted as a major requirement in the fight to stave off the world’s growing climate emergency. Governments have been slow to act, but prices continue to come down and the case for renewables grows stronger by the day.

However, renewables have always struggled around the issue of availability. Solar power only works when the sun is shining, and wind generators only when the wind is blowing. The obvious solution is to create some kind of large, grid-connected battery to store excess energy in off-peak periods, and use it to prop up the grid when renewable outputs are low. These days, that’s actually a viable idea, as South Australia proved in 2017.

Continue reading “The Hornsdale Power Reserve And What It Means For Grid Battery Storage” →

A Modular System For Building Heavy Duty 18650 Battery Packs

December 13, 2019 by Tom Nardi 42 Comments

With 18650 cells as cheap and plentiful as they are, you’d think building your own custom battery packs would be simple. Unfortunately, soldering the cells is tricky, and not everyone is willing to invest in a spot welding setup just to put the tabs on them. Of course that’s only half the battle, you’ll still want some battery protection and management onboard to protect the cells.

The lack of a good open source system for pulling all this together is why [Timothy Economu] created DKblock. Developed over the last three years, his open source system allows users to assemble large 18650 battery packs for electric vehicles or home energy storage, complete with integrated intelligent management and protection systems. Perhaps best of all there’s no welding required, the packs simply get bolted together.

Each block of batteries is assembled using screws and standoffs in conjunction with ABS plastic cell holders. A PCB is placed on each side of the stack, and with tabs not unlike what you’d see in a traditional battery compartment, all the cells get connected without having to solder or weld anything to them. This allows for the rapid assembly of battery packs from 7.2 VDC all the way up to 150 VDC , and means individual cells can easily be checked and replaced in the future should the need arise.

For monitoring the cells, a “Block Manager” board is installed on each block, which communicates wirelessly to a “Pack Supervisor” board that monitors the overall health of the system. Obviously, such a robust system is probably a bit overkill if you’re just looking to build a pack for your quadcopter, but if you’re looking to build a DIY Powerwall or juice up a custom electric vehicle, this could be the battery management system you’ve been looking for.

Tacking Against The Sun: Flying A Batteryless Solar RC Plane Is Almost Like Sailing

October 7, 2019 by Danie Conradie 28 Comments

Flying on the power of the sun is definitely not a new idea, but it usually involves a battery between the solar panels and the propulsion system. [ukanduit] decided to lose the battery completely and control the speed of the motor with the output of the solar panels. This leads to some interesting flying characteristics, almost akin to sailing.

When a load tries to draw more current than a solar panel can provide, its output falls dramatically, so [ukanduit] had to take this into account. Using a ATTiny85, he built a MPPT (Maximum Power Point Tracker) unit that connects between the RC receiver and the motor speed controller. It monitors the output of the panels and modulates the speed of the motor accordingly, while ensuring that there is always enough power to run the servos and receiver. The airframe (named the Solar Bear) is a small lightweight flying wing, with a balsa and carbon fibre frame covered with clear film, with the solar cells housed inside the wing. Since the thrust of the motor is directly proportional to how much sunlight hits the top of wings, it requires the pilot to “tack” against the sun and use momentum to quickly get through turns before orienting into the sun again.

If you want to build your own controller, the schematics and software is up on RC Groups. Check out the Solar Bear in action, flown here by [AJWoods].

Continue reading “Tacking Against The Sun: Flying A Batteryless Solar RC Plane Is Almost Like Sailing” →