By now, we’ve gone through LiIon handling basics and mechanics. When it comes to designing your circuit around a LiIon battery, I believe you could benefit from a cookbook with direct suggestions, too. Here, I’d like to give you a collection of LiIon recipes that worked well for me over the years.
I will be talking about single-series (1sXp) cell configurations, for a simple reason – multiple-series configurations are not something I consider myself as having worked extensively with. The single-series configurations alone will result in a fairly extensive writeup, but for those savvy in LiIon handling, I invite you to share your tips, tricks and observations in the comment section – last time, we had a fair few interesting points brought up!
The Friendly Neighborhood Charger
There’s a whole bunch of ways to charge the cells you’ve just added to your device – a wide variety of charger ICs and other solutions are at your disposal. I’d like to focus on one specific module that I believe it’s important you know more about.
You likely have seen the blue TP4056 boards around – they’re cheap and you’re one Aliexpress order away from owning a bunch, with a dozen boards going for only a few bucks. The TP4056 is a LiIon charger IC able to top up your cells at rate of up to 1 A. Many TP4056 boards have a protection circuit built in, which means that such a board can protect your LiIon cell from the external world, too. This board itself can be treated as a module; for over half a decade now, the PCB footprint has stayed the same, to the point where you can add a TP4056 board footprint onto your own PCBs if you need LiIon charging and protection. I do that a lot – it’s way easier, and even cheaper, than soldering the TP4056 and all its support components. Here’s a KiCad footprint if you’d like to do that too.
In the first article, I’ve given you an overview of Lithium-Ion batteries and cells as building blocks for our projects, and described how hackers should treat their Lithium-Ion cells. But what if you don’t have any LiIon cells yet? Where do you get LiIon cells for your project?
Taking laptop batteries apart, whether the regular 18650 or the modern pouch cell-based ones, remains a good avenue – many hackers take this road and the topic is extensively covered by a number of people. However, a 18650 cell might not fit your project size-wise, and thin batteries haven’t quite flooded the market yet. Let’s see what your options are beyond laptops. Continue reading “Lithium-Ion Batteries Are Easy To Find”→
[Debasish Dutta] has designed a few weather stations in the past, and this, the fourth version of the system has had many of the feature requests from past users rolled in. The station is intended to be used with an external weather sensor unit, provided by Sparkfun. This handles wind speed and direction, as well as measuring rainfall. A custom PCB hosts an ESP32-WROOM module and an Ai-Thinker Ra-02 LoRa module for control and connectivity respectively. A PMS5003 sits on the PCB to measure those particulate densities, but most sensors are connected with simple 4-way I2C connectors. Temperature, humidity, and pressure are handled by a BME280 module, UV Index (SI1145), visible light (BH1750) even soil humidity and temperature with a cable-mounted SHT10 module.
All this is powered by a solar panel, which charges a 18650 cell, and keeps the show running during the darker hours. For debugging and deployment, a USB-C power port can also be used to provide charge. A 3D printed Stevenson screen type enclosure allows the air to circulate amongst the PCB-mounted sensor modules, without hopefully too much moisture making it in there to cause mischief.
On the data collection and visualization side, a companion LoRa receiver module is in progress, which is intended to pass along measurements to a variety of services. Think Home Assistant, ESP home, and that kind of thing. Software is still a work in progress, so maybe check back later to see how [Debasish] is getting on with that?
Need some kind of battery for a project? You can always find a few Lithium-Ion (LiIon) batteries around! They’re in our phones, laptops, and a myriad other battery-powered things of all forms – as hackers, we will find ourselves working with them more and more. Lithium-Ion batteries are unmatched when it comes to energy capacity, ease of charging, and all the shapes and sizes you can get one in.
There’s also misconceptions about these batteries – bad advice floating around, fearmongering videos of devices ablaze, as well as mundane lack of understanding. Today, I’d like to provide a general overview of how to treat your LiIon batteries properly, making sure they serve you well long-term.
What’s A Battery? A Malleable Pile Of Cells
Lithium-Ion batteries are our friends. Now, there can’t be a proper friendship if you two don’t understand each other. Lithium-Ion batteries are tailored for human needs by the factory that produced them. As for us hackers, we’ll want to learn some things.
First thing to learn – a single LiIon “unit” is called a cell. An average laptop contains three or six Li-Ion cells, a phone will have one, a tablet will have from one to three. What we refer to as “battery” is typically one or multiple cells, together with protection circuitry, casing and a separate connector – most of the time all three of these, but not always. The typical voltage is 3.6 V or 3.7 V, with maximum voltage being 4.2 V – these are chemistry-defined, the same for most kinds of cells and almost always written on the cell. Continue reading “Lithium-Ion Batteries Are Your Friends”→
The pack is designed to be charged via solar panels, at 18 V and up to 5 A of current. It’s intended to work with a Maximum Power Point Tracking module to ensure the maximum energy is gained from the sunshine available. For storage, the pack relies on 75 individual 18650 lithium cells, arranged with 3 cells in series, each with 25 in parallel (3s25p). They’re spot welded together for strength and good conductivity. Nominally, the output voltage is on the order of 10-12 V. The included battery management system (BMS) will allow an output current up to 100 A, and the pack can be used with an AC inverter to power regular home appliances.
Overall, it’s a tidy pack that’s more than capable of keeping a few devices charged up for days at a time. If you’re building something similar yourself, though, just be sure to package it well and keep it protected. So many lithium batteries can quickly turn fiery if something goes wrong, so store and use it appropriately! Fear not, however – we’ve got a guide on how to do just that.
Despite the fact that we’re rapidly approaching the year 2022, there are still an incredible number of gadgets out there that you’re expected to power with disposable batteries. Sure you can buy rechargeable stand-ins that come in the various shapes and sizes of the traditional alkaline cells, but that’s a stopgap at best. For some, if a new gadget doesn’t feature an internal Li-ion battery and standardized USB charging, it’s a non-starter.
[Danilo Larizza] is one of those people. Bothered by the fact that his Oregon Scientific weather station required a pair of CR2032 coin cells, he set out to replace them with an integrated rechargeable solution. The conversion ending up being easier to implement than he initially expected, and by his calculations, his solution should keep the unit up and running for nearly 40 days before needing to be topped off with a standard USB charger.
The first step was determining how much power it actually took to run the weather station. Although the two CR2032 cells were wired in series, and therefore providing a nominal 6 V, he determined through experimentation with a bench power supply that it would run on as little as 3.2 volts. This coincides nicely with the voltage range for a single 18650 cell, and meant he didn’t need to add a boost converter into the mix. He notes the weather station does flash a “Low Battery” warning most of the time now, but that seems a fair price to pay.
Confident in the knowledge that the weather station could happily run with an 18650 cell connected in place of the original CR2032s, all [Danilo] needed to do was figure out a way to charge the battery up from time to time. To that end, he reached for a common TP4056 module. This handy little board is a great match for 18650 cells, and is so cheap that there’s really no excuse not to have a few of them kicking around your parts bin. You never know when you might need to teach an old gadget new tricks.
Who needs the city pool when you can party in the private pool over at Grandma and Grandpa’s house? No need to wait until Memorial Day weekend when it hits 90° F in the first week of May. But how can you placate grandchildren who want to know each and every day if it’s finally time to go swimming, and the pool itself is miles away? Although grandparents probably love to hear from you more often there’s no need to bother them with hourly phone calls. You just have to build a floating, remote pool temperature monitor which broadcasts every 30 minutes to an Adafruit MagTag sitting at kid’s eye level on the refrigerator.
Between the cost of commercial pool temperature monitors and all the reviews that mention iffy Wi-Fi connections, it sounds like [Blake] is better off rolling his own solution. Inside the floating part is an ESP32, a DS18B temperature sensor, and a 18650 cell. Most of the body is PVC, except for the 3D-printed torus that holds some foam for buoyancy. A handful of BBs in the bottom keep the thing pointed upright. For now, it shows the water temperature, but [Blake]’s ultimate goal is to show the air temperature as well.