For the price of a mid-range Android phone, [Kenneth Finnegan] turned a 50 caliber ammo can into a 50 amp-hour portable power supply. The battery pack uses four 3.5 V LiFePO4 cells wired in series to achieve a nominal 12 V supply that stands in for a traditional lead-acid battery. The angel of second-hand purchases was smiling on this project as the cells were acquired on eBay in unused condition, complete with bus bars and mounting spacers. All it took to fit them in the case was to grind off the spacers’ dovetails on the outer edges.
There are many benefits to Lithium Iron Phosphate chemistry over traditional lead acid and [Kenneth] spells that out in his discussion of the battery management system at work here. While the newer technology has a much better discharge curve than lead-acid, there’s a frightening amount of power density there if these batteries were to have a catastrophic failure. That’s why there are Battery Management Systems and the one in use here is capable of monitoring all four cells individually which explains the small-gauge wires in the image above. It can balance all of the cells to make sure one doesn’t get more juice than the others, and can disconnect the system if trouble is a-brewin’. Continue reading “Ammo Can Battery; 50 Ah LiFePO4 Clad In Army Green”
Over the last decade or so, battery technology has improved massively. While those lithium cells have enabled thin, powerful smartphones and quadcopters, [patrick] thought it would be a good idea to do something a little simpler. He built a USB power bank with an 18650 cell. While it would be easier to simply buy a USB power bank, that’s not really the point, is it?
This project is the follow-up to one of [patrick]’s earlier projects, a battery backup for the Raspberry Pi. This earlier project used an 14500 cell and an MSP430 microcontroller to shut the Pi down gracefully when the battery was nearing depletion.
While the original project worked well with the low power consumption Pi Model A and Pi Zero, it struggled with UPS duties on the higher power Pi 3. [patrick] upgraded the cell and changed the electronics to provide enough current to keep a high-power Pi on even at 100% CPU load.
The end result is a USB power bank that’s able to keep a Raspberry Pi alive for a few hours and stays relatively cool.
Knocking a microcontroller into sleep mode and waking it up on demand or in intervals is common practice in many low power applications, enabling devices to stay in operation for years on a single coin cell battery. Since there are tons of applications where you might want to do similar things with a Raspberry Pi, [Patrick Van Oosterwijck] created the LiFePO4wered/Pi. The module that snaps on to eight GPIO pins of a Pi, extending it by a long life LiFePO4 battery, a charging regulator, and a proper power management. Obviously, it also makes a great UPS.
[Patrick] realized this project by expanding his already available and equally useful LiFePO4wered/USB charging regulator module by a low power MSP430G2131 microcontroller and a load switch. A daemon on the Raspberry Pi speaks to the module over I2C, allowing you to schedule a wake-up timer, let your Pi autoboot after a power outage or just read out the current battery voltage through a command line tool. Once the Pi is safely shut down, the microcontroller will also go to sleep, resulting in a standby current of 8 uA for the whole system. Together with the 500 mAh LiFePo4 cell, that’s theoretically low enough to send your Pi-ncess into a seven-year-long sleep.
LiFePO4wered/Pi is not only good for sleeping, though. [Patrick’s] runtime tests show, that the 500 mAh cell will power a Raspberry Pi Zero and a WiFi dongle for about two hours. Because the Raspberry Pi and many USB peripherals won’t complain when only 3.2 V are present on the VBUS, [Patrick] was able to squeeze out even more runtime by dismissing the boost converter from the design and driving the Pi directly from the battery voltage. If that worries you, you can either read a detailed explanation on why that works so well or just have a look at the more compliant 5 V version.
Eventually, [Patrick] used his module to create a Raspberry Pi time-lapse camera. A little script lets the Pi take a picture on boot up, set a wake-up timer and go back to sleep again. Safely enclosed in a waterproof electric box and deployed into the wild, the camera took 120 pictures on a single charge.
We’re sure the module will find it’s way into many cool projects and we’re counting the hours until we can get one in [Patrick’s] tindie store. Until then, enjoy the time-lapse video:
You can go to any dollar store, gas station, big box store, or your favorite Internet retailer and get a USB power bank. It’s a lithium battery mashed into a plastic enclosure with a USB port, probably poorly engineered, but it does serve as a great power supply for the Raspberry Pi. For the Raspberry Pi Zero contest we’re running over on hackaday.io, [Patrick] built a lithium phosphate battery pack that’s much better engineered and has some features a simple USB power bank will never have.
[Patrick]’s Raspberry Pi UPS isn’t just a battery and charge controller attached to the power rails; this board has a microcontroller that has full control over when the Pi wakes up, when the Pi goes to sleep, and can put the Pi into a clean shutdown, even in headless mode. SD cards around the world rejoiced.
The electronics for this project are just a low-power MSP430 microcontroller and a boost regulator. The battery pack/power manager attaches to the Pi through the first few GPIO pins on the Pi’s 40-pin header. That’s enough to tap into the 3.3 and 5V supplies, along with the serial console so power events can be scripted on the Pi.
So far, [Patrick] has made a few time-lapse movies with his lithium battery backup, a Pi Model A+, and a Raspberry Pi camera. He managed to take 99 pictures over the course of about 24 hours, powered only by a single lithium-ion cell. You can check that video out below.
Continue reading “Battery Backup For The Raspberry Pi”
Nerd Ralph loves cheap and dirty hacks, and for that we applaud him. His latest endeavor is a LiFePO4 battery charger that he made out of parts he had on hand for under $0.50 US. (Although we think he really made it for the fun of making it.)
The circuit is centered around a TL431 programmable shunt regulator, which is an awesome and underrated chip in its own right. If you don’t know the TL431 (aka LM431), you owe it to yourself to fetch the datasheet and pick up a couple with your next electronics part order. In fact, it’s such a great chip, we can’t resist telling you about it for a minute.
Continue reading “Ode To The TL431, And A LiFePO4 Battery Charger”
We’re not using 9 Volt batteries to power our projects anymore; the world of hobby electronics has moved on to cheap LiPo batteries for most of our mobile power storage. LiPos aren’t the best solution, evidenced by hundreds of YouTube videos of exploding batteries, and more than a few puffy cells in our junk drawer. The solution? LiFePO4, or lithium iron phosphate cells. They’re a safer chemistry, they have low self discharge, and have more recharge than other chemistry of lithium cells.
LiFePO4 cells aren’t easy to deal with if you’re working with breadboard electronics, though. Most of that is because there aren’t many breakout boards for these cells. [Patrick] is working on changing that with his LiFePO4werd USB charger.
The concept is simple: use an off-the-shelf part for LiFePO4 batteries – in this case an MCP73123 – and make a board that charges the batteries with a USB port. It’s exactly the same idea as the many USB LiPo chargers out there, only this one uses a better battery chemistry.
[Patrick] is using a 550mAh battery for this project, but there’s no reason why it couldn’t be upgraded to a 18650-sized cell with more than 2000mAh stuffed inside. Add a boost converter to the circuit, and he’ll have the perfect power source for every portable electronics project imaginable.
[robin] has a Red Camera (lucky!), an absurdly expensive digital video camera. As you would expect the batteries are also absurdly expensive. What’s the solution? Battery packs from cordless drills.
Cordless drills are interesting pieces of tech that can be easily repurposed; there are huge battery packs in them, big, beefy motors, and enough hardware to build an Automatic Cat Feeder or a motorized bicycle.
What if those old Makita batteries don’t charge? That usually means only one or two cells are dead, not the whole pack. Free LiIon cells, but you need to charge them. Here’s a single cell charger/boost converter that will do the trick.
A problem faced by amateur radio operators around the world is the lack of commercial power. Plugging a portable shack into a wall will work, but for uninterrupted power car batteries are everywhere. How do you combine wall power and car batteries for the best of both worlds? With an In-line battery backup module.
All of the projects above rely on charging a battery through wall power, and sometimes even that is impossible. Solar is where we’re headed, with solar LiPo chargers, and solar LiFe chargers. That’s more than enough to keep a smartphone charged, but if you want to go completely off the grid, you’re going to need something bigger.
[Michel] has been off the power grid 80% of the time since he installed his home PV system a few years ago. How’s he doing it? A literal ton of batteries, huge chargers, and a 5kW inverter.