Connecting (And Using) High-Capacity Batteries In Parallel

For those willing to put some elbow grease into it, there is an almost unlimited supply of 18650 lithium ion batteries around for cheap (or free) just waiting to be put into a battery pack of some sort. Old laptop and power tool batteries are prime sources, as these often fail because of one bad cell while the others are still perfectly usable. [limpkin] built a few of these battery packs and now that he’s built a few, he’s back with a new project that allows him to use four custom packs simultaneously.

The problem with using different battery packs in parallel is that unless the batteries are charged to similar voltages, they could generate a very high and potentially dangerous amount of current when connected in parallel. This circuit board, powered by a small ATtiny microcontroller, has four XT-60 connectors for batteries and a fifth for output. It then watches for current draw from each of the batteries and, using a set of solid-state relays, makes sure that no dangerous overcurrent conditions occur if the batteries are connected with mismatched voltages. The code for the microcontroller is available on this GitHub page as well.

Using an array of batteries with a balancing system like this has a number of uses, from ebikes to off-grid power solutions, and of course if you build your own packs you’ll also want to build a cell balancer of some sort as well. Batteries go outsidelectrical e the realm of theory and into that of chemistry, so we’ll also provide a general warning about working in potentially dangerous situations without specialized knowledge, but you can see how [limpkin] built his original packs here if you want to take a look at one person’s strategy for repurposing old cells.

Continue reading “Connecting (And Using) High-Capacity Batteries In Parallel”

2024 Business Card Challenge: Adding Some Refinement To Breadboard Power Supplies

For small electronics projects, prototyping a design on a breadboard is a must to iron out kinks in the design and ensure everything works properly before a final version is created. The power supply for the breadboard is often overlooked, with newcomers to electronics sometimes using a 9V battery and regulator or a cheap USB supply to get a quick 5V source. We might eventually move on to hacking together an ATX power supply, or the more affluent among us might spring for a variable, regulated bench supply, but this power supply built specifically for breadboards might thread the needle for this use case much better than other options.

The unique supply is hosted on a small PCB with two breakout rails that connect directly to the positive and negative pins on a standard-sized breadboard. The power supply has two outputs, each of which can output up to 24V DC and both are adjustable by potentiometers. To maintain high efficiency and lower component sizes, a switch-mode design is used to provide variable DC voltage. A three-digit, seven-segment display at the top of the board keeps track of whichever output the user selects, and the supply itself can be powered by a number of inputs, including USB-C or lithium batteries.

Continue reading “2024 Business Card Challenge: Adding Some Refinement To Breadboard Power Supplies”

Implantable Battery Charges Itself

Battery technology is the major limiting factor for the large-scale adoption of electric vehicles and grid-level energy storage. Marginal improvements have been made for lithium cells in the past decade but the technology has arguably been fairly stagnant, at least on massive industrial scales. At smaller levels there have been some more outside-of-the-box developments for things like embedded systems and, at least in the case of this battery that can recharge itself, implantable batteries for medical devices.

The tiny battery uses sodium and gold for the anode and cathode, and takes oxygen from the body to complete the chemical reaction. With a virtually unlimited supply of oxygen available to it, the battery essentially never needs to be replaced or recharged. In lab tests, it took a bit of time for the implant site to heal before there was a reliable oxygen supply, though, but once healing was complete the battery’s performance leveled off.

Currently the tiny batteries have only been tested in rats as a proof-of-concept to demonstrate the chemistry and electricity generation capabilities, but there didn’t appear to be any adverse consequences. Technology like this could be a big improvement for implanted devices like pacemakers if it can scale up, and could even help fight diseases and improve healing times. For some more background on implantable devices, [Dan Maloney] catches us up on the difficulties of building and powering replacement hearts for humans.

Cyberpunk Guitar Strap Lights Up With Repurposed PCBs

Sometimes, whether we like it or not, ordering PCBs results in extra PCBs lying around, either because of board house minimums, mistakes on either end, or both. What’s to be done with these boards? If you’re Hackaday alum [Jeremy Cook], you make a sound-reactive, light-up guitar strap and rock out in cyberpunk style.

The PCBs in question were left over from [Jeremy]’s JC Pro Macro project, and each have four addressable RGB LEDs on board. These were easy enough to chain together with jumper wires, solder, and a decent amount of hot glue. Here’s a hot tip: you can use compressed air to rapidly cool hot glue if you turn the can upside down. Just don’t spray it on your fingers.

The brains of this operation is Adafruit Circuit Playground Express, which runs off of a lipstick battery and conveniently brings a microphone to the table. These two are united by a 3D print, which is hot-glued to the guitar strap along with all the boards. In the second video after the break, there’s a bonus easy-to-make version that uses an RGB LED strip in place of the repurposed PCBs. There’s no solder or even hot glue involved.

Want to really light up the night? Print yourself a sound-reactive LED guitar.

Continue reading “Cyberpunk Guitar Strap Lights Up With Repurposed PCBs”

A finger points at a stack of yellow plastic plates sandwiched together like on a bookshelf. A grey metal rectangle holds the top together and black plastic sticks off to the left. The top of the pack has copper and nickel (or some other silver-colored metal) tabs pointing up out of the assembly.

Tearing Into A Sparky Sandwich

We’re still in the early days of modern EV infrastructure, so minor issues can lead to a full high voltage pack replacement given the lack of high voltage-trained mechanics. [Ed’s Garage] was able to source a Spark EV battery pack that had succumbed to a single bad cell and takes us along for the disassembly of the faulty module.

The Spark EV was the predecessor to the more well-known Chevy Bolt, so its nearly ten year old systems might not reflect the state-of-the-art in EV batteries, but they are certainly more modern than the battery in your great-grandmother’s Baker Electric. The Li-ion polymer pouch cells are sandwiched together with cooling and shock absorbing panels to keep the cells healthy and happy, at least in theory.

In a previous video, [Ed’s Garage] takes apart the full pack and shows how the last 2P16S module has assumed a darker color on its yellow plastic, seeming to indicate that it wasn’t receiving sufficient cooling during its life in the car. It would seem that the cooling plates inside the module weren’t quite up to the task. These cells are destined for other projects, but it doesn’t seem like this particular type of battery module would be too difficult to reassemble and put back in a car as long as you could get the right torque settings for the compression bolts.

If you’re looking for other EV teardowns, might we suggest this Tesla Model S pack or one from a passively-cooled Nissan Leaf?

Continue reading “Tearing Into A Sparky Sandwich”

Ultimate Power: Lithium-Ion Packs Need Some Extra Circuitry

A LiIon pack might just be exactly what you need for powering a device of yours. Whether it’s a laptop, or a robot, or a custom e-scooter, a CPAP machine, there’s likely a LiIon cell configuration that would work perfectly for your needs. Last time, we talked quite a bit about the parameters you should know about when working with existing LiIon packs or building a new one – configurations, voltage notations, capacity and internal resistance, and things to watch out for if you’re just itching to put some cells together.

Now, you might be at the edge your seat, wondering what kind of configuration do you need? What target voltage would be best for your task? What’s the physical arrangement of the pack that you can afford? What are the safety considerations? And, given those, what kind of electronics do you need?

Picking The Pack Configuration

Pack configurations are well described by XsYp:X serial stages, each stage having Y cells in parallel. It’s important that every stage is the same as all the others in as many parameters as possible – unbalanced stages will bring you trouble.

To get the pack’s nominal voltage, you multiply X (number of stages) by 3.7 V, because this is where your pack will spend most of its time. For example, a 3s pack will have 11.1 V nominal voltage. Check your cell’s datasheet – it tends to have all sorts of nice graphs, so you can calculate the nominal voltage more exactly for the kind of current you’d expect to draw. For instance, the specific cells I use in a device of mine, will spend most of their time at 3.5 V, so I need to adjust my voltage expectations to 10.5 V accordingly if I’m to stack a few of them together.

Now, where do you want to fit your pack? This will determine the voltage. If you want to quickly power a device that expects 12 V, the 10.5 V to 11.1 V of a 3s config should work wonders. If your device detects undervoltage at 10.5V, however, you might want to consider adding one more stage.

How much current do you want to draw? For the cells you are using, open their spec sheet yet again, take the max current draw per cell, derate it by like 50%, and see how many cells you need to add to match your current draw. Then, add parallel cells as needed to get the capacity you desire and fit the physical footprint you’re aiming for. Continue reading “Ultimate Power: Lithium-Ion Packs Need Some Extra Circuitry”

Ultimate Power: Lithium-Ion Batteries In Series

At some point, the 3.6 V of a single lithium ion battery just won’t do, and you’ll absolutely want to stack LiIon cells in series. When you need high power, you’ve either got to increase voltage or current, and currents above say 10 A require significantly beefed up components. This is how you’re able to charge your laptop from your USB-C powerbank, for instance.

Or maybe you just need higher voltages, and don’t feel like using a step-up converter, which brings along with it some level of inefficiency. Whatever your reasons, it’s time to put some cells into series. Continue reading “Ultimate Power: Lithium-Ion Batteries In Series”