Battery Hacks

70 Articles

Maker [Dala] showing powerwall statistics

From Vehicle-to-Grid To DIY Home Powerwalls

August 13, 2024 by 44 Comments

As battery-to-grid and vehicle-to-home technologies become increasingly mainstream, the potential for repurposing electric vehicle (EV) batteries has grown significantly. No longer just a niche pursuit, using retired EV batteries for home energy storage has become more accessible and appealing, especially as advancements in DIY solutions continue to emerge. Last year, this project by [Dala] showcased how to repurpose Nissan Leaf and Tesla Model 3 battery packs for home energy storage using a LilyGO ESP32, simplifying the process by eliminating the need for battery disassembly.

In the past few months, this project has seen remarkable progress. It now supports over 20 different solar inverter brands and more than 25 EV battery models. The most exciting development, however, is the newly developed method for chaining two EV packs together to create a single large super-battery. This breakthrough enables the combination of, for example, two 100kWh Tesla packs into a massive 200kWh storage system. This new capability offers an accessible and affordable way to build large-scale DIY home powerwalls, providing performance that rivals commercial systems at a fraction of the cost.

With these advancements, the possibilities for creating powerful, cost-effective energy storage solutions have expanded significantly. We do however stress to put safety first at all times.

Hungry for more home powerbanks? We’ve been there before.

Continue reading “From Vehicle-to-Grid To DIY Home Powerwalls” →

Better Battery Design Through Science

August 2, 2024 by 6 Comments

Before the age of lithium batteries, any project needing to carry its own power had to rely on batteries that were much less energy-dense and affordable. In many ways, we take modern lithium technology for granted, and can easily put massive batteries in our projects by the standards of just a few decades ago. While the affordability of lithium batteries has certainly decreased the amount of energy we need to put in to our projects to properly size batteries, there’s still a lot of work to be done if you’re working on a bigger project or just want to get the maximize the efficiency and effectiveness of your DIY battery pack.

The main problem with choosing a battery, as [ionworks] explains, is that batteries can’t be built for both high energy and high power, at least not without making major concessions for weight or cost. After diving in to all of the possible ways of customizing a battery, the battery guide jumps in to using PyBaMM to perform computational modeling of potential battery designs to hopefully avoid the cumbersome task of testing all of the possible ways of building a battery. With this tool virtually all of a battery’s characteristics can be simulated and potential problems with your setup can be uncovered before you chose (or start production of) a specific battery system.

While customizing a battery pack to this extent might not be a consideration for most of us unless the project is going to be big enough to run something like an electric car or a whole-house generator, it’s a worthwhile tool to know about as even smaller projects like ebikes can benefit from choosing the right cell for the application. Some of the nuances of battery pack design can be found in this guide to building packs from the standard 18650 cells.

Header: Lead holder, CC BY-SA 3.0 .

A man's hand with a black ring touches a white box. It is square on the bottom and has a sloped top. Various AC, 12V, and USB ports adorn its surface. It's approximately the size of a human head.

DIY Off Grid Battery Pack From EV Battery

July 31, 2024 by 15 Comments

Car camping gets you out in the great outdoors, but sometimes it’s nice to bring a few comforts from home. [Ed’s Garage] has taken a module from a salvaged EV and turned it into a handy portable power station.

With 2.3 kWh of storage from the single Spark EV module, the battery pack can power [Ed]’s hotplate, lights, fridge, and other electric accessories while camping away from shore power. The inverter he selected can provide up to 1500W of AC power and his 12V converter can do 150W. Several USB ports and a wireless charging pad adorn the outside next to the waterproof AC ports. He even printed a small magnetic flashlight to reuse the light from the inverter which uses an 18650 cell that can be charged from the big battery in a charger built into the exterior of the pack.

The battery management system (BMS) has a Bluetooth module allowing for remote monitoring of state of charge and setting the maximum and minimum charge points for the pack. The whole thing comes in at 73 pounds (33 kg), and while he had originally thought to give it wheels to roll, he changed his mind once he thought more about what sort of wheels he’d need to maneuver the thing in the backcountry.

If you’re thinking of building your own power pack, why not checkout a few other builds for inspiration like this one from tool batteries or one designed to charge directly from a solar panel. Be sure you checkout our guide on how to select a BMS if you’re going to use a lithium-based chemistry.

Continue reading “DIY Off Grid Battery Pack From EV Battery” →

New Battery Has No Anode

July 7, 2024 by 28 Comments

Conventional batteries have anodes and cathodes, but a new design from the University of Chicago and the University of California San Diego lacks an anode. While this has been done before, according to the University, this is the first time a solid-state sodium battery has successfully used this architecture.

Sodium is abundant compared to lithium, so batteries that use sodium are attractive. According to the University of Chicago’s news release:

Anode-free batteries remove the anode and store the ions on an electrochemical deposition of alkali metal directly on the current collector. This approach enables higher cell voltage, lower cell cost, and increased energy density…

Continue reading “New Battery Has No Anode” →

Apple May Use Electrical Debonding For Battery Replacement

June 29, 2024 by 21 Comments

As a result of the European Union’s push for greater repairability of consumer devices like smartphones, Apple sees itself forced to make the batteries in the iPhone user-replaceable by 2027. Reportedly, this has led Apple to look at using electroadhesion rather than conventional adhesives which require either heat, isopropyl alcohol, violence, or all of the above to release. Although details are scarce, it seems that the general idea would be that the battery is wrapped in metal, which, together with the inside of the metal case, would allow for the creation of a cationic/anionic pair capable of permanent adhesion with the application of a low-voltage DC current.

This is not an entirely wild idea. Tesa has already commercialized it in the electrical debonding form of its Debonding on Demand product. This uses a tape that’s applied to one side of the (metal) surfaces, with a 5 bar pressure being applied for 5 seconds. Afterwards, the two parts can be released again without residue as shown in the above image. This involves applying a 12V DC voltage for 60 seconds, with the two parts afterward removable without force.

Continue reading “Apple May Use Electrical Debonding For Battery Replacement” →

TDK Claims Solid State Battery With 100X Energy Density

June 18, 2024 by 49 Comments

Regulations surrounding disposable batteries have accelerated a quiet race to replace coin cells, which on the whole are not readily rechargeable. TDK produces solid-state batteries and has announced a new material that claims an energy density of about 100 times that of their conventional batteries.

Energy density measures how much energy a system contains relative to its volume. The new battery has 1000 Wh/L. For comparison, old nickel-cadmium cells had about 150 Wh/L. A typical lithium-ion battery usually turns in about 200 – 250 Wh/L.

There aren’t many technical details, but a few things caught our interest. For one, it uses an oxide-based solid electrolyte and lithium alloy anodes. However, what really caught our eye was that it is “intended for use in wearables… that come in direct contact with the human body.” We don’t know if that means the material is safe for your skin or if it depends on being next to your body to operate.

While the energy density is high, keep in mind that the batteries of this type are usually tiny, so the total actual power available is probably not very high. Tiny batteries are definitely a thing. We are always hearing about breakthroughs, but we always wonder if and when we’ll see actual products.

Connecting (And Using) High-Capacity Batteries In Parallel

May 27, 2024 by 13 Comments

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 XT60 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 over-current conditions occur if the batteries are connected with mismatched voltages. The code for the microcontroller is available on this GitHub page as well.

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 outside 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” →