How To Run Alternative Batteries On The DJI Mavic Mini

Rechargeable batteries are ubiquitous these days, freeing us from the expense and hassle of using disposable cells. However, this has come with the caveat that many manufacturers demand their equipment only be used with their own official batteries. [aeropic] wasn’t a fan of this, so built a circuit to allow his DJI Mavic Mini to fly with any batteries he pleased.

The Mavic Mini uses I2C to communicate with official packs, making the hack relatively straightforward. [aeropic] built a board nicknamed B0B, which tells the drone what it wants to hear and lets it boot up with unofficial batteries installed. The circuit uses a PIC12F1840 to speak to the drone, including reporting voltage on the cells installed. Notably, it only monitors the whole pack, before dividing the voltage to represent the value of individual cells, but it shouldn’t be a major problem in typical use. Combined with a few 3D printed components to hold everything together, it allows you to build your own cheap pack for the Mavic Mini with little more than a PCB and a few 18650 cells.

It’s always good to see hackers getting out and doing the bread and butter work to get around restrictive factory DRM measures, whether its on music, printer cartridges, or drone batteries. We’ve even seen the scourge appear on litter boxes, too. Video after the break.

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Battery Swap Gives Nissan LEAF New Lease On Life

It’s often said that one of the advantages of owning an electric vehicle is reduced maintenance costs, and for the most part, that’s true. That is, until the vehicle’s battery pack starts to show its age. Then you might be on the hook for a repair bill comparable to swapping out the engine on your old gas-burner. Depending on the age of the vehicle at that point, you might find yourself in the market for a new ride.

But in his latest video, [Daniel Öster] demonstrates that you can replace the battery in a modern electric vehicle without breaking the bank. While it’s not exactly an easy job, he manages to swap the pack in his 2012 Nissan LEAF from the comfort of his own garage using common tools and with the vehicle up on jack stands. The old battery wasn’t completely shot, so he was even able to recoup some of his costs by selling it; bringing the total price of the operation to approximately €2,122 ($2,500 USD).

Splicing on a new diagnostic connector.

While that wouldn’t be a bad deal even for a simple swap, the operation was actually an upgrade. The car was originally sold with a 24 kWh battery, but [Daniel] has replaced it with a 30 kWh pack intended for the 2017 LEAF. His car now has a greater range than it did the day it rolled off the assembly line, though as you might expect, the installation was more complex than it would have been with a contemporary battery.

[Daniel] has produced a kit that has all the adapters required to perform your own battery upgrade, including a module that translates the diagnostic signals from the newer battery into something the older vehicle can understand. With all the electrical bits simplified, all you’ve got to worry about is drilling the new battery mounting holes in the frame.

The battery pack is truly the heart and soul of an electric car, so its no surprise that mechanics and hackers alike are eager to learn as much about them as possible. They’ll have their work cut out for them, as the technology is only going to get more advanced with time.

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Building An Open Source ThinkPad Battery

If you own a laptop that’s got a few years on the clock, you’ve probably contemplated getting a replacement battery for it. Which means you also know how much legitimate OEM packs cost compared to the shady eBay clones. You can often get two or three of the knock-offs for the same price as a single real battery, but they never last as long as the originals. If they even work properly at all.

Which is why [Alexander Parent] decided to take the road less traveled and scratch built a custom battery for his ThinkPad T420. By reverse engineering how the battery pack communicated with the computer, he reasoned he would be able to come up with an open source firmware that worked at least as well as what the the third party ones are running. Which from the sounds of it, wasn’t a very high bar. From a more practical standpoint, it also meant he’d be able to create a higher capacity battery pack than what was commercially available should he chose to.

A logic analyzer wired in between one of the third party batteries and a spare T420 motherboard allowed [Alexander] to capture all the SMBus chatter between the two. From there he wrote some Arduino code that would mimic a battery as a proof of concept. He was slowed down a bit by an undocumented CRC check, but in the end he was able to come up with a fairly mature firmware that even allows you to provide a custom vendor name and model number for your pack.

The code was shifted over to an ATtiny85, with a voltage divider wired up to one of the pins so it can read the pack voltage. [Alexander] says his firmware still doesn’t do a great job of reporting the actual battery capacity remaining, but it’s close enough for his purposes. He came up with a simple PCB design to hold the MCU and support components,  which eventually he plans on putting inside of a 3D printed case that actually plugs into the back of his T420.

This project is obviously still in a relatively early stage, but we’re very interested to see [Alexander] take it all the way. The ThinkPad has long been the hacker’s favorite laptop, and we can think of no machine more worthy of a fully open hardware and software battery pack.

Building A Serious Solar Inverter Battery Pack

If you’re out in the wilderness, having plenty of electricity on hand is a blessing. Eschewing fossil fuels, [LithiumSolar] is, as their name suggests, a fan of other technologies – undertaking the construction of a 3.5kWh solar generator that’s rugged and ready for the outdoors.

The build starts with 18650 lithium-ion cells sourced from a recycler, packed inside obsolete modem battery packs. After harvesting 390 cells, the best 364 are chosen and assembled into plastic holders to create a 14S26P configuration. A spot welder is employed to weld the pack together, with XT60 connectors used as the main bus connectors, albeit in a very non-standard configuration. Balance leads are hooked up to a 14S battery management system, to keep things in check. The huge pack is then installed inside a stout Craftsman toolbox, along with a MPPT solar charger module, and a 1500W inverter for output.

The build video is a great resource for anyone interested in building custom 18650 packs or battery solar power systems. [LithiumSolar] does a great job of clearly explaining each step and the reasons for part selections along the way. Of course, in a neat dovetail to this project, we’ve even seen solar-powered spot welders before – which would be useful if you need to replicate this build out in the field somewhere. Video after the break.

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What’s In A Name For A Tool Battery Pack?

Power tools have come a long way. It used to be you needed extension cords or a generator for your tools, but now you can get just about anything with a nice rechargeable battery pack. As it turns out, most of those packs are made by the same company, and [syonyk] wanted to see how similar two different Makita packs and a Rayovac pack were. What he found was surprising. The outsides were very similar, but what was on the inside?

The Rayovac pack was easy to open and had a controller, a thermal cutoff device, and two layers of 18650 batteries. The similar Makita pack looked identical from the outside until he tried to take it apart. The maker had plugged one screw hole and used security screws instead of the Phillips heads like on the Rayovac.

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

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]

A Modular System For Building Heavy Duty 18650 Battery Packs

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.