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.

Electric Longboard Quick Build Using Off-The-Shelf Components.

Building cool things completely from scratch is undeniably satisfying and makes for excellent Hackaday posts, but usually involve a few unexpected speed humps, which often causes projects to be abandoned. If you just want to get something working, using off-the-shelf modules can drastically reduce frustration and increase the odds of the project being completed. This is exactly the approach that [GreatScott!] used to build the 3rd version of his electric longboard, and in the process created an excellent guide on how to design the system and selecting components.

Previous versions of his board were relatively complicated scratch built affairs. V2 even had a strain gauge build into the deck to detect when the rider falls off. This time almost everything, excluding the battery pack, was plug-and-play, or at least solder-and-play. The rear trucks have built in hub motors, the speed controllers are FSESC’s (VESC software compatible) and the remote control system is also an off the shelf system. All the electronics were housed in 3D printed PETG housing, and the battery pack is removable for charging. We just hope the velcro holding on the battery pack doesn’t decide to disengage mid-ride.

The beauty of this video lies in the simplicity and how [GreatScott!] covers the components selection and design calculations in detail. Sometimes we to step back from a project and ask ourselves if reinventing is the wheel is really necessary, or just an excuse to do some yak shaving. Electric long boards are extremely popular at the moment, you can even make a deck from cardboard or make a collapsible version if you’re a frequent flyer.

Lessons In Li-Ion Safety

If you came here from an internet search because your battery just blew up and you don’t know how to put out the fire, then use a regular fire extinguisher if it’s plugged in to an outlet, or a fire extinguisher or water if it is not plugged in. Get out if there is a lot of smoke. For everyone else, keep reading.

I recently developed a product that used three 18650 cells. This battery pack had its own overvoltage, undervoltage, and overcurrent protection circuitry. On top of that my design incorporated a PTC fuse, and on top of that I had a current sensing circuit monitored by the microcontroller that controlled the board. When it comes to Li-Ion batteries, you don’t want to mess around. They pack a lot of energy, and if something goes wrong, they can experience thermal runaway, which is another word for blowing up and spreading fire and toxic gasses all over. So how do you take care of them, and what do you do when things go poorly?

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An Exhaustive Guide To Building 18650 Packs

Most of us know the basics of building packs of lithium-ion batteries. We’re familiar with cell balancing and the need for protection circuitry, and we understand the intricacies of the various serial and parallel configurations. It’s still a process that can be daunting for the first-time pack-builder though, because the other thing that most of us know about lithium ion batteries is that getting things wrong can cause fires. Rule zero of hackerspaces is “Don’t be on fire”, so what’s to be done? Fortunately [Adam Bender] is on hand with an extremely comprehensive two-part guide to designing and building lithium-ion battery packs from cylindrical 18650 cells.

In one sense we think the two-parter is in the wrong order. Part two takes us through all the technical details and theory, from lithium-ion chemistry to battery management systems and spot-welding nickel busbars, while part one shows us the construction of his battery pack. There are also a couple of videos, which we’ve placed below the break. It’s still not a job for the faint-hearted, but we’d say he’s produced about as professional and safe a pack as possible.

If spot welding worries you then it might be possible to build a pack without it. But it’s always worth considering: would you be better served buying one?

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