DIY LiPo Protectors

Spiderman’s Uncle Ben was known to say, “With great power comes great responsibility.” The same holds true for battery power. [Andreas] wanted to use protected 18650 cells, but didn’t want to buy them off the shelf. He found a forty cent solution. Not only can you see it in the video, below, but he also explains and demonstrates what the circuit is doing and why.

Protection is important with LiPo technology. Sure, LiPo cells have changed the way we use portable electronics, but they can be dangerous. If you overcharge them or allow them to go completely dead and then charge them, they can catch fire. Because they have a low source resistance — something that is usually desirable — short-circuiting them can also create a fire hazard. We’ve covered the chemistry in depth, but to prevent all the badness you’ll want a charger circuit.

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Are You Down With MPPT? (Yeah, You Know Me.)

Solar cells have gotten cheaper and cheaper, and are becoming an economically viable source of renewable energy in many parts of the world. Capturing the optimal amount of energy from a solar panel is a tricky business, however. First there are a raft of physical prerequisites to operating efficiently: the panel needs to be kept clean so the sun can reach the cells, the panel needs to point at the sun, and it’s best if they’re kept from getting too hot.

Along with these physical demands, solar panels are electrically finicky as well. In particular, the amount of power they produce is strongly dependent on the electrical load that they’re presented, and this optimal load varies depending on how much illumination the panel receives. Maximum power-point trackers (MPPT) ideally keep the panel electrically in the zone even as little fluffy clouds roam the skies or the sun sinks in the west. Using MPPT can pull 20-30% more power out of a given cell, and the techniques are eminently hacker-friendly. If you’ve never played around with solar panels before, you should. Read on to see how!

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Nanowire Batteries Never Need Replacing

In this day and age we’re consistently surrounded with portable electronic devices. In order for them to be called “portable”, they must run on batteries. Most, if not all, use rechargeable batteries. These batteries have a finite lifespan, and will eventually need to be replaced. UCI chemist [Reginald Penner] and doctoral candidate [Mya Le Thai] have been hard at work on making rechargeable batteries that last forever.

Nanowires are great candidates for rechargeable battery technology because the wires, thousands of times thinner than a human hair, are great conductors of electricity. The problem is repeated charging and discharging makes them brittle, which causes them to eventually fail. Typically, the researchers at UCI could get 5000 to 7000 cycles in before they failed. After some trial and error, they found that if they coat a gold nanowire with an acrylic-like gel, they can get up to 200,000 charge/discharge cycles through it before failure.

We’ve seen rechargeable battery hacks before, but making a battery that never needs replacing is sure to get everyone excited.

Maximizing a Solar Panel

Solar panels seem like simple devices: light in and electricity out, right? If you don’t care about efficiency, it might be that simple, but generally you do care about efficiency. If you are, say, charging a battery, you’d like to get every watt out of the panel. The problem is that the battery may not draw all the available current, basically leaving capacity on the table.

The solution is a technique called MPPT (Maximum Power Point Tracking). Despite sounding like a Microsoft presentation add on, MPPT uses a DC to DC converter to present a maximum load to the solar cell while providing the desired current and voltage to the load. MPPT is what [Abid Jamal] implemented to manage his solar charger.

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