A Li-ion Battery Charging Guide

Although [pinomelean’s] Lithium-ion battery guide sounds like the topic is a bit specific, you’ll find a number of rechargeable battery basics discussed at length. Don’t know what a C-rate is? Pfffft. Roll up those sleeves and let’s dive into some theory.

As if you needed a reminder, many lithium battery types are prone to outbursts if mishandled: a proper charging technique is essential. [pinomelean] provides a detailed breakdown of the typical stages involved in a charge cycle and offers some tips on the advantages to lower voltage thresholds before turning his attention to the practical side: designing your own charger circuit from scratch.

The circuit itself is based around a handful of LM324 op-amps, creating a current and voltage-limited power supply. Voltage limits to 4.2V, and current is adjustable: from 160mA to 1600mA. This charger may take a few hours to juice up your batteries, but it does so safely, and [pinomelean’s] step-by-step description of the device helps illustrate exactly how the process works.

[Thanks mansalvo]

An Obsessively Thorough Battery (and more) Showdown

There are a number of resources scattered across the Internet that provide detailed breakdowns of common products, such as batteries, but we haven’t seen anything quite as impressive as this site. It’s an overwhelming presentation of data that addresses batteries of all types, including 18650’s (and others close in size)26650’s, and more chargers than you can shake a LiPo at. It’s an amazing site with pictures of the product both assembled and disassembled, graphs for charge and discharge rates, comparisons for different chemistries, and even some thermal images to illustrate how the chargers deal with heat dissipation.

Check out the review for the SysMax Intellicharger i4 to see a typical example. If you make it to the bottom of that novel-length repository of information, you’ll see that each entry includes a link to the methodology used for testing these chargers.

But wait, there’s more! You can also find equally thorough reviews of flashlights, USB chargers, LED drivers, and a few miscellaneous overviews of the equipment used for these tests.

[Thanks TM]

Hacklet #9 Bugs and Fire

9 This week on the Hacklet, we’re spending some time looking at bugs and fire! honeybeeFirst up we have [Noel] who is saving the bees with Bee-O-Neo-Tweet-O. Bees are incredibly important, both to Earth’s ecosystem and the food chain we humans need to survive. Unfortunately bees are also sensitive to some of the chemicals humans dump into the atmosphere. Sometimes it results in colored honey, but more often than not it’s detrimental to the bees.

Neonicotinoids are a class of insecticide that has been causing problems to hives near where they are used. [Noel] is banking on sensors created with bismuth electrodes to detect the chemical near the entrance to hives. The data can be collected by beekeepers all over the world and sent to a central server. He’s using an Arduino Yun as a WiFi connected base station. Each individual hive has an Adafriut Trinket and a 433MHz radio link to send data to the base. [Noel] is even hoping to detect individual bees by the sound of their wings beating.


[Ken] is keeping his own bees, and wants to monitor more than just chemicals. His honeybee hive monitoring system keeps track of the temperature and weight (and thus the honey produced) by his hives. Rather than buy an expensive load cell setup, [Ken] modified a standard digital bathroom scale to suit his needs. The insects connect to the IOB (Internet of Bees) with a bit of help from the Apitronics platform and a BeagleBone Black. Ken even added a solar-powered weather station with the Apitronics system.

bug-killa[Mike] is taking a slightly different approach. He doesn’t want to save the bugs, he wants to kill the ones that bug him! [Mike] doesn’t want to get his hands dirty, so he’s created Lazy Killer 9000 for easy bug killing. Lazy Killer uses the business end of an electrified fly swatter to do its work. This project wouldn’t be complete without an Arduino, so [Mike] is adding one, as well as a WiFi shield. The entire system will have a friendly interface to turn the juice on. One of the best features of Lazy Killer is the internet connected kill count. [Mike] knows that there aren’t any bugs in the vacuum of space, so he’s entered Lazy Killer in The Hackaday Prize.


From bugs, we move on to Fire! [mr.jb.swe] needed a reliable portable power source. He found it in LiFePO4 batteries, but still needed a way to charge them. Toward that end he’s created The Multicharger, a watt meter and charger which can be powered from solar, wind, or thermometric power. A Powerpot X provides the fire and the power to charge the batteries. [mr.jb.swe’s] charger converts that into the standard constant current->constant voltage charging system needed by lithium chemistry batteries. The Multicharger isn’t a complete battery management system yet, but it’s well on its way.

Unitycandle candles have become a staple at wedding ceremonies.[Quinn] has taken things to the next level and beyond with this take on the classic unity candle. This candle throws fireballs 30 feet into the sky! We covered the candle back in June, but [Quinn] has been busy since then. With over 20 updates, [Quinn] has created one of the most well documented projects on Hackaday.io. Of course, being that this project is dealing with propane and monstrous fires, [Quinn] mentions you shouldn’t try unless you really know what you’re doing. Don’t set any brides on fire! That’s it for this week’s Hacklet! Tune in next week, same hack time, same hack channel, for more of the best of Hackaday.io!

Reviving a Stubborn Laptop Battery

We’ve all gotten bored of certain toys and left them on the shelf for months on end. But what do you do when this prolonged period kills the batteries? Well if you’re [Andrew] you take apart the battery pack and bring it back to life!

[Andrew] picked up one of those Panasonic Toughbooks awhile back and although it’s hardly a top of the line laptop specs-wise, it does have some pretty cool features: it’s shock-proof, splash-proof, and extreme-temperature-proof. It even had a touch screen before touchscreens were cool. Despite its durability, however, the laptop was left to sit for a bit too long, and the battery pack no longer accepted a charge.

[Andrew] quickly disassembled the battery pack and began measuring the cells with his trusty multimeter, assuming just one cell had gone bad. Curiously though, no cells reported 0V. What he did find was that each cell and sub-pack reported 2.95V, which is 0.05V below the “safe operating limits” of typical lithium ion cells. Continue reading “Reviving a Stubborn Laptop Battery”

$1 Coin Cell Charger

Sure, coin cells usually last a long time — but do you really want to buy new ones and throw the old ones out? The LiR2032 coin cell is a rechargeable lithium battery, for which you can build a charger at around $1.

The 5 minute hack starts with a TP4056 lithium charging circuit, which is a great DIY board designed to charge high-capacity cells at about 1A. Luckily, it is pretty easy to modify the board to charge lower capacity batteries. It’s just a matter of replacing resistor R4, and a little bit of soldering! Continue reading “$1 Coin Cell Charger”

Bicycle Generator for Emergency Electricity


[Hackett’s] back at it, this time with some practical advice for the next power outage to hit your city: why not prepare for the worst by building your own bike generator? You’ll no doubt recall that hurricane Sandy devastated New York City’s grid, even flooding substations and causing massive explosions. [Hackett] experienced the Sandy outages first-hand, and knows the value of having this simple build ready to roll.

The project uses a permanent magnet DC motor (around 250 watts), which you can find in electric wheelchairs or other mobility scooters. His setup’s gear reduction spins the motor 50 times for each revolution of the bike wheel. The apparatus [Hackett] built to press-fit the wheel to the motor’s spindle is particularly clever: a threaded rod adjusts the position of the motor, which is bolted onto a hinged platform, with the other part of the hinge welded to a larger frame that supports the bike wheel.

The motor is connected to a home-built charge controller based on Mike Davis’s design, which monitors the deep-cycle batteries and both kills the charge when it’s full as well as turns charging back on after it’s reached a set level of discharge. The rest is gravy: with the deep cycle battery connected to a power inverter, [Hackett] can plug in and keep phones charged, music playing, and even (some of) the lights on. If you’re a fan of [Hackett’s] straightforward, practical presentation style, check out his tripod build and his demonstration of stripping pipes of their galvanization.

Continue reading “Bicycle Generator for Emergency Electricity”

Modifying a knock-off battery charger to be safer


Sometimes buying a low-cost clone off of eBay is a great option, but [Martin] wisely decided to test his counterfeit IMAX B6AC, and found it grossly lacking. His detailed breakdown shows an alarming array of problems, including poor design and construction, and a lack of warning if the balance circuit fails. In addition, the charger wasn’t properly calibrated. By using a precision multimeter, Martin found that the charger actually brought cells above critical voltage. So really, using a charger like this out of the box can both destroy your battery pack and/or start a fire. One other interesting detail – this model can only be calibrated once. Sweet features.

[Martin] detailed his fixes in a well-illustrated blog post. He first had to re-enable the calibration menu using this method which requires bricking the device first! Once un-bricked, however, he could do the recalibration using a voltage divider and a reliable power source.

This project really underscores the need for a precisely calibrated multimeter. Not only would [Martin] not have been able to test his charger properly, but the re-calibration wouldn’t have been as accurate as needed. As hobbyists, this is a reminder that we can only trust our tools if they are accurate.