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]

PSP Lithium Hack Could Be Called the Franken-Cell

You assume that you’ll be able to get parts forever… after all: The Internet. But what if you can’t justify paying the price for them? [Cristi C.] was in this situation, not wanting to fork over $30+ for a replacement PSP battery. The handheld gaming rig itself was just discontinued this year but supposedly the batteries have been out of production for some time. What you see above is the controller board from an original battery, with the cell from a camera battery.

The key is protection. The chemistry in Lithium cells of several types brings a working voltage of around 3.7V. Swapping the cells — even if they are different capacities — should work as protection circuits generally measure current, voltage, and sometimes temperature as they charge in order to know when the cell is full. With this in mind [Christi] cracked open a used Canon NB-6L type battery and grabbed the prismatic cell as a replacement for the pouch cell in the Sony S110 case (PDF). The Canon cell is enclosed in a metal case and is just a bit smaller than the pouch was. This means with careful work it fit back inside the original plastic enclosure.

On a somewhat related note, be careful when sourcing brand-x batteries. Some manufacturers implement checks for OEM equipment but there are ways around that.

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]

The Reason Dead Batteries Bounce

For the last few years, very well-informed people have been able to tell if an alkaline battery is good or not simply by dropping them. When dropped from an inch or two above a hard surface, a good battery won’t bounce, and will sometimes land standing up. A dead battery, on the other hand, will bounce. Thanks to [Lee] and a few of his friends, we now know why this happens.

While hanging out with a few of his buddies, [Lee] was able to condense all the arguments on why dead batteries bounce to two theories. The first theory, the ‘bounce theory’ said dead batteries had an increase in outgassing in the battery, increasing the pressure in the battery, which increases the spring constant of the battery itself. The second theory, the ‘anti-bounce theory’, said the gel-like properties of the electrolyte worked as a sort of mass damper.

[Lee] designed an experiment to test the outgassing ‘bounce theory’ of bouncing batteries. Instead of dropping a battery, an object – in this case a brass slug – was dropped onto both good and bad batteries. There was no difference. Even after holes were drilled to vent any gasses inside the battery, the brass slug bounced off both good and bad batteries the same way.

This means the reason dead alkaline batteries bounce is due to the electrolyte. [Lee] cut open a few AA cells and found the electrolyte in a good battery was a mushy mess of chemicals. In the dead battery, this same electrolyte hardened into a solid mass. [Lee] compares this to an anti-bounce hammer.

Finally, more than a year after most of us learned about bouncing dead batteries thanks to [Dave Jones]’ video, we have an answer. It’s a chemical change in the electrolyte that turns it from a goo to a solid that makes dead batteries bounce.

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Electric Chainsaw Teardown

An electric chainsaw with its case removed

For his Beyond Unboxing series, [Charles] tore apart a Ryobi cordless chainsaw to get a better look at how this battery powered tool works.

Inside he found a three-phase motor and controller. This motor looks like it could be useful in other projects since it has a standard shaft. The battery pack was popped open to reveal a set of LG Chem 21865 cells, and some management hardware.

With all the parts liberated from the original enclosure, [Charles] set up the motor, controller, and battery on the bench. With a scope connected, some characterization of the motor could be done. A load was applied by grabbing the spinning shaft with welding gloves. [Charles] admits that this isn’t the safest way to test a motor.

While it is a very fast motor, the cut-in speed was found to be rather low. That means it can’t start a vehicle from a stop, but could be useful on e-bikes or scooters which are push started.

This chainsaw a $200 motor, controller, and battery set that could be the basis of a DIY scooter. It sounds great too, as the video after the break demonstrates.

[Thanks to Dane for the tip!]

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Tearing Down a Cheap External USB Battery

[cpldcpu] recently received an external USB battery as a promotional gift and thought it would be a good idea to tear it down to see its insides. At first glance, he could see that the device included a USB micro-b socket used as a 5V input (for charging), a USB-A socket for 5V output, a blue LED to indicate active power out and a red one to indicate charging.

Opening the case revealed that most space was taken up by a 2600mAH ICR18650 Li-Ion battery, connected to a tiny PCB. A close inspection and a little googling allowed [cpldcpu] to identify the main components of the latter: a battery mangement IC, a 2A boost converter, a 3A Schottky diode, a few 2A N-Mosfets, a 300mA 2.5V LDO and an unknown 6-pin IC. It is very interesting to learn that every last one of these components seems to be sourced from China, which may explain why this USB battery is given for free. Do you think they designed it in-house and outsourced the manufacturing, or is this a product Digi-Key simply bought and put their name on?

Editorial Note: Digi-Key is an advertiser on Hackaday but this post is not part of that sponsorship. Hackaday does not post sponsored content.

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CFL + Bugzapper = Battery Operated Camping Light


Knowing different ways of generating light is a great skill to have, so go ahead and add this one to your arsenal by combining a Bugzapper with a CFL Light Bulb.

Sure a CFL(Compact Fluorescent Lamp) works just fine on its own if you have AC mains, but what we’re talking about here is getting the light bulb to work off of a single D battery. We featured a similar hack a few months back by using a Joule-Thief to get the high voltage for the fluorescent tube, but if you can’t get your hands on discrete components, [Jan] shows us another way by gutting a tennis racket bugzapper for its booster board. Knowing that the bugzapper steps up the 3V to about 2000V, he decided to see if that same circuit would run off a single 1.5V D battery and achieve the voltage required to drive a CFL tube. After carefully removing the electronics from the CFL housing, [Jan] was able to directly connect the booster board to the electrode wires of the fluorescent tube, and voila; he now has a D-Battery operated camp light that has a run time of over 200 hours.

It would be interesting to see how this hack compares to the Joule-Thief method in terms of brightness and run-time. Before you go and scrap the parts out of the CFL light bulb, make sure you check out this detailed breakdown of popular CFL light bulbs.