Stefan's Electronic Projects Web Site

Choosing and Using Nickel-Metal-Hydride (NiMH) Rechargeable Batteries

Fri, 07 Mar 2008 09:03:49 GMT

The number of portable gadgets that we use has grown substantially in the last few decades. Many of these, such as TV remote controls, some digital cameras, handheld GPS units, and flashlights, are designed to operate on either disposable alkaline batteries or rechargeable, and hence reusable, Nickel-Metal-Hydride (NiMH) batteries.

At the same time as our battery-powered device use has increased, rechargeable battery technology has improved dramatically. Unfortunately, information on the proper care and use of these batteries can be hard to find. This article attempts to provide this information and answer the questions I am often asked.

Review: Testing Sanyo's USB Powered NiMH Charger

Thu, 17 Jan 2008 21:18:20 GMT

Just over a year ago, I wrote and posted an article describing how to build a USB powered AA battery charger. At that time I needed such a thing, and none of the commercially available solutions were satisfactory. When I later reviewed Sanyo's Eneloop rechargeable batteries, I caught the attention of a senior Sanyo Europe executive who, in addition to providing some feedback, informed me that Sanyo was about to release a USB powered charger that had none of the shortcomings of the other such devices available. He offered to send me one, and I gladly accepted.

I've been meaning to review this charger for a long time, but until very recently, it was not available here in North America, where about 75% of my readers are. Now it is, from Amazon.

USB NiMH Charger Update

Sat, 15 Dec 2007 19:47:30 GMT

Sanyo has introduced a USB powered charger for their Eneloop batteries. This charger has none of the drawbacks listed above, and will charge a pair of 2000mAh cells in about 5 hours, or a single cell in half that time. Although designed for Eneloops (see my review), it will work with regular NiMH cells as well.

Stefan's DIY USB Charger Project >>

BattMan II Documentation Update

Thu, 08 Nov 2007 01:07:56 GMT

I've received some questions about the algorithms used for charging the various battery chemistries that BattMan II supports. To answer those questions, I've added some information to the Software section of the page.

BattMan II Software Update

Mon, 22 Oct 2007 01:23:34 GMT

A reader who built his own BattMan II discovered some bugs in the calibration portion of the software. I've fixed this bug, and a few others, and posted the updated software to the web site. Before attempting to calibrate your own BattMan II, please go to the "Software" section of the construction article and download the latest version.

Sanyo Eneloop Test Update

Fri, 28 Sep 2007 01:12:21 GMT

I've tested another set of fresh-out-of-the-package Eneloops, manufactured eleven months earlier. They had an initial capacity of 72% of their fully charged capacity, which is much better than I had originally predicted. Together with my 74% results with six month old Eneloops, this lends credence to Sanyo's claims that the self-discharge curve flattens out, and that they are pre-charged to only about 75% capacity. See the updates marked September 2007 in the article.

BattMan II: A Computer Controlled Battery Manager

Sun, 09 Sep 2007 18:16:57 GMT

BattMan II is a computer controlled battery manager, intended for typical rechargeable batteries used by R/C and electronics hobbyists, as well as various consumer product batteries. BattMan II can charge, discharge, cycle, test, and monitor NiCd, NiMH, LiPo, LiNP, and lead acid batteries. A real time graphical display shows what's going on, and a log file keeps a history of all battery operations. Connects to any Microsoft Windows based PC using the parallel port.

EPROMs and Microprocessor Chips

Fri, 24 Aug 2007 02:15:10 GMT

I've added some 27128, 27256, and 27512 EPROMs to my surplus listings, along with a handful of Motorola 68705P3 single-chip microcomputers.

Electronic Surplus Items for Sale

Thu, 23 Aug 2007 02:07:13 GMT

I collect electronic parts. I keep stuff (like parts from obsolete equipment) that I think I might use someday. I also pick up stuff at surplus stores for potential future projects. After many years, I now have more stuff than I have time to make anything with, so I've decided to offer some of it for sale.

If you're looking for a part to use as the basis for your next great project, perhaps you'll find it here. If you can't find what you're looking for, ask, since I might have what you need. Please note that this is not a store. I generally only have one or two of any item you see here, so if you see something you want, you'll have to act fast!

Sanyo Eneloop Tests Revisted

Sun, 06 May 2007 23:37:56 GMT

My article, Testing Sanyo's Eneloop Rechargeable Battery has proven to be very popular, so I've updated it with some additional information:

For comparison, I ran the same series of tests on a traditional NiMH battery of a well respected brand. This test clearly shows the advantage the Eneloop has in charge retention during storage.
I received an e-mail from Sanyo Europe addressing some of the findings in my tests. I've added this feedback to the article in the appropriate places, and included a summary.

Go to the Article >>

Make a Dual-Boot IDE Cable

Tue, 24 Apr 2007 01:57:52 GMT

In early 2006, we replaced our two 500MHz P3 computers with 3GHz P4 machines running Windows XP Professional. The two old boxes were relegated to testing new releases of MotoCalc to ensure continuing backward compatibility, providing space for real-time backups of important files, and operating our old but reliable HP ScanJet 4C.

More recently, we decided to get rid of a lot of old "stuff", and the P3 boxes came up for disposal consideration. Each of these boxes consumes about $50 worth of electricity a year, resulting in about a quarter of a ton of CO2 emissions from Ontario's power plants.

After much discussion, it was decided that we still needed the ability to test MotoCalc on Windows 98 and 2000, but that other than that, we really only needed one of the two machines, and that it could be in a low-power standby mode most of the time. That's when I came upon the idea of installing the primary hard disks from both boxes into one of them, with a front panel switch to choose which operating system to load.

The Ultra-Portable "MoGo" Laptop Mouse

Wed, 18 Apr 2007 01:22:07 GMT

I've wanted an ultra-portable laptop for a long time because lugging a heavy full-sized laptop around on trips was just no fun. After much research, I had narrowed down the choices to a Toshiba Satellite U200-PT7 or a Lenovo 3000 V100. They were almost identical in features and price, and I settled on the Toshiba simply because it was immediately available locally (when I finally make up my mind what to buy, I want it now).

As for the mouse, more research was in order. If you've read my USB AA battery charger article, you'll know that I don't like a whole lot of cables and bulky items in my laptop bag, so I immediately ruled out any standard desktop corded mice. I should mention that at this point, I was under the mistaken impression that my new Toshiba had built-in Bluetooth (which the Lenovo does), so I began searching for a Bluetooth mouse.

Testing Sanyo's Eneloop Rechargeable Battery

Sat, 31 Mar 2007 23:12:17 GMT

Late in 2006, I found out about Sanyo's new Eneloop Nickel Metal Hydride (NiMH) rechargeable batteries, available in AA and AAA cell sizes. Unlike regular NiMH offerings from other vendors, Sanyo claimed the following benefits for their Eneloops: very low self discharge rate, ready to use right out of the package, and higher voltage.

One disadvantage of the Eneloops over normal NiMH cells is lower capacity. For the AA size, Sanyo claims a capacity of 2000mAh. Normal NiMH AAs are available with capacities of up to 2700mAh nowadays, but when you consider self discharge rate, such NiMH cells stored for about 30 days will drop to 2000mAh.

USB Powered Charger for Two AA NiMH/NiCd Cells

Mon, 01 Jan 2007 03:46:06 GMT

In a recent blog entry, I complained about all the chargers and wall warts I need to carry with me when going on a trip. This project, which can charge a pair of AA Nickel Metal Hydride (NiMH) or Nickel Cadmium (NiCd) cells using a laptop's USB port for power, arose to address part of that problem.

The charger in this project is designed to charge two AA NiMH or NiCd cells of any capacity (as long as they are the same) at about 470mA. It will charge 700mAh NiCds in about 1.5 hours, 1500mAh NiMHs in about 3.5 hours, and 2500mAh NiMHs in about 5.5 hours. The charger incorporates an automatic charge cut-off circuit based on cell temperature, and the cells can be left in the charger indefinitely after cut-off.