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Maha's PowerEx MH-C204W charger. Courtesy of Maha, with modifications by Michael R. Tomkins. Power to the people: Maha's updates their already-excellent MH-C204F AA charger
(Thursday, June 24, 2004 - 15:50 EDT)

Anyone who's read one of my reviews of an AA battery-based digicam will know that the Maha MH-C204F has been my favorite battery charger for a long time now.

My reasons for liking it so much are that it does a good job of quickly and completely charging NiMH AA batteries while keeping the maximum temperature within acceptable limits, and also incorporates discharge-conditioning circuitry. Discharge-conditioning is useful for revitalizing cells that have seen a lot of charge/discharge cycles, or that have sat on the shelf for a long time. While there are a lot of other chargers on the market, I'm not aware of any that have have offered the particular combination of features, performance, and component quality of the MH-C204F. (The discharge-conditioning capability in particular seems to be pretty rare.)

Now, Maha has updated the MH-C204F with a number of enhancements, calling the new product the MH-C204W. I'm waiting for eval samples of the new model to arrive so I can test them and write a proper review of the new model, but the initial list of features and capabilities look pretty impressive. Here's a short list of what's new and why it matters:
  • No power brick(!) While it doesn't affect charging performance at all, a huge convenience feature of the MH-C204W is that it now has an AC power supply built right into it. This means you only need to carry a small power cord, rather than a bulky wall transformer "brick." It also means that the MH-C204W is fully compatible with any AC power source in the world, accepting voltages from 100-240 volts at 50 or 60 hertz.
  • Improved charge-completion detection. The MH-C204W features zero delta-V and negative delta-V charge-completion detection, as well as an expanded use of thermal sensors to guard against cell overheating. The net result is faster charging with less risk to your batteries.
  • High-current "jolts" to recover previously unchargeable batteries. This has happened to me more than once: A set of NiMH cells has sat in a drawer for a couple of months and as a result, one or more cells have developed internal "micro shorts." When you put one of these cells into a conventional charger, they don't respond properly to the charging current, so the charger refuses to charge them. In the MH-C204W though, the high-current capability of the internal AC power supply is used to apply a "jolt" of high current to each cell before the charger evaluates its "chargeability." The high-current jolt is enough to clear most micro-shorts, so the MH-C204W can resurrect many cells that other chargers would reject. - This feature alone could pay for the charger in a year or two of use.
  • A new 4-step charging profile "tops off" batteries more effectively. It turns out that this is a feature I can claim some credit for: In my battery capacity testing (see my battery shootout page), I discovered that running cells in a moderate-rate trickle-charger for 12-24 hours after they'd initially been charged in a fast charger produced noticeably higher capacities. Based on this empirical data, Maha conducted research of their own, and found that they could "top off" batteries by adding a medium-current interval to their charging profile. As a result, the new MH-C204W uses a four-step charging cycle that consists of an initial ramp-up (the "jolt" mentioned above), a fast-charge cycle, a medium-rate "top off" cycle, and finally a low-rate, pulse-charging "maintenance" cycle. (This last lets you safely leave batteries in the MH-C204W after they're charged, to maintain them at peak readiness.)
  • Alkaline battery detection for safety. It's important that you *never* try to charge an alkaline battery in an NiMH charger. The very *least* that could happen is that the alkaline cell would get very hot, vent, and leak corrosive goo all over your charger. Worst-case scenarios involve explosions and fires. To help avoid such mishaps, the MH-C204W examines the current/voltage profile of each cell being charged, to make sure that someone didn't drop an alkaline cell into it by mistake. The process isn't foolproof, but better than 9 times out of 10, it'll successfully detect alkaline cells and turn off the charging current before any damage can occur.
  • Discharge conditioning. Nothing new here, but it's important to note that the MH-C204W carries forward the discharge-conditioning capability of the MH-C204F. Several battery-chemistry experts I've talked with over the years have insisted that, since there's no "memory effect" with NiMH cells, there's no need for discharge-conditioning circuitry in NiMH chargers. I'm not an electrochemist, but can definitely point to cases where cells with waning performance showed a clear increase in capacity after being discharge-conditioned. (I've seen this most consistently in cells that were left sitting on the shelf for long periods of time. Initially weak, a couple of charge/discharge cycles restored them to nearly full capacity again.) Hence, I highly recommend that you look for chargers that include this feature.
Overall, the MH-C204W looks like a real winner, with significant enhancements over the MH-C204F in several areas, while continuing to offer the rare but highly useful discharge-conditioning feature. My full endorsement will have to await the arrival and testing of some sample units, but based on past performance and the enhancements that Maha says they've made, it looks like the MH-C204W could become my new favorite.

Maha Energy can be found on the web at www.mahaenergy.com. Their products are also sold online by longtime IR site supporter Thomas Distributing, at www.thomasdistributing.com. Check them out!

Maha's PowerEx MH-C204W charger. Courtesy of Maha, with modifications by Michael R. Tomkins. Click for a bigger picture!

Original Source Press Release:

PowerEx Reinvents Worldwide Speed, Portability and Efficiency in the Charging Industry!

La Verne, CA - June 14, 2004 -- Maha Energy Corp., maker of PowerEx rechargeable batteries and chargers, is pleased to announce one of the market's lightest and fastest charger: The MHC204W One Hour Worldwide Travel Conditioning Charger.

After intensive research, Maha discovered that casual and professional users desire portability and reliability. Consumers need a small, trustworthy charger that could be taken anywhere around the world that actually fits in their camera bag. Consumers also require a charger that can even revive batteries thought ready for the recycle bin. With these needs in mind, Maha designed the MHC204W. This ultra compact and portable charger is up to 70% lighter than competitive models and charges batteries to their maximum capacity!

The MH-C204W can be used internationally without the need of a power brick! This travel charger is globally certified and compliant to nearly every major safety agency in the world. An integrated 100-240V 50/60Hz worldwide switching adapter is built into the charger and comes with an interchangeable AC cord.

The MH-C204W also magnifies battery longevity! An integrated battery conditioner rescues old and degraded NiMH batteries by applying high current pulses. In addition, this conditioning charger includes an alkaline battery detection device that prevents users from charging alkalines.

Through unique algorithms, the MH-C204W can reach a 98% charge level in the batteries when the lights turn green, without the risk of undercharging or overcharging!

The MH-C204W One Hour charger has four unique charging phases: startup charge, rapid charge, top-off charge and maintenance charge. The startup charge delivers a smooth ramp-up of current when the batteries are inserted. The top-off charge is applied for two hours after the completion of the charge to ensure that batteries are topped off to their maximum capacity. The low rate pulse maintenance charge ensures that batteries are not overcharged when left in the charger for extended periods of time and are always ready to use. Finally, the microprocessor driven negative Delta V, Zero Delta V and the temperature termination system ensure complete charging.

The MH-C204W One Hour Worldwide Travel Conditioning Charger's retail price is US $39.95 including 4 AA 2300mAh batteries and a battery carrying case.

Maha Energy Corp., maker of PowerEx, a leading provider of consumer and industrial battery and charging solutions operates a global network of manufacturing, design and distribution locations to serve both standard and OEM customers.

A Charger Redesigned from the Ground Up

What do you do when you want to launch the successor to a already successful product? You listen. You listen to your customers. That's exactly what we did when we designed the MH-C204W One Hour International Conditioning Charger.

We surveyed our customers, as well as put ourselves in the shoes of both casual and professional users. We discovered that they had many desires that were not directly addressed by manufacturers. Most manufacturers are caught up in improving the specs and making their product look good on paper. But what are the features that customers REALLY care about? We have learned a great deal by talking to current and perspective customers. Here is what they told us:
  • I really want a charger that will fit in my camera bag. Not a
    charger that needs its own bag.
  • I want a charger I can take anywhere in the world without having to carry a transformer.
  • I want a reliable charger, that charges my batteries fully when the lights turn green.
  • I want to be able to charge batteries that I haven't used for a few months and not have to throw them away.
  • I want a reliable charger that always works.
So we decided to address each of these needs.


The MH-C204W does not require an external power brick which significantly reduce its dimensions. This charger is about the size of a regular consumer digital camera.

The charger weighs less than 5 oz and the AC cord is only 3 oz. This is about 70% lighter than the competition!

We also decided not to make a "foldable plug" design that is popular in the industry. Instead, we opted to use an AC cord so that you will not occupy valuable real estate on your wall outlet and also allows you to position the charger in a comfortable position rather than behind the cabinet in your hotel room! The AC cord can also be easily changed for various regions, such as the European cord or the Australian cord.


The MH-C204W has a integrated 100-240V 50/60Hz international power supply. When traveling abroad, it is no longer necessary to bring bulky transformers or have the fear of not having the right voltage.

Not to mention the MH-C204W is globally certified for safety and electromagnetic compatibility. This charger bears the UL safety mark, as well as FCC, CE, GS, C-Tick, Australia DOIR, Argentina S and numerous others.

The AC power supply integrated in the charger is not just any power supply. Open up the MH-C204W and you will see the quality! The AC power supply is based on a patented "Top Switch" design that converts AC to DC power with over 75% efficiency. The charger is indeed an environmentally friendly product! We built the AC power supply well over spec to ensure high reliability.


One of Maha's unique strengths is the ability to develop a charging microprocessor in-house. We don't have to settle for an off-the-shelf product. Most of the features in a charger, besides it charging speed and size, depend mostly on its brain, the microprocessor. Maha's team of embedded systems architects and programmers designed a brand new microprocessor just for this charger: the MH-NM5000 series processor.

Through unique algorithms, we are able to reach nearly a 98% charging efficiency (that is a 98% charge level in the batteries when the lights turn green) without the risk of undercharging or overcharging. This is through an array of high-resolution 12bit A/D (analog-to-digital) converters and temperature sensors. After all, you don't want your 2300mAh NiMH AA batteries only charged to 1800mAh.

In addition, Maha's new processor also features a unique four stage charging process that is found in no other charger:
  • Ramp-up
  • Rapid Charging
  • Top-off Charging
  • Maintenance Charging
We know customers sometimes don't use their batteries for an extended period. By the nature of NiMH batteries, inactive batteries often degrade in performance significantly. That's why Maha designed a special "ramp-up" charge that "jolts" the batteries if needed to revive old batteries. This happens in the first two minutes after battery insertion. This "jolting" is a series of carefully timed high current pulses that can activate both new and inactive batteries. From the customer's point of view, they can put batteries of different health levels and rely on the charger to give them a complete charge.

The charger also features a unique "top-off" charge. Through extensive research, we have discovered that if, after charge completion, the charger abruptly terminates the rapid charge and go directly to trickle charge, batteries often fail to retain the most amount of charge. Therefore, we designed an intermediate, medium current, top-off charge. This is similar to slowly "topping off" a glass of wine, but not to the rate of drop by drop. Drop-by-drop is the job of the maintenance charge.

We know that customers sometimes need to leave their batteries in the chargers for extended period of time before they are used. The maintenance charge is an extremely low current pulse charging that gives the batteries a brief pulse charge every few seconds to ensure the batteries are charged but not overcharged. Instead of using a continuous current, the pulse maintenance charge allows the batteries to be in good shape even after being left in the charger for an extended period of time.


In addition to its superior charging algorithm, the MH-C204W also has a highrate built-in battery conditioner. The conditioner, which can be activated by pressing the conditioning button, will deep-discharge the batteries and recharge them automatically without further user intervention.

The conditioner has proven to be useful in reviving poorly performing batteries. Batteries that were previously thought ready for the recycle bin can often be brought back to life.


Maha is one of the very few companies that design, manufacturer, and market batteries and chargers all under one roof. The new MH-C204W only uses the highest quality components. These are assembled and tested in Maha's wholly owned state-of-the-art production facilities in Taiwan under ISO-9001 quality systems.

Before each unit is shipped, every charger goes through extensive automatic circuit board inspection as well as an automatic functional system. Maha has developed unique tools to characterize performance of EACH charger through simulated operation, not just sampling a small number of units. You can be assured that each charger is fully tested before it ships.

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