Powerex MH-C9000PRO Professional Charger-Analyzer with 4 Powerex PRO AA 2700mAh NiMH Rechargeable Batteries

The lowdown — This Powerex stands out among premium smart charger-analyzers. It is built like a tank and has several improvements over the C9000, its older sibling I gave away. A variety of operating modes gives your rechargeable AAA/AA NiMH and NiCd batteries their healthiest and longest life, more so than similar devices. And Maha Energy Corporation, maker of Powerex, is a global leader in battery and charging solutions on an industrial scale. This is their specialty and it shows.• Operating modes — it has four, but one deserves a shout-out. Maha calls it Break-In. Batteries work better and enjoy a longer life when they are properly conditioned before first use with a so-called forming charge. This is a charge/discharge/charge cycle at very low power based on the rated capacity you enter. It takes a long time, almost two days, so plan ahead. This cycle can also be used to attempt salvage of older batteries that have stopped working. This feature is not found on other chargers. I imagine it stems from Maha's deep expertise in industrial-size battery installations.A new and unique feature is that it now remembers the last settings you used, charging rates and so on, even after powering down. This is very handy since we tend to use these chargers in the same mode most of the time.The other modes are Discharge, Charge, Refresh and Analyze. Both charging modes lead to a full battery but only Refresh and Analyze lets you determine its exact capacity. This is essential when assembling matched sets where the weakest cell determines overall performance. To achieve this it tops off the battery first, then discharges it completely to obtain its capacity in mAh, and finally charges it once more. These extra steps take a lot longer than charging alone but are the only way to get an accurate number.Note that simple charging will also produce a mAh figure. But this overstates capacity because charging consumes more energy than what gets stored.• Cutoff circuitry — overcharging batteries is a surefire way towards destruction. Smart chargers stop the charging process for NiMH and NiCd once there is a tiny voltage drop after a steady rise. This is called the delta-V method. Unlike others in this genre, the Powerex also monitors temperature of each individual cell as failsafe.• Display — the LCD is large, backlit, and highly legible. It shows operating mode and progress for each battery in a repeating and easy to understand cycle.• Built like a tank — cast from heavy-grade ABS plastic it feels unusually solid. It is also slightly larger than similar units and has more heft. All contacts are nickel-plated and have very strong spring loading. This lowers contact resistance so improves charging rates and accuracy. Its famous older brother which I have been using for years is flatter and wider. The PRO is a little higher but with a smaller footprint. You could call it more elegant.Summing up —This Powerex is your best choice if you are likely to use the extra features and are ok paying more for sophistication and build quality._________________Charging rates — This is the question asked most often. A good rule of thumb when using a charger with automatic cutoff such as this one is to charge at half C, where C stands for battery capacity in mAh (milliamp-hours). So if the capacity is 1,000mAh then go for 500mA. Anything higher runs the risk of heating up the battery too much. This can cause capacity loss. A bit lower, say, 0.3C will increase the amount of charge but takes longer. A much lower current makes it difficult for the charger to sense proper cutoff, inviting the risk of overcharging.NiCd versus NiMH — NiMH cells are almost always the preferred choice because, being a modern development, they simply work better. For instance, their energy density is much higher than that of NiCd. This means they will last longer before needing a recharge. And NiMH batteries suffer fewer so-called memory effects that irreversibly reduce capacity over time.They are also much less polluting since they do not contain heavy metals.NiCd cells still has an advantage is in applications requiring very high discharge rates. This is almost never the case in consumer electronics. The device would have to mention it. They also keep working in Arctic temperatures.

I love how easy this is to use. I am able to recharge my AA batteries whenever I need to and they last quite a while. I never have to worry about running out of batteries ever again!

Rehabilitation of batteries takes days, but really works and it worth it. The “high” rating is good to know when the batteries need to be discarded and can not be reconditioned. The display could be better… angle of view has to be close to square which on a table needs to be angled upward more or else you can’t read it.

As advertised