Powerex MHRAA4 AA 2700mAh 4-Pack Rechargeable Batteries

BACKGROUND:I wanted a NiMH AA/AAA charging system that would remove the "mystery-of-the-charge" and provide more confidence in the rechargeable batteries I purchase. So, I did a little research like everyone does (or should do) before buying an item that's intended to last for years (find "The Best (aa/aaa)Charger Guide by John Dziadecki on Amazon - excellent read). I decided to buy two 4-packs of Powerex AA 2700's and two of Powerex AAA 950's to supplement some Duracell 2650's, Kodak 2550's, Energizer 2500's and an assortment of generic 2300's. I also bought two chargers: the MH-C9000 and the MH-C800S.For years I've used an assortment of chargers with idiot lights. I had no idea HOW MUCH of a charge those batteries were getting or whether they really held the advertised capacity. But, it was very clear (and frustrating), that some of these batteries and/or chargers were very limited (junk?). I'm not sure how many times I installed newly charged NiMH batteries into a digital camera only to have the low battery icon show up after a couple shots: "Hmmmm...how many of these batteries are duds?" And, generic battery testers really don't tell you much, i.e., how 'good' is "Good"; How 'low' is "Low"? .....So, it took me a while to get fed up.MH-C9000 Charger:This thing definitely took most of the guess-work out of my rechargeable AA/AAA energy supply. I was able to get rid of six old NiMH AA's in the first week and "rescue" seven others with this charger. The directions with the charger are a little sketchy but, if you know the advertised capacity of your battery and its age, you'll be able to figure out how to best charge it and how many mAh's are available to you afterwards. You'll also be able to determine if the battery is shot. This isn't something you get to do with idiot-light chargers (which work just fine for lots of people). I remain very impressed with this charger.MH-C800S Charger:I bought the MH-C800S to supplement the -C9000 because of its 8-battery capacity. This charger does not provide battery capacity values at the completion of a charge cycle. It does however, have a 16-hour 'conditioning mode' designed to re-juvinate and cycle (discharge and recharge) batteries: it works very well. If you don't care about actually 'seeing' the specific capacity of your batteries, the MH-C800S is a good choice at the right price. It too will tell you if your battery is shot. This charger is all that most people will need or want for AA and AAA re-chargeables.CAPACITIES:I have not used Powerex re-chargable batteries long enough to comment on their discharge rate. But, thus far I haven't seen a difference between my older 2300 and 2700 mAh re-chargeables and the Powerex batteries. It's also too early to determine if the Powerex batteries will last through 1000's of charges.The Powerex AAA batteries have an advertised capacity of 950mAh. They charged out between 956-967 in the MH-C9000's "Break-In" mode. Allowing for heat attenuation, full capacity is about 920. I'll know more when I recharge them.The Powerex AA batteries have an advertised capacity of 2700mAh. They charged out between 2556-2650 in the MH-C9000's "Break-In" mode. Allowing for heat attenuation, full capacity might be about 2300. I'll know more when I recharge them.Some of my older batteries charged out at significantly higher rates than advertised after putting them through the MH-C9000's "Refresh and Analyze" mode: these older batteries are holding charges longer and they discharge more consistently. I can tell that those instances of partially-charged batteries screwing up the camera's current requirement will be fewer. At least now, I'll be able to sort out the weak, lame and starving in the herd.SUMMARY:Of course, there are other ways to do what I did. The Powerex battery purchase was based on the charger purchase: I figured it best to stay with a certain brand and keep the system homogenous. Not necessary at all. The price was right for the batteries and they came with convenient storage cases. In time, if Powerex batteries don't perform well, I'll probably start replacing all my batteries with an assortment of Sanyo Eneloops. I'm in the process of learning what a good rechargeable AA/AAA battery really is.There are several other chargers that perform similar to the MH-C9000 and -C800S: LaCrosse, Sony, and/or Sanyo. Reviews for the Powerex MH- products appealed to my technical comfort level and budget. Good stuff!

After charging these batteries using the Break-In/Forming charge on my Maha/PowerEx C-9000 charger, the actual AH ranged from a low of 2580mAH to a high of 2623mAH, with an average of 2599mAH. Although advertised as 2700mAH batteries, the manufacturer's published minimum guaranteed capacity is 2500mAH, of which they all exceeded.After reading other reviews of this battery, I have not found the poor performance many others have experienced.One conclusion may be that the batteries are being improperly charged. Improperly charging a battery is a sure way to damage it. Typically a battery can be charged two ways; either a trickle charge (with the typical overnight or 16 hour chargers), or fast charge (1, 2, 4, or 8 hour chargers).When the battery approaches overcharge, a fast charger MUST reduce the charge rate. If the rapid charge rate is allowed to remain applied when the battery is fully charged, the battery risks damage, a blown overpressure seal, leaking electrolyte and so on. NiMH cells in particular are very sensitive to high overcharge current and can be easily damaged.When a battery is trickle charged, the charge rate is not sufficiently high enough to damage the battery when it goes into overcharge. While charging for 16 hours is not as convenient, it is the safest method of charging, and will actually charge the battery to a higher capacity than a fast charger (unless the fast charger is a combination fast/trickle charger).Since fast chargers must reduce their charge rate prior to going into overcharge, a method of sensing the battery's voltage, temperature, or a combination of the two must be employed so that the charger can detect when the battery is close to overcharge. For most fast chargers, there is a margin of of safety built into the charge profile so that the fast charge is removed well in advance of overcharge. This will result in the battery having less than 100% charge.Some of the better fast chargers do switch to trickle charge at the completion of the fast charge to complete the charge. This still takes time, and often requires several hours of trickle charge to put a 100% charge into the battery.Cheap fast chargers may not even sense overcharge, but simply provide a timed charge. With these chargers, unless the battery is fully discharged, the risk of high-current overcharge is significant.The mechanism used in a fast charger to determine when a battery is at the threshold of overcharge is somewhat dependent on the manufacturer's battery design variances, battery capacity, and other factors.Due to these factors, and efforts to keep charger costs low, a specific manufacturer's Fast charger may not be sophisticated enough to employ the proper circuitry to properly detect the overcharge point of another manufacturer's battery. Therefore, charging different brands of batteries on another manufacturer's FAST charger, while assumed as safe by many, may NOT safe in my opinion, and can cause battery damage.One exception are the high-end Charger/Analyzers made by Maha/PowerEx and LaCrosse. These chargers use sophisticated overcharge detection circuitry to monitor voltage, changes in voltage, and temperature. Even then, if you incorrectly setup one of these chargers, you may still damage a battery.Most battery manufacturers state that you will void the battery warranty by charging the battery improperly, which includes the use of other brand chargers. There is more to this than liability, there is a significant risk of battery damage.However, it is generally accepted that overnight/16 hour/trickle chargers are safe for charging any brand battery, and notwithstanding any manufacturer disclaimer, may be safely mixed brand-wise. While there are always exceptions to even this convention, the charge rates are (hopefully) generally low enough that overcharging the battery will not damage it.I am not sure why many folks are having problems with batteries, but perhaps it's due to improperly fast charging them.To restate, I would never recommend FAST charging a battery on another manufacturer's FAST charger, unless it was specifically designed for that purpose (most of which are not).

It's a little odd to see these batteries rated as "2700mAh", but user rated for a 'minimum' of 2500mAh.Of 12, 2 batteries so far are just under 2500mAh with the rest now at just over 2500mAh. I may try what Radio Control (RC) users try is a repetitive discharge/charge cycle to get some of the cells into shape, but to date have used the Break-in and refresh & analyze modes from my MH-C9000 charger. An 8-cell Maha Powerex charger is coming down the road - it's the best way to go to rotate spare batteries while some of the more time consuming charge modes are used.I want to point out that virtually nothing these days rounds down (they all stretch numbers up): MP3 players, hard drives, etc... all stretch capacities and levels. For that reason I rate this 4 stars. That said, if ALL batteries are rated like this, then these AA batteries still are better quality in terms of how long they hold onto their charge. They have performed well above average compared to Energizer 2100 & 2300mAh batteries and Energizer & Duracell alkaline batteries I've tried in a new Garmin Oregon 400t GPS - nearly double the life!Keep in mind: If someone were to use regular retail store NIMH batteries without a smart charger, then they would otherwise just attribute low battery life to poor battery quality or that their device is a power hog.These batteries are high capacity in comparison to what's out there, last as long or longer compared to the competition (like industry leader Sanyo), and can also be found at national stores like Batteries Plus. They are good batteries even if they follow the crowd and "round down" with their capacity rating.