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Powerex MHRAA4 Powerex AA 2700mAh 4-Pack Rechargeable Batteries
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- Nickel-Metal Hydride (NiMH) Chemistry
- Voltage of 1.2V and a capacity of 2700mAh
- Batteries can be recharged hundreds of times, and because they have memory-free operation, the will not develop memory effect, which can cause batteries to hold less charge
- These batteries will retain a charge at or near full capacities even after hundreds of charges
- A battery carrying case is included
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The Powerex MHRAA4 Rechargeable AA NiMH Batteries (1.2V, 2700mAh) - 4-Pack is a package of 4 AA nickel-metal hydride (NiMH) batteries. They have a voltage of 1.2V and a capacity of 2700mAh. The batteries can be recharged hundreds of times, and because they have memory-free operation, they will not develop memory effect, which can cause batteries to hold less charge. These batteries will retain a charge at or near their full capacities even after hundreds of charges. A battery carrying case is included.
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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).
We also used these in our church's wireless wearable mic packs after having a poor experience with Enloops. The Enloops couldn't get through our three morning services. Based on my history with Powerex, I bought more of these and the problem was solved.