Panasonic recommends keeping the batteries in a cool location to maximize charge retention. After five years, they retain 70% of their charge (when stored at 20 degree Celsius). After 6 months, they retain 90% of their charge. Eneloops can be recharged up to 2100 times, and they will retain their charged capacity even after years of storage. I do not recommend the Energizer or Duracell rechargeable batteries - these name brands seem to produce inferior rechargeables, perhaps to protect their sales of alkaline batteries.Įneloop Rechargeable Batteries by Panasonicīetter designed than other rechargeables, Eneloop batteries have become a best-selling battery. Generally, the best low self-discharge batteries are made in Japan (the others are made in China), these are: Panasonic’s Eneloops, Duracell, Energizer and Sony. The Eneloop Pro batteries from Panasonic definitely hold their charge the longest, and they are my top recommendation. However, they are ideal for use in high-drain electronic devices like digital cameras, where they out-perform alkalines. Because they can hold their charge for so long, they are suitable for low-drain devices like remote controls and flashlights. These batteries have a lot going for them: they come fully charged (like alkaline batteries), and they can hold their charge over many months (unlike regular Ni-MH rechargeables). Today, the best rechargeable batteries are the “low self-discharge” Nickel-Metal Hydride (Ni-MH) cells.
These Powerex are also low-discharge, high-capacity batteries ( 2400 mAh), but they do not perform quite as well as the Eneloop Pro (see this review for the details on their performance). For example, if you charged your batteries twice a week consistently, it would take 5 years to reach 500 charges.Īlso worthy of consideration is the Powerex battery, which is cheaper than the Eneloop Pro. But most people will never charge their batteries that many times. They can only be charged 500 times (versus 2100 times for regular Eneloops). They have a high energy capacity (2550 mAh), and they perform better than similar high-capacity AAs. Overall, the best rechargeable AA battery is the Eneloop Pro. If you are on a budget don’t mind a little less performance from your batteries - get the Powerex AAs (about $10 for pack of 4).If you want maximum recharge capacity (2100 times) - get the 4th Generation Panasonic Eneloops (about $11 for pack of 4).If you want the best energy capacity (2550 mAh) - get the Eneloop Pro (about $18 for pack of 4).They're really designed for 14V operation, which is an automobile with the engine running and the alternator spinning.Here are my recommendations for the best rechargeable AA batteries: They're questionable at 13.8V and get really bad at 12V and terrible at 11V. I wouldn't run a 500W linear mobile amp from a battery alone, like ever. When charging my tank battery, if the terminal voltage is below 11V it will output 50A for about 30 minutes, but after 12 hours it's down to <1A. Mine can output about 50A for a depleted battery, but can trickle down to 100mA or so for a float and is intended for larger batteries, which is all I'd ever use. When the battery is deeply discharged, the charging current is increased to the max the battery can handle, and then it tapers down as the battery charges until it's a "float." I build my own, never actually bought one. A smart charger senses the charge state and adjusts charging current based on discharge. But I've usually used a smart charging circuit, all linear and not switching, so no RFI of any kind. I've used Army tank batteries for Field Day stations, and one can run a 100W station (output power) using CW or SSB for 24 hours but a tank battery is about 3x the size and weight of a car battery.įor a float charge, usually the 13.8Vdc "station" power supply can be applied to a 12V lead-acid battery, whether wet or gel, and float it forever without damage in a reasonably cool environment. In my case, unless the battery can power what I need it to for at least four hours I wouldn't bother with it.
If your load is say 200W and you want it to last two hours, at 12V that is 33.3 AH but remember the AH ratings for batteries are never, ever at full discharge current. I don't know what the yellow top batteries are offhand, but to size a backup battery it pays to first determine the load and time requirements.