Eneloop
A low self discharge nickel metal hydride battery made by Sanyo, available in AA (2000 mAh) and AAA (800 mAh) sizes. They are sold pre-charged and due to the low self-discharge, can usually be used immediately after purchase. Eneloop batteries are good for photography and other high energy requirement applications. Due to the low self-discharge, they are also suitable for long-term intermittent or low-current uses; they might last up to a year between charges, much better than ordinary NiMH batteries.
Sanyo claims that Eneloop batteries retain 90% of their charge after six months, 85% after a year and 70% after two years, when stored at 20 degrees Celsius (68 °F).
They are priced at just somewhat more than ordinary NiMH batteries, in sets of 2 or 4 AA or AAA, with or without a charger. They are compatible with ordinary NiMH chargers. Sometimes they are marketed as "Sanyo", sometimes as "GE/Sanyo". These new type of batteries are marketed with over a dozen different brand names, but only actually made by two or three primary sources, so these Sanyo batteries are probably also marketed under other brand names.
Both ordinary AC plug-in chargers and USB chargers for pairs are sold.
Technology
"The chemical decomposition of the cathode has been reduced substantially by the use of a new super lattice alloy."[1]
"It appears that Sanyo is using a thicker separator (hence the lower mAh capacity) that is saturated with deionized water. This has the effect of shutting down the self discharge process."[2]
"...Eneloop cells need to be shipped in refrigerated containers, but the reason is to eliminate the normal self discharge associated with NiMh cells. If these cells are kept below 38 C (not 38 F), they will be ready to use right out of the package without having to charge them first. At higher temperatures, their self discharge rate increases."[3]
A Sanyo official has stated:
- "The Eneloop batteries are sold charged, but not necessarily 100% fully charged. In Europe we charge them about 75%."
- "Several long term tests have shown that the self-discharge rate decreases over time. This means that Eneloop batteries discharge relatively fast at the beginning and relatively slower the longer you store them."
- "Higher temperatures substantially increase self-discharging. It is best to store Eneloops as cool as possible to keep the charge in the battery. As a rule-of-thumb, every 10°C increase in storage temperature is equivalent to doubling the storage time."[4]
External links
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