Description

The eneloop rechargeable batteries were developed by Sanyo

Sanyo

is a major electronics company and member of the Fortune 500 whose headquarters is located in Moriguchi, Osaka prefecture, Japan. Sanyo targets the middle of the market and has over 230 Subsidiaries and Affiliates....

 and introduced to the market in November 2005. They lose their charge slower than previous NiMH batteries: 10% in the first year compared to about 20% on the first day and 1-4% on every successive day. Hence the name, low self-discharge NiMH battery

Low self-discharge NiMH battery

The low self-discharge nickel-metal hydride battery was introduced in November 2005. These batteries were developed by Sanyo, who called them "eneloop". Subsequently, other manufacturers also offered LSD NiMH....

. eneloop batteries are sold pre-charged and can be used immediately, while regular NiMH batteries lose their charge so fast that this isn't feasible. Due to the number of alkaline batteries they can replace during their lifecycle, they're eco-friendly when used appropriately.

eneloop

The original eneloops were introduced in AA and AAA size, with capacities of 2000mAh and 800mAh. They were rechargeable 1000 times and held their charge up to 75% for one year. Sanyo later improved them to be rechargeable 1500 times, along with switching to renewable energies for pre-charging. This revision holds 85% of the charge after one year and 75% after three years. The two revisions can be distinguished by the design of the label: They now state the minimal instead of the typical capacity, 1900mAh and 750mAh. The new revision also has a crown printed on the label.The new type numbers are HR-3UTGA (AA) and HR-4UTGA (AAA).

Sanyo introduced C and D sized eneloops with a minimal capacity of 2700mAh and 3000mAh in 2009, along with a new universal charger. As these sizes are only available in Japan, Sanyo also offers adapter sleeves to fit AA sized eneloops in devices that take C and D sized batteries.

In 2011, the batteries were again improved, now they hold their charge up to 90% after one year, and 70% after five years. Also, they can be recharged 1800 times.
The C and D sized eneloops now have increased stated minimal capacity of 3000mAh and 5700mAh.
They will be available in Japan only starting November 2011.

eneloop lite

eneloop lites were in introduced in 2010. They're intended to address two other downsides of regular NiMH and alkaline batteries: The initial cost and the long charging time, both achived by reducing the capacity of the battery. The eneloop lite AAs have 1000mAh, while the AAAs have 600mAh. Due to reduction of the capacity compared to the regular eneloops, the charging time is cut in half for the AA and to 3/4 for the AAA. On the other hand, they can be recharged 2000 times. The reduction in capacity also reduced the production cost, which decreased the initial investment for rechargeable batteries.

eneloop pro (XX powered by eneloop Technology)

eneloop pro (or XX powered by eneloop Technology in the US and Europe) were introduced in 2011. They have a higher capacity than regular eneloops, 2500mAh (Min 2400mAh). However, they retain only 75% of their initial charge after one year, and can only be recharged 500 times.

eneloop plus

eneloop plus have a PTC thermistor

Thermistor

A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor...

 built-in that cuts the power when the batteries are overheating. This makes them especially suitable for toys. Other specifications are identical to the second-generation eneloops.

Accessories

There are numerous chargers for eneloop, including USB chargers and eneloop-operated hand warmers, which double as chargers. Mobile power boosters are intended to recharge electronic devices via USB on the go using eneloops or built-in Lithium-ion batteries.

Sanyo also released plastic sleeves that turn AA into C and D sized batteries.

eneloopy is a dog-shaped battery tester. A LED on it's nose shows the battery level by changing colors.