Eneloop

The original Eneloop batteries were introduced in AA and AAA size, with capacities of 2,000 mAh and 800 mAh. They could be recharged 1,000 times and held up to 75% of their charge after one year. The part numbers for first generation cells are HR-3UTG (AA) and HR-4UTG (AAA).

The second generation of Eneloop AA and AAA batteries was introduced in 2010. It endured 1,500 recharge cycles for depth of discharge (DOD) 60% and held 85% of the charge after one year and 75% after three years.[10] The part numbers for second generation cells are HR-3UTGA (AA) and HR-4UTGA (AAA).

Sanyo introduced C- and D-sized Eneloop batteries with a minimum capacity of 2,700 mAh and 3,000 mAh respectively in 2009, along with a new universal charger.[11] As these sizes were only available in Japan and Singapore, Sanyo offered adapter sleeves to fit AA batteries in devices that take C or D batteries.

Eneloop 5th anniversary special glitter edition pack

In October 2011 the batteries were again improved to retain up to 90% of their capacity after one year, 80% after three years and 70% after five years. The batteries can be recharged up to 1,800 times, rather than the 1,500 times of the previous revision. The part numbers for third generation cells are HR-3UTGB (AA) and HR-4UTGB (AAA). At the same time, the C- and D-sized Eneloop batteries' stated minimum capacities were increased to 3,000 mAh and 5,700 mAh respectively. They were available in Japan from November 2011.[12]

European models went on sale from the beginning of October 2012.[13]

Following the acquisition of Sanyo by Panasonic, a fourth generation was introduced in April 2013. The number of charges per cell was increased from 1800 to 2100 cycles for both AA (BK-3MCC) and AAA (BK-4MCC) models.[3] In some countries the batteries are branded as Panasonic.

A fifth generation was introduced in 2022 (manufactured from at least April 2021). The minimum (guaranteed) capacity was increased from 1900 to 2000 mAh for AA (BK-3MCDx) and from 750 to 800 mAh for AAA (BK-4MCDx) models.[14] These batteries are supposed to hold up to 70% of their charge after 10 years of storage at 20°C.

The Eneloop Lite line was released in Japan in June 2010. They addressed two disadvantages of alkaline and other NiMH batteries: the initial cost and the long charging time—both achieved by reducing the capacity of the battery. The batteries find suitable applications in low-drain devices such as remote control devices and alarms, where low capacity is not an issue. The AAs have 1,000 mAh of capacity, while the AAAs have 600 mAh. Due to reduction of the capacity compared to the regular Eneloop cells, the charging time is halved for the AA and reduced by 25% for the AAA. On the other hand, they can be recharged 3,000 times. The reduction in capacity also reduced the production cost, which decreased the initial investment for rechargeable batteries. They also weigh 30% less. The product numbers are HR-3UQ (AA) and HR-4UQ (AAA).[15]

Along with the upgrade of the regular Eneloop cells in April 2013, the Lite version was also upgraded. According to Panasonic, it can now be recharged up to 3,000 times (life cycles for DOD 60%)[16] (model numbers BK-3LCC for the AA and BK-4LCC for the AAA battery). The upgraded batteries also retain 90% of the charge after one year like the regular Eneloop cells.

Sanyo Eneloop XX

The Eneloop Pro family have higher capacity in mAh, trading this off against poorer charge retention and shorter lifespan. They are better than standard Eneloops for high-drain applications. They are not recommended for applications where batteries are continuously charged, such as in DECT phones left on a charging base. Their higher self-discharge rate makes them unsuitable for very low drain applications such as clocks.[17] Their slightly larger diameter can be problematic where the batteries are a tight fit.[17]

The Eneloop Pro (or XX powered by Eneloop Technology in the US, Canada, and Europe) series was introduced in 2011. At that time, no AAA version was produced.[18] They have a higher capacity than regular Eneloop cells, 2,500 mAh (min. 2,400 mAh) for AA. They retain 75% of their initial charge after one year, and can be recharged 500 times, significantly less than the standard non-Pro Eneloop line. The product numbers are HR-3UWX (AA) and HR-3UWXA (AA).[19]

In January 2013, Sanyo announced the second generation of Eneloop XX (model HR-3UWXB, or Panasonic BK-3HCC), branded Eneloop Pro. The new generation has a 50 mAh higher capacity (2,550 mAh nominal, 2,450 mAh minimum capacity), and the self-discharge rate was improved, retaining 85% up to one year.[20] They also introduced an AAA version of the Eneloop XX (model HR-4UWXB) with a nominal capacity of 950 mAh (900 mAh minimum).[21] After the acquisition by Panasonic, they were renamed Eneloop Pro (model BK-4HCC) in Europe (BK-4HCCE) and the Americas (BK-4HCCA).[3]

In October 2015, Panasonic remodeled Eneloop Pro (BK-3HCD/BK-4HCD). The minimum capacity of the battery increased, by 50 mAh to 2500 mAh for AA and by 30 mAh to 930 mAh for AAA.

Eneloop Plus cells have a PTC thermistor built-in that cuts the power in case of overheating. This makes them especially suitable for toys and devices that generate significant heat. Other specifications are identical to the second-generation Eneloop batteries. The product number is HR-3UPT (AA), and the battery was released in Japan in December 2011.[19] It was later discontinued.[17]

There are many counterfeit Eneloop batteries; in particular batteries sold on online auction sites are often fake. Ways to distinguish genuine batteries have been published.[22]