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NiMH batteries and self discharge

18 January 2010 3 Comments


If you have been using NiMH rechargeable batteries for some time you might be familiar with the issue of these batteries getting discharged by themselves if  left for a couple of weeks / months, though all batteries self discharge with time, the rapid self discharge is a major problem with NiMH batteries they lose almost close to 1% charge every day and many batteries get discharged within 1-4 months.

This self discharge problem causes  a lot of problem and frustration with NiMH batteries, suppose you have a device like a digital camera / video recorded it might not be used for a couple of months but when you need to use the same it would not power up coz the NiMH batteries charge would have got depleted in the same, do note that I have noticed this self-discharge problem a lot in bad cheap brand NiMH batteries, sometime they get discharged within a week.

Is there a NiMH rechargeable battery that doesn’t self-discharge

Remember that every type of battery self-discharges over time, even alkaline batteries in around 4-5 years, it’s the duration of self-discharge time that is important, around the year 2005 Sanyo released a new brand of NiMH batteries called “Eneloops” these batteries have a very low self discharge rate, typically a Eneloop battery will retrain around 85% of the charge after one year of charge and around 70-75% after 2 years, so needless to say these NiMH batteries are the ideal NiMH batteries due to their very low self-discharge rate, these batteries come pre-charged and can be used straight out of the pack for the first time directly without charging.

Sanyo eneloop LSD NiMH Batteries

These new variants of  NiMH batteries are know as  low self-discharge nickel-metal hydride battery (LSD NiMH) some popular brands of manufactures that create NiMH LSD batteries are

1) Sanyo – Eneloops in AA /AAA sizes

2) Duracell – Pre Charged / Duraloops

3) Rayovac Hybrid

4) Uniross – Hybro

Though these LSD NiMH cost a little more than regular NiMH batteries its advisable to purchase them, the added advantage is that these LSD batteries can be charged in regular NiMH chargers and they also have higher efficiency and stable voltage under load than regular NiMH batteries, I expect that in a few years most of the NiMH batteries will be of the LSD kind.

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