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Ni-mh Batterys


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Hiya All, does anyone know the shelf life of NEW and UNUSED ni-mh batteries.

I have a pack of 'camplus 2300 mah' aa size, it doesnt look like i'll be using them in the next couple of years!!!!


Also if used ni-mh batteries are not going to be used in the next few months is it best to store them fully charged (even though they discharge a little day after day) or discharge them completely prior to storing them away?


Many thx


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Charged ones will slowly lose their charage over time (several weeks). And storing them without recharging them for like six months may case them get that memory effect. (yes I know were talking about NiMH, but it does still happen, slower though)

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does anybodies ni-mh batteries every charge to the fulliest? I got 4 pairs of AA and everypair that I just recharged ,rapid or overnight, when I plug them into my sportrack color never shows a full charge. I'm using energer and durcell 2300 AA ni-mh's


also any body try out those non name ni-mh 6 for 5.00 kind of deal 1600mah or similar from various websites?if so how do they compare to the durcell,etc



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Ni-Mh batteries even fully charged put out slightly less power than new alkaline batteries. So, yes your Ni-Mh's are indeed fully charged when taken from the charger. But the readout in the GPSr is calibrated for alkalines. Don't worry about that.


Some GPSr's have an actual setting you can adjust for when usingh Ni-Mh, and after that change the charger will show full when the batteries are full. But again, this is just eye candy & doesn't affect the use of the batteries.

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Excellent battery reference page

Welcome to Battery University



* Note the Li-ION differences (most cellular phone type batteries).


Storing and priming of batteries


"Nickel-metal-hydride can be stored for about three years. The capacity drop that occurs during storage is permanent and cannot be reversed. Cool temperatures and a partial charge slows aging. Nickel-cadmium stores reasonably well. Field test reveled that NiCd batteries stored for five years still performed well after priming cycles. Alkaline and lithium batteries (primary) can be stored for up to 10 years. The capacity loss is minimal.


Manufacturers recommend to trickle charge a nickel-based battery for 24 hours when new and after long storage. This service brings all cells to equal charge level and redistributes the electrolyte to remedy dry spots on the separator brought on by gravitation of the electrolyte. It is advisable to verify the capacity with a battery analyzer before use. This is especially important in critical applications.

Cycling (priming) is recommended to regain lost capacity after a nickel-based battery has been stored for 6 months or longer. A slow charge followed by one or several discharge/charge cycles will do this. The recovery rate is governed by the condition under which the battery was stored. The longer and warmer the storage temperature, the more cycles will be required. The Prime program of the Cadex battery analyzers automatically applies the number of cycles needed to regain full capacity.

Nickel-based batteries are not always fully formed when leaving the factory. Applying several charge/ discharge cycles through normal use or with a battery analyzer completes the forming. The number of cycles needed to attain full capacity differs between cell manufacturers. Quality cells perform to specification after 5-7 cycles. Those lacking formation may need 50 or more cycles to reach acceptable capacity levels.

What is the difference between priming and forming? For the user, both symptoms manifest themselves as insufficient capacity. The difference may be explained in that forming needs to be done only once when the battery is new, while priming must be repeated after each prolonged storage."


"While capacity loss during a battery's life cannot be eliminated, simple guidelines minimize the effect:

Keep batteries in a cool and dry storage area. Refrigeration is recommended but freezers should be avoided. When refrigerated, the battery should be placed in a plastic bag to protect against condensation

Do not fully charge lithium and nickel-based batteries before storage. Keep them partially charged and apply a full charge before use. Store lithium-ion at about 40% state-of-charge (3.75-3.80V/cell open terminal). Lead-acid batteries must be stored fully charged.


Do not store lithium-ion fully depleted. If empty, charge for about 30 minutes before storage. Self-discharge on a depleted battery may cause the protection circuit to trip, preventing a recharge.


Do not stockpile lithium-ion batteries; avoid buying dated stock, even if offered at a reduced price. Observe the manufacturing date, if available.


Never leave a nickel-based battery sitting on a charger for more than a few days. Prolonged trickle charge causes crystalline formation (memory).


"How long can the batteries hold their charge if I leave them on the shelf ?"


"At normal room temperature, NiMH batteries can generally retain 70% of their charge after 30 days. Normal self discharge of NiMH batteries is about 1 percent per day at normal room temperature. Of course, environmental factors and higher temperatures will play an important role in the above said value and will cause NiMH batteries to discharge at a slightly higer rate. Lower temperatures ( 40° to 60° F ) on the other hand will cause NiMH Batteries to hold their charge longer"




Just for general info... I haven't used any of these products below. I got to the point of finding these recommended computer controlled chargers and high mAH batteries. Getting a "package" looks like a very good deal, when I decide to go all out rechargable.


I'm still limping along with a serviceable but "dumb" Rayovac PS4 charger, replaced under warranty after partially frying my (relatively expensive) but widely sold at retail, Energizer 2300mAH AA batteries.

These smart computer controlled chargers appear much advanced.

Some chargers just time the charge.


BatterySpace.com - Batteries & Chargers



Reference forum...

Battery froum :: Index





Edited by Greenjeens
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"Standard" non-rechargeable alkaline cells have a nominal voltage of 1.5V.


Ni-CD and Ni-MH cells charge to a maximum of (nominal) 1.2V


The Sportrak uses two cells.

Alkaline = 3.0V

Chargeable cells = 2.4V


That's quite a percentage difference, and is why the battery indicator shows that the battery is not full. However, the rechargeable cells will last longer (even though the voltage is lower) due to their superior current capability.


Hope this helps.


(I believe that some Garmin products allow the user to specify the type of battery used, altering the battery level indicator to suit. Cool feature!)

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