Battery shelf life

[Frankie]

Loving these things I might be throwing money away, because I do not use all of them all the time. So, my big question now is: What approximately is the battery shelf life? How long before an unused / rarely used device is dead? Is it better to use/charge often, even if the device is rather a special occation use item? Seems more than one, but you know what I mean. Advice, please

[Bertrand]

You're meant to discharge it to 40%, store at 0 C and then lose about 2.5% capacity per year.

[usehername]

You're meant to discharge it to 40%, store at 0 C and then lose about 2.5% capacity per year.

Should a new battery still be charged the reccomended 12hrs even though it is planned to be stored? What would indicate 40% discharge?

[Bertrand]

No you shouldn't charge it if you plan to store it. It's likely to come out of the factory at 40% (the retailer may charge it though). You can use the voltage to estimate the state of charge, but it is temperature dependent and fairly inaccurate. Having said that, what else you gonna do? At room temperature you should be looking for something around 3.4V.

eg. Inaccuracies of Estimating Remaining Cell Capacity with Voltage Measurements Alone - Maxim

[tribalmasters]

Just leave erm hanging around as is they will be just fine! No technical explanation needed hehe!

[turbojunk]

Abstract: Implementing a battery fuel gauge can be done in a variety of ways including using voltage measurements or coulomb counting. Although the use of voltage measurement has been a popular method of choice, it does not produce the most accurate results available. This application note studies the voltage-based method of fuel gauging for both Li-Ion and NiMH battery cells. Data is provided that demonstrates the high degree of error introduced when implementing voltage measurement as a fuel gauge method when the battery is subjected to real world conditions of varying temperatures and discharge rates.

I'm with Tribalmasters.

Kev

[Bertrand]

hehehe. They did ask.

All you need to do to prolong storage life is run it down a bit and put it in the fridge. Fully charged at room temperature will die about 10 times as fast. Up to you.

[MagusSteele]

Keep it Dry, even if you throw it in the fridge.
If it does not corode up on you, they will be fine for at Least a year.
They do loose (so i was told) up to 2% a year sitting, but that means years of shelf life if chilled. I worked with Eveready for a while on battery machines, lithium as well as carbon. They do suggest if your storeing batteries for a long time, to throw in the fridge, or at least the Cliche "Cool, Dry Place, out of direct Sunlight"

[Bertrand]

Keep it Dry, even if you throw it in the fridge.
If it does not corode up on you, they will be fine for at Least a year.
They do loose (so i was told) up to 2% a year sitting, but that means years of shelf life if chilled. I worked with Eveready for a while on battery machines, lithium as well as carbon. They do suggest if your storeing batteries for a long time, to throw in the fridge, or at least the Cliche "Cool, Dry Place, out of direct Sunlight"

2% / year is under optimum conditions.

Permanent Capacity Loss versus Storage Conditions Storage Temperature
40% Charge 100% Charge
0 °C (32 °F) 2% loss after 1 year 6% loss after 1 year
25 °C (77 °F) 4% loss after 1 year 20% loss after 1 year
40 °C (104 °F) 15% loss after 1 year 35% loss after 1 year
60 °C (140 °F) 25% loss after 1 year 40% loss after 3 months

[usehername]

Wow Bertrand !
Great post. Never would have thought that. All mine are over 4 volts still in the plastic. Now does that mean I should bring thme down some and then store or should I first do the initial 12 hour charge and then bring them down????