[FONT="]Should cycling nickel based batteries be determined by the number of times they've been charged or the time span between discharges? Some say that NiCds should be discharged every 30-60 days and NiMHs every 60-90 days. But if they're not being used at all or very little why cycle them? It seems that cycling frequency should be based on the number of times the battery has been charged. If so, what is the number of charges at which NiCds and NiMHs should be discharged? Also, many believe that nickel based batteries should be stored at 40% charge. Does that mean that they should be charged at 40% and left alone even for years or should be kept at 40% charge by topping them up to 40% charge on a regular basis? Thanks for any replies. [/FONT]
Charging questions
- Thread starter 777qqq
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mdocod
Flashaholic
The concept of cycling cells every month or so has to do with breaking up large crystal formations within the electrolyte of the cell. Cells that sit around not doing anything with a full charge for months on end will develop large crystal formations which will lead to voltage suppression and eventually faster self-discharge.
The concept is that the nickel chemistry cells need to be "exercised" at least some-what frequently in order to stay in good health. A properly exercised cell can last for decades.
Storing at ~40% charge will minimize the effect of large crystal growth over time.
Everyone will have a different opinion on this but it really all comes down to tradeoffs... If you need your cells topped up and ready for emergencies just keep them charged up and do an exercise cycle on them monthly if you aren't using them otherwise. Even better, just get LSD cells and don't worry about any of this stuff as they don't seem to need much of any special treatment to work fine for years whether stored or used heavily.
-Eric
The concept is that the nickel chemistry cells need to be "exercised" at least some-what frequently in order to stay in good health. A properly exercised cell can last for decades.
Storing at ~40% charge will minimize the effect of large crystal growth over time.
Everyone will have a different opinion on this but it really all comes down to tradeoffs... If you need your cells topped up and ready for emergencies just keep them charged up and do an exercise cycle on them monthly if you aren't using them otherwise. Even better, just get LSD cells and don't worry about any of this stuff as they don't seem to need much of any special treatment to work fine for years whether stored or used heavily.
-Eric
SilverFox
Flashaholic
Hello 777qqq,
Welcome to CPF.
I have a little different take on this.
The best way to cycle your cells is to use them, and use them frequently.
In storage oxidation can take place inside the cell and that can cause damage. This oxidation is worse with the cell fully charged, and can also occur with the cell fully discharged. I find that I get better performance with cells in storage if I discharge them (at around 0.5C) down to 1 volt per cell, and store them in a cool area. Every 30 days I do a charge/discharge cycle to keep them vibrant.
Storing cells at 40% is a shipping requirement. This way the self discharge of the cells will allow for extended storage during the time between manufacturing and selling. This method of storage reduces the amount of dead cells sold and reduces returns. It is not the best way to store cells.
The low self discharge rate cells usually come with around a 70% charge on them. They are still too new to determine if there are issues with storing them fully charged or not. They reduce the self discharge rate by allowing an increase in internal resistance within the cell. After long term storage, it takes a cycle or two to get them back into good shape, but that seems to be acceptable. So far, with a few exceptions, the increase in internal resistance is reversible, until the cell wears out.
Tom
Welcome to CPF.
I have a little different take on this.
The best way to cycle your cells is to use them, and use them frequently.
In storage oxidation can take place inside the cell and that can cause damage. This oxidation is worse with the cell fully charged, and can also occur with the cell fully discharged. I find that I get better performance with cells in storage if I discharge them (at around 0.5C) down to 1 volt per cell, and store them in a cool area. Every 30 days I do a charge/discharge cycle to keep them vibrant.
Storing cells at 40% is a shipping requirement. This way the self discharge of the cells will allow for extended storage during the time between manufacturing and selling. This method of storage reduces the amount of dead cells sold and reduces returns. It is not the best way to store cells.
The low self discharge rate cells usually come with around a 70% charge on them. They are still too new to determine if there are issues with storing them fully charged or not. They reduce the self discharge rate by allowing an increase in internal resistance within the cell. After long term storage, it takes a cycle or two to get them back into good shape, but that seems to be acceptable. So far, with a few exceptions, the increase in internal resistance is reversible, until the cell wears out.
Tom
Flash_Gordon
Flashlight Enthusiast
As usual, I think SilverFox's response is spot on. (He did not get to be grand exalted battery guru based solely on good looks.)
Summed up well in the beginning: "The best way to cycle your cells is to use them, and use them frequently."
Yup, use rechargeable cells in devices that you use frequently. Rotate and recharge the cells frequently.
There are more frequent threads now about long term or deep storage of rechargeables. Even the best of them, LSD included, are not designed for this type of use.
I don't disagree with the idea of a rainy day or emergency stash of batteries. Primary cells are great for this. Even alkalines, when properly stored will last for many years and still be quite usable. Lithiums longer still.
Also, in the event of an extended power outage or bail out, you might not have any way to top off, charge or recharge your cells.
Mark
Summed up well in the beginning: "The best way to cycle your cells is to use them, and use them frequently."
Yup, use rechargeable cells in devices that you use frequently. Rotate and recharge the cells frequently.
There are more frequent threads now about long term or deep storage of rechargeables. Even the best of them, LSD included, are not designed for this type of use.
I don't disagree with the idea of a rainy day or emergency stash of batteries. Primary cells are great for this. Even alkalines, when properly stored will last for many years and still be quite usable. Lithiums longer still.
Also, in the event of an extended power outage or bail out, you might not have any way to top off, charge or recharge your cells.
Mark
