How to Store Batteries
The recommended storage temperature for most batteries is 15°C (59°F); the extreme allowable temperature is –40°C to 50°C (–40°C to 122°F) for most chemistries. While lead acid must always be kept at full charge during storage, nickel- and lithium-based chemistries should be stored at around a 40 percent state-of-charge (SoC). This level minimizes age-related capacity loss while keeping the battery in operating condition and allowing self-discharge.
Finding the 40 percent SoC level is difficult because the open circuit voltage (OCV) of batteries does not lend itself well to state-of-charge estimations. For lack of better methods, voltage is nevertheless used as a rough fuel gauge indicator. The SoC of Li-ion is roughly 50 percent at 3.80V/cell and 40 percent at 3.75V/cell. Allow Li-ion to rest 90 minutes after charge or discharge before taking the voltage reading to get equilibrium.
SoC on nickel-based batteries is especially difficult to measure. A flat discharge curve, agitation after charge and discharge, and voltage change on temperature contribute to the fluctuations. Since no other estimation tool exists that is practical, and the charge level for storage is not all too critical for this chemistry, simply apply some charge if the battery is empty, and then make sure that the battery is kept in a cool and dry storage.
Storage will always cause batteries to age. Low temperature and partial SoC only slow the effect. Table 1 illustrates the recoverable capacity of lithium- and nickel-based batteries at various temperatures and charge levels over one year. The recovered capacity is defined as the available battery capacity after storage with a full charge.
|
Temperature |
Lead acid at full charge |
Nickel-based at any charge |
Lithium-ion (Li-cobalt) |
||
|
40% charge |
100% charge |
||||
|
0°C 25°C 40°C 60°C |
97% 90% 62%
38% |
99% 97% 95% 70% |
98% 96% 85% 75% |
94% 80% 65%
60% |
|
Table 1: Estimated recoverable capacity when storing a battery for one year
Elevated temperature hastens permanent capacity loss. Depending on battery type, lithium-ion is also sensitive to charge levels.
Lithium-ion batteries are often exposed to unfavorable temperatures, and these include leaving a cell phone in the hot sun or operating a laptop on the power grid. Elevated temperature and allowing the battery to sit at the maximum charge voltage for expended periods of time explains the shorter than expected battery life. Elevated temperature and excessive overcharge also stresses lead and nickel-based batteries. All batteries must have the ability to relax after charged, even when kept on float or trickle charge.
Nickel-metal-hydride can be stored for about three years. The capacity drop that occurs during storage can partially be reversed with priming. Nickel-cadmium stores well, even if the terminal voltage falls to zero volts. Field tests done by the US Air Force revealed that NiCd stored for five years still performed well after priming cycles. It is believed that priming becomes necessary if the voltage drops below 1V/cell. Primary alkaline and lithium batteries can be stored for up to 10 years with minimal capacity loss.
You can store a sealed lead acid battery for up to two years. Since all batteries gradually self-discharge over time, it is important to check the voltage and/or specific gravity, and then apply a charge when the battery falls to 70 percent state-of-charge. This is typically the case at 2.07V/cell or 12.42V for a 12V pack. (The specific gravity at 70 percent charge is roughly 1.218.) Some lead acid batteries may have different readings and it is best to check the manufacturer’s instruction manual. Low charge induces sulfation, an oxidation layer on the negative plate that inhibits current flow. Topping charge and/or cycling may restore some of the capacity losses in the early stages of sulfation.
Sulfation may prevent charging small sealed lead acid cells, such as the Cyclone by Hawker, after prolonged storage. If seemingly inactive, these batteries can often be reactivated by applying a higher than normal voltage. At first, the cell voltage under charge may go up to 5V and absorb only a small amount of current. Within two hours or so, the charging current converts the large sulfate crystals into active material, the cell resistance drops and the charge voltage gradually normalizes, and at a voltage of 2.10–2.40V the cell is able to accept a normal charge. To prevent damage, set the current limit to a very low level. Do not attempt to perform this service if the power supply does not allow setting current limiting. Read about Charging with a Power Supply.
Simple Guidelines for Storing Batteries
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Primary batteries store well. Alkaline and primary lithium batteries can be stored for 10 years with moderate loss capacity.
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Remove battery from the equipment and store in a dry and cool place.
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Avoid freezing. Batteries freeze more easily if in discharged state.
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Charge lead acid before storing and monitor the voltage or specific gravity frequently; apply a boost if below 2.10V/cell or an SG below 1.225.
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Nickel-based batteries can be stored for five years and longer, even at zero voltage; prime before use.
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Lithium-ion must be stored in a charged state, ideally 40 percent. This assures that the battery will not drop below 2.50V/cell with self-discharge and fall asleep.
- Discard Li-ion if the voltage has stayed below 2.00/V/cell for more than a week.
| Caution: |
When charging an SLA with over-voltage, current limiting must be applied to protect the battery. Always set the current limit to the lowest practical setting and observe the battery voltage and temperature during charge. In case of rupture, leaking electrolyte or any other cause of exposure to the electrolyte, flush with water immediately. If eye exposure occurs, flush with water for 15 minutes and consult a physician immediately. |
Comments
Need to Store Batteries? Here’s how to do it safely:
1) Keep batteries in original packaging when possible.
2) Do not store new and used batteries together.
3) If a battery feels warm, it should be discarded.
Check here for 6 more battery storage tips:
http://www.buybattery.com/duracell_battery_storage.shtml
I just started to store my Panasonic cordless drill batteries in the fridge in a food preservation vacuum bag to keep the moister out. Working ok so far??
> Never leave a nickel-based battery sitting on a charger for more than a few days.
> Prolonged trickle charge causes crystalline formation (memory).
Does this account for chargers that monitor health of the battery and apply charge when necessary?
One of the things that is misleading about the chart is that the voltages aren’t specified. For example some Lithium Ion devices like my older laptop define 0% on its 6 cell as being 10.8V as opposed to a very small amount on some newer laptops. Similar to that of my PSP where “100%” encompasses slightly above 4 volts to 4.2. If I were to make a guess it would probably be because of USB charging is painfully slower at higher voltages.
The other is that some batteries protective circuits and other miscellaneous electronics slightly drain the battery. Some Lithium Polymer batteries exhibit zero discharge at all. I have an old Motorola cell phone that I haven’t charged for a few years and every once in a while I’ll turn it on and it’ll show one out of three bars…Just the way I left it.
To keep it short, assuming that 100% is 4.2V it would be theoretically impossible to hold the average device battery up there. There are some exceptions to this but the best bet to storing them is to monitor the device’s progress every few weeks and go from there.
It would be nice to see some more info on that chart. Especially in contrast on single cell versus multiple cell packs.
If you’re going to be storing a rechargeable battery, store it at the 40 percent state-of-charge (SoC), and then recharge / discharge back to the 40 percent state-of-charge (SoC) every month to keep the internal batteries in good condition. Store batteries just below room temperature, more specifically at 59°F.
Would storing a Li-Ion battery at 40% charge in a freezer at -18 C prolong the life more than storing it in a fridge at 5 C ?
Is it possible to store a Li-Ion at a temperature cold enough to damage it (say -25 C)? Will crystals form in the chemistry that could cause damage or a short?
Any specific concerns about condensation effects when taking a battery out of the fridge/freezer and plugging it immediately into your laptop for 1 hour of gaming (on batt power only)?
Thanks for the info! Great site!
There used to be a procedure to drain a charged lead-acid battery, for long term storage; in effect, making it a dry-charged battery. Does anyone still living remember what that was?
Where would be a good place to store a dead lead acid battery until they can be dispode of properly.
What would be better for a saving of a Lithium Ion battery: to be in every day working laptop using external power or in a fridge?
@Aleks For a laptop Li-Ion battery, well, the battery would be better off in the fridge at around 40% charge.
Keep in mind that you won’t be able to use Suspend-To-Ram without a battery attached.
Many laptops allow you to set them so they don’t charge to 100% while attached. Keeping your battery in your laptop but at 40% charge rather than 100% will prolong its life.
My battery temperature is around 30 degrees Celsius while sitting attached to my laptop on AC power neither charging nor discharging.
Not sure the fridge is a great idea. Don’t forget that temperature is not the only storage criteria. High humidity environnement may affect the battery life expectancy !
@Guillaume Thanks. Do you have better idea? If the battery is in a plastic bag?
Optimal storage conditions are :
Clean and dry location
Temperature below 25°C (10°C would be optimal if you want my opinion)
I dont know about your location. In my case, winter is cold (-10°C average) so I use the garage for battery storage. My garage is heated at 12°C so the humidity level is low and the temperature is good.
Keeping the battery on the laptop at 40% charge as suggest by NormMonkey could work but dont forget that the heat coming from the laptop will affect the battery so you may want to store it somewhere else.
For the bag idea, it may help to prevent dirt and other stuff to be in contact with the battery but I dont know about humidity. You might want to use the basement as it usually colder there.
I take it that no one watching here has ever heard of dry charged batteries. If that changes, please let me know.
Storing a fully charged lead-acid battery at -10 degrees C is absolutely perfect. The acid will not freeze. You can go down to - 20 but don’t go too far down. Self discharge is a chemical process. It speeds up with increase in temperature, slows down with decrease. It is not linear. Lowering temp. dramatically reduces self discharge.
Dry charged batteries were made decades ago when the industry had difficulty keeping the self discharge of batteries down. Simply charge to 100%, drain out all the acid, wash out residual acid, dry. Then seal the vents air tight. The negatives will discharge spontaneously in contact with air. When the battery is needed, refill with acid, charge. Very cumbersome. Easier to put the battery in the fridge!
‘Avoid freezing. Batteries freeze more easily if in discharged state.’
Do you really mean: Avoid freezing.Batteries discharge more easily if in freezed state.
Quite right, and thank you for your advice on dry charged lead-acids. I am among those burdened with a desire to know how and why things work, much to the amusement and consternation of the bulk of the populace. There are not enough of us to go around, so at least the net allows us to offer what we know.
Thank you again.
how long can you store AA and AAA if you have a lot of new ones
Ritch, Put your AA and AAA batteries in your fridge and they will stay fresh longer than storing them any other way. Some of mine have been there for more than 3 years and they come out working fine. The colder, the better but do not freeze.
I’m writing a guide regarding the computer’s battery. Can sleep mode damage the battery capacity in a lithium-ion battery.
When I bought a used laptop I automatically bought a new 9-cell replacement battery for it. When my laptop arrived, I discovered that the battery that came with it was basically new and also 9-cell. I’ve opened both batteries so I shan’t sell one. Is it better to store one of them at 40% charge to wait for the other to go bad, or should I rotate them once a month, always storing the other at 40% and trying not to let the charge drop below 40%?
Thom. What kind of laptop do you have?
It’s a Thinkpad T60. It dual boots Ubuntu 11.10 and WindowsXP, but I mainly use it for Ubuntu (I notice the predicted battery life is strangely longer under XP though).
It’s a Thinkpad T60 that dual boots Ubuntu 11.10 and WindowsXP (I use it mainly for Ubuntu but I notice a much longer predicted battery life under XP strangely).
I would guess that, but that’s only because I use a T60 and an X31. As for the two 9 cells what I would do is check the Power Manager and note the manufacture and the total capacity (you can check the total capacity in Ubuntu also). Panasonic batteries in my experience tend to hold better over time because of their better construction and their microcomputer doesn’t crap out like the Sanyo’s (my 9 cell is a Sanyo and my 6 cell is a Panasonic. So far the Panasonic seems to be more consistent and autocorrecting than the Sanyo).
It’s not too strange under XP. If you have the ATI chipset (X1300, X1400. Not sure the T60 has the CAD one) the power management features are enabled with the drivers. The Ethernet drivers are also programmed to disable the interface if not in use (not sure about Ubuntu). Your best bet is to check Thinkwiki for tips on it but not sure if it covers Ubuntu 11.1
Right now I have the replacement in which it says is a Sony at 95.7% Capacity. The battery that came with it is at home and is the original Lenovo/IBM. When this computer came in the mail it was *spotless* and looked brand new (except the windows XP sticker on the keyboard is partly rubbed off). I got quite lucky. There wasn’t even any wear on the touchpad or keyboard, these all had the slight matte finish found on new devices. It was supposed to have been used in a professionally capacity before it was resold by the computer shop in MA.
I installed PowerTop this morning but I’m only half sure that I’m using it correctly. I was going to fool around with CPU Frequency Scaling Monitor but wasn’t sure if that would make a difference. I saw something about installing proprietary drivers for the GPU. I’m not sure how to verify but I *think* that it uses the ‘Intel Graphics Media Accelerator 950 Graphics Card’. This is based on looking up the Product ID: 195143U.
Yeah, the Type 1951 has the GMA945 or something like that. As for the Sony battery I’d urge to make sure it’s not a part of the recall (if the battery was manufactured recently it should be OK). As for the quality I do not know. I’ve read they’re really bad but I don’t use them so I wouldn’t know. Finish wise mine was like that but the motherboard failed 3 months into ownership. However the keyboard, palmrest and the bezel can be removed with 9 screws and only about 5 minutes so it as skeptical as I am it could of been easily replaced.
On the Windows side most of the settings you’d want to mess around with would be in the Lenovo Power Manager or the ThinkPad Configuration Utility. They allow for fan control as well as other controls including the optical drive speed.
This information is confusing and misleading regarding the storage of batteries. I have never had any laptop Li-Ion batteries degrade 20% over the course of a year even if left installed with laptop connected to AC 100% of the time. Wondering what conditions these were tested under and how old the data is?
Can the Lifepo4 batteries can mount in any position during usage. Or any restriction of keeping it vertical as the leads always upwards.
The Li-Ion battery should be good for up to 500 cycles before it starts to lose its capacity, depending on its brand and quality.
need batteries for experiments
How many times can I recharge a lithium-ion battery? I have Sansa e200 player with the lithium-ion rechargeable battery.