Proper batteries storage – maintenance and inspection

Have you ever wondered if storing batteries in a refrigerator is the right way to ensure their longevity? We can help you answer that question.

In fact, the recommended storage temperature for most batteries is 15°C (that’s why they are refrigerated). The minimum storage temperature is minus 40 to minus 50 degrees Celsius. Lead-acid batteries should be fully charged when stored, while dry nickel and lithium batteries should be stored at a charge level of about 40% (SoC) so that they will self-discharge and be ready for use to minimize aging of their capacity.

Indicative voltage

Determining the magic 40% SoC is difficult because it is hard to estimate the open-circuit voltage (OCV) of a battery. It is best to use voltage as a rough indicator of energy. The SoC of a lithium-ion battery is about 50% at 3.80 V/cell and about 40% at 3/75 V/cell. The voltage of a Li-ion battery can only be checked after a 90-minute break after charging or discharging.

The most difficult SoC to determine is for nickel-based batteries. This is due to the flat discharge curve, mixing after charging and discharging, and voltage variations with temperature. There are no practical tools for assessing the condition of nickel-based batteries. The state of charge is not important. Add a charge if the battery is discharged (if not, do not add a charge) and store it in a cool, dry place.

Effects of high temperatures

Storage causes batteries to age permanently. On the other hand, high temperatures accelerate the permanent loss of battery capacity. Dry batteries in Pakistan, in particular, are often exposed to high temperatures. Keep in mind that many people leave their cell phones or laptops in warm places, such as the front seat of a car on a sunny day. Conversely, low temperatures and imperfect SoCs can slow the aging process, but not stop it.


Overcharging and holding the maximum charge voltage for an extended period of time are also factors that can shorten the life of the battery. Batteries are like people, they need to be rested after being charged, even if they are used with maintenance or trickle charge.

Sealed lead-acid batteries can be stored for up to two years. However, it is important to monitor the voltage and gravity and recharge the battery if it drops below 70% SoC. When the charge is low, an oxide layer forms on the anode plate and stops the flow of current. This is called sulfation and is the reason why small sealed lead-acid batteries cannot be recharged.

Here are some basic guidelines for battery storage.

  • Remove the battery from the unit and store it in a cool, dry place.
  • Lead-acid batteries must be recharged before storage. Check the voltage and gravity regularly and recharge the battery if the voltage is less than 2.10 V/cell or if the gravity is less than 1/225.
  • To prevent freezing, remember that batteries are more likely to freeze when discharged than when not charged.
  • Primary alkaline and lithium batteries can be stored for up to 10 years and lose capacity only moderately.
  • Nickel batteries can be stored for over 5 years at zero voltage but must be recharged before use.
  • Lithium-ion batteries should be stored in a charged state, ideally at 40%. This ensures that the battery voltage does not fall below 2.50V per cell during self-discharge and that the battery does not shut down. If the voltage remains below 2.00 V per cell for more than 7 days, the battery should be discarded.

Recharging the Battery

  1. Plugin the battery charger, making sure to observe the correct polarity.
  2. The battery should be charged at the normal charging rate. The battery is fully charged when the charging voltage and electrolyte level have not increased for more than 2 hours. And the battery can be charged for at least 4 hours. If the available current is lower than the indicated value, the charging time must be extended proportionally.
  3. During the charging process, the temperature of the acid must not exceed 50°C. Interrupt or reduce the charging current if necessary.
  4. Ensure that the specific gravity of all cells is 1.280 (0.010 at full load).
  5. After 2 hours of charging, install the drain plug and check the electrolyte level in all cells. If necessary, raise the electrolyte level to 15 mm above the plate or to the “MAX” line with distilled water.
  6. Metro2.

Visual check

Are there any powder accumulations on the poles or at the bottom of the battery, or is liquid leaking out? These can be a cause of corrosion. Check that the battery is not damaged or subjected to shocks.

Battery Maintenance

  1. The top of the battery and the poles should always be kept clean.
  2. Use petroleum jelly or a similar product sparingly to lubricate the terminals and connections.
  3. Never overtighten the terminals, but tighten them well.
  4. The electrolyte should extend 3 mm (1/8″) to 6 mm (1/4″) beyond the top of the plate. Check this regularly. If refilling is necessary, use distilled water or chemically pure water.
  5. Make sure the alternator/generator belt is tensioned according to the manufacturer’s recommendations. Check it regularly. Also, check it regularly for signs of wear.

Check the battery

Always perform a visual check of the battery before checking it.

  1. Corrosion of the poles: A white, powdery substance around the pole bolts may prevent the battery from charging.
  2. Check that all cells are filled with electrolytes. If the cells are dry, the case may be cracked.
  3. Check for loose terminals or other external damage.

Check with a hydrometer

Use a hydrometer to check the specific gravity and state of charge of the sulfuric acid in the battery.


  1. Do not add distilled water 2. Hold the container in an upright position.
  2. Hold the container upright and successively remove enough electrolyte from each cell to allow the float to move freely. If necessary, tilt the cell to add sufficient electrolytes. Count at eye level.

1.270 – 1.280 S G Full charge

1.220 – 1.230 S G Half charge

1.150 – 1.220 S G Discharge

All cell readings must be within 0.030 points. If the difference is greater, the battery probably needs to be replaced.

If the measured values of all cells are uniformly low, the battery may still be usable, but it is advisable to replace it as soon as possible.

Batteries for diesel generators

Few people think of diesel generators when they think of power systems and batteries, but batteries are an important part of emergency power generators. The battery is needed to start the generator immediately in case of a power failure, without which the generator would be useless.

In addition to the inverter battery, the alternator battery should also be checked and replaced if necessary. By following these simple guidelines, you can be sure that your battery will last longer and be used more efficiently.

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