Lithium-Ion Battery Care Guide – Part Five

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Lithium-ion batteries are the most common battery in consumer electronics. They are used in everything from cell phones to power tools to electric cars and more. However, they have well defined characteristics that cause them to wear out, and understanding these characteristics can help you to double — or more — the life of your batteries. This is especially useful for products that do not have replaceable batteries.

Battery wear is loss of capacity and/or increased internal resistance. The latter is not a well known concept, but over time the battery is able to put out less amperage as the battery ages and eventually the battery is unable to generate power quickly enough to operate the appliance at all even though the battery is not empty.

The standard disclaimers apply, all advice is for informational purposes only, CleanTechnica is not responsible for any damages caused by inaccurate information or following any advice provided. Also, new technology may change the characteristics spoken about, making them less or more relevant in the future or even rendering them obsolete.

Lithium-Ion Batteries Age From The Following Factors:

  • Time – Part One
  • Cycles – Part One
  • Storage/operating temperature – Part Two
  • Charging – Part Two
  • Discharging – Part Three
  • Depth of charge – Part Four
  • Time spent at near full/empty – Part Four
  • Depth of discharge – In this article
  • End Of Life – In this article
  • Summary – Part Six (upcoming)

Depth of Discharge (DOD)

According to many sources, lithium-ion doesn’t like being fully discharged, however test data on this is hard to find. Since there is so little information available about this phenomenon, the best advice is to try not to drain your batteries below, say, 25% very often, and if you do then to get it back above 25% as quickly as possible so the time spent near empty is minimized.

What percent actually causes this issue is difficult to find information on, so don’t take 25% as gospel.

Miscellaneous Battery Information

  • Lithium-ion batteries have no memory effect. This was a facet of Nickel Cadmium batteries that went out of style decades ago, yet this is a surprisingly common question people ask about any rechargeable battery.
  • Most name-brand devices use quality name-brand batteries, but some devices (such as cheap power banks or no-name products) use off-brand or grey market batteries that will not last for years no matter how much you baby them. Try to avoid buying products with these batteries because the money you save buying them translates into reduced product life.
  • For some devices, the charge gauge can fall out of calibration and give you incorrect readings. This can typically be fixed by either fully charging or fully discharging then recharging the battery back to full. However this is hard on the battery, so it’s not something you want to do regularly, but in the rare instance that this is the cause of your issues, then a full charge or charge-discharge cycle will solve it. Quickly draw the battery back down to 80% before putting it back in service.
  • Everything stated above is quite generalized, and with the various battery chemistries on the market, all of them have slightly different characteristics. Once facet may be stronger in one chemistry vs. another but in general the advice provided is applicable to all lithium battery chemistries.

End of Life (EOL)

End of life for a lithium-ion battery typically occurs when the battery can no longer perform the function the user requires of it. Commercially, when a battery (pack) has reached 80% of its design capacity it is considered EOL, but for end users, it’s typically looked at as when the device (or battery pack) becomes unusable. This can be due to capacity fade or terminal increases in internal resistance (or both). If you find your device has a decent amount of charge yet does not operate correctly or randomly shuts down when you try to use it or put any stress on it (say opening apps on a cell phone), then it’s possible that high internal resistance is causing the problem. Otherwise the battery may not be lasting as long as the user expects it to due to capacity loss. These issues indicate the batteries have likely reached their end of life. At present there is no known way to mitigate high internal resistance or capacity loss in lithium-ion batteries besides replacement.

Other battery chemistries can sometimes be rescued with varying degrees of success, as pulse charging lead acid or running multiple cycles on Nickel Cadmium or Nickel Metal Hydride batteries can sometimes restore the batteries to normal operation or at least buy some more cycles till they become unusable.

These are some of the strange quirks you may run into that can occur with old rundown lithium batteries:

  • Device shuts down stating low battery even though it should have plenty of runtime left, even if it stated a decent percent charge remaining just minutes before
  • Capacity tests can give random values, sometimes low, sometimes high
  • The battery percentage meter drops randomly
  • Charging terminates prematurely even though the cell/pack did not accept much power
  • Sudden capacity drops without warning
  • Self-discharge rate soars and is often uneven
  • The battery (pack) gets very hot during charging (sometimes the charger shuts down due to this)
  • Pouch batteries can start bulging (seen on some cell phones)
  • The measured internal resistance does not stay constant on repeated tests over time

Sometimes in a multi-battery powered device, one cell has prematurely failed due to being defective, causing the entire pack to stop performing correctly. This is usually very difficult to remedy because replacing the cell would cause battery capacity mismatches which can lead to dangerous outcomes if you don’t understand what you are getting yourself into. Ideally you want to use matched cells in a pack. However some enthusiasts have successfully replaced a single defective cell, but this can be a dangerous thing to attempt if you do not have the knowledge and experience needed to do it safely (and understanding what effect it will have on the control circuitry such as messing up the charged and empty indicators, causing reverse charging or other possible effects).

Be sure to recycle all batteries at the end of their life as they contain valuable materials that can be recycled into new batteries.

Stay tuned for Summary of Battery Care Best Practices.

A summary of the terminology used in the battery world:

Charging algorithm = Battery is charged at Constant Current, then near full charge (typically over 80%) the charger switches to Constant Voltage. The charging rate slows until the battery reaches 100% charge. Many EVs modify this algorithm.

C = Capacity of the battery

  • Battery ability to output power is measured in 1/C. 1C means the battery drained in one hour, 2C means 30 minutes (1/2 hour), 3C means empty in 20 minutes (1/3 of an hour) and so forth.
  • Charging can also be measured in C, 1C means charged in 1 hour, 0.5C charged in 2 hours, 2C charged in 30 minutes and so forth.
    Charge rates are not typically linear, the battery is typically charged more rapidly until it reaches the Constant Voltage stage.

Series = Multiple batteries linked in a chain to increase the total voltage of the pack.

Parallel = Multiple batteries linked side by side to increase amperage instead of voltage.

(x)S(x)P configuration = explains how multiple batteries are linked. 4S2P for example means 8 cells, four in Series and two Parallel rows

Volts (V) = Electric potential. Power outlets are measured in volts.

Amps (A)= Number of Coulombs of electrons carrying those volts.

Watts (W)= Volts x Amps. Energy/Power usage is often measured in watts. A kilowatt is 1000 watts. kWh is Kilowatts per hour.

Energy is measured in Joules and is convertible to Watts/second if you have a time component.

Power = Energy over time. Typically measured in Watts. One Joule per second is 1 watt. The same number of Joules or Watts in half the time is twice the power.

Nominal voltage = Voltage used to calculate Watts of a battery.

Battery capacity = How many Ah of power the battery can output (when new).

Load = Device that uses the power from the battery.

Internal resistance of a battery affects its Power output. Increased internal resistance is the reduction in rate of Power output the battery can deliver. Energy output is affected somewhat by increased internal resistance.

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