Battery basics for electronics

Batteries are used in portable devices and for backup energy storage.

Learn all you can about the particular batteries you are interested in using by doing a google search, reading books, etc. This is just a quick introduction to battery basics and only covers the most commonly used battery types.

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Quick list of general battery topics:

  • Short circuit danger. Never connect the positive terminal of a battery directly to the negative terminal of that same battery. Always have a load between them that limits the power to a safe level for both the load and the battery.
  • Positive terminal (Cathode). Never connect directly to the negative terminal of the same battery.
  • Negative terminal (Anode). Never connect directly to the positive terminal of the same battery.
  • Cell chemistry.
  • Voltage.
    • Nominal voltage. Approximate average voltage that you can expect from a cell or battery made up of series of cells when you use it from fully charged to fully discharged.
    • Fully charged: Cell/Battery will be at it’s highest safe voltage, and will be able to provide the most power.
    • Fully discharged: Cell/Battery voltage is low and won’t be able to provide much power. It will be more dangerous to recharge a lithium based battery if it is over discharged.
  • Current.
  • Primary battery. Simply a battery that is not rechargeable.
  • Secondary battery. Simply a battery that is rechargeable.
  • Series connected cells for increased voltage. Connecting the positive terminal of one battery to the negative terminal of a different battery. Can keep stacking multiple batteries like that as long as the 2 ends of the series batteries never come in direct contact with each other (a short circuit). Only use cells/batteries of the same chemistry, that are at the same voltage, and that have the same capacitance.
  • Parallel cells for more current over time. Make sure they are equally charged (no more than 0.1V difference) while connecting them together or one will rapidly charge the other.
  • Capacity
    • Ampere hour, amp hour, AH.
  • C rate.

Cell chemistry:

Knowing the cell chemistry is important for a number of reasons.

  • Rechargeable or not. And how to recharge if rechargeable.
  • Nominal voltage plus maximum, and minimum safe voltages if rechargeable.
  • Energy density.

Common chemistries:

  • Alkaline:
  • LiFePO4 (lithium Iron Phosphate):
  • Li Ion (Lithium Ion):
  • Lead Acid:

Alkaline cells/batteries:

Disposable batteries (recycle them when they die). Mostly used in portable devices that aren’t rechargeable. Always verify the specifics of the battery you are using.

  • Nominal cell voltage.
    • Typically 1.5V
      • About 1.6V when new.
      • Voltage drops and the ability to provide current goes down the more it provides power.
  • Usually connected in series for a higher voltage, which is limited to the current of one cell.
    • 4 series cells = 6V nominal.
    • 6 series cells = 9V nominal.
    • 8 series cells = 12V nominal.

LiFePO4/LFP (Lithium Iron Phosphate) cell/batteries:

Rechargeable batteries. Commonly used for backup power for households and RVs. Less likely to combust than li ion and LiFePO4 chemistries. Always verify the specifics of the batteries you are using.

  • Nominal cell voltage: 3.2V
    • While being used, the cell voltage mostly stays close to 3.2V.
  • Fully charged 3.4V
  • Fully discharged: 3V
  • Charging voltage: Up to 3.65V. LifePO4 cells can be given some extra charge by applying a little extra voltage above it’s working voltage. 
  • Usually connected in series for a higher voltage at the same current as the individual cells.
    • 4 series cells = 12.8V nominal voltage.
    • 8 series cells = 25.6V nominal voltage.
    • 12 series cells = 38.4V nominal voltage.
    • 16 series cells =  51.2V nominal voltage.

Li ion (Lithium Ion) batteries:

Rechargeable batteries. Typically used to in lower power rechargeable devices that have a USB charging port.

Lead Acid:

Rechargeable battery that is commonly used to start internal combustion automobiles.

LiPo (Lithium Polymer):

Rechargeable battery that is commonly used to power devices that need a lot of power from a lighter weight battery, such as flying drones.

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  • Information on this site is not guaranteed to be accurate. Always consult the manufacturer info/datasheet of parts you use. Research the proper safety precautions for everything you do.
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