Why is my battery voltage not accurate for showing how much charge I have left?

Please take a moment to watch the video below for step-by-step guidance, or follow the step-by-step written directions.

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1. Don’t rely on voltage alone for lithium batteries

• Lithium batteries keep a very similar voltage for most of their charge.

• Because of this, voltage readings can be misleading.

2. Understand how lithium voltage behaves

• A full lithium battery: ~13.6 volts

• About 50% charged: ~13.3 volts

• Around 20% charged: ~13.0 volts

• Small voltage changes can mean a huge change in actual battery charge, so voltage is not a reliable indicator of remaining power.

3. Compare with lead-acid batteries (for context)

• Lead-acid batteries give more useful voltage readings:

  • 12.6V = full

  • 12.2V = half

  • 12.0V = empty

• Their voltage drops steadily as they discharge, unlike lithium.

4. Use “State of Charge” (% battery) instead

• The percentage reading is the most accurate way to know remaining power.

• This is called State of Charge (SOC).

5. Understand how SOC is measured

• A device called a shunt tracks all energy going in and out of the battery.

• It counts amps used and replenished.

• This works like a fuel gauge for your battery system.

6. Don’t ignore voltage completely

Voltage still matters in certain situations:

• Sudden voltage drops = high power draw

• Very low voltage (below ~12V) = potential battery problem

7. Make sure your battery monitor is set correctly

• The monitor must match your battery type (lithium vs. lead-acid).

• Wrong settings = incorrect battery percentage readings.

8. Key takeaway

• Trust the percentage (State of Charge) for remaining runtime.

• Don’t rely on voltage alone for lithium batteries.

• Proper setup = accurate battery tracking.