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Battery Load and Required Capacity Estimate

The lithium estimate divides load current times duration by the usable fraction of charge. The lead-acid mode applies the captured empirical duration factor 0.02 times duration in hours plus 0.6.

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

Worked example: load current = 10; remaining capacity Li = 25; remaining capacity Pb = 39.0625. See the assumptions for units and model limits.

application_load = voltage * load_current; remaining_capacity_Li = 100 * load_current * required_duration / (100 - remaining_charge); remaining_capacity_Pb = (100 * load_current * required_duration) / ((100 - remaining_charge) * ((0.02 * required_duration) + 0.6))

Worked example

Enter these known values and leave the other values blank.

Battery type
Lithium-ion
Application load
100 W
Voltage
10 V
Required duration
2 hrs
Remaining charge
20 %
Load current
10 A
Remaining capacity
25 Ah

Assumptions and limitations

  • The lithium estimate divides load current times duration by the usable fraction of charge. The lead-acid mode applies the captured empirical duration factor 0.02 times duration in hours plus 0.6.
  • The lead-acid duration adjustment is an illustrative captured model rather than a battery-specific discharge curve. Rated capacity, temperature, age, load profile and cutoff voltage require manufacturer data for actual sizing.

Common questions

What does this model assume?

The lithium estimate divides load current times duration by the usable fraction of charge. The lead-acid mode applies the captured empirical duration factor 0.02 times duration in hours plus 0.6.

Can I solve for a different value?

Clear the desired editable unknown and enter sufficient independent known values. Unit selectors preserve quantities; singular or unsupported inverse branches remain incomplete.

References

Reject singular physical denominators and fractional discrete counts using exact isInteger checks.

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