Calculator inputs
Use the fields below to model electrochemical cell voltage, internal resistance, bank arrangement, and conductor losses.
Example data table
This sample shows a lithium-ion bank under moderate load. Your actual results depend on measured resistance, wiring, state of charge, and temperature.
| Chemistry | Series | Parallel | Current (A) | Cell IR (mΩ) | Cable | Bank EMF (V) | Drop (V) | Loaded V |
|---|---|---|---|---|---|---|---|---|
| Lithium-ion | 4 | 2 | 20 | 35 | 1 m copper, 6 mm² | 15.84 | 1.57 | 14.27 |
| Lead-acid | 6 | 1 | 40 | 4 | 1.5 m copper, 16 mm² | 12.48 | 1.24 | 11.24 |
Formula used
This calculator combines electrochemical voltage estimation with classical ohmic resistance equations.
For lithium-ion, LiFePO4, lead-acid, AGM, gel, NiMH, and NiCd cells, the tool estimates cell open-circuit voltage from chemistry, state of charge, and temperature unless you enter a direct override value.
How to use this calculator
- Select the battery chemistry that best matches your cell type.
- Enter the number of series cells and parallel strings in the bank.
- Set state of charge and temperature, or enter a measured cell OCV override.
- Enter load current, cell internal resistance, and total contact resistance.
- Choose cable material, then enter one-way cable length and cross-sectional area.
- Enter cell capacity to estimate pack capacity, C-rate, and ideal runtime.
- Press Calculate Voltage Drop to show results above the form.
- Use the chart and export buttons to review, save, and compare scenarios.
FAQs
What is battery voltage drop?
Battery voltage drop is the reduction between open-circuit voltage and loaded terminal voltage. It comes from internal cell resistance, interconnect losses, and cable resistance when current flows through the bank.
A bank of batteries total emf calculate the voltage drop
First calculate total EMF as series cells multiplied by cell EMF. Then calculate total resistance for cells, contacts, and cables. Multiply load current by that resistance to get the voltage drop.
Calculate the ohmic voltage drop in the lithium ion battery
Use Ohm’s law with total resistance. Multiply discharge current by the sum of lithium-ion cell internal resistance, connector resistance, and cable resistance. That product gives the ohmic voltage drop.
How to calculate internal voltage drop of battery?
Multiply current by internal battery resistance. For a pack, add series cell resistances and divide by parallel strings. Include extra contact resistance if you want a practical internal drop value.
Why do parallel strings reduce voltage drop?
Parallel strings share current. Because each path carries less current, effective pack resistance falls. Lower effective resistance produces a smaller ohmic drop for the same total load.
Does cable size matter in battery drop calculations?
Yes. Smaller cable area raises resistance, so the voltage drop increases. Longer cables also raise resistance. Thick, short conductors usually improve loaded voltage and reduce heat loss.
How does temperature affect battery voltage drop?
Temperature changes both cell behavior and conductor resistance. Cold batteries often show lower voltage and stronger sag, while warmer conductors can gain resistance and increase wiring losses.
Is this calculator exact for all battery chemistries?
No. It is a practical engineering estimate. Real cells also show polarization, aging effects, dynamic recovery, and chemistry-specific discharge curves that can shift measured terminal voltage.