Convert capacitor farads and voltage to amp hours, milliamp hours, coulombs, and stored energy, or solve for capacitance and voltage across a selected discharge range.
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Farads To Amp Hours Formula
The following formula gives ideal capacitor charge in amp hours for a voltage change. For discharge to zero volts, the change equals the starting voltage.
Variables:
- Ah is electric charge in amp hours, not energy. One amp hour equals 3,600 coulombs.
- F is the capacitance of the capacitor, measured in farads (F)
- Vstart and Vend are the starting and ending voltages in volts (V); Vend = 0 for a complete ideal discharge.
Multiply capacitance in farads by the voltage drop, then divide the charge in coulombs by 3,600 to express it in amp hours. Energy over that range is E = ยฝ C(Vstartยฒ โ Vendยฒ) joules, a separate quantity.
| Capacitance (F) | Ampere Hours (Ah) |
|---|---|
| 0.001 | 0.000003 |
| 0.01 | 0.000033 |
| 0.022 | 0.000073 |
| 0.047 | 0.000157 |
| 0.1 | 0.000333 |
| 0.22 | 0.000733 |
| 0.47 | 0.001567 |
| 1 | 0.003333 |
| 2.2 | 0.007333 |
| 2.7 | 0.009000 |
| 5 | 0.016667 |
| 10 | 0.033333 |
| 22 | 0.073333 |
| 47 | 0.156667 |
| 50 | 0.166667 |
| 100 | 0.333333 |
| 200 | 0.666667 |
| 500 | 1.666667 |
| 1000 | 3.333333 |
| 2000 | 6.666667 |
| * Rounded to 6 decimals. Formula: Ah = (F ร V) รท 3600. Assumes V = 12.0 V. Example: 1 F at 12 V โ 0.003333 Ah (3.333 mAh). | |
What Does โFarads to Amp Hoursโ Mean?
Farads and a voltage change determine the ideal charge transferred from a capacitor. Amp hours measure charge, while joules and watt-hours measure energy. Capacitor voltage falls during discharge, so its charge in Ah should not be treated as the same capacity as a battery at a fixed voltage. The calculation assumes constant capacitance and omits losses.
How to Calculate Farads To Amp Hours?
The following steps outline how to calculate the Farads To Amp Hours.
- First, determine the capacitance of the capacitor (F).
- Next, determine the starting and ending voltages; use an ending voltage of 0 V for a complete ideal discharge.
- Next, use Ah = F ร (Vstart โ Vend) / 3,600.
- Finally, calculate the Farads To Amp Hours.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
capacitance of the capacitor (F) = 10
voltage across the capacitor (V) = 5, ending at 0 V. Charge = 10 ร 5 / 3,600 โ 0.01388889 Ah; energy = 125 J โ 0.03472222 Wh.
