2025 Battery Charge Time Calculator
Calculate battery charge time, runtime, amp hours, watt hours, and sizing for solar, RV, UPS, and 18650 battery systems. Add multiple batteries and loads, customize efficiency, and export results to CSV for energy planning.
Battery Bank Configuration
Add Load
Charger Parameters
Optional Parameters
2025 Battery Standards
| Metric | Formula | Description |
|---|---|---|
| Total Battery Capacity (Ah) | Battery Ah × Number of Batteries × (1 - Degradation/100) | Total usable Ah |
| Watt Hours (Wh) | Total Ah × Voltage | Total energy capacity |
| Usable Capacity (Ah) | Total Ah × (DoD/100) | Usable Ah based on DoD |
| CCA to Ah | CCA ÷ 7.25 | Converts CCA to Ah (approx.) |
| Reserve Capacity to Ah | Reserve Capacity ÷ 2 | Converts minutes to Ah (approx.) |
| Total Load Power (W) | Sum(Watt × Qty) | Total power consumption |
| Runtime (hours) | (Usable Ah × Voltage × Efficiency/100) ÷ Total Load Power | Time battery lasts |
| Charge Time (hours) | (Total Ah × (100 - Initial SoC)/100) ÷ (Charger Current × Charger Efficiency) | Time to charge |
Factors Affecting Battery Performance
| Factor | Description | Impact | Typical Range |
|---|---|---|---|
| Battery Type | Lead-Acid, Lithium, etc. | Affects efficiency, DoD | 70-95% efficiency |
| Voltage | Battery voltage | Higher voltage increases Wh | 12-48 V |
| Capacity (Ah) | Per battery | Higher Ah increases runtime | 50-200 Ah |
| Number of Batteries | In parallel | Increases capacity | 1-10 |
| DoD | Depth of discharge | Higher DoD shortens life | 20-80% |
| Charger Current | Charging amps | Higher current reduces charge time | 5-50 A |
| Degradation | Battery wear | Reduces effective capacity | 0-20% |
Frequently Asked Questions
How do I calculate amp hours from CCA?
Enter CCA value; calculator divides by 7.25 for approximate Ah.
What is depth of discharge (DoD)?
Percentage of battery capacity used (e.g., 50% for lead-acid to prolong life).
How do I use this for solar systems?
Select solar charger and enter panel current (A) for charge time.
Can this calculate UPS or RV battery size?
Yes, add loads and desired runtime to estimate required Ah.
How accurate are the results?
Based on 2025 standards; actual performance varies with temperature, age, and internal resistance.
Tips for Battery Management in 2025
- Use lithium batteries for higher efficiency (95%) and DoD (80%).
- Enter accurate load wattages; overestimate for safety.
- For solar, match charger current to panel output.
- Account for degradation in older batteries (e.g., EV, UPS).
- Export to CSV for off-grid system design or cost analysis.
Disclaimer: Estimates based on 2025 battery standards. Consult professionals for critical system design.
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