The runtime of a 100Ah battery depends on the load it is powering and the type of battery. Here’s how to estimate it:

Key Formula

Runtime (hours)= Battery Capacity (Ah)/ Load Current (Amps)

Where:

Battery Capacity: For a 100Ah battery, the capacity is 100 ampere-hours.
Load Current: The current (in amps) drawn by the device(s).

Example Scenarios

1. Load Power in Watts

If the load is rated in watts (e.g., a 100W light bulb), convert it to current:Current (Amps)=Power (Watts)Voltage (Volts)Current (Amps)=Voltage (Volts)Power (Watts)

For a 12V system: Current=100W/12V=8.33A
Runtime: Runtime=100Ah/8.33A≈12 hours

2. Smaller Load

For a 20W device at 12V:

Current:Current= 20W/12V=1.67A
Runtime:Runtime= 100Ah/1.67A≈60 hours

3. Larger Load

For a 300W device at 12V:

Current: Current=300W/12V=25A
Runtime: Runtime=100Ah/25A=4 hours

Factors Affecting Battery Life

Depth of Discharge (DoD):
- Most batteries shouldn’t be fully discharged.
- Example: Lead-acid batteries are typically discharged only to 50% DoD, halving the effective capacity to 50Ah.
Battery Type:
- Lithium-Ion or LiFePO₄: Can use most of their capacity (80–100%) without damage.
- Lead-Acid (AGM, Flooded): Limited to 50% DoD for longevity.
Efficiency Loss:
- Energy losses in inverters, wiring, and battery chemistry reduce runtime (typically ~85–90% efficient).
Age and Condition:
- Battery performance declines over time, reducing capacity.
Temperature:
- Extreme cold or heat affects battery efficiency.

Quick Runtime Estimates (12V Battery at 100% DoD)

Load Power	Current Draw	Estimated Runtime
10W	0.83A	~120 hours
50W	4.17A	~24 hours
100W	8.33A	~12 hours
500W	41.67A	~2.4 hours

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