How Long Will a 300Ah Battery Last?
A 300Ah battery bank provides 3,600Wh total capacity at 12V - serious power for off-grid applications. This capacity allows comfortable living with refrigeration, regular inverter use, and occasional high-power appliances.
Capacity
300Ah
Total Energy (12V)
3600Wh
Usable (80% DoD)
2880Wh
Typical Use
Off-grid cabins
Runtime Calculator
Runtime at 100W
24.5 hours
1.0 days if running continuously
Total Capacity
3600Wh
Usable (80% DoD)
2880Wh
Solar Charging
* Actual runtime varies based on temperature, battery age, and load consistency.
Runtime Examples at 300Ah
| Device | Power Draw | Runtime |
|---|---|---|
| Fridge | 50W | 48 hours |
| Multiple devices | 100W | 24 hours |
| Power tools | 300W | 8 hours |
| Microwave/Blender | 500W | 4.8 hours |
| Space heater | 1500W | 1.6 hours |
* Based on 12V LiFePO4 with 80% depth of discharge and 85% inverter efficiency.
- ✓Off-grid cabins
- ✓Large RV systems
- ✓Serious backup power
- ✓Small homestead
- ✗Full house backup
- ✗Running central AC
- ✗Electric vehicle charging
- ✗Large workshops
300Ah Battery Tips
- •Enough for comfortable off-grid cabin living with 12V appliances
- •Can handle occasional 1000W+ loads without stress
- •Consider upgrading to 24V system at this capacity for efficiency
- •Pair with 600W+ solar for reliable daily recharging
- •Three 100Ah batteries in parallel is a common configuration
Frequently Asked Questions
Is 300Ah enough for off-grid living?
For a small cabin with efficient appliances, yes. You can run a fridge, lights, laptop, and phone charging comfortably. Not enough for electric cooking, AC, or electric heat.
Should I use 12V or 24V for 300Ah?
At 300Ah, either works. 24V reduces wire size needs and is more efficient for larger inverters. 12V is simpler if you have 12V appliances. Above 400Ah, 24V is strongly recommended.
How long to charge 300Ah with a generator?
With a 50A charger, about 6-7 hours from 20% to full. A 30A charger takes about 10 hours. Running a generator is less efficient than solar for daily charging.