One of the most common questions we get at All 12 Volt is:
“How long will my battery last?”
Whether you’re powering a fridge, running lights, or charging devices, knowing your battery’s runtime helps prevent flat batteries, spoiled food, and inconvenient power failures during your trip.
In this guide, we’ll break down how to calculate 12V battery runtime, explore real-world examples using ZENOT batteries, and show you how to get the most out of your power setup.
A 12V battery’s capacity is measured in amp-hours (Ah)—this tells you how much current it can supply over time.
A 100Ah battery can theoretically deliver 1 amp for 100 hours
Or 10 amps for 10 hours, and so on
But there’s a catch—usable capacity depends on the battery type:
| Battery Type | Usable Capacity |
|---|---|
| AGM | ~50% (to avoid damage) |
| Lithium | ~90% (safe deep discharge) |
To estimate runtime:
Battery Ah × Efficiency ÷ Device Amps = Estimated Hours
Or for multiple items, add up total amps in use and divide.
Device amps = Watts ÷ Volts (12V)
Appliances:
45L Fridge (2A) = 48Ah/day
LED lights (1A for 4 hours) = 4Ah/day
Phone charging (0.5A for 2 hours) = 1Ah/day
Total: ~53Ah/day
Runtime:
135Ah × 0.5 (AGM) = 67.5Ah usable
→ ~1.3 days runtime
Same appliances as above
135Ah × 0.9 (Lithium) = 121.5Ah usable
→ ~2.2 days runtime
Add a 200W solar panel (adds ~60Ah/day), and you can go indefinitely.
Battery Age: Older batteries hold less charge
️ Temperature: Heat or cold impacts performance
Inverter Use: Running 240V devices through an inverter draws more power
⚙️ Cable Size: Voltage drop from thin or long cables wastes power
Hidden Loads: Standby gear like trackers or WiFi boosters may slowly drain power
Use LED lighting and low-draw devices
Pre-cool your fridge before your trip
Add solar panels for extended stays
Use a battery monitor to track your draw in real time
Choose ZENOT Lithium for deeper, longer-lasting discharge
| Battery | Usable Ah | Fridge Only | Fridge + Lights + USB |
|---|---|---|---|
| 100Ah AGM | ~50Ah | ~1 day | <1 day |
| 135Ah AGM | ~67Ah | ~1.3 days | ~1 day |
| 135Ah Lithium | ~121Ah | ~2.5 days | ~2.2 days |
| 200Ah Lithium | ~180Ah | ~4 days | ~3.5 days |
Estimates based on ~2A average fridge draw + LED/charging.
Still unsure what size battery you need for your setup? We’re here to help. Our team at All 12 Volt can guide you based on your gear, vehicle, and trip length.
Explore our AGM & Lithium battery range now
Plan smart. Power longer. Travel further—with All 12 Volt.
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