it’s summer and you’re wondering how long will a 12v car/Rv or deep cycle battery will power a fan while camping. You, my friend, have come to the right place.

This is going to be a short but on-the-point guide to figuring out the 12v battery runtime on any size fan.

To determine how long will a 12v battery run a fan will depend on a few factors

**Battery Capacity (Ah)****Battery DoD limit****Fan wattage consumption****Inverter efficiency**

**How Long Will A 12 Volt Battery Run A Fan? **in short, a 12v 70Ah lead-acid battery (with a 50% DoD limit) will run a portable 12v 50W DC fan for about 8.4 hours

**Need a simple solution? **use this calculator

## Battery Runtime Calculator

Now let’s dive deep into some calculation stuff so again you’d never have to use any calculator to figure out the backup time of your battery

## 12v Battery Capacity in watts

There are mainly 3 types of batteries, lead-acid, AGM, and lithium batteries.

**Lead-acid, and AGM batteries have a DoD (depth of discharge) limit of 50%. Which means you can only discharge them half. But the lithium (LiFePO4) batteries can be fully discharged up to 100%.**

This was just a basic overview of batteries if you’re a noob. Now let’s get into some calculation stuff

First, let’s calculate the battery capacity in watts from amp-hours (because the fan’s capacity is measured in watts)

**Battery capacity in Watt-hours = Battery Ah * Battery Volts **

### For Example

let’s suppose you have a 12v 100Ah lead-acid battery

`100*12 = 1200Wh or 1.2kWh`

To calculate the useable Wh multiply the value by 2 for lead-acid, AGM, and gel battery types (Because of their 50% depth of discharge limit)

`1200 * 0.5 = 600Wh`

**You have 600 Wh of useable power stored in a 12v 100Ah lead-acid battery **

This guy has explained wonderfully about batteries. watch this if you’re a beginner

**Related Post: **Amps To Watts Calculator: How Many Watts In A 12-volt Battery?

## Inverter Efficiency

An inverter will be required to run an AC fan (which consumes 120-220V input). But some small fans required DC current (12v) which you can run directly from a 12v battery

When converting DC into AC there will be some power loss because usually, inverters are only 85-90% efficient.

This means a 100W inverter will consume 100W DC power from the battery bank and only will be able to output 85-90 AC watts

So if you’re running an AC or DC fan with an inverter with a 12v battery then minimize the DC to AC conversion loss from battery watt-hour capacity

**For example: **

let’s continue with the previous example. 12v 100Ah lead-acid battery

`600 * 0.85 (for 85% inverter efficiency) = 510 AC watts`

**You would get 510 AC watts from a 12v 100Ah lead-acid battery with a 50% depth of discharge limit **

**Related Post:** Solar DC Watts To AC Watts Calculator

## How Long Will A 12 Volt Car or Deep Cycle Battery Run A Fan? Chart

Here’s a chart with how long will a 12v 50Ah lead-acid battery run a fan

Fan Type | Wattage Consumption | Est. Runtime (hrs) on 12v 50Ah Battery (50% DoD limit) |
---|---|---|

12v Small Portable DC Fan | 10 watt | 30 hrs |

12v Medium Portable DC Fan | 30 watt | 10 hrs |

12v Ceiling DC Fan | 60 watt | 5 hrs |

Medium AC Fan | 70 watt | 3.6 hrs |

Ceiling AC Fan | 130 watt | 1.9 hrs |

_{chart – How long will a car battery run fan}

**Note! **Check the input wattage consumption of your fan in the product description session (usually is on the back side of every fan) and make the calculations for you accordingly

## What size inverter do i need to run a fan

There is one rule of thumb. Multiply the wattage consumption of your fan by 1.2 when selecting the size of an inverter

For example, **to run a 50W fan you would need a 60-watt inverter**.

But yes obviously you’re not just gonna run a fan with an inverter. So keep in mind the above rule of thumb to select the size of an inverter according to your need.

**Related Post: **How Long Will a 12v Battery Last With 500w Inverter?

**Summary**

To calculate how long a car or 12v battery will run a fan, Divide the battery amp-hours by the fan input amps. but it will completely discharge the battery which you can achieve only with a lithium battery but, if you have a lead-acid, AGM, or Gel battery type then the runtime will be half

**Related Post**

- What Will An Inverter Run & For How Long? (With Calculator)
- Solar Battery Charge Time Calculator
- Amps To Watts Calculator: How Many Watts In A 12-volt Battery?

I hope this short guide was helpful to you, if you still have any queries LEAVE A COMMENT or contact us. Thank You!