How Long Will a 12v Battery Last with an Inverter?


Many people want to know much acknowledgment about solar inverters, now, in this post, i would like to introduce that how long will a 12v battery last with an inverter? In general, you need to calculate the 12v solar battery time with an inverter multiply battery amp-hours (Ah) by 12 to find watt-hours, and divide by the load watts to find run time hours. Finally, multiply run time hours by 95% to account for inverter losses.

How Efficient Are 12v Inverters?

Fisrt, Let’s assume that almost many people would buy the pure sine wave inverter variety. They are much more efficient than their modified sine wave cousins and the price reflects that.

Considering the possible negative effect on appliances and possible interference with electronics, it is the best option. However, even the best quality electronics devies have losses.

The best inverters have an efficiency of between 93% and 97percent and the price increases accordingly. This kind of efficiency only occurs if the inverter is reasonable loaded.

You can see form the graph in the image below that below 30% load most inverters lose efficiency rapidly, which means you’re wasting your power.

What Do Inverters Do?

In fact, many people want to know just how long your 12 volt battery would last running an AC load through an inverter. To answer this question fully we need to define these 3 things:

  1. The type of battery being used
  2. The size of the battery in amp-hours (Ah)
  3. The AC load size in watts

Why Is Battery Type Important?

On the flip side, other battery technologies determines how much of a battery’s capacity you can actually use. It sounds great having a 100Ah battery to power an inverter, but what if you could only use 15 percent of that without damaging it?

Now, you can see the specifications in other places show that a car battery gradually loses it’s capacity if it’s discharged regularly more than 10 to 15 percent.

Automotive batteries are often call SLI (Starting, Lights and Ignition) and they are designed to do just that. They can provide up to 900 amps to crank a cold engine but don’t handle medium current draw for long periods of time very well.

In face, if the car battery has delivered that enormous starting power, the engine alternator immediately starts to charge it rapidly. Within minutes it’s fully charged again!

Table – Pure Sine Wave Inverter VS Square Wave Inverter

Pure Sine Wave Inverter

Modified Sine Wave

Perfect sine wave output

Practically square wave

High quality electronics

Minimum electronic components

Low level hum

Can be noisy, can hear definite buzz

Does not interfere with other electronic gear

Can cause interference on TVs, cell phones

Safe for all appliances

Some appliances may overheat

90% to 95% efficient

75% to 85% efficient - wastes power

2 to 3 times more expensive than modified

Cheaper option