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How Fast will Power Inverter Drain Battery

How Fast Will Power Inverter Drain Battery

The power inverter is an electronic device that transforms the direct current voltage (DC) into alternating current (AC) at 220V. We can find this in any plug of a house or establishment or cigarette lighter socket of a vehicle.

The advantage of carrying an power inverter is that it will allow us to use everyday devices.In places where there is no direct access to a power outlet, we will use these devices.

This guide will learn how fast will power inverter drain battery, which makes it drain faster and more. So, let’s start.

How Fast Will Power Inverter Drain Battery?

This question is very common, and its answer is very broad. In order to answer it, we have to have several considerations and several clear concepts before reaching the desired answer.

Type of battery:

One of the factors to take into account is to know what battery we are using. It must be a deep cycle battery and not for general purposes, vehicles, trucks, or stationary as it is very simple.

The latter are not prepared for the charging and discharging process that batteries undergo when used with current inverters.

If you want to see more details, you can see them in the same section of the Battery Glossary section.

Keep in mind that batteries already discarded from others are usually used in Productive processes on many occasions. These batteries, if they have already been discarded, are useless. They do not work, nor are they suitable to be used with an inverter.

Percentage of discharge:

Another factor is to know the percentage of discharge of the battery you are going to use.Not all brands or all models have the same discharge percentage.This data is very important.

It will allow you to know how much is the maximum charge you will obtain from the battery.Also, you will understand what amount of charge you can extract from its nominal capacity.

For example:

If you have a 12V 200Ah battery, you will not extract 200Ah from it.But you can extract the percentage that you indicate the manufacturer for that model.

You should also refer to the technical data of the manufacturer.It will allow you to know how much charge you can extract in a certain amount of time. It is worth mentioning that more charges can be extracted from a battery at lower consumption than with higher consumption.

If you have more than one battery, it is advisable to have the same brand and battery model.In that case, the banks behave correctly.

Minimum working voltage:

Another parameter that you should know is the minimum working voltage that the inverter should generate 220Vac. For example, some inverter models work with 10.5Vdc as the minimum voltage with an error of + – 0.5V.

This indicates that according to the speed of consumption extraction and battery consumption when it reaches the minimum working voltage, the inverter will cut without generating 220Vac.

That is why it is important to know all these data previously.

Percentage of the consumption to generate 220Vac:

Another piece of information you need to know is the percentage that the inverter spends/consumes to generate 220Vac.Regardless of the consumption applied, the expense must be added both in standby and in the operating process.

The way you can estimate the ampere consumption of your battery bank using the following formula:

Consumption applied in watts + Consumption of the inverter for this applied consumption/input voltage = Amps necessary (to supply this consumption in one hour if it were to remain stable without variation over time)

How Long Will A 12v Battery Last With An Inverter

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

If we use our car battery as the main energy source to power our devices, we must be careful not to discharge it completely.Its duration is very limited depending on the connected device.

First, we need to understand the fundamental specifications of a vehicle battery:

12V battery characteristics:


The battery voltage is usually 12V in most vehicles (cars, vans, motorcycles) and 24V in some trucks.

This voltage remains constant during almost the entire discharge process (varying slightly) until it is almost completely discharged.It is when the voltage begins to drop drastically until the battery is completely discharged.


The capacity is what will determine how long the battery will last before it is completely discharged.

It is measured in Ampere-Hours (Ah).It indicates the amount of energy that it is capable of supplying during one hour, that is:

If our battery has a capacity of 75Ah, it can supply 75 amps for one hour or 10 amps in 7.5 hours.

However, in practice, the capacity is usually lower.It depends on the age and condition of the battery and the losses that occur during discharge.

On the other hand, we have the peak current (or starting current) that the battery can provide during vehicle start.This current refers to the maximum current that the battery can supply for a short period.

Discharging the battery for long periods at its maximum current can cause permanent damage to the battery plates.It is, therefore, not recommended.

Next, we will see an example to calculate the maximum use time of a 12V car battery and 75Ah capacity:


It is important to remember that it is not advisable to discharge the battery of our vehicle completely. Not only could it be damaged, but it would also prevent us from starting the vehicle again.

Example with 12V and 75Ah Battery

Suppose we connect a fan that consumes 60W to the inverter. We assume that it has an efficiency of approximately 90%.

  1. We calculate the power that we are going to need to drain from the battery: Battery power = Device power / efficiency = 60W / 0.9 = 66.67W
  1. We must estimate the current that we are going to need from the battery: Battery intensity = Battery power / Battery voltage = 66.67W / 12V = 5.55A
  1. Finally, we calculate the theoretical maximum time of use of the battery: Maximum time = 75Ah / 5.55A = 13.5 hours

That is, the maximum time that we could use the fan continuously would be 13.5 hours.

Of course, this calculated time is ideal.It is assumed that the battery is new, fully charged, and maintains the voltage at 12V throughout the discharge:

In a real case, the battery could not be completely discharged (unless you short-circuit it).Otherwise, the inverter would disconnect if the battery voltage was too low (<< 12V).

Another quick way to calculate battery life would be by applying the following formula: Maximum time = Battery capacity x Battery voltage x Inverter efficiency / Device power.

In our fan example:

Maximum time = 75Ah x 12V x 0.9 / 60W = 13.5 hours

Some examples with other devices:

Electric equipment Power consumption (W) Maximum usage time (h) *
Portable fridge 70W 11.6h
Amazon basics toaster 800W 1 hour
Mobile charger 18W 45h
Electric oven 1000W 0.8h
Sandwich maker 700W 1,2h

Criteria of a Power Inverter to Get Maximum Battery Benefits

If you want to use an inverter optimally, you have to choose by taking specific criteria into account.

In fact, when purchasing this type of power electronic device, the emphasis must be placed on

  • Its functionalities,
  • Its power,
  • It’s a level of autonomy or
  • Its performance.

Speaking of autonomy, considering elements such as the efficiency and the charging time is a question.It must have an average duration of between 5 and 6 minutes.

As for power, it must be chosen according to the devices to be supplied. Thus, if it is to supply a 90 W element, it is necessary to opt for an inverter of at least 150A.

You should choose an inverter offering functions such as noise filtering or distortion attenuation in terms of functionality.

In general, the user must choose his inverter, taking into account his needs.


When choosing a power inverter, it’s natural that everyone wants maximum benefits. It is legit to ask how fast will power inverter drain the battery. But that is difficult to answer in a few words. That’s why we tried to help you with the answer. Hopefully, this was enough