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How Long will a Car battery Last Using a Power Inverter?

Power inverters are a great tool to have for your vehicle rather it be your daily driving car, truck, motorhome, or even a boat. Whatever application you have in mind the purpose of power inverters remains the same. They provide you with a source of alternating current (AC) power so that you are able to run appliances or electronics that you would normally run at your home or office.

These power inverters will hook up directly to your vehicle’s battery and on the other end will typically have one or two one-hundred and twenty volt outlets. These are the same outlets found in your home. The inverter draws its energy from the power stored in your battery. If the vehicle’s engine is turned on then the battery will be constantly recharged through the alternator. However, if your engine is off then you are relying on the battery and the battery alone to provide you with a source of power for your inverter.

A common question here is exactly how long you can expect your vehicle’s battery to last with the engine off and the inverter drawing power. Now there is no magic number here. There are so many variables it is difficult to give you an exact time. Think about it for a moment, there are all different sizes of power inverters out there. There are different sized batteries out there. Each battery can have a different charge level as well. All of these points factor into how long the battery will last.

Now, that all being said what I can do is give you an estimated time. Your standard battery found on a vehicle is meant to store enough energy to give a short burst of power to start your vehicle. These twelve volt batteries are not meant for long term use but instead short bursts. It is recommended to not let the charge on these batteries drop below ninety percent capacity. If that does occur then you risk damaging the battery or perhaps even ruining it.

With that in mind your vehicle’s battery can expect to last between thirty to sixty minutes when providing power to your inverter. As I stated before, this is an estimate and each application varies. If it was me though I would not run the power inverter with my engine off. The risk is high that you could end up draining your battery until it is dead and then your vehicle will not start and you are stranded.


If you have your heart set on running your power inverter while your engine is off then there is an alternative option. Perhaps you wish to do a tail-gating event. Or, you plan on camping and would like to have warm coffee in the morning. Whatever the reason is you should know there is another option out there that allows you to run power inverters from your vehicle while the engine is off for hours at a time.

This alternative method is installing a secondary battery on your vehicle. This secondary battery would have to be a ‘Deep Cycle’ battery. These deep cycle batteries are meant for long term use and their capacity can drop as low as fifty percent without damaging the battery. These are the type of batteries found in motorhomes and recreational vehicles. These batteries can last for hours and sometimes even days.

The secondary battery is charged along with your standard twelve volt battery by the alternator while your engine is running. When the vehicle is off the power inverter will draw power from the secondary battery and preserve the energy stored in your main starting battery. This will help to prevent the scenario with a dead battery and your car will not start.

Installing a secondary battery can be a bit tricky. If you are an experienced tinkerer with vehicles the you should be able to handle it by following this guide that I found. However, if you are no as comfortable working on vehicles then I recommend taking your vehicle into the dealership or a local mechanic and tell them that you want a secondary deep cycle battery installed. If you also already have the power inverter purchased you can ask them to install it as well. Otherwise, you can install it after the fact.


To close out this article folks and to answer your question your car’s battery will last between thirty to sixty minutes when running a power inverter with the engine is off. This is an estimated time though and there are many factors that can impact these numbers. If you plan to run your power inverters for an extended period of time then you should either run it with your vehicle’s engine on or you should look at installing a secondary deep cycle battery.

Thanks for reading,

Alec Johnson

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