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Batteries are available in different sizes and types, so when someone asks how long a deep cycle battery can run a TV, we have to know the battery volt and amps and how much power the TV consumes.
A 150ah 12V deep cycle battery can run a 40 inch LED TV for 35 hours and a 65 inch TV for 15 hours before it is completely discharged. The running time will be shorter if you connect a video game console or movie player to the TV.
How to Calculate TV Runtime with a Deep Cycle Battery
To determine how long you can watch TV, we must have the following information.
- How many amps the TV draws per hour
- The battery voltage
- Usable battery amps per charge
The formula is:
TV amps x hours = battery size
A 120ah AGM 12V battery for instance, can run a 32 inch LED TV for about 33 hours.
A 32 inch LED TV draws 3.5 amps an hour on average. 3.5 x 33 = 115, so the TV will draw 115 amps after 33 hours.
After 33 hours your 120ah battery will be almost fully drained. If you do not want the capacity to drop below 50%, reduce the runtime in half (about 16 hours) or double the capacity to 240ah.
Another way to calculate the runtime is:
Battery size / TV amps
Suppose you have a Mighty Max 150ah deep cycle battery and a 60 inch LED TV. How long before the battery runs out?
Assuming the TV draws 120 watts, that would be 10 amps an hour:
120 / 12 = 10
A 150ah battery can run a 60 inch TV up to 15 hours before it is completely empty. Most likely however the runtime will be 13 to 14 hours because batteries discharge faster as capacity drops.
These calculations are only estimates. Batteries discharge faster when higher amps are drawn, so it is better to be conservative with your estimate.
The TV watt and amp draws given here are for discussion purposes only. TV power consumption varies depending on the manufacturer, make, model and settings used.
How Many Batteries Do I Need to Run a TV?
It depends on how long you want to use the TV and how much it is discharged. The following examples assume you will be using a 12V battery.
If you have a 100ah battery the calculations are simple. But there are other battery sizes and types so let us look at them.
You installed a 21 inch TV in your RV and watch 5 hours a night. You have a battery bank, but how many amps must you set aside for the TV?
A 21 inch TV draws around 2.5 amps an hour. You only need 12.5 amps to be able to watch 5 hours every night. Most RVs have at least a 100ah battery so you have plenty of power.
But let us say you have a 32 inch TV and a video game console. You play for a couple of hours every afternoon and watch another 5 hours of TV later.
Typically these TVs draw 3.5 amps an hour but you have to add another 2.5 for the gaming console. That is 6 amps in the afternoon and another 17.5 in the evening for 23.5 amps total.
Even if you play video games every night the TV and gaming console combo only draws 6 amps an hour. As long as you have a good sized battery bank there won’t be any issues. Of course if you have a 10kwh battery system you can run pretty much anything you want.
Battery Discharge Rate and Why it Matters
Simply put, FLA and SLA batteries like gel and AGM should never be emptied. In fact they have to be recharged when the capacity is half drawn. This is to ensure the longevity of the battery, as emptying it will cause long term damage.
This means you can only use half the battery for each full charge. If you follow this guideline for AGM batteries, you have to double the capacity.
The exception to this are lithium batteries. They have a discharge rate of 90% to 100%, so you get full use of its power per charge. However these batteries are more expensive. You can however, think of lithium batteries as a long term investment that will pay itself off with a longer life cycle.
Why is My Battery Draining Fast?
So you did the calculations and have your TV running. But then you notice that the battery runs out of power faster than they should. Did you make a mistake in your calculations? Let us look at the possibilities.
TV Peripherals. One possibility is you have peripherals connected to the TV. These devices consume watts just like any other appliance.
- Satellite TV box 30W
- Movie player 30W
- Video game console 30W
If you have these on your TV, the system will draw more power. 30 watts an hour might not seem much. But if you spend hours playing video games or binge watching daily, it adds up.
Too Many Appliances Running. Because TVs consume little power, we can run it alongside other appliances. While convenient this will drain the battery and not leave enough for the TV. When calculating the TV running time, include how many appliances will be loaded on the battery.
Old Batteries. New batteries fill up faster and last longer per charge. As the battery gets older, the opposite happens. the battery takes longer to recharge and loses capacity quickly. Even if the battery is filled up, it will lose power faster even if the TV doesn’t pull a lot of amps.
If your battery is losing power rapidly, look at these as the most likely causes. You might also check the wiring. Loose cables can lead to significant performance drops.
Do I Need an Inverter to Watch TV Off a Battery?
Some TVs are DC and others are AC. But if you have a TV in your RV chances are you have other appliances that run on AC. So yes, you should get an inverter.
We have an in-depth guide for running TVs on an inverter here. But you can use any modern inverter to run a TV. Most TVs in RVs are 19 to 32 inches and use up 35 to 40 watts. With portable inverters providing 400 watts, capacity will not be an issue.
There are a few things to keep in mind though:
- An inverter needs an energy source to run any load. In this case it is the battery bank. The inverter can keep the TV going as long as there are enough amps in the battery.
- While TVs are not resource hogs, other appliances are. You might have a 2000 watt inverter installed, but that will get filled up if you run several appliances simultaneously.
- Some TVs run better with a pure sine wave inverter. Others work fine with a modified sine. Contact the TV or inverter manufacturer to find out which works best.
- Do not run the inverter at maximum capacity. If your 1000 watt system is always maxed out, it is time to replace it with a larger inverter.
Tips For Running a TV on Deep Cycle Batteries
- Check the TV specifications. Find out how many amps and watts it draws per hour. There are many types of TVs so you have to check the specific model and make.
- Choose a battery. We have been using 12V deep cycle batteries as examples here. But there are 24V and 48V batteries. You also have to choose between SLA, FLA and lithium.
- Consider what other appliances you will be running. The more appliances you run, the faster the battery will drain.
- You need an inverter to run any type of AC appliance. Here is a guide on what inverter size to choose.
- You must install a charge controller to prevent the battery from overcharging. This should be included if you bought a solar panel kit.
TVs have come a long way in terms of energy efficiency. Today with the right set up you can get any screen size you want and run it for several hours. With battery costs dropping, things will only get better.