How Long Will a Deep-Cycle Battery Run a TV?
If you are inclined to bring a little home-style comfort while camping, or you like to tailgate at football games on the weekend, solar power and a good-quality deep-cycle battery are essential. Solar batteries allow you to store a reserve, maximizing your ability to access solar power when you are outdoors with limited or no direct access to the power grid. But how long will a deep-cycle battery run a TV?
A deep-cycle battery of around 100 AH can power a 50-watt TV for up to 20 hours. The amount of time a deep-cycle battery will run a TV depends on battery capacity, measured in amp-hours. The voltage, type of battery, discharge rate, the inverter’s size and the watts usage of the TV also impact this.
This article will start off with a basic explanation of solar power and then clarify what “battery capacity” actually is. You’ll gain insight into which factors influence how long a deep-cycle battery will run a TV, enabling you to pick the right battery size for your outdoor and camping needs.
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Plus, you’ll discover how to extend battery life through the help of four tips to protect your investment.
Solar Power in a Nutshell
A photovoltaic (PV) cell, also known as a solar cell, converts sunlight into an electric current with usable electricity as a result. Sunlight is composed of solar energy particles, also referred to as photons. Incoming sunlight gets absorbed by the semiconductor material of a solar cell and produces electricity (source).
A solar panel is composed of numerous solar cells. While similar to battery cells, cells in a solar panel are designed to generate electricity by capturing sunlight. A solar array is a collection of several solar panels that generates electricity as a system (source).
Solar panels are not directly used to charge a device. In most cases, the solar power generated charges a battery. Apart from the storage factor, having the ability to regulate the power flow to appliances is a real advantage of batteries.
If you wish to learn more about how much power solar panels produce, read our helpful article on How Many Amps Does a Solar Panel Produce?
Deep-Cycle Battery Capacity
Battery capacity is the actual quantity of electricity that you can extract out of a battery from one cycle of a fully charged battery to a fully discharged battery. Most battery systems provide both a kilowatt (kW) rating as well as a kilowatt-hour (kWh) rating. Before we clarify both terms, let’s address what a deep-cycle battery actually is.
What Is a Deep-Cycle Battery?
A deep-cycle battery is any lead-acid battery that can be completely discharged and charged with minimal damage. They are preferred in solar power systems due to their ability to have many hard cycles during their lifespan without losing capacity.
The traditional flooded deep-cycle battery has been overtaken by the absorbent glass mat (AGM) version since its charge is up to five times faster (source).
Power Rating vs. Energy Rating
The power rating, measured in kW, signals the amount of energy that moves in and out of the battery at any given time. This matches the volume classification of a PV system, also measured in kilowatts.
The energy rating, also known as the battery capacity, is measured in kWh and offers an approximation of the amount of power that can be stored. Again, this is similar to the power production of a PV system, also measured in kWh (source).
How to Calculate Amp-Hours
An amp-hour is one amp for one hour. Amp-hours are calculated by multiplying the number of amps (A) a battery provides by the discharge time in hours (h).
Let’s take a look at an example. Let’s assume that you have a smartphone hooked up to a solar battery that pulls 20 amps for the duration of 20 minutes. See the step-by-step calculation into amp-hours by using the below equation:
Equation: Amps (A) x discharge time in hours (h) = Amp-Hours (AH)
Step 1: Calculate how much 20 minutes is in hours
20/60 = 0.333 hours
Step 2: Enter both variables in the equation to produce the result
20 A x 0.333 h = 6.67 AH
The result indicates that 20 amps for 20 minutes will use 6.67 amp-hours.
The above, however, is an ideal scenario and does not take the Peukert effect into account. We’ll describe this phenomenon in the next section, so keep reading.
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Discharge Rate, aka, Peukert Effect
The discharge rate of a battery, also known as the Peukert Effect, is important when deciding how much battery capacity you need for a specific device. The principle is simple; the more current you draw, the lower the capacity of the battery, and the quicker it discharges. For a lead-acid battery, the Peukert’s constant is usually between 1.1 and 1.3 (source).
How Long Will a Deep-Cycle Battery Run a TV?
To determine how long a deep-cycle battery will run a TV, we’ll have to address voltage, the type of battery used, its discharge rate, the energy rating, the size of the inverter, and how many watts a TV uses. We’ll break down a specific scenario to clarify the calculation.
A volt is a unit measuring the electric potential difference. Voltage essentially measures how many electrons want to be somewhere. It’s also described as electromotive force and, in this sense, can be best compared to the workings of water pressure. The most common deep-cycle batteries on the market have a voltage of 12 volts.
Battery Chemistry & Discharge Rate
Choosing a flooded or AGM deep-cycle battery will influence how long a TV will run. The depth-of-discharge of an AGM battery is 80%, outlasting the 50% for flooded batteries (source).
The energy rating of deep-cycle batteries varies a lot and can range from as much as 200 amp-hour to as little as 10 amp-hour ratings.
Size of the Inverter
You need an inverter to change the direct power (DC) stored in the battery, usually at 12 volts, into alternating current (AC), at 230 volts, in order to operate appliances. The bigger the inverter size, the longer you can run a TV.
An inverter generally has a 15% loss of efficiency when powering your devices, producing an 85% efficiency rate.
How Many Watts Does a TV Use?
Both the TV size in inches and the type of TV — i.e., LED or LCD — influence how long a deep-cycle battery can run.
An LED TV is far more energy-efficient and uses about 20% less energy than an LCD TV. However, even with the LED category, wattage can vary by as much as 50-70 watts depending on the size and make (source).
While TVs produce about three to four percent of global residential electricity, consumption is forecasted to remain the same due to technological advancements, despite increased TV sales and bigger screen sizes (source).
Let’s break down a specific scenario and tackle how long a 100AH AGM battery can power a 50 watt TV. To answer this question, we need to make use of Peukert’s formula — C = C m /(1+(i/i0)n). C is the energy rating in amp-hours, I is current in amps, T is time in hours, and n is the Peukert number for the battery (source).
In this scenario, we assume:
- C to be 20 amp-hours
- Voltage to be 12 volts
- 0.85 inverter efficiency factor
- Peukert’s Constant to be 1.1
Peukert’s formula C = C m /(1+(i/i0)n)
50 watt TV / 12 volt = 4.16 amps.
4.16 amps / 0.85 efficiency of inverter = 4.9 amps needed from the battery to overcome the 15% loss of the inverter and still provide 4.16 amps to the TV.
20 (((100AH / (4.9 * 20))^1.1)) = 20.4 hours until a 100AH AGM battery is fully discharged.
Tips to Extend Deep-Cycle Battery Life
Deep-cycle batteries come with a certain price tag. To ensure you reap the benefits of your investment for as long as possible, we have compiled four tips.
To safeguard long battery life, make sure to charge your battery fully in a complete cycle. Avoid opportunity charging by plugging and unplugging your battery as the need arises.
Check the Discharge Rate
Deep-cycle batteries handle between 50% and 80% discharge rate. When you recharge at a lower discharge rate, while not lower than 20%, you’ll end up with more full cycles.
Proper storage of batteries requires a fully charged battery protected against extreme weather conditions. Storing inside a cool spot, preferably temperature regulated, is crucial to avoid damage.
Slow but Steady
Make use of a solar charge controller to avoid overcharging, ensure a slow but steady charge rate, and prevent battery discharge at night or when the sun is not shining. Introducing periods of extended slow and low current charges will help equalize and keep cells in balance and extend battery life (source).
Storing solar power in a deep-cycle battery enables you to enjoy all the modern conveniences while camping in the outdoors. In fact, a decent size deep-cycle battery of 100 AH will power a 50-watt TV for up to 20 hours. You might also be interested in my post on running a refrigerator on solar power as well.
By charging in full cycles, at a slow pace, at an optimum discharge rate within a safe and regulated spot, you’ll reap the benefits of longer battery life.