A 200Ah LiFePO4 deep cycle battery is a great choice for powering your appliances while off-grid. This battery lasts longer and is more resilient to weather, capacity loss, and physical damage than lead acid batteries of similar size. A space heater on the other hand is a highly demanding appliance. So can a 200Ah lithium battery run a space heater?
A 200Ah battery can run a space heater for a max of 19 minutes. It is possible to stretch this for a couple of minutes but it is better to use this intermittently.
In this article, we look at the power demands of a space heater and if a 200Ah battery can match its requirements.
Power for a space heater
A typical space heater will use between 1000 and 3000 watts, depending on the model. A low-wattage unit will be fine if you’re just looking to warm up a small area.
A high-wattage unit will produce more heat but might take longer to do so because it takes more energy to get from room temperature up to 70°F or whatever temperature setting you’ve set. You will need 10 watts of heating power for every square foot of floor area in a room.
A typical space heater will need around 1500 watts of power.
Space heater Watt-hour Requirement
Electrical energy is measured in watt-hours. One watt-hour equals one watt expended for one hour. The number of watt-hours used by an appliance over a period of time equals the total amount of power consumed by that device over that period.
To calculate watt-hours, multiply the watts used by an appliance over a period of time by the number of hours that appliance is used.
If you use a 1500 Watt space heater for 1 hour, it will consume about 1500-watt-hours or 1.5kWh.
How Many Amps will a 1500-watt Space Heater Draw?
A 1500-watt space heater will need around 12.50 amps to run when using it from the standard 120V outlet. This is the number of amps that it will be drawing from the inverter. Depending on the DC voltage of the inverter you can calculate the number of amps the space heater will be drawing through the inverter.
To find the number of amps you need for the inverter you divide the watts by the voltage. In the case, you have a 12-volt system, so you divide 1500Watts by 12V, and for a 24V system, you divide by 24V.
1500/12 = 125 Ah
So you need a battery that you can safely pull 125 amps per for the 12v system
Will a 200ah battery support this?
How Many Amps Can a 200Ah Battery Provide?
Amp-hour rating in batteries gives the charge in amps that can be drawn from a battery over a specific time given in hours.
A Deep Cycle Battery is intended to produce the charge for a long period of time like 20 hours. So for a 200 Ah battery, it should produce at least 10 amps over a 20-hour period.
However, you can go higher or lower depending on the appliance you are using. Deep cycle batteries are recommended to be discharged at 20% of their capacity so for a 200 Ah battery the max discharge per hour would be 40 amps meaning it can last 5 hours.
How many watt-hours is a 200 Ah Battery
You can use the following formula to determine how many watts can be drawn from a battery.
Watts = Volts x Amps
So if your battery is 12v and has a 200 Ah capacity, then you can draw 2400 Watts from it. This is for the full battery cycle. With the 40 amps max draw it means you can get 480 watts max per hour. You can push this to 50 amps or 600 watts per hour with LiFePO4 batteries.
How Long Can a 200Ah Battery Run a 1500-Watt Space Heater?
From the looks of things, a 200Ah battery cannot support the amps required to run the space heater. But we already know the battery can support 480 watts but we need 1500 watts for the space heater to run for an hour. So we have enough power to run the space heater for a fraction of the time.
So how long is 480 watts?
(480/1500) = 0.32 hrs
In minutes 0.27 x 60 = 19.2 minutes
A 200Ah 12v battery will run a space heater for 19.2 minutes. This is without any other appliance drawing power from the battery at the same time. You can choose to run the space heater intermittently over time and you can use up to 5 times or boil some water with an electric kettle.