How Long Does an Inverter Battery Last?
Inverter battery is a deep cycle lead-acid or lithium battery or battery pack, providing DC electricity (12V, 24V, 36V, etc.) which is converted to AC electricity (mostly 110V or 220V) in order to provide power to various tools and appliances.
In order to calculate how long will an inverter battery last, one has to know inverter load, its efficiency, battery voltage, capacity, and discharge characteristics - perhaps it sounds a lot, but it is fairly simple ...
Published: August 26, 2021.
Little Bit of Theory ...
An inverter is an electronic device that converts (inverts - hence the name) one form of electricity into another with a certain efficiency.
On average, inverter efficiency varies depending on many things, but on average, it is around 85-95%.
For example, Renogy 1000W 12V Pure Sine Wave (Amazon link, link opens in the new window), features an efficiency of ≥90%, maximum continuous output of 1000W, surge power of 2000W, has 12V input, and features pure sine wave output, allowing the user to power even rather sensitive devices and electronics.
When powering power inverters using batteries, it is important to match battery voltage with the input voltage of the inverter (logical, right?) and to calculate the actual capacity of the battery (or battery pack) using its discharge charts.
Note: nominal capacity of the lead-acid batteries is given for 20h discharge, however, when such battery is discharged in, for example, one hour, its actual capacity drops down to 55-75% of its nominal capacity, depending on the model.
Lithium batteries don't suffer from such capacity loss and it is safe to assume that when they are discharged with 0.5-1.0C currents, their actual capacity is approximately their nominal capacity.
How Long Will a 500W Inverter Last?
An inverter with an efficiency of 90% and output power of 500W, requires ~560 input watts, which is:
- @12V: ~47 Amps,
- @24V: ~24 Amps,
- @36V: ~16 Amps.
Since most 500W power inverters feature ~1000W surge power, input currents can periodically be doubled for a very short time.
For short, if You have a 500W power inverter, it requires at least 47Ah 12V, or 24Ah 24V, or 16Ah 36V battery in order to operate for one hour.
Note: most 500W power inverters are 12V units.
How Long Will a 1000W Inverter Last?
Calculations for 1000W inverters are very similar to the 500W power inverters.
An inverter with an efficiency of 90% and output power of 1000W, requires ~1115 input watts, which is:
- @12V: ~93 Amps,
- @24V: ~47 Amps,
- @36V: ~31 Amps.
Since most 1000W power inverters feature ~2000W surge power, input currents can periodically be doubled for a very short time - for example, a 12V inverter providing 2000W surge power draws ~186 Amps from its battery.
Such surge current can be a problem for lithium batteries with the built-in BMS (Battery Management System).
For short, if You have a 1000W power inverter, it requires at least 93Ah 12V, or 47Ah 24V, or 31Ah 36V battery in order to operate for one hour.
Note: most 1000W power inverters are 12V units, although, in order to increase the efficiency, some brands offer 24V models.
How Long Will a 1500W Inverter Last?
An inverter with an efficiency of 90% and output power of 1500W, requires ~1670 input watts, which is:
- @12V: ~140 Amps - 140Ah 12V battery required for one hour of operation,
- @24V: ~70 Amps - 70Ah 12V battery required for one hour of operation,
- @36V: ~47 Amps - 47Ah 12V battery required for one hour of operation.
Since most 1500W power inverters feature ~3000W surge power, input currents can go up to 280 Amps @12V, or 140 Amps @24V, or 94 Amps @36V.
For short, if You have a 1500W power inverter, it requires at least 140Ah 12V, or 70Ah 24V, or 47Ah 36V battery in order to operate for one hour.
Note: most 1500W power inverters are 12V units, but 24V units are also rather popular.
How Long Will a 2000W Inverter Last?
2000W power inverters are a very popular class of power inverters with 12V, 24V and even 36V power inverters being popular - as the voltage is increased, the current is decreased to manageable values (50-60 Amp or less!).
Math is very similar to previous models: an inverter with an efficiency of 90% and output power of 2000W, requires ~2225 input watts, which is:
- @12V: ~186 Amps,
- @24V: ~93 Amps,
- @36V: ~62 Amps,
- @48V: ~47 Amps.
And since most 2000W power inverters feature surge power of at least 4000W, input currents can periodically be doubled for a very short time - 372 Amps @12V, 186 Amps @24V, 124 Amps @36V, 94 Amps @48V, etc.
That is why most modern RVs and Golf Carts operate at 48 or even more volts.
Note: some 200W power inverters are 12V units, while other units operate at 24V, 36V, 48V, or even more volts.
Best Inverter Battery
Inverter batteries or battery packs must be able to provide the required power for the required time, allowing the user to calculate if one battery is enough, or one has to get a larger/stronger battery or one has to create a larger battery pack.
In order to help with calculations, we will use 5 very popular dual purpose and deep-cycle AGM lead-acid and lithium batteries:
Odyssey 31-PC2150S Heavy Duty Commercial AGM Battery
Odyssey 31-PC2150S belongs to the BCI Group 31 batteries and features a nominal voltage of 12V, nominal capacity of 100Ah, and is one of the best dual-purpose AGM batteries on the market.
Odyssey 31-PC2150 dual-purpose AGM battery is manufactured in several versions, with each version being optimized for a specific use, having slightly different battery terminals. But, the electric characteristics of these versions are practically the same.
The battery's physical dimensions are 13 x 6.8 x 9.41 inches (330.2 x 172.7 x 239.0 mm) and it weighs 77.8 lbs (35.3 kg) - it is anything but a small and lightweight battery.
But, the Odyssey 31-PC2150S battery also features 1150 CCA Amps, an RC rating of 205 minutes, excellent deep discharge recovery, and excellent low-temperature performances.
The following chart lists discharge characteristics of the Odyssey 31-PC2150 battery:
|Time||Watts (W)||Amps (A)||Capacity (Ah)||Energy (Wh)|
As one can see, if the Odyssey 31-PC2150 is used to power a 90% efficient power inverter, it can power:
- 2h: ~410W,
- 1h: ~750W,
- 45 min: ~950W,
- 30 min: ~1300W,
- 20 min: ~1780W, etc.
Also, since it is a very robust AGM battery, the Odyssey 31-PC2150 battery tolerates short power surges very well.
For more reviews and recommendations, feel free to check the Odyssey 31-PC2150S Heavy Duty Commercial AGM Battery Amazon link (link opens in the new window).
Mighty Max Battery ML4D 12V 200Ah 4D SLA AGM Battery
Mighty Max ML4D battery is a deep cycle AGM battery featuring a nominal voltage of 12V and a nominal capacity of 200Ah.
The battery is fairly large and it belongs to the BCI Group 4D.
The following chart lists constant power discharge values for Mighty Max ML4D battery - values are given in watts, at 77° (25°C):
|End Cell Voltage||End Battery Voltage||15 min||30 min||45 min||2h||3h||5h||10h|
In order to protect the battery and increase its number of charging/discharging cycles, it is recommended not to discharge this and similar batteries below 10.5 volts, not even when being discharged under one hour.
When Mighty Max ML4D battery is discharged down to 10.5 volts, the battery can power:
- 15 min: ~2760 watts,
- 30 min: ~1800 watts,
- 45 min: ~1340 watts,
- 2h: ~640 watts, etc.
Although Mighty Max ML4D is a deep cycle battery, it tolerates strong currents rather well, especially when the normal output power is kept below 1000W.
For more reviews and recommendations, feel free to check the Mighty Max Battery 12V 200Ah 4D SLA AGM Battery Amazon link (link opens in the new window).
Battle Born BB10012 12V 100Ah LiFePO4 Deep Cycle Battery
Battle Born BB10012 is one of the most popular 12V lithium deep cycle batteries.
Depending on the Depth of Discharge (DoD), it can withstand 2000+ deep discharges easily.
Battle Born BB10012 belongs to the BCI Group 31 and it weighs only 29 pounds (~13.2 kg). It features a nominal capacity of 100Ah, with almost no capacity loss due to the strong discharge currents.
The battery is based on the Lithium Iron Phosphate (LiFePO4) chemistry and features an internal Battery Management System (BMS) that protects the battery from unwanted events like overcharge, over-discharge, overcurrent, short circuit, and similar.
Battle Born BB10012 is able to provide 100 Amp continuously and 200 Amps for 30 seconds.
Also, unlike many other lithium deep cycle batteries, Battle Born BB10012 can be connected in series (up to 4 batteries) in order to create battery packs up to 48V and can be connected in parallel to create battery packs of larger capacity.
Note: When connecting lithium batteries in series and/or parallel, always connect them according to the manufacturer's recommendations.
Due to the limited current, Battle Born BB10012 is able to provide ~1200 watts continuously and ~2400 watts for 30 seconds.
This means that the single Battle Born BB10012 battery is able to power ~1080W 12V power inverter with 90% efficiency for practically one hour or ~2160W 12V power inverter with 90% efficiency for 30 seconds.
Personally, just to be on the safe side, Battle Born BB10012 should be used continuously for power levels of up to 700-800 watts - better safe than sorry - as long as the battery is not getting too warm.
For powering stronger inverters, feel free to create the battery pack of required voltage and capacity - again, according to the manufacturer's recommendations!
For more reviews and recommendations, feel free to check the Battle Born BB10012 12V 100Ah LiFePO4 Deep Cycle Battery Amazon link (link opens in the new window).
ExpertPower EP12200 12V 200Ah Lithium LiFePO4 Deep Cycle Battery
ExpertPower EP12200 is another very popular Lithium Iron Phosphate (LiFePO4) battery featuring a nominal voltage of 12V and a nominal capacity of 200Ah.
According to the manufacturer, the battery belongs to the BCI Group 4D, but it is slightly larger than 4D and it actually belongs to the 6D group.
ExpertPower EP12200 is able to provide 150 Amps continuously and 200 Amps for 3 seconds.
As such, ExpertPower EP12200 is able to provide ~1800 watts continuously, allowing it to power ~1600 watts 12V power inverter with 90% efficiency practically for one hour. Also, it can supply ~2400 watts for 3 seconds, which is generally enough for spikes up to 2100-2200 watts.
Personally, if You are looking for a single 12V 200Ah lithium battery for powering a 12V 1000W power inverter, ExpertPower EP12200 is one of the best possible choices.
For more reviews and recommendations, feel free to check the ExpertPower 12V 200Ah Lithium LiFePO4 Deep Cycle Battery Amazon link (link opens in the new window).
Ampere Time 24V 100Ah LiFePO4 Deep Cycle Lithium Battery
Ampere Time 24V 100Ah lithium battery is also based on the Lithium Iron Phosphate (LiFePO4) chemistry and it features a nominal voltage of 24V with a nominal capacity of 100Ah.
Ampere Time 24V 100Ah lithium battery is labeled as a 4D battery, but it is also somewhat larger than 4D and it practically belongs to the 6D battery group.
The battery weighs just 47.4 pounds (~21.5 kg) and is able to provide 100 Amps continuously and 280 Amps for 5 seconds.
As an inverter battery, Ampere Time 24V 100Ah lithium battery is able to provide ~2400 watts for one hour and if required, ~6700 watts for 5 seconds, making it almost ideal for 24V power inverters up to 2000W.
If required, Ampere Time 24V 100Ah lithium battery features BMS that allows the user to connect up to 2 (two) batteries in series to create a 48V 100Ah battery pack, or to connect up to 4 (four) batteries in parallel to create battery packs up to 400Ah.
Again - when connecting lithium batteries in series and/or parallel, connect them as recommended by their manufacturer!
For more reviews and recommendations, feel free to check the Ampere Time 24V 100Ah LiFePO4 Deep Cycle Lithium Battery Amazon link (link opens in the new window).
Long Story Short: When calculating how long will inverter last with its battery or battery pack, be sure to know the inverter's load and the battery's discharge characteristics.
While AGM and Gel-Cell batteries are heavier and can support fewer charging/discharging cycles than lithium batteries, they are much more reliable in situations where there are many power spikes present - for example, when a power inverter is used to power electric pumps, winches, and similar loads that draw plenty of Amps when being turned on. Such loads, if the lithium battery is not dimensioned properly, may cause BMS to disconnect the battery from the electric system.
On the other hand, lithium batteries can support much more charging/discharging cycles than lead-acid batteries, they are much lighter, feature a very low self-discharge rate, and don't suffer from capacity loss when being discharged using strong currents.
In the end, it is up to the user and the user's personal needs and preferences to decide which battery is actually the best ...
Note: all these batteries are capable of providing really strong currents - whatever You do, it is your own responsibility. Stay safe ...