How long will 150ah battery last while running a load will depend on various factors, such as output load, battery discharge efficiency, speed of discharge, and temperature.
Most answers out there will give you a 'theoretical' number. However, the actual runtime of a battery is influenced by many real-world factors, including the battery's discharge chemistry, how quickly it is used, and the temperature of the surroundings.
Looking for a quick answer? Try using our battery runtime calculator to calculate your battery's runtime.
Amp-hours, Watt-hours, and Battery discharge Efficiency
Power is measured in watts. Here are some formulas to remember:
- Watts = Volts × Amps
- Amps = Watts ÷ Volts
- Volts = Watts ÷ Amps
Amp-hours (Ah) is a way of measuring how much electrical charge a battery can provide over time, measured in amps. If a battery has 150ah capacity, it means it can supply 150 amp of current for one hour "theoretically".
Watt-hours (Wh) is a unit of measurement that tells us how much energy an electrical device consumes over time. It's like the energy consumed by a 1-watt device for one hour.
Lead acid vs Lithium battery discharge limit (DoD): Lead acid, AGM, and gel batteries are suggested to only be discharged 50% while lithium batteries can be completely discharged. This means that from a 150ah lead acid battery, you can only use 75 amps.
Battery discharge efficiency: Unfortunately, batteries are not 100% efficient when discharging. The efficiency rate will depend on the battery type.
Based on directscience.com data:
- Lead-acid batteries discharge efficiency ≈ 80 − 85%
- Lithium-ion batteries discharge efficiency ≈ 90 − 95%
Here’s a table on 150ah battery usable amp-hours after considering discharge efficiency (Lead acid: 85%, and Lithium: 95%).
| Battery type | 150ah battery usable capacity (in ah) |
|---|---|
| Lead acid | 127ah |
| Lithium (LiFePO4) | 142ah |
150ah battery how many watts?
150ah or 150 amp-hours battery means it can provide 1 amp for 150 hours or 150 amps for 1 hour.
In order to determine how much power a battery can actually hold, we typically measure its capacity in watt-hours.
Formula: Battery capacity Wh = Ah × Volts
12v 150ah battery capacity in watt-hours:
150 × 12 = 1800 watt-hours
24v 150ah battery capacity in watt-hours:
150 × 24 = 3600 watt-hours
12v 150ah battery is equal to 1800 watt-hours and 24v 150ah battery is equal to 3600 watt-hours. This means 150 amp-hour 24v battery stores double the power of a 12v 150 amp-hour battery.
Now, let's crunch some numbers, and after this, I'll explain why it's not possible to achieve a 100% accurate runtime.
Related post: Battery Amp Hours To Watts (Ah To Watts) Calculator
5 steps To Calculate 150ah Battery Runtime
Let's figure out your 150ah battery backup time, follow these steps.
Steps
1. Converter battery amp-hours (Ah) into watt-hours (Wh). Let’s say you have a 12v 150ah battery.
150ah battery in watts = 150 × 12 = 1800 watt-hours
2. If you are using a lead-acid battery, make sure to multiply its watt-hour capacity by 0.5, which takes into account the depth of discharge limit. For example, if you have a 150ah lead-acid battery.
Battery capacity in wh after DoD limit = 1800 × 50% = 900wh3. To adjust battery discharge efficiency, multiply the battery's capacity by a certain factor. For lead-acid batteries, multiply by 0.85, and for lithium-ion batteries, multiply by 0.95.
Battery usable watt-hours: 900 × 0.85 = 765wh4. To adjust for the inverter's efficiency, multiply the battery's usable capacity by 0.9, which is a typical efficiency rate for inverters.
Battery AC watts = 765 × 90% = 688 AC watt-hours 5. Divide the battery's AC watt-hours by the sum of all the devices that are connected to it. Let’s say you’re running a 100-watt appliance with a 12v 150ah battery.
150ah battery runtime on 100 watt appliance = 688 ÷ 100 = 6.8 hours
Turns out, a 12v 150ah lead acid battery will run 100-watt appliance for about 7 hours.
effect of discharging rate on your battery's performance
A battery will not provide the same amount of energy as its label if used quickly, known as Peukert's law. This is because more energy is wasted as heat when a battery discharges quickly instead of being used to power devices.
But this only applies to lead-acid batteries. On the other hand, lithium batteries can be safely discharged at 50% of their capacity without any power loss.
This means you can discharge your lithium battery in 2 hours without causing any power losses. However, lead-acid batteries are made to be discharged over a longer period of 20 hours, and if you discharge them too quickly, their efficiency will go down.
Related post: Battery Charge And Discharge Rate Calculator: C-Rating To Amps
This table displays the usable capacity of a 150ah lead-acid battery in amp-hours based on the rate of discharge.
| Usable 150ah lead acid battery capacity | Hours of discharge |
|---|---|
| 150ah | 20 hours |
| 135ah | 10 hours |
| 130ah | 8 hours |
| 123ah | 6 hours |
| 120ah | 5 hours |
| 105ah | 3 hours |
| 90ah | 2 hours |
| 75ah | 1 hour |
How Temperature Affects Battery Performance
Batteries are sensitive to temperature changes, and extreme temperatures can affect their discharge efficiency.
- When the temperature is too high, the battery's internal resistance increases, causing it to lose capacity and discharge efficiency.
- When the temperature is too low, the battery's chemical reactions slow down, reducing its ability to produce the required power.
Therefore, it's crucial to keep your batteries in the right temperature range, which is typically between 68°F and 77°F (20°C to 25°C). Ask your manufacturer for a more accurate number or look at your battery specs sheet data.
As a general rule, a temperature increase to 77ºF or 25º C can cut battery performance by 50%.
How long does a 150ah battery last? - chart
Here are charts on how long will 12v 150ah lead acid and lithium batteries will last running different small household appliances.
12v 150ah lead acid battery
| Appliance power required | 12v 150ah lead acid battery runtime |
|---|---|
| 50 watts | 14 hours |
| 100 watts | 7 hours |
| 200 watts | 3.5 hours |
| 300 watts | 2 hours |
| 400 watts | 1.7 hours |
| 500 watts | 1.3 hours |
| 600 watts | 1 hour |
summary
- 12v 150ah lead acid battery will last between 14 hours (running a 50w load) to 1 hour (running a 600-watt load) while running different appliances.
12v 150ah Lithium battery
| Appliance power required | 12v 150ah lead acid battery runtime |
|---|---|
| 50 watts | 31 hours |
| 100 watts | 16 hours |
| 200 watts | 8 hours |
| 300 watts | 5 hours |
| 400 watts | 4 hours |
| 500 watts | 3 hours |
| 600 watts | 2.5 hours |
summary
- 12v 150ah lithium battery will last between 30 hours (running 50w load) to 2 hours (running 600-watt load) while running different appliances.
