Portable Power Stations – Frequently Asked Questions

Portable Power Stations do all these things without making a sound.

What is a Portable Power Station?

Simply put, a portable power station is the combination of a rechargeable battery and a DC-AC inverter. Charge the battery and use it to power virtually anything that requires power—whether it requires DC or AC—provided it is within the capacity rating of the power station.

In this sense, a portable power station is an energy storage device. Depending on the battery capacity, it might store a few hundred to several thousand watt-hours of energy. The battery capacity and the rate at which it can safely discharge are what limit the rated output power. 

It’s important to understand the difference between the rated output capacity and the storage capacity. 

• Storage Capacity: Rated in Watt-Hours (Wh) or Kilowatt-Hours(kWh). For example, a 100Wh storage capacity means the power station’s battery can store enough energy to output 100 watts continuously for 1 hour, 50 Watts for 2 hours, or 25 watts for 4 hours.
• Rated Output: Rated in Watts (W) or Kilowatts (kW). A rating of 100 running watts means the power station supplies up to 100 watts of power to operate any device. Most also have a starting watts or maximum watts rating required for starting a motor that is 1.5–2 times the rated output. This becomes important to know if you plan to operate an appliance with a motor, like a refrigerator.

Understanding Running Watts vs Starting Watts

The cost of recharging the power station is minimal, but it takes time. A power station requires a little more than the unused storage capacity to recharge. For example, a 1000Wh power station at 20% charge can hold an additional 800Wh of energy. Plug it into an outlet, and it will use a little more than 800Wh of electricity to charge. If the electricity costs $0.15 for each kWh used, then charging the power station costs less than 15 cents.

How Does a Portable Power Station Work?

A power station converts energy stored in a battery to electricity. Charge the power station battery, plug in your device, and it has power. As the device operates, the energy stored in the battery depletes at the same rate as the device uses it. A 100Wh power station charging a cell phone at 25 watts will run out of power in 4 hours (4 x 25W=100W). 

Some power stations allow you to swap batteries. Use one battery while the other battery is charging. This has the added benefit of extending the life of the power station because batteries have a limited number of charges over time. 

Extra batteries in other models can extend storage capacity well beyond the single battery. In one example, a power station for an RV with 2000Wh capacity with a single battery extends the power to 8000Wh with the addition of 3 additional batteries.

Additional batteries increase the output capacity. A 1000-Watt Output becomes 2000 Watts with the addition of a second battery.

5 Ways to Keep the Power On

How Long Does a Portable Power Station Last?

Energy capacity—the amount of run time you get before recharging.

Battery chemistry—how many times you can recharge the battery.

Energy Capacity

Terms to know:

• Energy capacity—the amount of run time you get before recharging.
• Battery chemistry—how many times you can recharge the battery.

Energy Capacity

The rated watts and the energy storage capacity can be confusing. You might see a power station advertised as a 1000-watt power station, meaning it can output 1000 watts. If it has a battery capacity of 2000 watt-hours, the power station will last 2 hours at 1000 watts, or 4 hours at 500 watts, 8 hours at 250 watts, etc. Just divide the capacity by the total load you intend to put on it, and you can determine how long it will last for that particular load.

Capacity (Wh) / Total Load (W) = Hours (h).

Capacity = 2000Wh.

Total Load = 500W

2000 watt-hours / 500 watts = 4 hours run time.

Battery Chemistry

All batteries have a limited number of charge cycles. A charge cycle is one complete charge followed by a complete discharge. 

The power station specifications should include a charge cycles rating. This is entirely dependent on the battery chemistry and the quality of the charge controller. Some Lithium-iron-phosphate batteries maintain 80% of their original charge capacity through 4000 or more charge cycles, while many Nickle-cadmium batteries have a lower rating of around 600-800 cycles.

The state of the battery charge when you store it is also important. Check the manufacturer's owner manual for best storage practices. 

A power station could last many years before it needs replacement. With a 1000 charge cycle rating, you could do a complete charge/discharge cycle every day for 2 years 9 months before reaching 80% original capacity. That’s an unlikely scenario for most people, but it makes a good example of how long a portable power station lasts.

In practice, at one-two charge/discharge cycles per week, a portable power station with a 1000 charge cycle rating will last 10-20 years unless you’re doing a complete charge/discharge cycle every day as might be the case with off-grid homes. In that case, choose a power station with a 3000-5000 charge cycle rating.