Buying Guide - Portable Power Stations
Before we start its useful to consider what a Portable Power Station can do
A portable power station is essentially a large battery pack. It can be used to both run and charge various electronic devices. The choice between using a portable power station to charge a device or run a device largely depends on the device's power requirements and the power station's capacity. Here are the key differences:
- Running a device: When you use a portable power station to run a device, the device will draw power directly from the power station until it is turned off or the power station runs out of energy. This is often used for devices that don't have their own internal battery or need constant power, such as a portable refrigerator, a fan, or a lamp.
- Charging a device: When you use a portable power station to charge a device, the device's internal battery is replenished. This is generally used for devices with their own batteries, such as smartphones, laptops, or cameras. Once the device is fully charged, it will stop drawing power from the power station.
Now, regarding AC and DC devices:
AC devices: Alternating current (AC) is the type of electricity that is delivered to homes and businesses, and is the form in which electric power is produced. Many household appliances run on AC power, like your refrigerator, air conditioner, microwave, etc. A portable power station needs to have an inverter, which converts the DC power from the battery into AC power. Many AC devices also draw a lot of power at startup (surge) before settling down to their power run rate. You need to factor this in to your calculations by making sure the unit will handle that load even for a short time look for the surge rating.
DC devices: Direct current (DC) is a type of electrical current that moves in a single direction continuously. Many portable electronic devices like laptops, cell phones, and cameras use DC power. Batteries, including power banks and portable power stations, provide DC power. To charge DC devices from a portable power station, you typically use a USB port or other DC outlets.
Now in deciding what Portable Power Station best suits our needs we should consider the following:
- Power Output
- Power Input
- Battery Chemistry
- Features
- Size / Portability
- Warranty / Support / Brand
- Price
We will discuss each item above and what needs to be considered then we will provide some examples on how to calculate the power output required for a range of devices.
1. Power Output
- Create a list of the devices you need to power.
- Determine the power Watts (W)) required by each device.
- Determine how long in hours (h) you will need to power each device and multiple by the device power (W) to get required (Wh)
- Add the total power required for each device up to get the total power required in Watt hours (Wh)
Each device has a power rating in Watts (W) usually found on a label or in their specification, however the wattage can be calculated from the voltage (V) and current (I) see full examples at the bottom. This is the amount of power a device needs to operate.
If a laptop had a rating of 35W and a cell phone a rating of 20W then you would need a total of 55W of power. If you wanted to power those devices for an hour you would need 55 Wh of output power. a PPS (Portable Power Station) with an output capacity of 1000 Wh would be able to power those devices for a total of 1000Wh / 55 Wh = 18.18 hours.
In simple terms a PPS rated at 1000W max output power and 1000 Wh capacity would be able to power a single 1000W device for 1 hour or 10 x 100W devices for 1 hours or 1 x 100W devices for 10 hours. To power a 1000 W device the max output power has to be at least 1000W.
Power or output capacity is measured in Wh (Watt hours), the greater the Wh the larger and more expensive the unit. Ideally you will want to have a unit with adequate capacity to meet all your current needs with room for a little extra.
Units range in capacity from a few hundred Wh all the way up to several thousand Wh for heavy duty jobs like a home backup system. Some units have expansion ports allowing scalability according to your needs. You don't want to be running your PPS at 100% capacity for any length of time so aim to buy a unit with 30-50% more output capacity than you need.
*Refer to the examples at the bottom of the buying guide for more details on the calculations.
- How long does it take to charge from the mains supply?
- Does it support vehicle charging and if so at what rate?
- Does it support solar charging, if so what is the max solar input capacity?
- Does it support multiple input source charging?
- Can I charge and use the unit at the same time?
Charging via an AC power source is the quickest method followed by charging with a vehicles 12v supply. Off the grid you can power with solar panels, typically the slowest method but charging rate will depend upon the size of the connected solar array. You might want to consider the maximum solar input capacity a higher number will allow you to harness the charging capability of more solar panels thus increase charge time albeit at a cost of more units. Some units will allow solar plus mains charging simultaneously thus charging at a combined rate, something to consider.
3. Battery Chemistry
What are the major types of batteries used in PPS and what do I need to be aware of?
Portable Power Stations typically use 2 types of Lithium-ion battery
- NMC Batteries: NMC batteries typically use a combination of nickel, manganese, and cobalt in their cathode chemistry. This blend allows for a good balance between energy density and power capability.
- LFP Batteries: LFP ( LiFeP04) batteries, use iron phosphate as the cathode material. They are known for their high thermal stability and safety characteristics.
It depends on your particular requirements what to choose however the market seems to be moving towards LPF or LiFeP04 batteries as the chemistry of choice.
They have some disadvantages in terms of power and energy density vs NMC however their improved safety characteristics and much improved cycle time (3000 vs 500) means they will last much longer 10 years vs possibly only 3-4 years. Check the charge cycles that the unit can handle that will give an indication of how long you can expect the unit to last based on how often it can be charged.
** See ION Juiced blog on battery chemistry for more details
4. Features
What features do I need to consider?
- Does it have all the output AC, DC & USB connectors needed to power all my devices?
- Does it have all the monitoring and safety features that I will want?
- Does it have UPS/EPS capability?
Each unit will come with a number of inputs (how it will be charged - AC, DC and Solar) and outputs (AC, DC, USB-A and USB-C ).
Most will have a digital display showing battery status, others allow monitoring via an mobile app via WiFi and Bluetooth. Typically PPS units use an Battery Management System to monitor the voltage, current and temperature and protect against short circuits, overheating, low voltage and overcharging. Check what monitoring and protection features that you would find useful.
Back-up power supply (BPS) systems are generally categorized as being either uninterruptible power supply (UPS) or emergency power source (EPS) systems. PPS typically don't have UPS capability but some claim EPS which means that in the event of a mains power failure the unit will take over within a very short period.
- I will be carrying while hiking so needs to be quite small and light.
- It needs to be portable enough for me to carry on my bike.
- I will be transporting in my vehicle then a short distance by foot.
- I will be using it in my RV or only a short distance from my vehicle
- It will be mainly used in my house / garage and not moving far.
- It will be used daily and on and off vehicles so needs to be handle a lot of bumps and knocks.
- How portable is it, does it have handles or wheels for pulling or carrying?
- How weatherproof is it, can it be left outside for periods?
In general NMC will provide more energy density than LPF and thus are lighter for the same power output, but do check the specifications for weight and size.
6. Warranty / Support / Brand
I see lots of different companies are making these devices and there are some really good deals, should I just go with the cheapest that meets my needs?
This is a new and rapidly developing market with new entrants coming and going. Because these products are technically advanced and have useability and safety as important features its important to select a brand that is well respected, established, that will stand behind its products with good warranty and support.
Check the reviews not just on our site or the suppliers but look for independent reviews on sites such as TrustPilot to get a feel for how well others have experienced the products. See if the suppliers have help/support available on Facebook or other social media.
Check the offered warranty which may differ between the brands and also consider that products with different battery chemistry may offer longer warranty periods. A new company may seem to be offering a great deal at a lower cost with good warranty but you need to consider if they will still be around to support you in a few years from now.
Note that ION Juiced will only offer products from reputable suppliers who stand behind their products and offer good warranty and support.
7. Price
What major factors and features that impact the price?
Ultimately the cost will related to maximum power output (W) and power output capacity (Wh) plus supported options and features. In general terms you should be looking to budget 1$ per Wh, so a 1000Wh portable power station will be around $1000 as a rough guideline.
However there will will typically be cost differences between PPS units with different battery chemistry with NMC (Nickel Manganese Cobalt) typically cheaper than units using LFP. LFP has improved safety and much longer lifetime and can handle more charging cycles up to 6x over NMC. If you are only planning on using a unit for a weekend getaway every few weeks then perhaps a lower cost NMC with equivalent power capabilities will suffice. What about the features can you forgo the WiFi or Bluetooth App connection? You can also consider your device use, perhaps you can reduce what you need, or use for less hours.
However if the PPS is for critical emergency backup use or frequent use, then it's probably money well spent to go for the best you can afford.
Power Calculations Details & Examples
The electrical unit of power is the watt (W), which measures the rate at which electrical energy is transferred or used. In simple terms, it quantifies how quickly work is done or how fast energy is consumed or produced in an electrical system.
For portable power stations, the power output capacity is crucial. It is usually measured in watts or kilowatts and represents the maximum amount of electrical energy the power station can supply to connected devices simultaneously.
The relationship between power (P), current (I), and voltage (V) is given by the formula:
Power (P) = Current (I) x Voltage (V)
Where:
- Power (P) is measured in watts (W).
- Current (I) is measured in amperes (A).
- Voltage (V) is measured in volts (V).
Many devices will have the wattage specified on the device but for the example we will calculate from the voltage and current. Note that an inexpensive useful device to have is a Power Meter that allows you to determine the actual power used by any device.
Now, let's calculate the power required for each device based on the provided usage time:
For our example we are going to assume an short duration overnight camping trip with a modest power requirement, where we will require to power 5 devices.
- Laptop for 4 hours
- iPhone for 4 hours
- Camera for 4 hours
- LED light for 10 hours
- CPAP Machine for 8 hours
Now, let's calculate the power required for each device based on the provided usage time:
- Laptop:
Assuming the laptop's current and voltage are 3 amperes (A) and 19 volts (V), respectively, we use the formula:
Laptop Power (P) = 3 A x 19 V = 57 W
To power the laptop for 4 hours:
Total Laptop Power = Laptop Power x Time
Total Laptop Power = 57 W x 4 hours = 228 watt-hours (Wh)
2. iPhone:
Assuming the iPhone's current and voltage are 2.2 ampere (A) and 9 volts (V), respectively, we use the formula:
iPhone Power (P) = 2.2 A x 9 V = 19.8 W
To power the iPhone for 4 hours:
Total iPhone Power = iPhone Power x Time
Total iPhone Power = 19.8 W x 4 hours = 79.2 watt-hours (Wh)
3. Camera:
Assuming the camera's current and voltage are 0.8 amperes (A) and 7.5 volts (V), respectively, we use the formula:
Camera Power (P) = 0.8 A x 7.5 V = 6 watts (W)
To power the camera for 4 hours:
Total Camera Power = Camera Power x Time
Total Camera Power = 6 W x 4 hours = 24 watt-hours (Wh)
4. LED Light Bulb:
Assuming the LED light bulb's current and voltage are 0.5 amperes (A) and 12 volts (V), respectively, we use the formula:
LED Light Bulb Power (P) = 0.8 A x 12 V = 9.8 watts (W)
To power the LED light bulb for 10 hours:
Total LED Light Bulb Power = LED Light Bulb Power x Time
Total LED Light Bulb Power = 9.8 W x 10 hours = 98 watt-hours (Wh)
5. CPAP Machine:
Assuming the CPAP machine's current and voltage are 2.5 amperes (A) and 24 volts (V), respectively, we use the formula:
CPAP Machine Power (P) = 2.5 A x 24 V = 60 watts (W)
To power the CPAP machine for 8 hours:
Total CPAP Machine Power = CPAP Machine Power x Time
Total CPAP Machine Power = 60 W x 8 hours = 480 watt-hours (Wh)
To get the total power required for all the devices combined, add up the individual power requirements:
So, you would need a portable power station with a minimum capacity of at least 909 Watt-hours (or 0.909 kilowatt-hours) to power all these devices for the specified durations. Keep in mind that it's always a good idea to have a good bit of extra capacity in the power station to account for inefficiencies, unexpected power fluctuations, additional devices, longer operational/charging time and to maximise the life time use of the Portable Power Station.
Based on the above requirements we would aim for a PPS with 909 + 30% so we would be looking at a PPS with 1200Wh capacity.