OAUSA Net - August 10, 2023 - Power Stations

[KK6DYO]

Introduction

• What is a "Power Station"?
• Electrical Basics
• Batteries
• Chargers
• Converters and Inverters
• DIY "Power Station"
• Power Stations

What is a Power Station?

A box that stores electrical energy (i.e., battery) and that provides electrical output to a variety of standard outlets. It also facilitates recharging the electrical storage from standard sources. It is conveniently portable commensurate with its energy capacity.

• Portability (size and weight limitations)
• Store power
• Make stored power available to run appliances and electronic devices via standard interfaces
  • Prevailing home electrical standard (120VAC in U.S., NEMA 1-15P two pole without ground and NEMA 5-15P two pole with ground)
  • Universal Serial Bus (USB, Type-A and Type-C, various modes such as Power Delivery)
  • 12V DC
    • Vehicle power outlet, though not typical of devices most people use
    • DC5521 (standard DC power supply using 5.5mm diameter plug (negative) accepting 2.1mm pin (positive))
• Replenish/recharge stored power

  

  Charging Options.jpg (82.77 KiB) Viewed 3022 times

  • Prevailing home electrical standard (120VAC in U.S.)
  • Vehicle 12V (alternator via power outlet)
  • Solar panels (often proprietary interface, sometimes Anderson Powerpole, sometimes DC5521, sometimes XT60i)
  • USB
• Monitor and display state of charge (percentage remaining) of stored power
• Monitor and display utilization of power outputs
• Protect battery and power station electronics from damage due to incorrect use

NEMA (National Electrical Manufacturers Association) Standard Outlets

First number is outlet designation, second is maximum current.

NEMA Outlets.jpg (245.34 KiB) Viewed 3162 times

12VDC Vehicle Power Outlet and Plug

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DC5521

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XT60i

IMG_7574.jpeg (34.32 KiB) Viewed 2978 times

USB, Type-A and Type-C, Plugs

IMG_7573.png (316.08 KiB) Viewed 2980 times

Power Station Examples

EcoFlow River 2 with 300W power, 256Wh capacity, 9.6” x 8.5” x 5.7”, 7.7 pounds, $210, $0.82/Wh.

IMG_7575.jpeg (596.24 KiB) Viewed 2967 times

River 2's NEMA 1-15 and NEMA 5-15 outlets, USB, and 12V.

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EcoFlow Delta Pro 3600W power, 3600Wh capacity, 25” x 11.2” x 16.4”, 99 pounds, $3200, $0.89/Wh.

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Delta Pro's NEMA 6-20 and NEMA TT30 outlets and USB, with 12V output in rear.

EcoFlow Delta Pro Outlets.jpg (113.77 KiB) Viewed 3020 times

Prior net on this topic: OAUSA Net - September 22, 2022 - Off-Road Electrical Power

[KK6DYO]

Electrical Basics

Most problems understanding electricity arise from unfamiliarity with basic concepts. The most common questions I've seen on various off-grid and overlanding forums is: "How long will X run my Y for?"

The best analogy for electricity (ignoring the concept of resistance which normally doesn't matter much to us) is a stream.

• The speed at which water passes a particular point is analogous to voltage (Volts)
• The width & depth of the stream is its current (Amperes or Amps).
• The amount of water passing at any particular time depends on both its speed and the width / depth of the stream is its power, analogous to Watts.
• The total amount of water passing during an interval of time is its energy (Watt-Hours).

Watts = Volts * Amps.
Watt-Hours = Watts * Time (in hours).

• Voltage (Volts, abreviated "V")
• Current (Amperes, "Amps", abbreviated "A")
• Power (Watts, abbreviated "W") = Volts * Amps = V * A.
• Energy / Power Consumed (Watt-Hours, abbreviated "Wh") = Watts * Hours = Wh.

Note: These abbreviations are capitalized since they arise from the names of prominent people who studied properties of electromagnetism and electricity.

When the particular voltage is given, such as for a battery with nominal voltage, say 12.8V, the power is sometimes expressed as Amps ("A") while the energy capacity is expressed as Amp-hours ("Ah"). (Note: start battery capacity are often expressed as Cold-Cranking Amps (CCA) which we are not interested in.) As an example, the energy capacity of device batteries (e.g., lithium-ion batteries in sizes 18650 or 21700) of a given voltage is usually expressed in mAh (milli-Amp-hours). (Note: The capacity of current day batteries is well into the Amp-hours.)

The answer to the question: "How long will X run my Y for?" is fairly simple. Check the rating of your Y device / appliance in watts (W), check the capacity of your X power station / battery in watt-hours (Wh), and divide X Wh by Y W for hours of runtime.


Considerations Using Higher Voltage

Since Watts = Volts * Amps, power (Watts) can be delivered over a longer run using higher voltage (Volts) at less current (Amps) with less loss.

Longer runs with thinner wire, but more dangerous.

DC Wire Gauge Selection.jpg (281.18 KiB) Viewed 3197 times

Direct current (DC) voltages at 50V are considered hazardous at currents above 25 mA, being more likely to cause a victim to "freeze" in muscle tetanus during a shock scenario than alternating current (AC).

For AC outlets (60 Hz, 120 V) currents above 10 mA are considered hazardous, being likely to cause a victim's heart to fibrillate, which is a more dangerous condition for the victim after the shocking current has been halted.

Note: Two 100W solar panels in series can generate around 40V at 8A!

[KK6DYO]

Batteries

Let's talk about the components of a power station if we were to build one. Before a handful of years ago, this was the main option if you needed primary power.

Concepts

• Rechargeable - a battery which can accept and store a charge
• Starter - a battery designed to provide a large but short lasting amount of current to power a starter motor to get ("crank") an engine turning before the alternator takes over
• Service (sometimes called "house" or "auxiliary") - a battery designed to power appliances, not to start a vehicle
• Deep Cycle - a battery designed to provide continuous power over a long period of time, not a starter battery
• Voltage - standard charging voltage of 14.4V, 13.5V is a nominal charged "float" voltage
• Capacity = total energy available in Amp-hours (given a particular voltage) or Watt-hours
• State of Charge = percentage of battery capacity remaining
• Depth of Discharge = 100% - SOC

Comparison

• Types
• Chemistries
  • Lead Acid - unless you already have a big investment in these, they're no longer interesting; dead technology
    • Sealed Lead Acid - "Maintenance Free"
      • Gelled Electrolytes (Gel)
      • Absorbent Glass Mat (AGM)
  • Lithium
    • Lithium Ion - has an advantage when lowest possible battery weight is the concern
      • Higher energy density than LiFePo, thus somewhat lighter weight for given energy capacity
      • 32°F to 113°F
      • Hundreds of cycles

        

        Lithium-ion DoD Service LIfe.jpg (21.51 KiB) Viewed 3052 times

    • Lithium Iron Phosphate (LiFePo[4], LFP) - this is a battery of choice for all power stations
    • More stable than lithium-ion, less prone to overheating or starting a battery fire
    • -4°F to as high as 140°F
    • Thousands of cycles

      

      LiFePo DoD Service Life.png (41.73 KiB) Viewed 3052 times

    • Self-discharge rate of 2% per month, roughly the same as lithium-ion
      • Rate may increase dramatically in a power station

In various other nets, we've talked about the advantages of Lithium batteries over Lead-Acid batteries. To summarize:

• For a given capacity (Ah or Wh), lead-acid batteries weigh twice as much as lithium batteries.
• Lithium batteries don't degrade as much when discharged to low levels
  • A lead-acid battery will have a greatly shortened life if discharged over 50%
  • Lithium batteries can be regularly discharged to 0%, though will last longer if discharged to only 20%
  • Thus the effective life cycle capacity is a lithium battery is much greater
• Lead-acid batteries can be cycled in the low hundreds of times
• Lithium Ion batteries can be cycled in the high hundreds of times
• LiFePo batteries can be cycled thousands of times

Life Cycle vs DoD.gif (60.31 KiB) Viewed 3117 times

State of Charge

Difficult to determine for LiFePo

LiFePo SOC.png (34.12 KiB) Viewed 3073 times

Battery Management System (BMS)

The BMS is essentially a computer which controls the battery. It monitors the battery, and can optimize battery performance by balancing internal cell voltages. Additionally, it can protect the battery from damage by shutting down if the State of Charge goes too low, if a load attempts to draw too much power, or if a charger attempts to charge with too much power. It may also shut down the battery if it becomes too hot or too cold, or may disable charging when the battery is too cold. Some BMSs contain Bluetooth which enables the BMS to report status parameters such as voltage, current charge / discharge, temperature, and maybe even history of this information to another device for display.

[KK6DYO]

Battery Chargers


Cost is roughly commensurate with the amount of current provided to charge a battery which equates to the speed with which a battery is charged.


AC Charger

AC chargers charge batteries from household 120 VAC power. We all have many of these around the home, to charge electronic device batteries, or perhaps a vehicle battery.


Victron 30A AC battery charger. $202

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NOCO 10A AC battery charger. $100

NOCO Genius 10.jpg (128.81 KiB) Viewed 3147 times

Solar charger / "Controller"

Solar chargers charge batteries from power generated by solar panels. Many "controllers" have a load output which they keep powered by taking power from solar panels and/or battery as necessary. All night all power of course comes from the battery. During the day, if there is sufficient solar power, the load is powered and the battery is charged. Otherwise, solar power goes toward the load and may be assisted by battery power.

Victron solar controller. $214

Victron Solar Controller.jpg (187.93 KiB) Viewed 3144 times

DC-DC (Alternator) Charger

DC-DC chargers charge batteries from power generated by a vehicle alternator. Many accept solar panel inputs and can charge both a service battery and the starter battery.

This Victron Orion charger does not take solar power input. $258.

Victron DC-DC Charger.jpg (55.63 KiB) Viewed 3146 times

The Manager30 can charge both a vehicle's starter battery and service battery from either solar panels or the alternator. $1476

REDARC Manager30.jpg (72.73 KiB) Viewed 3145 times

This Renogy 30A DC-DC charger provides similar capabilities as the Manager30. $210

Renogy DC-DC 30A Charger.jpg (78.58 KiB) Viewed 3141 times

[KK6DYO]

Converters and Inverters


Converters

Converts AC to DC, or convert DC to a different DC voltage.

AC to 12V and USB Converter.jpg (140.05 KiB) Viewed 3137 times

Inverters

Converts AC to DC.

Giandel 1200W Inverter.jpg (561.79 KiB) Viewed 3138 times

[KK6DYO]

Power Uses


The big advantage of a power station over typical chargers is that they can provide sufficient power of sufficient duration using standard home appliances to accomplish useful work. The use of lithium battery technology has made them reasonable to carry around.

But what can they really be used for?

Since we're focused on Outdoor Adventure, we'll mainly talk about that, but having backup electrical power in case of grid failure or outage (e.g., to keep your refrigerator, freezer, and maybe Internet running, or some lights on) has been a new focus of power station vendors.

2021 Texas power crisis


Happy Campers!

Not one but two 50-pound power stations, perhaps a total of 4kWh, used to power a fan, charge a camera, and probably run the fridge. Not showing much creativity. Looks like cooking is still done with a propane or butane stove, as is water heating / coffee making with the kettles / percolators.


Some marketing pictures:

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Does this one actually provide fire, or is the battery in thermal runaway?

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Realistically...

What kinds of appliances would you like to run?

A refrigerator? Water heating kettle? Margarita or Frappuccino blender? Coffee maker? Electric blanket or mattress warmer? Induction hob (cooking)? A mobile amateur radio?

Your choice, but remember to calculate how much power you'll need.


This kind of electric water kettle will boil water as fast as a JetBoil, and is very efficient.

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An induction hob for cooking:

Nuwave Induction Hob.jpg (113.61 KiB) Viewed 3037 times

"Well, doggies!" (Jed Clampett) Frying up some octopus tentacles! Yummy!

Nuwave Hob Use.jpg (160.13 KiB) Viewed 3037 times

A Reminder: Electrical vs. Gas (Propane) Power

During past nets we've compared propane to electrical power and found that:

• 3.4 BTUs is equivalent to 1Wh
• a 100Ah battery (12.8V) provides 1280Wh or 376 BTUs
• 1-pound of propane provides about 21,548 BTUs (note: 21,300 BTUs for 1-pound of butane)
• a 1-pound propane cylinder provides 57 times the BTUs as a 20 pound 100Ah battery

Heating and cooking are most efficiently done with propane.


Lighting

LEDs are fairly efficient sources of light.


Electronic Devices

The power stations USB power output can charge your electronic devices. Some power stations have built-in wireless chargers on top.

[KK6DYO]

Do-It-Yourself "Power Stations"

Collection of battery(s), charger(s), adapter(s), converter(s), and inverter(s) plus monitoring and status displays
Don't forget fuses / breakers and wiring

Battery

LiFePo batteries have become commodity items. I purchased my first such battery (Renogy 100Ah) five years ago for $800 when it dropped temporarily in price.

The LiTime 100Ah Mini with the same capacity is today available for $320. The "Mini" designation is due to packing the cells into the smallest possible space, not trying to make the dimensions conform to one of the standard battery sizes using foam fillers in the battery case.


Standard Battery Sizes

Standard Battery Sizes.png (38.69 KiB) Viewed 3186 times

The LiTime 100Ah Mini measures 10.24 x 5.2 x 8.96. A number of vendors (LiTime, Redodo, Power Queen) are selling what is probably the same battery for the same price. This battery has a 100A Battery Management System which limits charge and discharge to 100A but allows peaks of 250A for five seconds. Note that the 100A discharge limit implies the battery is limited to 1280W (100A * nominal voltage of 12.8V).

LiTime 100Ah Mini.jpg (91.44 KiB) Viewed 3188 times

Here's a video from HOBOTECH showing how he fit 300Ah of Mini LiFePo batteries into the space previously used a Group 27 AGM battery:
Van Batteries To Lithium For TRIPLE (or more) Capacity!


Inverter

This is a somewhat typical inverter which provides 1200W of 120VAC "pure sine wave" output when connected to a 12V battery. $180 for this 1200W model. $27 for a 300W model; $510 for a 4000W model. Temporary peak power is twice the rated power. All of this brand's inverters have 4.5+ ratings. Note that the output current of your battery bank must support the inverter's output power.

Giandel 1200W Inverter.jpg (561.79 KiB) Viewed 3189 times

Note that it provides a USB adapter with two Type A ports and one Type C port in addition to two 120VAC power outlets.

Giandel 1200W Inverter Ports.jpg (147.06 KiB) Viewed 3189 times

With just the above battery, the inverter, and the appropriate gauge wiring (provided with the inverter), you'd have a 1280Wh system that rivals power stations in capability if not sophistication. Provides 120VAC, USB power, and if you need 12V output, just connect additional wires directly to your battery terminals.

But wait ... how do we recharge the battery?



AC Battery Charger

Victron 30A Battery Charger AC.jpg (147.75 KiB) Viewed 3156 times

Solar Controller

Victron Solar Controller.jpg (187.93 KiB) Viewed 3156 times

Vehicle Battery Charger

Victron DC-DC Charger.jpg (55.63 KiB) Viewed 3156 times

An advantage of DIY versus an all-in-one power station is that you'll have a better understanding of the components, know how to identify which one if any go bad, and be able to replace the component at much lower cost (and warranty hassle) than an entire power station.

[KK6DYO]

Power Stations ("Solar Generators")

Wouldn't it be convenient of you didn't need to bother with wiring or worrying about component compatibility and had something that provided all of those Do-It-Yourself capabilities in a single unit? Of course. I never quite understood this when friends opted for such units after I described the virtues of Do-It-Yourself and offered help.

Putting this net together, starting to question if DIY wasn't somehow better, I again realized the simple beauty of the all-in-one power station. You can build something more efficient (say you just need an AC charger, battery, and inverter), but having all of the capabilities of a power station without external wiring is, well, awesome.

The last time we did this net (link in Post #1) the power generator field was starting to explode, but now they have become commodity items like the LiFePo batteries most of them use. (Note: some still use Lithium-ion to save weight, but these have fewer life cycles.)

Description

EcoFlow Power Station.jpg (130.63 KiB) Viewed 3190 times

Compared to Gasoline Generators

Features

• Capacity
  • Maximum Power: Watts - total power available to simultaneously run appliances
  • Maximum Energy: Watt-Hours - how long those appliances can run; note that battery capacity is reduced by inverter inefficiency, so your 1000 Wh battery may only deliver 800 Wh of energy at the plug; around 80 to 85% is considered normal efficiency
  • Life Cycles (Battery) - degradation over time due to recharging battery
• Inputs
  • Solar Panel - typical recharging strategy of off-road use, maximum voltage and wattage varies by model
  • Vehicle/Car Alternator ("Cigarette"/Power Outlet) - often limited to 120W as are most vehicles
  • AC/"Shore" Power - maximum wattage (and charging speed) varies by model
  • Universal Serial Bus (USB) - some support USB input for charging as USB Type-C can support up to 100W
• Outputs
  • AC - number of outlets and maximum combined wattage vary by model
  • 12V - many have a 120W power outlet, just like a vehicle; some support DC5521
  • Universal Serial Bus (USB) - Type-A and Type-C supported, wattage varies
• Monitoring Display - basics: input wattage, output wattage, and battery state of charge, after that, anything goes (e.g., number of minutes remaining at current discharge level)
• Expandability - connecting additional standard or proprietary batteries

  

  EcoFlow Whole Home Backup Kit.jpg (67.92 KiB) Viewed 3103 times

  • Greater Capacity - increase in Watt-hours
  • 240 Volts - sometimes additional units are designed to support 240 and higher current
• Warranty
• History of manufacturer
• Size - most power stations are designed to be portable
• Weight - currently seems to be roughly 20 pounds per kilowatt-hour

  Is a unit such as the "EcoFlow DELTA Pro Portable Power Station" measuring 25" x 11.2" x 16.4" and weighing 99 pounds realistically portable?

• Surge Capability - some units provide up to two times the rated power to start appliances which require a surge of power to start
• Uninterruptible Power Supply (UPS) - ability to switch from AC power to battery quickly enough that sensitive electronics (e.g., laptop computer) aren't affected
• Emergency Power Supply - ability to switch from AC power to battery, but maybe not quickly enough that sensitive electronics stay on
• Soft Start - some units are able to ramp up voltage to start appliances (e.g., like an air conditioner) that would otherwise require a surge
• X Boost - some units are able to run appliances which exceedsthe unit's maximum power by reducing the voltage
• Connectivity (WiFi/Bluetooth) - connect to power station through WiFi or Bluetooth?
• Remote Monitoring - monitor power station status on remote devices such as phones and tablets
• Remote Control - control power station status on remote devices such as phones and tablets
• Transfer Switch - manual or automatic switching of home from grid to battery power; requires electrician

  

  EcoFlow Transfer Switch.jpg (76.99 KiB) Viewed 3100 times

Brands

• Jackery https://www.jackery.com/
• EcoFlow https://us.ecoflow.com/
• Bluetti https://www.bluettipower.com/
• Goal Zero https://www.goalzero.com/
• Anker https://www.anker.com/collections/power-stations
• Milwaukee https://www.milwaukeetool.com/Products/MXF002-2XC
• BougeRV https://www.bougerv.com/collections/power-station
• DeWalt https://www.dewalt.com/product/dcb1800b ... ry-charger
• Generac https://www.generac.com/specialpages/po ... er-station
• Renogy https://www.renogy.com/renogy-gear/power-stations/
• ... and many more made by Uyghur labor too numerous to mention

My main gripe about power stations is that you get locked into the manufacturer's proprietary "ecosystem" with potentially significant additional cost. I'm hoping someday that a power station is developed which can take arbitrary additional batteries, and after perhaps a calibration (e.g., run them down to zero and back up to 100% SOC), it would be able to manage the batteries.

I was able to get around this on my EcoFlow power stations by getting a cheap 12V to 24V voltage converter from Amazon. The 24V simulates a solar panel. I then plug this into the solar input port with a modified proprietary cable which allows input at 15A, or 360W. This pulls 30A from the 12V battery (360W), not near it's maximum of 100A (1280W), but it works ... allowing charging from an arbitrary 12V battery. That 30A gets the 10AWG wires WARM.

An EcoFlow Delta 2 "Extra Battery" with roughly 1kWh of capacity costs $800. A "raw" LiFePo battery with 1.3kWh costs under $300.

[KK6DYO]

The Holy Grail: Air Conditioning

This is not a power station but has a number of power station capabilities in addition to being an air conditioner.

Wouldn't it be great to hang out in your tent on the hottest Anza Borrego days?

Wave 2 Stupidity.jpg (109.65 KiB) Viewed 3078 times

Running an AC inside a screen tent seems, well, uneducated.

EcoFlow has developed the Wave 2 air conditioner, a 5100BTU air conditioner (and 6100BTU heater).

EcoFlow Wave 2.jpg (59.94 KiB) Viewed 3077 times

It takes 450 watts to run in cooling mode. While unit's solar charging input is 400W, it can be connected directly to a Delta 2 with up to 500W of solar power. With sufficient solar panels, you can run this all day. It can be attached to the Delta 2 as an add-on battery.


EcoFlow Wave 2 Air Conditioner


HOBOTECH's review considers it a very quiet unit. He liked it so much he now uses it for air conditioning his lab area.

HOBOTECH Wave 2 Review


Other manufacturers make small AC units, but this one seems to have the best set of capabilities.

[K9Nigel]

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