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Power setups for events

Small power setups for events

Author: Ben

Date: 2024-03-13

Overview

When you want to power things at an event, you’ll need a power system.

Power Systems are comprised of

  • A way to generate power
  • A way to store it
  • A way to convert it to the desired type
  • A way to monitor how much energy you have left
  • Safety equipment
  • Tools, cords, and accessories
  • The load itself that you’re using

The Situation

flowchart LR
    load["Projector"]

You have a projector at a party.

We will assume the projector uses 100 watts continuous and your event is 5 hours long.

Key concepts
ConceptDescription
100 wattsThe power consumption of a projector. Similar to 10 LED light bulbs, 1 TV, or 1/10 of a microwave. Watts are a unit of power
5 hoursThe load’s duty cycle. Hours are a unit of time
500 watt-hoursThe projector will use 100 watts for 5 hours, or 1h*500w or 500wh. Watt-hours are a unit of energy
Shopping List
  • ☑️ A projector
  • ☑️ A party

Scenario 0 — Running a projector at home

flowchart LR
    outlet["Power Outlet"] --> load["Projector"]

This is the simple case. All you need to do is plug it in to your 110v AC outlet

Key concepts
ConceptDescription
110 VoltsThe voltage of domestic outlets in the US
9 AmpsThe current that a projector pulls. 100 watts / 110 volts = 0.9 amps
AC (Alternating Current)The type of power you get at home
Shopping List
  • ☑️ A house with electricity

Scenario 1 — Running a projector at a park

flowchart LR
    battery["Battery"]
    battery --> inverter["DC -> AC Inverter"]
    inverter --> load["Projector"]

Your party is outside, such as in the Presidio of San Francisco. You haven’t asked permission to use the government’s power plugs.

You need to bring a DC battery, and an inverter to transform your DC power to AC power.

You’ll need to be sure your battery is big enough, and you’ll need to choose a system voltage. The author prefers 48v

Key concepts
ConceptDescription
12 voltsThe ‘nominal’ voltage of car batteries in the US
12-15 voltsThe ‘actual’ voltage range of car batteries in the US
48 voltsThe ‘nominal’ voltage of batteries that the author suggests
DC (Direct Current)The type of power batteries provide
InverterA conversion device between DC and AC power
Shopping List
  • ☑️ A 48v lithium iron phosphate battery that has a capacity of at least 500 watt-hours
  • ☑️ A 48v to 110v inverter
  • ☑️ Battery cables to connect the battery to the inverter

Scenario 2 — Your battery is not charged yet

flowchart LR
    outlet["Power Outlet"] --> charger["Battery Charger"]
    charger --> battery["Battery"]

You’re getting ready for the party but the battery is not charged

You’ll need a battery charger that is designed for the voltage and chemistry of your battery

Key concepts
ConceptDescription
Battery ChargerA conversion device from AC —> DC for charging batteries. Make sure it supports your battery voltage and your battery chemistry
Battery ChemistryThere are many types of batteries. You’ll usually want Lead-Acid (aka car) batteries only if you own them already or Lithium-Ferrous(Iron)-Phosphate (aka LFP or Lithium) batteries if you’re buying new ones
Voltage MeterDevice that measures voltage
Voltage response of a batteryAs batteries drain, they decrease in voltage. As they charge, they increase in voltage
Non-linearThe voltage response does not decrease smoothly. It is usually pretty minimal slope until the battery is low, then the voltage decreases rapidly
Shopping List
  • ☑️ Battery charger for 48v Lithium Iron Phosphate batteries
  • ☑️ Voltage meter (many battery chargers have one built in)

Scenario 4 — Your buddy wants to plug in a speaker

flowchart LR
    battery --> inverter["DC -> AC Inverter"]
    inverter --> load["Projector"]
    inverter --> load2["Speakers"]
    battery <-. measure .-> voltage["Voltage Meter"]
    inverter <-. measure .-> amperage["Power Meter"]

You’re at the party and your buddy needs to power his speakers. You wish you knew how much energy you have left in the battery.

You’ll want a voltage meter or a battery charge meter, and the user manual for your battery. Many inverters include a voltage meter. The voltage of the battery can be checked against the product’s datasheet and you can determine what percentage charge is left. This will allow to you calculate the number of watt-hours remaining.

You’ll also want to know how fast you’re using up your energy (aka how much power you are drawing). A power meter (or wattage meter, or amperage meter) will tell you.

The inverter might not be big enough to power speakers, so you can compare the current wattage of your system with the additional power demand of the speaker. Usually inverters can provide slightly more than their rated power for a short time.

Once you know how much energy you have in the battery and how much power you’re drawing, you can determine if your buddy can plug in his speakers for the rest of the party time, or if that extra power demand would force you to turn off the projector earlier in the night.

Key concepts
ConceptDescription
Power MeterDevice that measures watts (power). Also called a wattage meter
Current MeterDevice that measures amps (current). Also called an amperage meter or an ammeter
CapacityAmount of energy the battery can hold (ideally in watt-hours, but often will tell you in amp-hours. You can multiply by the voltage of the system to get watt-hours.
ChargeAmount of energy the battery holds right now. Usually a percentage (50% charged)
Shopping List
  • ☑️ A friend
  • ☑️ Voltage meter (many inverters have one built in. If you were using your battery charger in the last scenario, you’ll need a new voltage meter for this scenario)
  • ☑️ Power meter (aka wattage meter)
  • ☑️ Current meter (aka amperage meter or ammeter). Not needed if you have a power meter

Scenario 5 — Your party needs a power distribution system

flowchart LR
    battery["Battery"]
    battery --> inverter["Inverter"]
    inverter --> surge["Surge protector"]
    surge --> load["Projector"]
    surge --> extension["Extension cord"]
    extension --> load2["Other devices"]

Your decor team finds your power system “not very aesthetic” and prefers that you move it somewhere else

Key concepts
ConceptDescription
Surge ProtectorsProvide some electrical protection for your devices. Usually has a helpful switch and multiple outlets
Extension cordsDifferent extension cords support a different amount of power. Check the label and use something big enough, or your cables will get hot
Shopping List
  • ☑️ Surge protectors
  • ☑️ Extension Cords
  • ☑️ Power switches

Scenario 6 — Your party has some 12v LED strips

flowchart LR
    battery["Battery"]
    battery --> inverter["Inverter"]
    inverter --> rectifier["AC->DC Rectifier"]
    rectifier --> led-strip["LED strip"]
    battery -- alternative\n option --> dc-dc["DC->DC step down"]
    dc-dc --> led-strip

Your buddy just learned what addressable LED strips are, and she wants to drape them over the bar to provide some ambiance. They are 12v DC led strips. Sometimes they are 5v (such as for USB-powered strips)

You’ll need to either convert your AC power back into DC, or connect to the battery and step down the voltage from 48v/24v/12v/etc to an exact 12v.

Don’t plug into the battery directly, even if the battery claims it is “12v”; it is probably 12v ‘nominal’ instead, and could vary from 11 to 15v in practice.

Many people on electricity forums will tell you that converting DC->AC->DC is a wasteful use of resources. Instead, the author suggests you buy a bigger battery and not worry so much about efficiency. Choosing which foods you eat that day makes a bigger environmental impact :)

Key concepts
ConceptDescription
AC->DC RectifiersConverts from AC to a constant DC voltage (usually 12v or 5v)
DC->DC step downConverts from variable, possibly high voltage DC to a constant DC voltage (usually 12v or 5v)
Shopping List
  • ☑️ Surge protectors
  • ☑️ Extension Cords
  • ☑️ Power switches

Scenario 7 — Your party is in a big field and your battery is low

flowchart LR
    solar["Solar Panels"] --> charge["Charge Controller"]
    charge --> battery["Battery"]
    battery --> inverter["DC -> AC Inverter"]
    inverter --> load["Projector"]

Your party is in a sunny and beautiful setting without nearby power, and you need to charge your batteries from the sun; you’ll need solar panels.

Key concepts
ConceptDescription
Solar panelsUse the energy from the sun to generate power
Charge ControllerDevice that optimizes the voltages on solar panels and converts the voltage to the battery’s target voltage. Provides power to batteries to charge them
Shopping List
  • ☑️ A really bright light (usually the Earth’s Sun)
  • ☑️ Solar panels
  • ☑️ Charge Controller
  • ☑️ Solar panel cables (get an extra pair)
  • ☑️ Wire strippers (for cutting off the ends of the solar panel cables)
  • ☑️ Screw driver (for attaching the wires to the charge controller)

Aside — Notes about solar panels

Solar panels have a rated wattage, which usually describes how much power it could generate at midday pointing toward the sun

Solar panels have an open circuit voltage (Voc), and solar charge controllers support a range of open circuit voltages. You can wire panels in series up to the maximum Voc. You must wire panels in series such that the voltage is inside the range the charge controller suggests. You can also wire multiple strings of the same number of panels in parallel up to the maximum power of your charge controller / battery.

Solar panels should be placed at a low angle (~30 degrees up from horizontal)

Per day, you’ll generate about 5 hours * the wattage of the solar panel. For example, a 200w solar panel will generate: 200w * 5 hours equiv. = 1000 watt-hours. For more information look up ‘solar irradiance charts’ for your area and time of year.

Scenario 8 — Your party is in a dusty desert far from any shops

flowchart LR
    solar["Solar Panels"] --> charge["Charge Controller"]
    subgraph Protective Box
        charge --> battery["Battery"]
        battery --> inverter["DC -> AC Inverter"]
    end
    subgraph Protective Box
        inverter --> load["Projector"]
    end


    charge2["Charge Controller"]
    subgraph Backup gear in your vehicle
        charge2 -.-> battery2["Small battery"]
        battery2 -.-> inverter2["DC -> AC Inverter"]
        inverter2
    end
    inverter2 -. off by\n default .-> load["Projector"]

Your party hosts decided it would be wise to make the physical environment WAY more physically challenging, so you can bond better with your friends through shared adversity.

Key concepts
ConceptDescription
Trauma bondingThe ability for a group of people to come together in adverse circumstances
EnclosurePutting your devices in somenthing to make them more weather resistant
Shopping List
  • ☑️ A ticket to your favorite ephemeral desert city
  • ☑️ Enclosures for your sensitive electronics
  • ☑️ A shade structure to protect your enclosures from direct sunlight
  • ☑️ Backup gear for when things inevitably break
  • ☑️ Suntan lotion

Scenario 8 — You want to leave your system on while you walk around with your cute date

flowchart LR
    solar["Solar\n Panels"] -- solar\n disconnect --> charge["Charge\n Controller"]
    subgraph Protective Box
        charge -- \nbattery\n disconnect*\n\n* I personally\n dont use these --> battery["Battery"]
        battery -- battery\n disconnect --> inverter["DC -> AC\n Inverter"]
    end
    subgraph Protective Box
        inverter -- surge\n protector,\n fuse, or\n circuit\n breaker\n+++\n a timer\n switch to\n automatically\n turn off--> load["Projector"]
    end

You met someone last night. You’re not sure what to make of their sequined tuxedo-dress that leaves parts of itself behind on the ground. You want to learn more about them. What lies on the other side of a night of exploring and deep eye contact?

Safety, if you put the appropriate fuses, disconnects, and circuit breakers in your system.

Key concepts
ConceptDescription
PrioritiesThe agency you have to make choices based on your values
Battery disconnectsSwitches rated for high current DC applications, which are not the same as at home light switches
FusesSmall pieces of wire deliberately designed to burn before your valuables do
Circuit breakersDevices that will reversibly turn themselves off if too much current is drawn for too long (such as with a short, where two wires connect directly)
Shopping List
  • ☑️ DC Battery Disconnect (x2 optional)
  • ☑️ Fuses
  • ☑️ Circuit Breakers
  • ☑️ A timer switch that can automatically turn on or off your devices
  • ☑️ Gloves for working with electricity
  • ☑️ Introspection about what is important to you

Summary

You can power that projector; I believe in you. Just make sure you get the compliments and gratitude you deserve and that you embrace that problems out of your reasonable control could occur any time.

Happy partying!

Questions: ben @this_domain_you’re_on.com

Further Reading