How to build a portable 120V power pack for studio strobes

Warning: Building any kind of power pack has inherent risk and can result in injury or death. If you are to attempt such a project, you should have basic working knowledge of electrical principles and understand all safety issues regarding working around electrical devices. If you don’t know what you are doing, buy a commercial power pack instead.

Photographers who want to use strobe in the field are often confronted with the problem of powering their lights. Many commercial options are available for purchase but they are often expensive. Alien Bee offers the Vegabond II system for $300.00. It consists of a 12 volt battery, a pure sine wave inverter, a charger, and a carrying case. If you want convenience, buying a commercial product is your best option.

There are several reasons you may want to go with a D.I.Y. solution. A system you build yourself is often less expensive, more flexible, and more powerful than a pre-built system. A custom power pack solution offers you the flexibility of choosing a battery size to suit the shooting needs. It also allows you to power your system from your car battery if you will be shooting near your vehicle.

Here is a list of items you will need:

  • 12 volt battery. You have many options here. For one or two lights shooting about 300 shots, you can go with a relatively light weight sealed lead acid battery. SLA batteries are convenient because they can be stored in any orientation while car batteries must remain upright. Generally, you want to get something in the 8-12 amp hour range. More amp hours equals more flashes at the expense of more weight. Some options for 12v SLA batteries: Batteries America ZBattery. A good compromise between weight and power is the # UB12180 12V 18A (12.5 lbs) for $50. For more demanding applications, you can go with a law mower battery or a deep cycle marine battery. It’s preferable to go with a deep cycle batteries because they do not require frequent charging as car batteries do. If you have an old 1000 va UPS lying around, you can take it apart and see what battery is in it. They often use 12v or 2 6v batteries. A typical lawn mower battery will give you up to 500 flashes at full power using one Alien Bee 400. A full size marine battery will give you well over 1000 flashes.
  • Pure Sine wave inverter. This is a critical component. You cannot just hook up a cheap square sine wave inverter from the local auto shop. I recommend at least a 300 watt inverter for $130. Some may choose a 600 watt inverter for $200. This 300 watt inverter from AIM has dual ac outlets and is smaller than the unit from Samlex. If you have a need to power high wattage devices such as a computer with a large screen, go for the larger wattage rating to give you more flexibility. 600 watts is really overkill for powering strobes but it comes in handy if you go camping or want to power an in-the-field office.
  • Two hose clamps to connect black and red 4 AWG cable to heavy duty locking female extension plug. I used the ones made for air conditioners so regular plugs cannot be plugged in. You can use any plug but I did this for safety. This step is not required but using clamps to connect the battery is risky due to reverse polarity. It is important to use a thick cable rated at 4 AWG or better. A regular lamp cord will not carry enough amps to power the load needed. Keep the cable as short as possible and use a thicker cable is possible.
  • Male plug to 4 AWG cable to connect to pure sine wave inverter.
  • The inverter I used has a 40 amp fuse built in so I opened the inverter and bought a matching 40Amp auto fuse and taped it to the inside as a spare. Reversing the polarity will blow the fuse. This can save your shoot in the event of a short or power spike.
  • Giant nail to serve as a grounding stake to connect inverter’s ground cable. This is a safety feature. It will work without a ground.
  • 12 volt battery charger. You may have one lying around. I bought a Vector 12 volt 2/6/10 charger from Lowes.
  • Carrying case. Look for a tool box or some kind of case that will hold everything in place. For a lightweight SLA battery system, you can even put everything in a back pack. For a large marine battery, you may need to put it on wheels.