Last week I promised I would not only tell you about a new DIY project to compliment my Fovitec StudioPro 400W/S monolight kit, and their StudioPro Softboxes, but how you could possibly keep the costs around $100. My homemade “Vagabond II” unit turned out quite nice and works 100% as I imagined. So if portable A/C power is something you have considered, but found the costs prohibitive, perhaps this can get you going at less that half the costs of buying from a named brand retailer.
As a wedding and portrait photographer, many times I have found myself in situations where I really wish I had the capability of studio strobes on location when there was no source of 110v power. Speedlights were just not enough and that smaller softbox just wasn’t really soft and a large enough light source to fully illuminate your subjects(s). You just needed that really large light source and a really powerful light to get the job done.
Over the years, a few manufacturers have developed larger, battery powered, studio strobes for outdoor and location work. Paul C. Buff was one of the first with their Vagabond power system that worked well with their various monolights. Many used either the Einstein or AlienBees units and they had more flexibility in their lighting. You could provide 110v A/C power to a couple of monolights and have several hundred flashes per head.
The price tag was around $300 and many of us just didn’t have the opportunity or funds to buy that at will- myself included. Now, Buff has moved to a lithium powered pack and the costs are even more. Sure, they get the job done, but why not a DIY build with the same capabilities, only try to keep the costs around $100? So I put my electrical background to good use and began studying what components would make a solid and reliable build and still have the safety margin needed to keep from getting electrocuted.
Any A/C inverter starts with input voltage. I wanted a 12v input and an inverter with enough wattage to power two, 400w/s strobes. I knew that the recharging of the capacitors didn’t require a ton of watts, but the modeling lamps would be the largest draw of current/amperage. I also know that A/C current on your power company lines are pure sine wave power too. After doing the calculations, I knew I would need a 300 watt inverter to power 2 monolights and have a surge rating of 500 watts or above. I ALSO knew it had to be a pure sine-wave inverter, and NOT a modified sine-wave because of the electronics in most monolight heads. I won’t get into the technical details, but take my word for it that electronics DON’T do well with modified sine-wave current over the long haul. So if you opt to buy one, make sure it is pure sine-wave output on the 110-120 plugs.
I also discovered that the Vagabond II used a 12V, 20AH SLA (sealed lead acid) battery. These are specialty batteries that are acid filled, but use fiberglass separators and are totally sealed from spillage, gassing, or any number of issues lead-acid batteries can have. They are also build for deep cycle, constant power and deliver their amperage evenly across the voltage provided. You will find these in a lot of UCP backup power supplies as well as in wheel chairs, emergency lighting, and any number of applications where a long lasting voltage is needed and can handle short surges of amperage with no problem. This is exactly what you need for monolight power since the first few milliseconds of capacitor charge is your only surge. And this size battery fits the inverter specs very well too and their size is smaller and lighter than one for your lawn tractor.
So where do you go shopping for deals? Ebay of course! I found a 300/600 watt full sine-wave inverter on auction and I knew I didn’t want to go over $45 for it to be a “deal”. Otherwise I could buy one for around $60-80. So here it is, and perhaps you too can snag one. http://www.ebay.com/itm/331199459958?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649. I won the auction at $41 and reasonable shipping. They also sell them as “Buy it Now” items, so look in the Ebay sellers store if you can’t wait for an auction.
Now I like to shop locally when I can, and I priced a 12V, 20AH SLA battery locally. It was around $70, so back to Ebay I went, hoping to keep it under $50. Yep, there it was! http://www.ebay.com/itm/271486889591?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 for around $40 and free shipping! I love free shipping and it only took 3 days to arrive!
I had an old, small camera bag that I wasn’t using and the battery and inverter fit perfectly inside once I moved the dividers around. So now to the wiring. I took the supplied harness and clipped off the alligator clips and used a crimped eye-ring on each end that fit the 12 gauge wire and holes for the supplied battery bolts. You COULD use the clips, but I would recommend direct bolting to your battery. DO NOT cross polarity since you will fry your inverter (RED IS + POSITIVE). You can also put in a disconnect inline that connects only one-way for about $20 if you wanted, but since I always carry a couple of tools, it was no problem to disconnect the ground wire when not in use. If you want added fuse protection, over and above the built in 35 amp in the inverter, you could splice one in the positive side (red wire) of your harness, but with the short wiring and no real chance of chaffing, I didn’t see the need.
If you find your 12V wiring a tad warm when in use, consider getting a couple of 18 inch, 10 gauge wires (black and red). No 2 strobes are exactly alike in current draw, so you may need to adjust your wire size to accommodate yours. This will help too, if your recycle times are really slow. Use stranded wire, NOT solid since you will be moving them around. Just crimp on your eyelet connectors to fit your terminals and wire and attach to your inverter and battery. Again, watch your polarity.
Since you are going to be using this outdoors, I do recommend a GFCI (ground fault circuit interrupter) that plugs into your A/C outlet. Most of your big-box suppliers like Home Depot or Lowe’s carries these. I found mine at Home Depot- http://www.homedepot.com/p/Defiant-Plug-In-GFCI-Adapter-3-Wire-Grounding-30339036/203741464 for $13. Remember, you are dealing with 120V and enough amperage to kill you if you are on damp ground or it starts raining. Be safe and let the CFCI do it’s thing and disconnect all A/C power from your equipment should something happen. You WILL live to tell about it.
So now for “The Test”. First, it does work as designed. In order to see if it could handle the load, I started with 1 of my 400W/S monolights. You CAN use the modeling light, but ONLY long enough to set your light and then turn it off. The halogen bulbs draw a LOT of current. If you have 2 lights hooked up, use only ONE modeling lamp at a time and again, for just enough time to set your lights. This was the only time the fan in the inverter actually came on too.
So I fired the first light and waited for the recycle. It was almost identical as if it was plugged into the wall! So I added 2 lights and the same thing- almost identical recycle times! So how would it do over a number of flashes? So I adjusted the power to about 1/2, which is a ton of light, and fired them off as I would in a shoot- probably 100-150 firings and even though they slowed a little in recycle time, it still held up. I checked the battery voltage and it was holding up nicely, so I calculated a LOT more flashes left on a full charge. If you need to add an extension cord, get a heavy duty one- 12-14 gauge since you lose current due to line loss in extension cords, and keep it as short as possible.
Now, I have a small battery charger and since SLA batteries require a trickle charge, you should not use anything over 1-1 1/2 AH charge rate. Overnight charging is almost required with these batteries. Again, you can find them on Ebay for around $10 and the Battery Tender brand, which is automatic, for around $20-30 if you shop around.
So were are we in terms of cost? An Inverter for $41, a Battery for $40, a CFCI for $13, and a charger for around $20 if you don’t have one. Total cost- $113-115. Compared to the Vagabond line, I would say you did well. If you need a bag to carry it in, Walmart has several for under $10 and any canvas bag will do as long at your battery and inverter will fit it snugly. Or if you want, you can get a Vagabond II bag for $20 from Paul C. Buff. But since my inverter and battery are both real close to the same height, the camera bag works beautiful with a bit of built in padding! The long shoulder strap makes carrying it easy and it hangs nicely on a light stand for added weight like a sandbag. I take a short board and put it between the light stand spreaders and sit my battery pack on that and keep it off the ground and still get weight.
I can’t stress enough that your number one concern must be SAFETY with your unit once it’s built. You are dealing with HOUSEHOLD VOLTAGE AND CURRENTS so the same danger applies in the field as you have in your home. KEEP IT DRY and use your GFCI when you connect your monolights. And since you don’t have a circuit breaker to protect you from shorts, your only line of defense is your GFCI since it trips the instant it detects a short to ground of any kind. It’s the same thing built into your hair dryer so you don’t electrocute yourself if it gets dropped into water.
So now, the next shoot where I need that portable A/C power, I have the tools needed to power a couple of monolights for key and fill lighting and still have the flexibility of using speedlights for other lighting in the shoot for backlights and hairlights if needed. And since great photography begins with great light, you have in your possession something that can really add that impact you need to advance even further with your photography. I know my brides will LOVE it and so will I since I can now do things with larger modifiers I can’t do with speedlights. And at this kind of cost, I can afford to build a couple of them for use in engagement shoots as well as family portraiture outdoors.
If I have learned one thing about the great names in photography- they ALL started with DIY builds of some sort and surprisingly, MANY still use them to this very day. So build it, use it, and let me know how it works out for you.