Instructables

A Portable Power Box for Photographers

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Many photographers have built Vagabond style portable power systems to use with their strobes. This is an attempt to incorporate several design ideas and safety features. The power box can also be used with laptops or other delicate electronic equipment.

Materials:

Metal tool box (18'x8'x9' or larger)
300 watt Samlex pure sine wave inverter (Frys.com $130)

(I have been told that Samlex's new 300 watt inverter with usb will not work with a power box. Based on Samlex's new design, a 600 watt inverter is needed to run just one 300 watt strobe. There must be other pure sine inverter alternatives out there, that people can recommend)

Scooter/wheelchair battery 26AH-35AH ($40-$100)
40 amp Square D Breaker QO (single pole AC/DC breaker $14 electrical supply store)
8 AWG Braided Electrical Cable (SOOW 8GA $12)
Bolts and lock washers
(2) Brass washers
(2) 2 1/2' and 3' angle brackets
Ground Fault Circuit Interrupter (GFCI) and Box Housing ($16+$5 Home Depot)
Old scrap extension cord with plug
Large nail or spike
Hose clamp
Zip ties
Flat piece of hard plastic
Copper ground wire stripped from an electrical cable
Battery clamps


SAFETY: Disconnect the battery when working on the circuit. Wear gloves when handling the battery.
 
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Step 1: Angle Brackets

Use a metal tool box to house the power supply. It will serve as the common ground for all the components. The box should be tall enough so that when closed, the lid doesn't touch the battery terminals. Place the battery as close to the centre as possible for even weight distribution. Do not use a car battery for this project as it quickly will become damaged from being repeatedly discharged.

Mark and drill holes for the angle brackets. Remove the paint from under the left 3" bracket. This bracket will attach to the ground spike. 2 1/2 " brackets were used on one side because the box was not wide enough for 3 inch.

Mark and drill holes for the inverter and the inverter ground bolt. Remove any paint from around the holes so there is a good electrical contact.
TBKVideo3 years ago
This is awesome. I'm building mine this weekend. What kind of strobes do you use?
Divet (author)  TBKVideo3 years ago
I have used the power box with Alien Bee and Elinchrom strobes.
hey Divet,

whish elinchroms you use?
I have 2 - 500ws BXri. Do you think it will work ok with my strobes as they are a digital model?

Is your DIY portable power pack still working ok after all this time?

Best regards
Miguel
Divet (author)  mrosenstok2 years ago
I've used the pack with the digital Elichrome Style 600RX, but I haven't ever used the Bxri and couldn't say for sure it would work (tho there is a decent chance it would).

Three months ago I loaned the pack to someone and they burnt out the inverter by shooting too quickly with a 1000 watt load. The design of Samlex inverters have been changed so they now shut down with a low voltage. I haven't found a decent replacement inverter locally to rebuild it with. I guess in Portugal another option might be the Paul Buff vagabond mini, if you have the cash. http://paulcbuff.eu.com/cms/
thepaul934 years ago
Very nice. I guess if you wanted to you could add a charge controller and a solar panel.
Dude, thats way overkill on the wire, 300watts/ 12volts= 25 amps DC.
25 amps for less than a foot= 12 guage flexable wire is fine.

I use #10 on my 400 watt inverter system.
Divet (author)  ElectricMan14 years ago
I tested with scraps of 12, 10 and 8  gauge wire when building the box. 8 gauge allows more watts.


darkride5 years ago
Um, a GFCI doesn't protect against a short, it protects you from being electrocuted by touching the hot wire while having a path to ground, such as when in a wet environment. Since this project is not using commercial power (which has a good ground path), I doubt it is of much use, just added cost, leave it off. Lose the ground spike (which is not long enough to be of any use anyway.) and there is no path to ground. With no connection to earth ground the only way you could electrocute yourself would be to touch both AC wires at the same time. By the way, it doesn't matter which battery lead you attach first, just make sure the breaker is off.
Divet (author)  darkride5 years ago
Using a power box in wet environment with a sync cord can result in a photographer receiving shocks through the camera. Installing a GFCI and a ground spike is an attempt to minimize the possibility of damage to either equipment or personnel.

GFCI- GROUND fault circuit interrupter.
The inverter is poorly grounded if at all, the best thing to do is not get electrocuted.

vodo5 years ago
field bought a battery at radioshack. it is an alarm battery, here air the specks: charging voltage: 14.4-15.0v 13.5-13.8v. application:normal charge standby/trickle max charging current: 1.5a 1.5a. can I use it to build it? oh,an its 12v.
Divet (author)  vodo5 years ago
See if there is an AH marking. I think most 12 volt batteries at Radio Shack are under 8 AH. 10AH would be the minimum I would try.
ReCreate Divet5 years ago
I used a 700MAH battery for an inverter and it ran a 60 watt fluorescent light for a while,So its about 1 amp hour,if the Light consumed 100miliamp hours(i know it does not though)it would last for 7 hours,if it consumed 700miliamp hours it would last,1 hour
In a perfect world, batteries don't drain 100%.
I learned that the hard way!
Sandisk1duo6 years ago
The battery is a bit heavy? anyone got links to cheap Li-Poly batteries?
HO NO,LITHIUM-ION COSTS THAUSANDs Really They are very expensive,and they are dangerous to charge too! just overcharging them by a hundredth of a volt and you get KABOOM
if you over charge by 1/100 of a volt, you only slightly damage the battery
Ha yeah,its a 1/10 of a volt not a 1/100
1/100 of a volt actually decreases the cycle life by just a tiny bit if a battery is charged to 4.20v it has less capcity, but lasts longer then a battery charged to 4.235V
the battery is rated 3.7 Volts,if it is at 4.20 that means that it is overcharged,big time
and that....................... is where you're wrong 3.7V is just nominal cell voltage When fully charged, the battery is at 4.15-4.25 Volts same thing for nicad, nimh, and Lead-acid batteries, they are said to be a certain voltage, but they need to be charged more then that.
I don't get it,so batteries are not really what they say? But much higher?
not 'much' higher and only rechargeables regular batteries have the voltage that is printed on them
SO lithium ion batteries to get overchagred,to 4.20 volts,when they are rated 3.6 volts,so what are their real voltage? 4?
there is no 'real' voltage the voltage changes when fully or partially charged
I guess so...So what would be an over charged lithium ion?
An overcharged i-ion would be 4.2+ V a charged li-ion would be 4.2V a fully drained li-ion would be 3.6V
I guess you learn something new every day!
over the course of two days
I meant that that you said that day,i thought that it was to 3.7.not 4
HA ok they should come up with another name for Lithium Polys: BOMBS
dooj4 years ago
and plese give me i link
Divet (author)  dooj4 years ago
dooj4 years ago
where did you get the battery
brian31405 years ago
The concept is good, but electrical theory in the comments is very confused. definitely put the GFCI on the outside of the box and don't worry about rain or water. it'd never be ideal to do it on purpose, but the GFCI will protect you even if you sprayed it with a hose. In rain there is a high likely hood that it will never even trip the GFI on the outlet, but if it does... oh well. that is what it is designed for. And no rain cover is necessary. People trying to make the system lighter should just stick with the heavy battery, but a smaller cheaper inverter could be used. I bought a 400 watt inverter at Wallmart a few years ago for $40 and never had any trouble.
ReCreate5 years ago
The Inverter should provide you 300 WATTS for 1 hour...I think
So according to my calculations,IT should last... few days at 30 or so watts
josh.wingo5 years ago
you should cut a hole on the side for the gfci to face outwards. so you do not need to run power out of the box, the box can stay sealed. when facing the gfci out, get a weatherproof box cover, it will keep water from getting in it and you can still safely use it in the rain.
animes256 years ago
and the million dollar question is: How do I recharge the battery when is worn out?
Divet (author)  animes256 years ago
Use an intelligent car battery charger.
ReCreate Divet5 years ago
or any charger,or any supply of 12-15v
ReCreate5 years ago
what are the specs of the battery?(other than voltage of course its 12v) Lets see...50 ma is lethal,the battery being 12v will let only 0.20(about) ma through your skin,therfor.0.20 out of the lethal 50.0 ma is going through you,your safe touching the leads,just as long as you don't have salt water on your hands
mbainrot5 years ago
One thing i noticed is that you have set the inverter up in a way which puts it in an enclosed space, if your not careful you can overheat the inverter.

With the AH question, in theory you can get away with as low as 7AH, (which is what i use to power computers etc), the important calculation you need to make is how long you get, MINUS the safety cut off (most inverters will shutdown when the battery voltage gets too low), also you need to compensate for the efficiency of your inverter, batteries, etc.

For example :)
To calculate approximately how long a 7AH battery will last on a 300 watt load (my inverter @ 100%), you would do the following :)

1) Convert the watts into "dc amps", this is down by dividing the wattage by the operating voltage of the inverter (so in this example its 300 divided by 12, which gives you 25A)
2) Then you add the inefficiency amount (so if its 95% eff, the inefficiency is 5%) to the amperage (so in this example, 25*1.05, which gives you 26.25A), then you add the approximate efficiency of your battery (Sealed lead acids trend around 90%, so in this example, 26.25*1.10, gives you 28.875A)

3) With the final figure from the last calculation (in this example its 28.875A). you divide the amp hour capacity of your battery (or total capacity of your battery bank) by the amp figure (e.g. 7AH / 28.875A = 0.24 hrs or approx 15 minutes)

Please note that the voltage cut off will usually prevent the battery from getting lower than about 10.5volts, which leaves you with piss all power from the battery.

Other notes are with measuring equipment to determine your needs, please note that inductive loads sometimes cannot be measured (no idea why)

Hopefully my 5 cents is of use to people :)
brandegor5 years ago
Would this be safe to run video cameras as well?
Divet (author)  brandegor5 years ago
Yes. Power supplies for video cameras are usually under 20 watts.
lgcalex5 years ago
this is great! I didnt see how much shooting you can do off of one of these. How many watts are you strobes/ number of times you can fire them? I will most likely be building one of these in the near future. The strobist method doesn't allways work if you need more light
Divet (author)  lgcalex5 years ago
The portable power box with a 33AH battery will run two 600 watt strobes (not at maximum settings and with some use of the modeling light) for over 210 flashes.
mattccc5 years ago
can i use a 4.5 ah battery instead
Divet (author)  mattccc5 years ago
A 20AH battery is the lowest I've seen used for photography purposes. Some people have said that 15AH is the minimum.
Dipankar6 years ago
Your Photography is of excellent quality.
animes256 years ago
I will make this one but, I will use a laptop bag instead the metal box, hope never to fall in a river or swimming pool :D
animes256 years ago
I have a 300 watt pure sine wave inverter, and it haves a fuse, I think thats enough
friezer6 years ago
Very nice. Any reason you didn't point the GFCI outlet upwards so it was easier to plug into? I like how you took into account the weight of the battery and centered it in the box. This thing could get rather awkward if the battery was at an end. What are you using for a charger? I think I'll be building one of these myself.
Divet (author)  friezer6 years ago
I didn't install the GFCI on the bottom of the box because I was worried that any water that got in would pool and get into the housing. A large spacer might work though to keep it dry. The charger is a $40 4/6 amp intelligent car battery charger.
tlockney Divet6 years ago
friezer wasn't suggesting installing the GFCI on the bottom, just having it pointed upward. Another possibility would be to actually punch a hole in the side of the box and have the plugs exposed on the outside. You could possibly even get one of those outdoor outlet covers to protect it when it's not in use. All in all, this project looks handy for lots of different uses. I might have to put something like this together myself.
can i suggest to keep the container tight is to put rubber sealing make's it a bit water proof in case anyhing happens *accident happens*
Good idea, definitely less expensive than some of the other boxes.
John Smith6 years ago
This is a great idea, not just for photographers. You need to enter this in the book contest, i'll vote for it.
darus676 years ago
In step 2 you say, "Whatever surface you mount the inverter on, it must be horizontal or the internal fan will not work properly." but then you go ahead and mount the inverter on a vertical surface. 'sup with that?
Divet (author)  darus676 years ago
The surface may be vertical, but the inverter is mounted horizontally.