A Portable Power Box for Photographers

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.

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.

Comments

[TBKVideo]

This is awesome. I'm building mine this weekend. What kind of strobes do you use?

[Divet]

I have used the power box with Alien Bee and Elinchrom strobes.

[mrosenstok]

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]

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/

[thepaul1993]

Very nice. I guess if you wanted to you could add a charge controller and a solar panel.

[ElectricMan1]

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]

I tested with scraps of 12, 10 and 8  gauge wire when building the box. 8 gauge allows more watts.

[darkride]

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]

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.

[ElectricMan1]

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

[vodo]

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]

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]

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

[ElectricMan1]

In a perfect world, batteries don't drain 100%.
I learned that the hard way!

[Sandisk1duo]

The battery is a bit heavy? anyone got links to cheap Li-Poly batteries?

[ReCreate]

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

[Sandisk1duo]

if you over charge by 1/100 of a volt, you only slightly damage the battery

[ReCreate]

Ha yeah,its a 1/10 of a volt not a 1/100

[Sandisk1duo]

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

[ReCreate]

the battery is rated 3.7 Volts,if it is at 4.20 that means that it is overcharged,big time

[Sandisk1duo]

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.

[ReCreate]

I don't get it,so batteries are not really what they say? But much higher?

[Sandisk1duo]

not 'much' higher and only rechargeables regular batteries have the voltage that is printed on them

[ReCreate]

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?

[Sandisk1duo]

there is no 'real' voltage the voltage changes when fully or partially charged

[ReCreate]

I guess so...So what would be an over charged lithium ion?

[Sandisk1duo]

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

[ReCreate]

I guess you learn something new every day!

[Sandisk1duo]

over the course of two days

[ReCreate]

I meant that that you said that day,i thought that it was to 3.7.not 4

[ElectricMan1]

HA ok they should come up with another name for Lithium Polys: BOMBS

[dooj]

and plese give me i link

[Divet]

Search on Ebay for a wheelchair/scooter battery.

http://shop.ebay.com/?_from=R40&_trksid=m38&_nkw=wheelchair+battery&_sacat=See-All-Categories

[dooj]

where did you get the battery

[brian3140]

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.

[ReCreate]

The Inverter should provide you 300 WATTS for 1 hour...I think

[ReCreate]

So according to my calculations,IT should last... few days at 30 or so watts

[josh.wingo]

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.

[animes25]

and the million dollar question is: How do I recharge the battery when is worn out?

[Divet]

Use an intelligent car battery charger.