power inverters for Studio flash outdoors - Flash Feeder compact?

Hi,

 

Hope I'm not breaking any rules, but I posed a related question on the lighting forum with basically no

response - and in the past I've got great advice in the LF forum on power sources for high powered

strobe output away from mains power supply (i.e. in the landscape), so I'm back!

 

As implied above, I've been experimenting with ways of illuminating a landscape scene at night for a

number of years, using generators, travelites, high powered flashlights etc.

 

For what I'm doing, ideally I'd like to be able to use about 10000 ws of studio flash, but most

manufacturers do not recommend use of generators to power studio lights. 10K of battery power is

both expensive and troublesome (I have 3k ws of Travelites already which doesn't cut it). But I just

discovered something called a Flash Feeder compact which is a fancy battery driven power inverter that

produces enough pure-sine wave AC to run up to 12k ws of studio flash. It's expressly designed for

running studio flash in the field. It sounds really interesting, but there's almost no information about it

on the internet and I know nobody who has used one. They are made in Slovenia, and don't seem to

have much distribution in the English speaking world - at least going by the results that appear from

internet searches. The company web-site is here:

 

http://www.elektrona.si/flash_feeders.htm

 

but the site doesn't seem to be updated to feature their most recent model which is here:

 

http://www.gsl.be/shop/product_info.php/products_id/1433

 

http://www.robgalbraith.com/bins/content_page.asp?cid=7-6460-7297

 

 

 

Does anybody have any experience of this product in terms of reliability and functionality?

 

ps. I'm in Europe so the spec of 230v AC is what I need.

dynalite makes a Jackrabbit power supply

they have a website.

Honda generators are fine for powering high voltage , high power electronic flash. 10,000 Watt-seconds is a lot of juice however and you'll be well advised to use multiple packs on seperate generators.

Thanks for the responses, but this doesn't really get to the crux of my question. I would need

nine of the Dynalite units suggested (1100ws) to match the output of the unit I'm

investigating, and that would be likely around tens time the cost, weight and bulk! I don't

think that's a match. As to the generators, I've learned from Photo.net before that Honda are

the name to go with for generators, but again they are not cheap, even to rent, and may be

hard to find near my locations. Also a 10Kw generator is a lot heavier and noisier then the

device I'm investigating which comes in a medium sized Pelican case! Anybody used this

thing?

Well one thing is battery weight = power capacity. A lightweight inverter with a small battery can put out lots of current for a few minutes only. Just remember to carry a couple of fully charged (30kg) batteries to connect to the external inputs on the inverter.

In the movie industry portable AC generators are used when there is no local AC power. Their setup is made to be professional; secure; safe with no jackleg/bozo/duffus electrical settups. The pickle with amateur work is the jackleg factor. Many folks run a zoo of cords that are too small; they get pulled out. Electronic devices then get zapped because of the inductive spike as the other loads dump into your devices.<BR><BR> Thus many makers of flash units and other devices dont want you to use generators because you will blame them; instead of the duffus/kilroy who has a jackleg setup. <BR><BR>If one has some motors and fluorescent lamps on the AC generator along with the flash unit; and the cord comes out of the generator; the collapsing field in the ballasts can create spikes of several thousand volts. <BR><BR>In almost every thread on photo.net about generators some newbie interjects that AC generators put out square waves; thats as absurd as saying all lenses are square; its BS. <BR><BR>The reason most all folks fry their electrical items with ac generators is due to the duffus factor; jackleg setups. A cord to the generator gets tripped; your stuff gets fried; you blame the generator instead of you own duffus self. Amateur folks use false economy; they buy cheap cords; non twist lock; they overload their units. They don't even contact they device's maker to find out the inrush current requirements; they run blind and guess.<BR><BR>Other duffus things folks do with AC generators is they don't ground them; stuff gets plugged in the voltages can be wonky for a few AC cycles. Folks run generators in closed building and then die of carbon monoxide; they get shocked with jackleg setups; they refuel a hot generator and start a gasoline fire. <BR><BR>Another failure in US systems is where the 230 volt (two 115 volt with neutral) twistlock plug vibrates out of the generator and the neutral (approx ground voltage) comes loose; and the two hot 115 volt legs stay connected. Here the sum of the two legs stays at 230 volts ac; but an unbalance load might cause one leg to be 180 volts and another 50 volts; or 230 and zero! PLUS the voltage of each nominal 115 volt AC leg can RING a few thousand volts for a few AC cycle; and your stuff gets fried by the voltage; then later again by the 180volts on the 115 volt leg.

If one connects a resistive load like a toaster to a AC circuit; its in rush current is about the same as its operating current. Thus for a 1150 watt 230 volt toaster; its 1150/230 = 5 amps. A simple incandescent 100 watt bulb would draw 100/230 = 0.43 amps steady state; but can be say 20 to 50 amps at the start of the first ac cycle; depending when the cycle starts; the filament has a low resistance value when cold. For a refrigerator thats drawing say 2 amps at 230 volts steady state; it might be 10 to 12 amps at start; the so called "locked rotor current" in American EE lingo.<BR><BR>From an EE standpoint you need to know the steady state AC current draw of your 12Kw second ACME flash unit <b>at XYZ flashes per minute</b> ; and its inrush requirements too; and NOT guess; ie so the choice and sizing of AC generator is based on real electrical engineering and not touchy feely emotional stuff.

Bob,

 

Point taken, - but I should have explained that I don't need lots of flashes, so I likely won't

need lots of battery back-up. It's a static subject and I will shoot less than ten sheets of

film per set-up - what I do need is power. I'm shooting on a roadside, so the idea of

ganging up 10-12 jackrabbits or travelites outdoors with temperamental Northern

European weather is not easy - that's why I'm after using fewer high power studio heads

(2400ws each or more) rather then the limited power output of battery powered heads.

The attractive thing about this Flash feeder is that it can be connected to a car battery to

give additional juice.

 

Kelly,

 

I'm not sure I get your argument - you are citing human factor (we are all human) but then

you are not clearly stating whether you believe that AC generators can work despite our

humanity. The common knowledge is that most generators do not provide the appropriate

supply (special Honda generators excepted), and I've received information from a Bowens

engineer which is pretty clear - no generators recommended! You can make arguments

about the use of generators in the film industry - but they are not using strobes in the

film industry, and even at that they are also pretty fussy about what generators they are

using.

 

I guess nobody has any idea about the Flash Feeder Compact though?

Kelly,

 

apologies,

I wrote my previous post before reading your last post. I get your point about avoiding the

hocus-pocus vodoo approach. Thanks for the sound advice.

Poor solid state inverters are usually worse than generators for frying equipment. Almost all gasoline generators produce true sine wave 60hz power, if the regulation and peak output power are not the best, the frequency way wander a fair bit when large inrush current equipment is turned on.

 

A lot of inverters produce square or near square wave output which is hell on transformer operated electronics. Determine the peak draw of ALL your ac powered equipment and purchase a true sine wave inverter with an output of approx 10x your peak draw and you should be good to go. Running time is a factor of battery capacity, so you could also buy a decent deep discharge 12v battery that you could hook up to your vehicle to recharge it if necessary. This is really not recommended as your cars charging system is not designed to do this, but is could save you in a pinch.

 

An easy way to check on sine wave output is to check the light output from a halogen desk lamp. If the light output is brighter or weaker when plugged into the inverter than a mains supply, the waveform is suspect. Very small differences in wave form will change the rms voltage, and halogen lamps are very sensitive to differences in ac voltage vs light output. Use a lightmeter to show slight differences.

Bob,

 

Thanks for your advice on how to monitor the output from an inverter. The one I'm looking at

claims 'pure sine wave' output as a selling point. What would be useful to know is how best to

practically measure the peak draw of the studio flash units when they are recycling. Can I do

that with an amp/volt meter connected to the mains AC supply that the units would be

connected to?

Well peak draw would be no more than the mains fuse in the flash unit power pack. Yes you could use an ac amp meter to check the current draw.

Hi, I saw the flash feeder compact at the last sonimagfoto. It was in the stand of the same

importers as the elinchrom stuff, so I think it should be a serious product.

I didn't see it working, but they told me the maximun load was 6000 w/s, maybe they have

improved the design since then, or maybe the dealer wasn't informed at all (talk about

12000 w/s in the specifiactions).

It looks pretty good, but I think maybe a little expensive.

 

I also need to buy something to feed my 3 elinchrom units. I'm actually hesitating between

3 tronix XT (2400 w/s max announced, abut 350$ each) or doing it myself.

I measured with an amperimeter the load when the flashes are charging just after the shot,

and was about 9,5A each one (This is where the pointer of the amperimeter arrived, but

taking into consideration is not a stable load, and the fraction of a second the

amperimeter's pointer takes to arrive there and inmediately return to zero, I know this is

not an exact measurement)

So 9,5A x 3= 28,5A total, and 28,5A x 220V= 6270W peak power.

 

If I try to do it myself, I'm considering a 55 Ah good battery (Optima yellow top) and a

3x1000 or a single 3000W inverter (peak 6000W, I guess should be enough). This would

be around 900-1500 euro, depends of the inverters, but still cheaper than the flash feeder

compact.

Probably with this configuration I'd have the better performance, but the whole thing could

weight 45-60 Kg. I don't want to think to carry it up to a 5th floor location without an

elevator.

With the 3 tronix configuration, except performance, I also have the advantage of just

carry one if I only need 1 flash head. Or if one gets broken in the middle of a shooting I

can go on with the others.

I'm thinking in buy one, and if I like the real performance buy the another two. Cheap

enough to try this.

But still hesitating about the whole thing.

As the former rep for Broncolor who had a major account who tried to use their Broncolor

monopacks with a 12V to 120 stepup converter in their studio van I can guarantee you that

that inverter put out a wave form that was a square wave and that square wave blew up the

transformers in several thousand $ worth of Broncolor C70 strobes in the early 1980's.

 

The moral? Make sure that your flash units will function properly on inverters and

generators before you buy the inverter/generator.

Bobs words needs to be tattooed on folks arms <i>The moral? Make sure that your flash units will function properly on inverters and generators before you buy the inverter/generator.</i><BR><BR>AC Generators are on planes; ships, at power plants; a work sites; and come in all sizes. As an electrical engineer I have seen folks do dumb stuff with AC generators; then they blame the generator instead of their totally hokey jackleg settup when stuff fails. Companies that sell products know this; thats why if there are doubt its easier to say dont use XYZ. If I was a REP like BOB S.; I probably would be afraid to recommend AC generators becuase of the goober factor. Folks dont even use electrical terms properly; they use watts per second. Its like selling parachutes to to folks who dont know what altitude is in feet; but call in mph per psi per loonly bird. .

If I'm not wrong, the w/s definition in flashes its not about the power consumption, is a way

to describe its lighning power, something like a 1500 w/s flash generates the same light in

one shot as a 1500W lamp switched on for 1 second. (Don't know what kind of lamp they are

talking about..., I think is more a way to compare between different models of flashes)

"like a 1500 w/s flash generates the same light in one shot as a 1500W lamp switched on

for 1 second"

 

No watt seconds is how much energy the capacitors can store. It can not in any way be

converted to an output. Watt seconds are also called joules in some markets.

 

The output of a flash is determined by the shape and coverage of the reflector, shape and

diameter of the flash tube, length and diameter of the wires from the caps to the tube,

number and size of the connectors between the caps and the tubes and probably some

things I don't remember. And, oh yes, a capacitor will not put out more then 80% or so of

its' stored capacity - if it is a good cap in an efficient system.

 

So a bare bulb 1500WS power pack with a 15' cord would put out considerably less light

then the same flash head with a 40? head. And that head with a 70? reflector would still

be 1500 ws but the 70? reflector would put out less light then the 40? reflector and more

then the bare bulb system.

 

Conversely if those same capacitors were in a monopack system with the same caps then

the 1500 ws monopack with the same reflectors would put out more light.

 

Never buy a flash based on watt seconds. It is never an indicator of the output.

 

Output can be expressed as a specific f stop at a specific angle of coverage, as ECPS at a

specific angle of coverage, as a guide number at a specific angle of coverage or as BCPS

at a specific angle of coverage.

 

Buying watt seconds is like buying a car and trying to determine the MPG from the

horsepower or the top speed based on horsepower or the 0 to 60 time based on

horsepower.

 

Buy output not input. And make sure the manufacturer offers a reflector that will cover

the angle of coverage you need at the distance you need to shoot. As you pull the

reflector back the light changes it's characteristics so it is very important that the flash

does what you want at the distance you want it.

 

I once sold a studio a very nice Broncolor outfit for his fairly small studio. Someone else,

prior to delivery, convinced him to cancel the order and buy a bigger Broncolor power

pack. The only problem was that he could not shoot at less then f45 until we added two

additional heads to split the output and put those two extra heads in a close closet.

 

That was a very expensive lesson for the photographer.

Watts per second would be the rate of change of wattage; ie the slope. Seeing W/s written in threads about flashes to an EE is like fingers on the chaulkboard; one just looks for other technical errors. Its like saying one shot at F8 millimeters; used an fstop of 1/30 second; one developed film in Hypo; Printed on B&W Kodachrome paper; or ones car gets 30 gallon miles. <BR><BR>Watt-seconds has been used with strobes since the beginning. One has a bank of caps at XYZ capacitance; running at a ABC voltage. The caps may have nominal numbers; one measures are the DC voltage and tries not to get zapped. the Joules=watt seconds= 1/2 C V**2.<BR><BR>There are losses in trigger circuit; caps; wiring; alot as darn heat in the flash tube. Then there is the reflectors; or maybe its a bare bulb like on a my strobotac unit. <BR><BR>Thus the conversion of watt seconds to usable light is murky; sort of like cubic inches in gas engines to horsepower. <BR><BR>Both a 400cc gas motor or a 400 watt second flash can have a wide range of outputs.

Thank you for your answers, I like to know exactly what the things are.

 

And I agree, when the manufacturers of these flash feeders talk in terms of w/s, I think they

aren't talking in the proper terms, at least as a maximun load. I guess a small flash with fast

rechargue should generate a high load than a bigger one with slow rechargue.

But as far as I know, no flash manufacturer says the peak current load in the specifications,

so maybe the w/s as a aproximate calculation is the best they can say.

" so maybe the w/s as a aproximate calculation is the best they can say."

 

Most professional flash manufacturers give you ECPS/BCPS or a guide number. Makers

trying to hide the power of their flash systems give you watt seconds as a power

measurement.

 

We have sold flash units that fired at 1/10,000 of a second at recycle times of less then 2

seconds (to greater then 100% of full charge) as well as flash systems capable of lighting

most of 1/2 of a professional hockey arena from 100' in the air at f8 over the entire

illuminated area with recycle times under 5 seconds.

 

It is the technology and the purpose that determine the specifications. But if you need

fast and true recycle times with power with UV correction, etc. it will not be cheap. One

unit we sold featured continuously variable flash duration and continuously variable

power output with absolutely proportional modeling lights. So proportional that the flash

exposure could be determined at any output with a standard exposure meter by reading

the modeling light only.

 

But boy was it expensive in the 1970s.

" so maybe the w/s as a aproximate calculation is the best they can say."

 

Sorry, I think I didn't explain very well there, I was talking about the flash feeder systems

and the announced max flash power you can plug. They talk about w/s when I think this

could vary a lot according to the type of flash and recharguing speeds. Maybe they should

talk about peak loads, but then is when you won't know your flash system peak load...

All you need to know is the output. For a flash the output is expressed as ECPS, BCPS, guide

number or an actual f stop. All of these are given at a specific angle of coverage and, in the

case of an f stop, at a specific distance. All of these can easily be converted from one to

another.

 

A watt second rating can not be converted to an output unless you know the technical

specification of the system. The formula is complicated and would require knowledge of

specs of the flash that no manufacturer gives.

For the sake of posterity:

 

I eventually rented two Flash Feeder Compact Units, from The Flash Centre, London. A

brief comment for anyone interested:

 

Really nice build quality, very sensible design, and generally very user-friendly, in that

they have no memory effect, can be charged off a car battery etc. These are the positives.

 

The negatives are that I found capacity limited. One Flash feeder did not like running two

Profoto 2400ws pack at all! - Got maybe ten pops at full power, despite having it

connected to a car battery during use. When connecting one Profoto to a Flash Feeder

Compact, and a Bowens Quad pack which was also 2400ws power to the second Flash

Feeder Compact, I got approx 15 pops at full power for the Profoto, and somewhat more

(20 - 25) for the Bowens pack. So it likes Bowens better than Profoto. I also found that the

Flash Feeder Compacts seemed to work well with the 2400ws packs turned down to half

power, again doing better with the Bowens than the Profoto. However, I generally found

my Bowens monobloc 750 ws Gemini Esprits gave many more pops from their travelite

battery than the Flash Feeder provided - which would beg questions about why you would

buy a Flash Feeder to do what something like a Travelite battery can do much better for a

lot less money.

 

Another note about the Flash Feeder Compacts - they were heavy - at over 20 kgs each.

 

Given how little information there seems to be about these units on the net, I felt obliged

to pass on some notes on my experience.

<p>I remembered this thread, <br>

if its useful for someone, I have an innovatronix explorer XT from some months now. I haven't used it too much, but I think it's a good value for the money.<br>

To test the capacity, I plugged a total of 3000 w/s (elinchrom universal 1500+750+750) and it worked, though with a slow recharging time, not very practical with that load if you need a lot of shooting, but if it's just a few shots and you can go with the slow recharging, it works. Anyway, at least with my type of flashes, I think is more to plug just 1 flash per unit.<br>

As for the number of shots, in a job few weeks ago, I get around 120 shots with 1 elinchrom universal 750 w/s at full power before the unit shut off, with a recharge time about 3-4 sec, and a total time working of 1:45 hours.</p>

 

<p>If it shut itself off then it is probably overheating and as you are not shooting rapidly there is probably something in the output of that inverter that your flash does not like. Be careful!</p>