Although they are both lead/acid cells, accumulator cells in portable flash units are not the same as car batteries. The invertor units in self contained systems will also be 'matched' to the job and only step up the voltage one time.

You are right the capacitor charging system may not like the output of the invertor. You could try a conditioning choke in series with its output. This would not loose any voltage (unlike a lamp) but round off the square wave to more like a sine wave.

I assume your needs would be served by something like this.

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

You might also find the data on this american site of interest

http://www.repairfaq.org/sam/strbfaq.htm#strdefb

 

yes, that's something which would work, but I don't think they are under $1k
do you have a schematic/diagram for a conditioning choke circuit?

 

Turning on a cold photoflash unit with a transistor oscillator is for all intent and purpose a dead short, until the main capacitor is about half charged, when the oscillator goes supersonic, they do draw a respectable current at the start.

Do your flash units operate with a thyristor that controls the cutoff of the flash [ pulse length ] based on light feedback, or do they dump the whole main cap per burst, and start over each time ?

 

http://www.thomasnet.com/products/chokes-power-line-14020986-1.html

This seems to be a US trade directory.

I suggest looking in radio amateur fairs etc for some beefy mains chokes. Alternatively you could experiment with the primary of a mains transformer. A 1:1 unit would have a better waveshape appearing on the secondary.

 

I don't really understand your question... the flashes charges again each time, even if I use only 20% of flash power, but the charge is much faster...
a full power charge takes 1,3seconds and 50% flash power takes 0,65s

 

It has also occurred to me that the choke or ballast unit out of an old flourescent light fitting might be just right for your purposes. These are used to slow down the inrush current at first switch on. You should obviously not use the starter capacitor though.

 

It has also occurred to me that the choke or ballast unit out of an old flourescent light fitting might be just right for your purposes. These are used to slow down the inrush current at first switch on. You should obviously not use the starter capacitor though.

I don't have an old fluorescent light, but I will buy a small cheap new one, it is important the power of the fluorescent light ? Also how I must connect it ? inline ?

 

You might try just an isolation transformer. Basically, they have a 1:1 turns ratio on the primary and secondary, with a suitable power rating. The transformer would be a pretty good filter, too.

Trying to adapt a flourescent ballast transformer would be problematic. What StudioT has in mind may not be available in your area. Besides, why try to adapt something that was made for a different purpose, when you can buy the right item in the first place?

 

Now I'm confused, you say that I should try with light bulbs and that the fluorescent ballast transformer does not work, studiot says that the light bulbs may not work and to try the ballast transformer...
I will buy the right item when I will have $5k to invest in two professional portable flashes, but right now I have spent 11000euros in photographic equipment and I have decided to not invest anymore until I will earn some money from it.
I got these two flashes with $1k which was reasonable for me as a starting point, but I like outdoor photography and I have beautiful models.

 

Now I'm confused, you say that I should try with light bulbs and that the fluorescent ballast transformer does not work, studiot says that the light bulbs may not work and to try the ballast transformer...

The problem you are experiencing is due to excessive surge current.

Light bulbs are a somewhat crude approach to a solution, however they are cheap. They have an initial "surge current" themselves, until the filaments become heated; whereupon they have a much higher resistance than they did when they were cold. As they cool off, their resistance again decreases. This is a rather unique characteristic for such an inexpensive solution. See the attached conceptual schematic. The wattage of the bulbs is to be determined by experimentation. The lower the wattage, the less the instantaneous load on the UPS.

Try four 100W incandescent bulbs to start. If that still trips your overload, start swapping the 100W bulbs one at a time for 60W bulbs. If it doesn't trip with four 100W bulbs, try increasing their wattage, one at a time.

When you find the highest wattage bulbs that won't cause the UPS to trip at any reasonable battery level (12.7v down to 11.5v), then you will have found the most efficient spot for this somewhat inefficient adaptation.

I will buy the right item when I will have $5k to invest in two professional portable flashes, but right now I have spent 11000euros in photographic equipment and I have decided to not invest anymore until I will earn some money from it.

I can't disagree with you there. It will take you quite a few commissions in order to recoup your investment. I sincerely wish you good luck with that.

I got these two flashes with $1k which was reasonable for me as a starting point, but I like outdoor photography and I have beautiful models.

I demand proof. Send me a link offlist to where you've hosted the photos.

An isolation transformer or choke would be much more efficient, but the lightbulb experiment will give you valuable insight as to how much current your UPS can take before it triggers. Besides, cheap-but-effective is not a bad place to be at the moment.

 

I demand proof. Send me a link offlist to where you've hosted the photos.

An isolation transformer or choke would be much more efficient, but the lightbulb experiment will give you valuable insight as to how much current your UPS can take before it triggers. Besides, cheap-but-effective is not a bad place to be at the moment.

Thanks for the diagram, tomorrow I will try to experiment.
my website http://www.MarioMercea.com is under construction, but if you want to see some photos then give me an e-mail address.

 

The problem you are experiencing is due to excessive surge current.

Light bulbs are a somewhat crude approach to a solution, however they are cheap. They have an initial "surge current" themselves, until the filaments become heated; whereupon they have a much higher resistance than they did when they were cold. As they cool off, their resistance again decreases. This is a rather unique characteristic for such an inexpensive solution. See the attached conceptual schematic. The wattage of the bulbs is to be determined by experimentation. The lower the wattage, the less the instantaneous load on the UPS.

Try four 100W incandescent bulbs to start. If that still trips your overload, start swapping the 100W bulbs one at a time for 60W bulbs. If it doesn't trip with four 100W bulbs, try increasing their wattage, one at a time.

When you find the highest wattage bulbs that won't cause the UPS to trip at any reasonable battery level (12.7v down to 11.5v), then you will have found the most efficient spot for this somewhat inefficient adaptation.


I can't disagree with you there. It will take you quite a few commissions in order to recoup your investment. I sincerely wish you good luck with that.

I demand proof. Send me a link offlist to where you've hosted the photos.

An isolation transformer or choke would be much more efficient, but the lightbulb experiment will give you valuable insight as to how much current your UPS can take before it triggers. Besides, cheap-but-effective is not a bad place to be at the moment.

Hi,
I finally tried the experiment with 4x100W bulbs and it works !
The flash is trying 3 times to charge itself, so instead of 1,5seconds it takes approx. 5 seconds, but this is ok. The bulbs are turning on after 1 second and they stay on for 2 seconds then off then on again for a much shorter period, then off again and on for less than 1 second and then the flash is ready/charged. The light bulbs are orange when they are on, they don't glow at full power.
Now what can I do to replace the bulbs with something else much smaller and less fragile, to slow down the power draw?

Thanks !

 

I have tried again with 3x100W bulbs and it works, but the flash charges somewhat slower, in approx. 8 seconds and with 2x100W bulbs after 15 seconds I get an error on the flash display and it does not charges.

 

OK, so we're narrowing down what the UPS can supply vs what your flash requires.

When the four bulbs glowing orange, they were limiting the current to your flash by their higher resistance. I don't know why your flash cycled power several times; perhaps it was getting warm due to the lower amount of current available. What would be most helpful is to know what the voltage across the bulbs vs the voltage output of the UPS is when the flash is charging. This voltage may change rapidly as the flash charges.

When you removed a bulb leaving just three, you further limited the current available to the flash, which is why it took longer to charge. The bulbs would've been brighter, too.

When you got down to two bulbs, they must've been significantly brighter than with three or four bulbs. The brighter the bulbs get, the more resistance they have, so the more voltage they drop across themselves, leaving less voltage for the flash.

Are you following me?

 

yes, but now I have only 3 bulbs left, as I have destroyed one when I used the soldering iron on the middle contact.

 

Yikes! Soldering directly to a bulb?? I meant for you to use bulb sockets! I should have explained that more completely. I had no idea that you might attempt something like that.

 

the sockets are too expensive just for this experiment
I did a good job just with the wires soldered I have a fire extinctor in case of fire

 

Sockets from the hardware store are around $1 each, the base type that will bolt into hardwood. I've used similar to make a light tree. Plus, if a bulb burns out makes replacement a snap.

Solder isn't desirable around current for other reasons too. Basically it's not safe. Much better to build a cheap box for under $10 (which is worth under 5 pounds?).

 

I really had absolutely no clue that you were so inexperienced, and I blame this on myself, for a poor evaluation of your experience with high voltage/high power electricity.

I'm very glad that you are still alive. This "little experiment" could easily have cost you most dearly.

Bill Marden's correct - sockets for lamps are quite inexpensive - at least here in the States. We can purchase bulb sockets from $0.50 to $3.00 each. Bulbs are about the same.

You can't solder on light bulbs. They will eventually burn out, or break; much sooner if you solder wires to them.

I am not familiar with what is available in your country. Replacement lamp sockets might be an option, if you can obtain them for a reasonable price.

 

I have enough experience with electric/electronic devices, as this is one of my hobbies for the last 15 years, so don't worry, really what can happen if I have positioned the bulbs with distance from each other and placed on a non conductive matt, and when I have plugged the bulbs I was 2 meters away from them.
4 sockets would cost me here $15, for just 1 minute experiment and then throw them away it wasn't worth.