Power supply for studio lights

[surenj]

I am sure this has been explored before But I had an idea...

Could you power a small studio kit; For example the Golden Eagle 3 light kit by using your car lighter with an inverter??? Would this be enough to overpower daylight or at dusk??

This could expand one's possiblities??

[who]

You could - but would want better wiring I expect.

Have you got the kit? Can you advise what the rated wattage of the whole assembly is per light (ie globe wattage + other power usage).

Are these constantly on, or a flash?

If - they are rated at 240V 150 watts - you would need to supply about 12 Amps at 12.8V per light - so for 3 lights - you are looking at 36 Amps - well beyond a cigarette lighter, but not necessarily beyond a 12 volt battery solution.

You also need to consider battery size and capacity, a small car battery wouldn't last that long, and the alternative is to have the car running -- above idle, prob about 1400-1800rpm to have the alternator charging at a suitable rate.

You would have to consider a number of factors, but it could be done relatively easily I reckon.....

I have some experience with 12volt vehicle power systems from a camping/4wding background & iunverters..... but not with studio lights.

But - if you don't have all the gear to start with, you might find it cheaper to buy a good quality small & quiet gennie?

[Mr Darcy]

With a couple of extra points.
Just look at Watts.
Add up the wattage on your lights. (Power in not Power out) FInd an inverter that will handle this with about 15% margin to allow for errors in calculation.
Next look at the battery Power = Amps X Volts so a Car battery rated at 50Ah will supply 12x50 = 600W for about an hour (and leave your battery dead and probably damaged!)
Car batteries are designed for high current bursts, not continuous discharge. The will often be damaged by this type of load. So you need a different type of battery, generally called a "deep cycle" battery. These are designed to supply a smaller current over a longer time, and be able to recover better from flat

The third thing to look at is the wiring. Cigarette lighters are designed to power a cigarette lighter. They usually have quite small wiring (=low power) going to them. Your car manual may tell you. YOu will almost certainly need to replace the wiring, or, better, run a separate circuit to the inverter. The simplest way to do this is pop the bonnet & connect the inverter directly to the battery with heavy duty alligator clips. It would be better to screw connect through a terminal block though.

The way I have resolved these issues in my car is to install a second battery. This is a deep cycle type. I have separate dedicated wiring to the inverter. That is then wired to a standard 240V outlet in the back. I use a simple pushbutton/Relay setup to connect the second battery to the car's charging circuit at need. There are automatic systems, but I couldn't justify the cost given how often I use it. The way I use it, I press a momentary action button that fires the relay after the car has been running for a while to charge the main battery. The relay puts the second battery parallel with the main one in the circuit, and holds the connection till the car is switched off. Then it reverts to a completely isolated system.

[surenj]

Have you got the kit? Can you advise what the rated wattage of the whole assembly is per light (ie globe wattage + other power usage).

Are these constantly on, or a flash?

If - they are rated at 240V 150 watts - you would need to supply about 12 Amps at 12.8V per light - so for 3 lights - you are looking at 36 Amps - well beyond a cigarette lighter, but not necessarily beyond a 12 volt battery solution.

Thanks for the quick reply.
I haven't got the kit but they are 180W X 3 lights. They are flash lights. Check out this thread...

http://www.dslrusers.com/viewtopic.php?f=49&t=29467&p=349668&hilit=golden+eagle#p349668

[who]

Being flash lights will help a lot - depending on how heavily you use them - the load will not be as bad as constantly on lights I guess.

Mr Darcy raises a lot of good points - I disagree about the statement that car batteries don't handle this usage well & that a deep cycle is required.

That is not my experience with dual battery systems in my 4wd -- I used 2 Calcuim starting batteries for about 5 years - one died, one is still the aux battery....... the start battery is now an Exide Extreme.

I would state that the larger the battery the better & that depending on the amoutn you use it and how portable you require I would perhaps suggest a good 3 stage 240 volt battery charger (C-Tek is a brand name I hear a lot of), a plastic marine battery box & a large battery - a 80 or 90AH Exide Extreme 4WD battery.

This is instead of wiring it into your car & alternator -- which incidentally generally will only charge a battery to maybe 85% of total capacity.

Obviously can only be charged at home and would weigh at a guess maybe 30kg to lug around, but could be used away fromt he car with an inverter etc -- consider buying a small hand trolley or similar.

It's a shame you don't live near me -- I have nearly all the gear to do this but for a set of the studio lights -- I have the batteries, the inverter (mine is about 350watt, but could test 1 or 2 lights), cabling galore......

[Mr Darcy]

Mr Darcy raises a lot of good points - I disagree about the statement that car batteries don't handle this usage well & that a deep cycle is required.

This was based on (a) Scuttlebutt and (b) the first second battery (does that make sense?) I used. It was identical to my primary at the time as I was thinking it would also double up as an emergency jump-start if needed. I ran it flat running a car fridge about a month after I bought it & it never really recovered. My next battery was a deep cycle & it is still going (just) 8 years later. I have jump started and run it flat several times in the period.

[surenj]

Thank Mr Darcy and Who.

The idea was to overpower sunlight with the studio lights however it looks like it can be done with speedlights on location?? Because this would provide more portability and less hassle in terms of cabling etc...I have seen a few photos o the strobist flickr group that may suggest this is possible. Have to investigate.

[zafra52]

How good it the Golden Eagle 3 light kit? I am thinking of getting a small lighting set for a reasonable price.

[surenj]

How good it the Golden Eagle 3 light kit? I am thinking of getting a small lighting set for a reasonable price.

I don't own the Golden Eagle. Not sure Zafra but the general consensus seems to be good with the exeption of replacing the bulbs when they blow. It appears that they are exeedingly hard to find the required globes. I think the set is really good value for a 3 light set. I am not sure whether it's enough to overpower sun light during midday for example.

[surenj]

I thought I might rekindle this thread.

Zafra, I now own the Golden eagle and it's really good for my amateur/experiment type of needs. I have used it for about 8 months without any issues. The softboxes are smallish and I am not sure whether these are 'bowen' type mount or not. So I am not sure whether you can add any light modifiers to the set but it comes with enough to get you started. [warning: you will start wanting beauty dishes and the like really quickly]

Mr Darcy and who,

I have found a cheap 350W inverter that may or may not do the job.
http://cgi.ebay.com.au/350W-DC-12V-to-AC-230V-POWER-INVERTER-FOR-CAR-BOAT_W0QQitemZ390052876888QQcmdZViewItemQQptZAU_Car_Parts_Accessories?hash=item5ad0f69258&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A15|39%3A1|240%3A1318|301%3A0|293%3A2|294%3A50

I am not really keen on modifying my car. It's got a standard small car NRMA battery.

I will not use the modelling lights. I will probably use two strobes at 150W or so. Nearly full power. There will be few seconds gap [strobes will recharge slowly] in between shots. I wouldn't shoot for more than 1/2 hour at a time. Maybe 100 shots or so.

Do you think I will need to do anymore than buy the inverter? [ie modify wiring, second battery, deep cycle battery etc]

[photoaffinity]

a very important thing to note is that a studio strobe is basically a big capacitor. inverters generally don't like this kind of load, it basically presents a short circuit to the supply for a very short time, and this can cause all sorts of havoc.

You will need a sine wave inverter to do this properly, otherwise you will end up cooking the inverter and/or the capacitors in your lights very quickly.

here's a pdf from jaycar/electus that might help explain it, look at the section for florescent lights: http://www.electusdistribution.com.au/i ... verter.pdf

HTH

Jon

[Mr Darcy]

That is one CHEAP price
My brother was in ALDI the other day and saw one for $69 which I thought was cheap too, but not compared to this. When I bought my first inverter, the going rate was $1/W the second one I bought at $0.5/W. They seem to be geting cheaper and cheaper.

Do you think I will need to do anymore than buy the inverter? [ie modify wiring, second battery, deep cycle battery etc]

This depends.If you connect straight to battery, you won't need to worry about anything. Except flattening the battery of course
If you plug in to the cigarette lighter, you may need to upgrade the wiring to it and/or upgrade the fuse. If you the inverter is running at full power, you would need a 30A fuse.Assuming 350W is the INPUT power.
All electrical devices have two power ratings: an input rating (How much electricity it uses) and an output rating (how much "work" it does) The difference is a measure of the efficiency of the device. Unfortunately, the manufacturers are generally very poor at stating both, and even poorer at saying which they are using. It is a fairly safe bet that they use the one which makes the device look best.

To work out whether your car battery will do the job, you need to check the INPUT power of your flash system. It will be much lower than 150W as this is almost certainly the output power in this case, and delivered in a 1/1000 sec burst. The recharge will take longer and therefore spread that power over a greater period. (say 3 sec so maybe as little as 10W on the input side). Once you have that number, multiply it by 100 ( the number of flashes you say you will be using), and compare it to the rating of the battery. It is simpler to "suck it and see" i.e. try it in practice & see if you can still start the car when you have finished. I'd have a spare battery on hand, or a mate's car & a set of jumper leads in case you can't.