Battery powered fixtures, take two


I have a director who would like three moveable fixtures on deck. Something like an ETC S4 ellipsoidal on a rolling spotlight base, with the fixture at chest height. My job is power.

I have a few inverter/battery setups in mind, but can anyone answer the following?

- What amperage for a ETC S4 Ellips. running at full? (ETC's site is not helping.)
- Does the Shakespeare actually run on DC as well as AC, as their spec sheet tells me? Meaning, could I rent Shakespeares and skip the inverter? Or am I missing something?

I am concerned about cost. The higher the amperage, the more these parts are going to cost me. Does anyone have a suggestion for a fixture that looks pretty good at around 65% and has a relatively low amerage requirement?
I'll probably be running three 575w fixtures at 375w for no more than 30 minutes a show, for a run of, say, 10 shows. If each fixture pulls two amps per hour (I'm guesstimating here) that would mean one amp so so per show.

Now, if I set up three lights on batterys with 12 amp hours, does anyone think that, by the last show, the light would be signifigantly dimmer? I'm not certain about how effective a battery with two ah left on it would be.

Another idea would be a dimmer on the unit, rather than a switch, and we could regulate the power draw a little more. Plus, more flexibility! And more money...

I've thought a little about the cord and track... this director is just getting started and, given my past experience with him, I see where he is trying alot of new things and I'd like to offer him a lot of flexibility. He understands, though, that he will have to balance cash vs flexibility. I also think he is imagining a lot of free form running about with these fixtures, crossing paths and doubling back on stage, and I don't think he would go for tracks and cables in the end.
I'm not really sure why everyone this site it hooking batteries up to fixtures but hey what ever floats your boat. :lol:

Why not try a few car batteries. :)
There was something about that last post that was extremly amusing to me.... maybe i am just strange lol
A lamp needs current to warm it's filament. It does not care if it's alternating current or direct current. As long as you have voltage sufficient to run the lamp, it's not going to care if it's AC or DC. There are some filament notching issues on the subject of DC current and your halogen effect might not work sufficiently to extend the life of the lamp (buy extra because the lamps are more likely to blow given their high output and temperature in this condition). Otherwise, running a light off a battery should be just fine. If you can dim it, I would recommend starting it on a low dimmer setting if not starting it before the show and leaving it powered up and on a low dimmer setting thru the show so as to ensure both the filament is warm and if it's going to blow it's more likely that would be during start up. Sort of a soft start to it.

Osram makes a HPL lamp that is 550w/64v, it's part number 54813. Otherwise the rest of the dimmer duplexing lamps operate at 77v. Voltages available are 64, 77, 100, 115, 120, 230, 240 on HPL lamps currently. As long as you can get into the range of the desired voltage such as five batteries at 60v, than you should have sufficient light output with some color correction. Since the wattage is over what you desired you would have to compensate for that in amp hours, but it would be a brighter beam of light which would compensate for the gel thus your lamps can either be dimmed or as intense given the color media in front of it. /Unfortunately at this time there is no dimmer duplexing lower voltage lamps available for the Altman line of fixture so the best you could do would be a 115v lamp on a 120v circuit. There is also yet to be introduced a 375w lamp in the dimmer duplexing range of voltage.

Use of these lower voltage lamps especially the 64v one would allow less voltage on a battery thus a cost savings in both materials and amp hours. The lower voltage lamps under battery might also not have as much a problem with the DC current where filament notching is in effect also. (Basically the current from one direction wears away at the filament from the direction faster under DC current than AC current.)

Yes, by the end of the run, if you did not re-charge the batteries they would grow progressively dimmer. That voltage from a battery starts from the moment you plug it in and every hour used it gets dimmer. It's like a flash light, you don't notice it's getting dimmer but it is every minute it's on it does. I would recommend buying batteries that are sufficient for the expected usage plus about half to double than re-charging them every night. This would assure your intensity is constant every night and the same. It would also be cheaper to do.

Otherwise I believe if the last conversation on the subject was here, there were other options for power transfer on a moving surface given line voltage on a rotating platform, if not just enough cable to twist as needed or manually fed and twisted as it rotates. This might be a good idea to look back at since teaming together a bunch of batteries to boost their voltage could be considered very dangerous to be around, not to mention that you than need to hide the batteries.

Be very careful about safety on such a thing because a screw driver thrown across a car battery will arc and weld if not start a fire. Such things are very dangerous and if possible especially even at 60v, much less 120v attempt if at all possible to figure something else out. In addition to all of that, be sure to compensate for the extra fixture and battery weight on the turn table.

The lower the voltage you go with the more safe the feature and more cost effective it will be. If you go battery, I would give serious effort to the lower voltage lamps, also given the lower voltage that dimming with battery power will be much easier to compensate for.

When it's done, be sure and write up a paper for us on what you did and how it worked out. Such things are of interest to note and log for others in the future. Detailed information if not even pictures are very helpful. Just remember if not safe for others to use don't do it much less post it. Be careful. I get paid to do such things after years in the industry and an open budget for parts. If in doubt on doing it safely or on the cheap, don't. Otherwise hire a professional to do this for you. There is no excuse for ego over common sense and liability when it comes to doing things you have not done before. It very much might be more cost effective to have someone build such a thing for you and let it be on their liability insurance than your's.

Primary source for such a thing I would recommend for you is Movable Power as a company. The owner/manager knows what the heck he is doing and while expensive you would get what you pay for and he might just rent such a thing for you instead of you needing to purchase the materials that are of limited value afterwards. Otherwise there must be at least 10 lighting companies in the Chicago area with sufficient skills to construct such a thing for you. Don't know if we have time but I would probably be on the list. If your call list is in lighting companies includes where I work and my boss thinks it worth my effort I might end up constructing such a thing. Otherwise at least, Carl at Design Lab can probably construct such a thing if he still works there. DMX tools if he wanted the liability could probably also construct such a thing. Let's leave it as chance as to figuring out where I am because doing so is not something I would really look forward to much less have time for. Plus I don't do business on line.

A final option is to contact The Mayor's Office of Special events if your school is part of Chicago. Actually you will want the scene shop as contact Ralph, Jim or Jay. John Trick would be the person to talk to at the front office if you want results otherwise. A few years ago, I took apart a spinning snow man float and what ran them and the X-Mass lights was a huge one ton 120v power transfer plate possibly even having the spinner motors on them you would need for the platform. (Been a few years thus I don't remember if the motors were saved but it's likely.) The things were probably rated for at least 30 amps in load and there was at least two in good condition plus one for spare parts otherwise needing work.

Curse myself for leaving them when I left there because nobody else would know what to do with them and they were swag for the most part in being heavy and useless. Thus it might be possible that if you are in the Chicago school system you can get such power transfer plates for free, otherwise if not rent them. Ravenswood Special Events AKA, Ralph or Brian would be the contacts on rental or otherwise managing the scene shop. (Good summer work by the way, but about a month too late to apply.) In this way, you would get some huge center of your platform pivot points with 120v power transfer, and possibly more than one circuit. Sufficient to both hold some extremely heavy spinning 8' tall spinning steel framed Snow Men and light them up. I saved the parts and remember at least two such units plus one needing work, otherwise in perfect condition. I kind of doubt such things will have been thrown out. Just a thought as to the best option I would look into were I doing this. At this point, all the weight is centered and all you need to do is add floor outlets for power. Plus you could control them from the light board.

[How many amps on a 750w lamp operated at 115v even if you use a 120v rating usually given a normal 118v power source? Might want to re-check the math. A 600w load at 120v is 5 amps should be a good thing to remember. Thus any 575w lamp is going to be 5 Amps with a safety factor. The less the voltage the more the amperage thus that safety factor.]
Well, thanks for the exhaustive information. If i do make this work, I will indeed post it. I'll forge ahead with the utmost caution, as you have suggested.

And thanks for the stellar peice of info about the snow man rig... that's a great resource! It isn't, however, an option for me, since I am not a student, although I'm rather chagrined that I have come off as one! Ah well. Live and learn.
My apologies for inferring such a thing. Sometimes I forget who is who and in the beginning of the post I caught the wrong signal in I have a director. Sorry again but why not check into it anyway?

Users who are viewing this thread