Paul C. Buff, Inc. Technical Forum

I was on a remote shoot at a booth today for about 7 hours.

Had the Einsteins set at 1/16 power.
For the entire day (7 hours) I had under 500 shots... but the Vagabond Minis were down to the 1/4 light by shot 350-400 so I'm pretty sure they were close to done.


Now, I was a moron and packed up the batteries the night before. So I'm lucky they lasted as well as they did. :oops: (I have read the other posts about the expected drain over night).

But made me wonder if anyone else has experience in using these with Einsteins for extended ful-day use...

With the fans and other electronics (back display, etc...) running continuously in the Einsteins, does this draw any significant power from the Vagabond Minis?

I had powered off the strobes when not in use for this event, but was wonder if this would have any significant impact on how long the minis would last.

If someone was not an idiot, and left the batteries charging up to only a few hours before the event like they were supposed to, should this someone still expect near the 500 full power flashes from an Einstein on a VML over the course of a seven hour event?

Or is it best to power off the Einsteins whenever not in use so that the ancillary electronics do not cause continuous draw throughout the day?


Thanks

The VML battery will hold its charge overnight or for an extended period of time if it isn't in use. The previous posts referred to people who had left the VML turned on overnight.

The inverter in the VML slowly drains the battery so if it's left on it will eventually run down even if no strobes are ever fired using it. The VML fan also drains the battery.

The Einstein does also drain the battery just by being turned on and plugged in.

So there's no need to charge the battery right up to the point of using it. But it would help if you turn both the Einstein and the VML off if you won't be using them for a while.

Just because you were down to 1/4 power doesn't mean you couldn't get lots more shots from the battery. It's designed to work well right up to the end.

If you'll be on 7 hour remote shoots routinely it'd probably be best to have an extra battery for each VML.

Were your model lamps off? 1/16 power on the model lamp would be about 7 hours (for one lamp). Also, the fuel guage is only guranteed to be accurate under no load (i.e. no lights plugged in or on). It will read lower when in use.

Any Vagabond can easily handle sitting charged overnight off the charger. The Vagabond Mini will retain its charge for months off the charger, and will not sulfate.

Hmm, in that case I am worried they are not lasting as long as they should.
Both of the VML's were powered off.
I did not use modeling lights at all. I ensured they were off prior to packing up the strobes the night before.

I would have expected a much longer session at 1/16th power. I tried to extend the life by turning off the Einsteins after use. Would this actually have caused excessive drain on the batteries, rather than leaving them in stable state when not in use?


If 500 full power shots is expected on a full charge, would it normally be safe to assume 8000 shots at 1/16th power? (under "perfect" conditions of course). :-) I was only hoping for well over 1000.

I know the power gauges of any battery are not 100% accurate, but I do not believe they would have been capable of firing several thousand additional shots on the last 1/4 remaining battery power. (Maybe they would?? Its my first time using them so I really don't know what to expect yet.)

Does the experience I had with these sound like an expected one?

I don't have a problem buying more batteries, but if I'm only getting 1/10 the number of expected shots, or less, it doesn't seem like that would be a wise investment.

Thanks!

amoringello,

The charge-to-charge capacity of the VML battery is at least partially dependent upon the ambient temperature when the battery is being used. The hotter the battery gets, the less stored energy you will get from it.
Keep in mind also that the Einstein units consume about 9 Watts when idling, and about 4 Watts when inactive but connected to a power source. For a single Einstein, that means about 28 Watt hours in a 7-hour day even if the unit is not active. Given the efficiency of the inverter, the VML battery delivers just over 110 Watt hours of net power. When you "guesstimate" your power budget, be sure to include the standby power of the Einstein(s) in you calculations. Also keep in mind that the published number of full power shots actually measured when using the VML with Einstein or any other light is obtained by firing the lights continuously from the intial shot with a fully charged battery at a rate that is normally three frames per minute or four frames per minute, totalized until the battery protection circuitry shuts the battery down. The numbers are accurate, but only in terms of the highly contrived circumstances of the test procedure.
Also, the VML inverter will not slowly discharge the battery if the power switch is turned off. The lithium ion battery chemistry does, however, exhibit a higher self-discharge rate than most other battery chemistries, especially when fully charged and then operated at or in an elevated temperature. I'm not implying this is the case for you, but you should be aware of it.

Super. Thanks, that helps a bit.
So out of a possible 130 watt hours, lets say 30 were used just by the lamps being idle.
Of course, I had them powered off perhaps 20% of the day.
Still, lets go with the worst case scenario and put this at 25% of the battery used just to power the idle strobes.

So with 75% of the battery left I should get about 6000 shots at 1/16 power. (500 @ 1:1, 100
1:2, 2000 @ 1:4, 4000 @ 1:8, 8000 @ 1:16) 8000 * .75 == 6000
That is under perfect conditions of course, as you mention. I get this.

So, over an extended period of time, would one expect to get only 500+ shots instead of several thousand?

The batteries were on the 1/4 power light for about 100-200 shots, so lets say the light was still nearer 1/2 power to give a wide benefit of the doubt.

Would 1000 shots v.s. 6000 be a normal expected value over an extended period of time for this setup?

I've got another long shoot in a few weeks, and just need to try to determine how many batteries to get. Or if the behavior I am seeing is normal.

FYI, last week it was 45-55 degrees most of the day (yeah, cold long day).
Next shoot will be indoors so probably nearer 75 degrees, so I suspect slightly shorter expected life.

I would of course err on the side of being conservative for this application. Still, I would certainly expect to get more than 500 shots when using a new, fully charged battery and a single Einstein! I am going to research this in more depth, as you certainly have aroused my curiosity. If you will give me an average frame rate per hour, I will repeat your setup as nearly as I can here in the lab, and get some answers for you. Are you using a new VML and new battery, or do you have a hundred or more charge-recharge cycles on the battery in question? Are you shutting down the VML between shots, or simply turning the Einstein(s) off? Any additional information will help me help you.
I'll close for now by thanking you for using our products, and I will find an answer for you!

I have the following information...
10:00 - 10:15 (15 minutes) 45 shots
10:50 - 11:10 (20 minutes) 40 shots
11:50 - 11:55 (5 minutes) 30 shots
12:20 - 1:20 (1 hour) 140 shots
1:45 - 1:55 (10 minutes) 60 shots
2:40 - 2:50 (10 minutes) 50 shots
3:30 - 3:45 (15 minutes) 75 shots

I guess that a about 72 shots per hour. (435 shots total, 1/16 power, bettery's 1/4 light noticed at about 1:30-2pm)
Now between these long periods, I generally turned off the strobes about five minutes after no one showed up. So they were probably powered down 10 to 30 minutes in between most of these sets.

Hope that helps.

Oops, forgot to include, the VML are brand new.
I had charged them once overnight, and did some test shots at home.
They were then left plugged in and charging probably for about a week before the event.

Not very good math here. S Engineering stated, E640 draws about 9 watts when on but idle, and about 4 watts when off. So 9W times 80% times 7 hours = 50 watt hours, and 4 X 7hours x 20% adds 5.6 watt hours. Also, the inverter itself probably adds another 20-30 watt hours over 7 hours when turned and not connected to anything.

So 80 WH or so of the potential 110 watt hours was used in seven hours without taking a single shot, leaving only about 30WH for actual shooting. If 400 shots took the indicator down to 1/4 that means 3/4 of the power fired 400 shots and the math says the battery would be depleted at 533 shots. Had you done he shoot over a 1 hour period you would likely have gotten around 500 shots at 1/16 power.

All of this assumes the numbers you and Engineering were accurate and that you didn't leave the inverter turned off the night before. Everything stated here was "approximately".

Also, everything stated here applies equally to all other battery packs (including Profoto, Innovatronix, etc, except that the other systems use SLA batteries that deliver only about 1/2 their capacity to the load, so you could expect to see about fewer pops per charge, relative to VML, at a given WS setting on the light(s).

Finally, your original posts refers to "Einsteins" implying your were using more than one Einstein. If you were using two Einsteins, the quiescent draw would be double that stated above and would indicate the quiescent draw would use the entire capacity of the VML in around 7 hours with no shots taken.

Please see http://www.robgalbraith.com/bins/multi_ ... 1314-11226 for comparison to other battery packs.

Finally, in any number of VML tests taken by myself, my staff and by Rob Galbraith, at 640WS power and one shot per 10 seconds using PW Intervalometer, One Einstein 640 consistently produced 460 shots per charge and one AB1600 at 640 WS produced 550 shots. The difference is that AB draws less idle current than E640.