ChauvetDJ Geyser P7 fog machine/light issues

[Ravenbar]

THe school I work with just bough a pair of ChauvbetDJ Geyser P7's and borrowed another that's a couple years old from another school.

During tonight's rehearsal, the borrowed machine started having a very limited discharge time. It's being uses withing a scenic element, the bridge scene from Shrek over the lake of molten lave, being pushed by skeletons across in front of the curtain. Power source for this and the alter scene are Ryobi multiple 40v inverter packs, putting out over 2k watts(fog machine draws 1300w.)

I did some testing after the rehearsal, and found the machine in question would put out 8 seconds of fog, before shutting down back into a reheat state, so the limitation is the heating elements ability to remain hot enough to generate fog for that long. I did test one of the new machines, and it didn't seem to generate fog for much more time than the borrowed machine. I suggested intermittent firing, via the remote,

 

[TimMc]

Current demand from the heater after the first few seconds is exceeding the inverter's current capability. Repeat the test and watch the batteries/inverter.

 

[almorton]

We had exactly this problem recently. 3kW inverter was having problems with a 2 1/2 kW fogger because when the heater came in the inverter was derating to something like 60% output. Switching to a lower power fogger solved it. We were using substantial leisure batteries - think small truck sized - but the problem lay in the inverter power limiting.

 

[Ravenbar]

Current demand from the heater after the first few seconds is exceeding the inverter's current capability. Repeat the test and watch the batteries/inverter.

My tests were conducted plugged into the wall.

We had exactly this problem recently. 3kW inverter was having problems with a 2 1/2 kW fogger because when the heater came in the inverter was derating to something like 60% output. Switching to a lower power fogger solved it. We were using substantial leisure batteries - think small truck sized - but the problem lay in the inverter power limiting.

The battery pack being used used (4) 40v Ryobi batteries. These packs(the bought a couple), are rated to 2800w, and load is 1300w, so it would have to derate to ~40% to go below the power needed.

My postshow testing was plugged into the wall, so not a battery issue.

 

[TimMc]

Then it's time to call Chauvet.

 

[almorton]

, are rated to 2800w, and load is 1300w

Peak or continuous rating? i.e. is the battery rated to supply 2800W continuously? Battery capacity drops as you approach maximum load, even for modern high density batteries. But yeah, contact Chauvet.

 

[Ravenbar]

Peak or continuous rating? i.e. is the battery rated to supply 2800W continuously? Battery capacity drops as you approach maximum load, even for modern high density batteries. But yeah, contact Chauvet.

Not sure, as that's not my area. The set guy/school superintendent is the one who purchased them. From looking on Home Depot's site, they look to be these:https://www.homedepot.com/p/RYOBI-4...-4-Port-Charger-Tool-Only-RYi1802BT/314809255 , which have an 1800w running and 3000w starting ratings, and they've been equipped with 4 of the 5Ah batteries each.

 

[almorton]

So that's 3kW instantaneous but not sustained. A 5Ah battery is usually the 10 hour rate so is specified to deliver 500mA continuously (for 10 hours). At 5A you'll usually get a lot less than one hour running time. As you indra increase the load the run time derates, although it depends on the battery chemistry  how it derates

The smallest batteries we use for small LED fixtures are 7Ah gel acid. But our "standard" size is 14Ah and these are about 7" x 3" x 3" the one that struggled with the fogger (we had a pair of them load balancing) were the size of truck batteries and were 130Ah I think.

But that all said, your wall socket tests do suggest that even with enough power the fixture itself was the limitation.