There has been a revolution with battery power the past few years. Batteries have gotten smaller, lighter, more powerful, and more affordable.
One of the most useful tools available to me, as a gaffer, are "power stations." These are large watt-hour batteries with built-in DC-to-AC power inverters.
I own 4 of these 1500 watt-hour batteries. At work, I generally just call them "block batteries."
These power stations usually have multiple Edison 120-volt receptacles. They have other power options, too, like DC and USB outputs.
One of the most useful features of these batteries is the digital readout. You can see: the charge level of the battery; the output in watts; and the estimated run-time at the current load.
.jpg)
This screen shows the battery with no load. It is fully charged. There is zero output. It shows a runtime of 93 hours with the battery on but I don't know if those numbers mean anything without a load.
.jpg)
This screen show the battery with a load; a 1K Molepar. It shows an output of 897 watts. That is a lot of power. The estimated runtime is 1 hour and 30 minutes. I have found these estimated runtimes to be reasonably accurate.
It is amazing to me that I can plug in a 1200D and run it at full power for a little over an hour! That is a huge amount of power. These batteries handle it with no problems.
There are so many uses for these batteries on location, I automatically put at least one on the truck even if I don't have any plans for needing one.
PS: I'm not endorsing any brands. I think any of the major brands will be reliable.
My first purchase of a power station was a Jackery with 1000 watt-hours. It has been great.
Wanting a power station that could power a 1200D, I started buying the Pecron 1500 watt-hour batteries. They have worked great with no issues.
PPS: What first got me looking at power stations were my Aputure 600Ds. These lights were so revolutionary when they came out; so bright and affordable but could not be powered by my 14 volt gold mount batteries.
PPPS: My Pecron power stations sometimes have an issue with powering large resistive loads like a 1K Molepar when first turning the light on.
I had to turn the battery off-and-on a couple times for it to finally energize the Molepar for the picture in this post. Once the light is energized, there is no problem. The power station powers it.
I think this is happening; the power station has circuitry to protect it from a dead short. The surge of current when turning on the 1K light is mistaken for a dead short and the battery does not turn on.