Imagine you’re on a shoot with only enough battery power to last you the standard 12 hour day. You’re diligent about charging the batteries, you don’t use any excessive power, and you haven’t had any issues the past couple of days when you’ve wrapped early.
But one scene is taking forever to shoot and soon you’re an hour behind schedule. Another scene goes by and another hour. Before you know it, you’re looking at a 15 – 16 hour day of shooting.
You’re also looking at the battery power you have left and the situation is grim — at this point, you’re close to running on empty. What do you do?
The Gatekeeper of Batteries
One of the overlooked responsibilities of a camera assistant is to keep all batteries for the camera and its accessories charged. This includes batteries for:
- On-board monitors
- Video village
- On-camera accessories (i.e. syncboxes)
- And more…
Maintaining and keeping all equipment within the camera department operational includes keeping batteries charged and ready to go.
This is usually a team effort between all players in the camera department: the 1st assistant camera (1st AC) will keep an eye on the batteries on the camera while the 2nd AC keeps an eye on those charging and helps swap fresh batteries in/out. You don’t always get as many batteries as you would like, or possibly even need, but you have to work with what is handed to you.
If all goes well, there should never be a delay in shooting because of a lack of battery power.
Staying Ahead of the Curve
Have you ever noticed when you plug your iPhone in to charge it takes almost no time for it to get some juice, but to get a full charge, you have to leave it plugged in for awhile?
The battery is designed to get maximum charge at first for when you need it most.
It’s the way that most rechargeable batteries work — including the kind you strap onto an Arri Alexa. They charge very fast right when you plug them in and then charge slower the closer they get to 100% capacity.
Knowing all of this about batteries isn’t just knowledge to have, but to use to your advantage.
Let’s go back to the scenario mentioned at the beginning of this article: you’re encroaching on long day with limited battery power left. The director can’t figure out what they want, the actors are flubbing lines because they’re tired, and you’re sweating knowing your batteries lose more power with each delay in shooting.
Fortunately, if you understand battery technology sufficiently enough, you can stay ahead of the curve for just a little bit longer.
So you take a moment to go check your batteries charging, are they at about 75%?
If they are, take them off and put on completely dead ones. Dead batteries charge much faster to a limited charge than the one battery would take to charge to 100%.
By doing this, you stretch the potential power of your batteries for a much longer period of time. The trade-off will be more frequent battery changes, but that price is small compared to the alternative of finding yourself without any way to power the camera.
When worried about having enough battery power, be diligent about having somewhat charged batteries over fully charged batteries. It will take less time, you’ll have more power in the long run, and you just might make it through that long day.
Understanding Battery Charging Technology
So why don’t they just design batteries to charge that fast the entire time? Well, because it would shorten the lifespan of the battery substantially.
To quote from Anton Bauer’s Video Battery Handbook:
As a cell nears full charge, the voltage of the cell, its temperature and pressure all will rise. The art in charging a cell is to obtain the most charge without the increase in these parameters exceeding safe limits specified by the design of the cell.
Exceeding the limits of any of these factors, depending on the chemistry, can lead to unreliability, shortened service life or in some cases catastrophic failure of the cell, including explosion and/or fire.
As you can see, for reasons of safety and expanded battery life, manufacturers must be careful as a battery approaches a full charge.
And at a couple hundred dollars a pop, you want to have batteries that work for awhile.
Battery Case Study: Anton Bauer DIONIC 90 and RED Brick
To illustrate this fast-to-slow charge concept, let’s take a look at a chart from the manual of Anton Bauer’s DIONIC 90 battery — a battery that is typical for use with high end video and digital cinema cameras.
On the left side of the chart are the various types of chargers that are compatible with the DIONIC 90. On the right side is the charging times for the batteries up to 90% and 100%.
It is worth noting that in every instance, no matter which charger, it takes a few hours to get up to 90% charge and then another hour to crest all the way to 100%.
To give you a comparison, RED’s batteries charge in a similar fashion by front-loading the charge and leveling it off at the end.
Even though it takes 210 minutes to fully charge one of the RED Brick batteries, the initial 80% of the charge comes in the first 120 minutes.
RED knows this and it’s why, when two batteries are charging simultaneously, they bring both up to 80% then work on charging them fully.
It takes substantially less time to give a battery an initial jolt of power than it does to fill it up completely.
It Keeps Going and Going…
Being acutely aware of your battery situation and the power you have left is an understated part of camera assisting, but that doesn’t mean it isn’t important. Without the power to the camera, you don’t have any way to keep on shooting.
You may find yourself in situations where your power is dwindling and you fall back on your knowledge of how batteries work to stay ahead of the curve — at least for a little bit longer.
Of course, this tactic will only last for so long before it catches up to you. Having more batteries is always the best option to keep shooting because who doesn’t want to work for 17 hours at a time?