Intro to Portable Power for Photo and Video

In today’s fast-paced modern world, supplying power for our mobile devices is everything. For photographers, whether it’s your smartphone or your DSLR, keeping your electronic devices powered can make or break getting to the right spot and nailing the shot.

Battery technology has advanced in recent years and prices have come down from where they were just a few years ago. Modern batteries, such as Lithium Ion, are not only cheap but also light and powerful. Picking the right battery for the job can be a daunting task, requiring careful consideration of many technical terms and physical properties.

Questions quickly pile up when you start to think about batteries for photo and video use. How many iPhone charges can I get out of a 10,000 milli-Amp-hour (mAh) battery? Does a 10,000 mAh 12 Volt battery provide more power or more current for a 12V time-lapse dolly motor than a 12V 7 Ah battery, and which is more important? What in the world is a milli-Amp hour anyway? Should you buy exclusively Canon, Sony, or Nikon batteries? What about the “off-brand” cheaper batteries – are these lower-cost alternatives viable for the job? When do you need to think about getting a heavier “traditional” battery?

I will demystify portable power in this post and arm you with the knowledge to make the right selections from the many options available for powering your gear on the go.

Volts, Watts, and Amps – Oh My!

Before we dive into battery terminology and carefully consider battery tech as it pertains to the photography world, let’s first go back to high school physics class and establish the foundation of knowledge needed to pick the right tools for the job.

One of the best ways to communicate the fundamentals of electrical energy is via an analogy of electricity to water. Picture in your mind that electricity is akin to water rushing through a round pipe, with a tank above it. Three of the most relevant and important-to-understand properties of electricity are volts, amps, and watts. Let’s consider these one at a time through the lens of our water analogy.

Voltage

Voltage, which is measured in volts, is equivalent to the water pressure (how much water is above the pipe, in the tank). If you drain some water out, the amount of water above the outlet decreases and, thus, so does the voltage as a battery runs down (think of a flashlight getting dimmer if left on all night). In some cases, there may not be enough voltage left to safely operate a device connected to your battery if enough power is drawn out and the voltage drops below a certain level. Higher voltage electricity is equivalent to higher potential energy in the electrical system. Remember that the voltage of the battery you choose has to be matched to the design voltage of your equipment, or you risk irreparable damage!

Amps

Amps, or current, is the volume of water flowing through the pipe (for example, gallons over time), out a hose at the end. Picture two hoses at the outlets of two identical water tanks, one with a narrow diameter, and one with a wider diameter. When opened completely, the tank with the narrower hose will expel less water than the wider-hosed tank over the same amount of time. The wider-hosed tank has a higher flow (more amperage, or current) than the narrow-hosed tank. If you want the same amount of water to flow from both tanks, you have to increase the amount of water in the tank with the smaller outlet (higher voltage).

Watts

Watts refer to the amount of power in a system. In our water analogy, this is akin to how big of a water wheel the rushing water can turn. It’s not a far stretch to imagine that a trickling stream has less power than a raging river.

To keep things simple and come back to batteries, you sometimes see “Watt-hours” as a rating on batteries. This property does matter, especially to those using batteries to power motion-control video gear, such as a time-lapse dolly, where stepper motors move cameras and lenses along a rail and you need to know how much power your battery can provide to move gear. In this case, you need to consider that Power (measured in watts) is the product of multiplying Voltage and Current. So, to move a lot of heavy gear, you want a battery with a bigger Watt-hour rating, which is nothing more than your current system’s volts x a higher mAh.

Current Flow

One final thought: keep in mind that with batteries we are talking about DC or Direct Current, where voltage flows one way from high voltage and high current to a ground or other location with low current. This is different than “wall power” which is AC or Alternating Current.

Battery Properties: What Every Shooter Should Know

Now that we’ve covered electrical fundamentals, let’s come back to batteries. In our analogy, we talked about how a battery is like a water tank where “electricity” is stored but in the real world of photo and video most people want to know how “big” of a battery is needed for a given use.

Answering this question requires an amalgamated assessment of the properties we introduced above: how much water sits in the tank to be drawn out later (voltage)? How much water needs to come out of the outlet (current)? How much power does the stream of water need to have (power = voltage x current)?

Battery capacity is commonly given in milli-Amp hours. A battery rated for 1000 milli-Amp hours (1 amp hour) should, at least in perfect conditions, be counted on to provide a current of 1000 milli-Amps (or one amp) over 1 hour before being completely discharged. Some manufacturers of portable power gear, such as GoalZero, give their product’s battery power in Watt-hours, which is another good measure of a battery’s “size.”

Real World Examples

What about a 10,000 mAh battery in a real-world example? If you have a device that takes ~2,000 mAh (example: a smartphone – the iPhone 7 battery is 2,750 mAh), you might think that you could use the battery to charge it five times before needing to recharge the battery. This is not the case because of a common property of batteries – they decrease in efficiency over time, which might put the “charge efficiency rate” at 80%.

That’s not all! You also need to consider the decrease in the charging health of the battery in your phone, which also diminishes over time. Fortunately for smartphones – which are invaluable as photo assistants in providing directions to locations, for sun ephemeris planning, or for time-lapse dolly remote control – there are many great free apps to help you monitor this, such as Battery Doctor (if you can get past the ads).

So, add that all up, and instead of 5 times out of 10,000 mAh, you get 10,000 mAh x 80% charge efficiency rate x 80% battery health/phone battery capacity = 3.2 charges out of the battery (as opposed to the 5 charges we thought we’d get). This will decrease as well as both batteries age.

Types of Batteries in the Video/Photo Industry

There are many different types of batteries available in today’s market. Here’s a quick run-down of the options:

Lithium Ion (Li) and Lithium Polymer (LiPo)

Found in most smartphones and laptops, including the iPhone/MacBook Pro, have the highest energy density, are somewhat costly but improving. Can be drawn all the way down and recharged but will die over time if unused. Requires careful charging with onboard monitoring circuitry. Can’t check in luggage. Examples of these in the industry include, but aren’t limited to, the following:

Anton Bauer Digital 90 Gold Mount Battery: High-capacity but requires a plate to attach to your device and your device needs a P/D-Tap port.
Canon LP-E19 Battery: Designed to fit the form factor of pro DSLR bodies. Many people are familiar with the smaller versions, like the LP-E6N.
Sennheiser BA 30 Rechargeable Battery Pack: Can be charged with a generic USB charger – a feature of some Lithium Ion batteries.

Sealed Lead Acid (SLA)

Found in security systems. Sealed but can spill acid if damaged. Cheap and heavy. Can charge with common charger – best to be trickle-charged when not in use. Can be damaged by drawing all the way down. Self-discharge is 50% that of Lithium. The most common example of where you might see these in the industry is in computer UPS backup systems (you may have your storage setup connected to one).

Absorbent Glass Mat (AGM)

Used for deep-cycle RV and Marine purposes and also found in cars and sometimes in very large audio systems. No acid. Can be drawn down and recharged.

NiMh/NiCad

Older technology rechargeable AA, AAA etc. Examples of these in the industry include, but aren’t limited to, the following:

Ikan EC1 Beholder Battery Kit: Small, convenient, rechargeable. Can take a long time to charge back up.
Bolt Cyclone Battery Pack for Flash: Affordable and reliable alternatives to Lithium Ion in some cases. Convenient for powering flashguns and small strobes. See also the Lumedyne HV Ultra Megacycler for Flash or the Quantum Instruments Turbo3 Battery Pack.

Alkaline

Single-use, inefficient. Ubiquitous and cheap. Bad for the environment. You can use these or their rechargeable cousins in things like Pocket Wizards or handheld audio recorders.

Which one is the right one for you? Wherever your budget can support it, go for Lithium Ion or Lithium Polymer batteries, as they provide the highest amount of capacity and power per unit weight  (a.k.a. “energy density”). Li and LiPo batteries do have to fly in carry-on luggage, though, and typically can’t be shipped due to potential fire hazards. For years before Li battery prices came down, I chose SLA and AGM alarm system batteries to power my time-lapse gear. No longer do I need to break my back (or my wife’s!) by lugging these to mountaintops since now there are many Lithium batteries capable of supplying the power I need at a fraction of the weight and only slightly more cost.

How Much Power Do I Need for Time-Lapse and Other Projects?

The first stop on the journey towards figuring out how much power you need for a particular application is to consider the power draw of what you are powering up. I’ll give two examples: first, a Canon 5D Mark IV. According to the specs, a fully-charged, fresh, new battery should provide 300 shutter actuations in Live View and 900 without. By “shutter actuations” Canon means short shots like 1/500th of a second.

Cold Weather and Power

But what about long exposures at night in the cold? This number will certainly go down. I know from experience that two fresh, newish batteries in a battery grip will provide around 6-7 hours of 30-second exposures (so around 600 frames), with the image preview turned off, and not shooting in Live View. You can only familiarize yourself with these properties from experimentation, so I encourage you to go out and shoot (even just out your window at night or off your back porch) to figure this out before heading into the wilderness.

Second, what about powering time-lapse equipment? These require more power, as we have motors moving heavy gear along tracks and/or rails. Start with the specs given by the manufacturer of your gear. I use the Dynamic Perceptions Saffire Pro setup for my time-lapse work. This gear draws ~0.2 amps (~2,000 mA) total at 12 volts. This includes the controller and all three stepper motors. This ships with a Lithium-Ion pack that provides either 12V or 5V, has an 8,000 mAh capacity and lasts 3-4 hours under a normal load.

DP also sells a “Pro” battery (23,000 mAh) that lasts up to 8 hours. Extenuating factors such as cold temps, or a vertical-up move may diminish this result. But you can implement the power-save feature in the NMX Motion App. This puts the motors to sleep between exposures to increase battery life.

If you have hard numbers for any of your gear and want a mathematical answer, the popular DIY electronics website DigiKey has a handy calculator.

OEM vs Off-Brand Batteries for Cameras

The batteries that ship with your camera are typically the most robust and replacing them can be expensive. The Canon LP-E6 that powers the 5D series of cameras is 1,865 mAh and 7.2 V. The larger battery that powers the 1D series is the LP-E4N. It’s 2,450 mAh and 11.1 Volts. Both are Lithium Ion. Off-brand replacements are available for both models with similar specs. Nikon’s EN-EL15 battery is 1,900 mAh, and 7.0 Volts DC. One common off-brand replacement is the Watson EN-EL15, which specs at 2,000 mAh and 7.0V.

Working professional photographers need a collection of batteries available to keep shooting and get the job done. Not everyone can afford OEM batteries and most shooters have a mix of OEM and off-brand batteries in their kit. The OEM Nikon/Canon batteries always last longer over time, both in the camera and over thousands of recharge cycles. Pay attention to the “recharge performance” ratings given in your camera’s menu system. When these dip, it’s time for new batteries. You do get what you pay for here. Whichever brand you choose, make sure to write the date of purchase on your camera batterie. Replace them when they age and performance drops.

Beyond Batteries: AC Adapters

Sometimes batteries aren’t enough. For those instances, all major manufacturers offer some type of AC 120V adapter. These can provide power to your camera as long as it is plugged into the wall. For some time-lapse applications or studio video interviews, I’ve used the Canon ACK-E6 AC unit in lieu of batteries to achieve 24-hour time-lapses, or an entire day of interviews without having to worry about a battery dying at a crucial moment. This bit of kit can be a lifesaver in certain circumstances.

You may be a time-lapse photographer camped on the rim of the Grand Canyon. You’re looking to have your three-axis dolly last through the rise of the Milky Way behind a gnarled Juniper. Or perhaps you’re a professional documentary shooter on location recording interviews in the steamy Amazon. There are no outlets and you have to pack the right batteries for the job. Hopefully planning for this will become second nature to you after reading this post. Please feel free to ask any further questions in the comments section.