Best Power Bank for Urbex: How Much Capacity You Need

The best power bank for urbex is a big one you can carry on a plane, with enough capacity to recharge your camera, your mic and your phone more than once, and a label that states its watt hours. I carry the 35,000mAh power bank with built in cables from my gear list, and this post walks through the math so you can size your own.

This is gear talk, not a guide to getting into anywhere. Abandoned buildings are dangerous and can carry legal consequences, and nothing here is a reason to go inside one.

Disclosure. The 35,000mAh power bank is the one I carry and link to, and my Amazon links are affiliate links that earn me a commission if you buy through them, at no extra cost to you.

Why do you need a power bank at all?

Because nobody is going to give you an outlet. Some places have power and most don’t, and you can’t plan around it. The post on why vacant buildings still have power explains how the lights stay on in some of them, but that isn’t something to count on, and it isn’t something to use. Whatever you need for the day, you bring in with you.

Batteries are the whole system. A camera, a wireless mic and a phone each run on their own cell, and a long explore outlasts any one of them. The Catholic school video runs 36 minutes and 46 seconds, and the high school video runs 37 minutes and 53 seconds.

A power bank doesn’t make those hours easier. It means the phone you’d use to call for help is never the thing that goes dead first.

How much power does your gear actually use?

Less than you’d guess, and the spec sheets show it. DJI lists the Osmo Action 5 Pro’s battery as 1950 mAh, 3.87 volts and 7.5 watt hours, with a runtime of 240 minutes at 1080p 24 fps. That figure was measured at 25 degrees Celsius with Wi-Fi and the screens off, and DJI tells you to refer to your actual experience, so expect less when you shoot 4K.

The DJI Mic 3 is smaller still. Its transmitter has a 137 mAh battery rated at 0.531 watt hours with 8 hours of operating time, and the receiver has 275 mAh at 1.065 watt hours with 10 hours. The charging case holds 1950 mAh, or 7.55 watt hours, and DJI says it can fully charge two transmitters and one receiver about 2.4 times.

Apple lists the iPhone 17 Pro Max at up to 39 hours of video playback. Playback is the easy case, and filming with the screen on and the radios working will use more.

The pattern is clear. The camera is the biggest single draw, at about 7.5 watt hours a charge, and the mics are tiny.

What is a watt hour, and why does it matter?

It’s the number that actually compares batteries, and it’s the one airlines care about. The math is in DJI’s own spec. The camera’s 1950 mAh at 3.87 volts works out to 1.95 amp hours times 3.87 volts, which is about 7.55 watt hours, matching the 7.5 on the page. Watt hours equal volts times amp hours.

Milliamp hours alone don’t tell you much, since they depend on voltage. The 35,000mAh on my bank’s name is 35 amp hours. If its cells run at about the same 3.87 volts as the camera battery, that’s roughly 135 watt hours. That’s my arithmetic and not a rating, so check the label on the bank you buy. If it only lists mAh, ask the maker for the watt hours.

On paper, 135 watt hours is about 18 full charges of the camera’s 7.5. Treat that as a ceiling and not a promise.

Can you fly with a power bank?

Yes, in your carry on, and watt hours decide how many. The TSA says spare lithium ion batteries, including power banks, must be carried in carry on baggage only, with a limit of 100 watt hours per battery.

The FAA’s packing poster adds the tiers. Spares from 0 to 100 watt hours are allowed. From 101 to 160 watt hours you are limited to 2 batteries and need your air carrier’s approval, and they aren’t permitted in checked baggage. Above 160 is forbidden in both. It also says airlines may set stricter limits of their own.

That matters for a bank like mine. If a 35,000mAh pack lands near 135 watt hours, it falls in the 101 to 160 tier, which means getting airline approval before you fly, and carrying no more than 2. If you’re flying to explore, call the airline first. A bank that stays under 100 watt hours avoids the question, at the cost of fewer charges.

What about cold weather and charging limits?

Batteries have temperature limits, and the spec sheets list them. The Action 5 Pro operates from minus 20 to 45 degrees Celsius but charges only between 5 and 40. The DJI Mic 3 charges at 5 to 45 degrees Celsius and operates from minus 10 to 45. Apple’s operating range for the iPhone 17 Pro Max is 0 to 35 degrees Celsius.

Put those next to each other and the cold season gets tricky. A camera that can shoot at minus 20 can’t take a charge below 5, and a phone is rated only down to freezing. A power bank in a cold bag may not be able to charge anything. Keep it warm and against your body, and check its own temperature range on the label, which I haven’t verified for mine.

The winter post covers what cold does to people, and this is the same problem for the gear.

How do you keep a power bank from becoming the hazard?

Buy from a known maker, read the label and retire a bank that misbehaves. The CPSC’s recall of portable power banks sold by Amazon covered about 260,000 units, and it stated that the batteries can overheat and catch fire. Amazon reported 53 overheating incidents in the U.S., including one case of chemical burns from battery acid and four cases of property damage from fire and smoke. The CPSC’s advice was to stop using the recalled banks right away and unplug them.

That recall is from 2018, and it’s one example and not a verdict on any brand. It’s here because the bank rides in your pack for hours, in a building with debris and no help nearby. Keep it in its own pocket, away from loose metal, and pull it out of the bag if it gets hot or looks swollen.

What does this look like in practice?

My kit is the DJI Osmo Action 5 Pro, the DJI Mic 3, an iPhone 17 Pro Max and the 35,000mAh power bank with built in cables. The bank goes in the pack with the heaviest things against my back.

The bigger point is to count before you go. The camera is about 7.5 watt hours a charge, each mic part is between half a watt hour and one watt hour, and the bank is the reserve for all of it. Add it up for your own kit, and pick the bank that covers it without crossing an airline’s line.

How I find places, stay safe and film without burning locations is in my guide, How to Find Abandoned Places.

Count your watt hours before you count your charges.