Recommend Power Bank for Outdoors?

I run fishing charters in Alaska and want to use my GoPro Max 360 running all 8 hours on my fishing charters. I’ve got a housing to allow A USB-C to run from the camera to a Power Bank. I can charge my GoPro Max from USB-C to USB-C VS USB-C-USB-A not sure if it is any better for charging but I could do either.

Would it really matter if I charge from USB-C - USB-C VS USB-C-USB-A ?

Depending on if I did USB-C or USB - A into the Power bank which Power bank would you recommend for charging outside, it will be dry just outdoors and cold morning. The cable will need to be six feet.


Yes it can matter, you will need to do also get a USB meter and do a controlled test at home to be sure which is best.

You have two opposing electronic aspects which makes it too theoretical to be sure, a test is required.

  • step up / down efficiency losses. The cells in the Powercore and in the GoPro are at some voltage. Typically it is 3.7V but internally can be connected in series or parallel so could emerge 3.7V or 7.2V or … The voltage presented externally via USB is whatever is this internal voltage with a buck-boost converter. The ineffiency, losses, is linear on the ratio of the internal to external voltage. So say its internally 3.7V but externally 9V, there is more loss than if internally 7.2V and externally 9V. Short of stripping the Powercore down, destructively, you have to use a USB meter and count energy in and out. You have losses in the Powercore and the GoPro. The losses are a function of the two devices, so some losses will be worse for C-C, other for A-C.

  • Power losses in the cable. For a given amount of Watts, the higher the Amps in the cable, and the longer the cable (you said 6ft) the more the loss in the cable, it is to the square power of Amp and linear on cable length. So for a given Wattage, a USB-C may allow a higher voltage, so lower Amps, so a lower cable power loss.

These two combined to a big fat “we don’t know” , you have to measure it and find out. What I do know is at 6ft, you need to buy the physically thickest cable, in general that is the most expensive, to reduce power loss.

Anker Powercore which do C also usually do A , two port types out.

For the GoPro, find it’s cells Wh. Find it’s life on a full charge. You’ll then divide these to get a W. So suppose its 10Wh and it lasts 4 hours, so your 8 hours thus needs 20Wh. Then use the 2/3rds rule so it becomes 30Wh. That then picks the size of the Powercore needed. If you can find out the Wh of the GoPro then I can do the calculation for you.

If this is too many words, then simply buy the biggest Powercore, or buy two. Or buy one medium size, do a test, and if not enough then buy another. Buying two smaller ones is more likely the most useful investment as bigger powerbanks tend to be left at home as they’re big so don’t used as much. I’d suggest by whichever 10000mAh is lowest cost right now, and do a test, if it’s not enough then buy whichever 10000mAh is the lowest cost. 10000mAh is a good size for any problem.

You can smoke out the answer through a test if you don’t want to do the math.


Good information as always from @professor! I’ll only add in regards to the cold mornings: batteries should be fine in colder weather (it’s better on them compared to hot weather!). However, if the temperatures goes below freezing, then the chemicals in the battery will slow down and the power output may drop to a point where they do not provide enough power to charge the camera. This should only be temporary and should resolve itself once the temperatures warm back up above freezing, but it may require you to tap the button on the powerbank to turn it back on.


Anyone who has camp cooked with alcohol knows to put breakfast’s fuel in the sleeping bag with you.

I am not surprised the battery Eufy products are failing after a year and puzzled why anyone would want it in black.

Really Appreciate the Reply @professor so the information I recived on my specific battery for the GoPro Max is:

Battery Capacity: 1600 mAh, 6.16 Wh, 3.85 V
Battery Chemistry: Lithium-Ion

My verbose math reply is “teach to fish”, it is deliberately trying to show how to do these calculations.

I am using these simple electrical rules:
- Watts = power. Volts x Amps.
- Watts-hours “Wh” = energy, Watts x time.
- 1000mA = 1A. Definition of milli “m”.

How long does that last for your type of usage?

I see it varies 1h27m - 2h30m

Hence you said 8 hours.
So if 6.16Wh = 1.5 hours,
then 8 hours = 6.15 * 8 / 1.5 = 32.8Wh
Apply the 2/3 rule (for ineffiencies in the transfer) 3 / 2 * 32.8 = 49.2Wh.
At a typical 3.7V that is 13000mAh.

A 10000mAh Powercore is typically 37Wh, a 20000mAh is typically 72Wh.

So you’re talking mid-way between the two.

As you also need Watts, not Wh, If 6.15Wh = 1.5 hours, then that is 4.1W, apply the 2/3rds rule = 6.15W.

As 6.15W is less than 10W, you don’t need more than the standard USB-A of 5V 2A 10W. So you don’t need USB-C > 10W output.

For simplicity, one 20000mAh, such as this:

You’d then have to do a home test, try using different cables and verify you comfortably hit your 8 hours. My best guess is as the GoPro is only 1600mAh and 3.85V, that is probably a single cell at 3.85V, so I suspect in this case it will be most efficient if you made it use 5V.

It seems the camera comes with a USB-C cable and I see its 5V 2A input so all of Anker’s Powercore will work that are 13000mAh upwards. So pick one on price, deals vary through the range over time.

I did a quick look at USA deals today, an example fit around the 13000mAh is :

Cost $25.49

The final question is how fast do you need this to recharge? The 20000PD Essential 18W input recharges in about 7 hours, the 13000mAh I give as another example is also 7 hours. If you’re wondering why different size recharge same time its because the 20000 PD is 18W input vs the 13000 is 10W input.

My best advice for your use case is for fast recharging and simplicity, headroom is buy this:

Today is is $34

And this:

What combined will give you:

  • that 20000 should comfortably keep you going 8 hours with spare capacity for other items like also your phone
  • it will recharge in 7 hours
  • that charger will recharge the 20000 and recharge your GoPro in parallel in 1 wall socket.
  • Important: your GoPro does not need USB-PD so the 18W number here is not related to your GoPro, you’d use the 20000 PD’s bundled cable to recharge the 20000 at 18W using the USB-C port on the dual-port 30W charger, you’d then use your GoPro’s cable to then keep your GoPro charged off the 20000’s USB-A port. This is just to mean the entire lot recharges comfortaby while you sleep. Your GoPro does not need 18W, it cannot benefit from more than 10W.

Prices vary, so if you’re not in a hurry, patience and a deal will come up in next 1-3 weeks.

Did that make 100% sense?

The 20000 is $34 with code here:


You went above and beyond with that answer :clap: