USB Power All Round

By | 2022-11-09

A small collection of results from playing with USB powerbanks. USB power is a really interesting way of powering devices: there’s lots of capacity options, charging is easy and they’re reusable across devices. And prices are low compared to NP-F batteries and certainly first party batteries for devices. The biggest issue is finding quality options amongst the piles of no-name products.

Zoom F8

When I bought the F8 I wrote about power options including a USB-A to 12V adaptor (stable up to 96KHz) and a SQNR NP-F battery adapter, which is, unfortunately, rubbish as although it can run the F8 it won’t power it up unless the battery is fully charged.

I’ve recently been playing with a pair of USB Power Delivery (PD) based options. One is a Blind Spot USB-C to 12V barrel cable, and the other is a HangTon USB-C to Hirose cable. Both of these work in a similar way to each other and perform no voltage conversion. Instead, the cables signal a request for 12V to the power source using the Power Delivery spec. Note that not every PD source will supply 12V. For example, every Anker PD powerbank I looked at only supports 5V, 9V and 15V.

Both of the cables say they require 3A minimum, but this isn’t actually a requirement, it just means you won’t reach the cables maximum power capacity of 36W without 3A.

I tested two powerbanks, one by Ugreen and one by Tecknet. The Ugreen was more expensive (but not very expensive) and has a named battery cell manufacturer (ATL). Both are rated at 10,000mAh (so ~37-38Wh) and supply 12V at 1.5A for 18W total power. 18W is plenty for the F8, given the USB-A adaptor covered nearly everything at slightly under 10W. The Ugreen is lighter at 190g vs 230g for the Tecknet.

I suspect that internally they’re using similar circuitry:

  • Same 4 lights, 1 button interface
  • Same input and output specs (at least for PD)
  • Same refusal to charge from my Anker PD wall adaptor for some reason
  • Same slightly below spec 12V output

Both power banks worked with both cables, and failover from barrel to Hirose worked in either arrangement. The 12V output isn’t quite 12V with the Zoom reporting 11.7V. This should definitely be fine for the Hirose connector which is rated at 9-15V, but also turns out to be OK for the barrel connector.

My previous tests with USB-A adaptor showed the average power draw using all 8 channels, 192KHz, dual card recording, headphones and phantom power was around 9W, so my expectation was each power bank should be good for around 4 hours even when maxed out. The Ugreen beat that easily, recording for 5h10m (For reference a 64GB card holds 3h50m in this config). The Tecknet came in slightly under 5 hours.

Panasonic Lumix G9

Running my G9 off USB power would be sometimes useful when it’s used as a static camera for on-location shooting.

The G9 doesn’t require a Power Delivery source, but it is very picky. For starters you cannot run purely off USB power and must have a battery as well. The bigger issue is that it doesn’t work with the majority of power banks, and out-of-the-box neither of the above powerbanks worked, nor an Anker or Ravpower.

The problem, as best I understand it, is that at some point in the startup process the camera does not draw enough power from the powerbank (presumably as it’s leaning on the battery) and that causes the powerbank to go into power saving mode and stop providing power. Or something to that effect anyway. The result is the camera warns you that the USB power source is not providing enough power and continues to run off battery only.

There’s a few solutions to this. One is an “always on” powerbank designed for low current devices, but these are rarer and/or more expensive. Another, is an inline keep-alive device that keeps a minimum amount of current flowing. Another idea I read was to plug a USB light into the power bank simultaneously.

I tried the last option, adding a small USB hub to allow the light to be connected in parallel. What I found is that running the hub by itself it enough to keep the power bank active and supplying power to the camera. So that’s a pretty neat and cheap solution.

A standard G9 battery is 14Wh so a 10,000mAh powerbank (£30) should be the equivalent of 2.5 batteries (£150). To test, I took a fully charged original battery and recorded 4K/25p 10-bit (150Mbps). The battery by itself lasted just over 2 hours (which lines up nicely with the 1h51m you can fit on a 128GB card). This implies an average consumption of around 7W.

With an Anker PowerCore 1000 powerbank added the G9 lasted 3h13m, well below expectations. The problem is that the camera doesn’t take enough power over USB to fully power itself and so the internal battery still drains. At the point the internal battery gave up, the powerbank still had 75% power remaining (almost exactly, the 4th light went out shortly after this test).

The camera should be capable of drawing more power. When charging the battery internally (camera off) it’s pulling around 7.5W (1.5A) over USB, but when actually running only 4.5W.

Do these numbers line up? Well, we gained 73 minutes of runtime at an assumed 7W so 8.5Wh. This is indeed 25% of the powerbanks capacity, which makes sense. What’s weird is that if the camera was taking 4.5W from the powerbank the whole time it would have supplied 14.5Wh of power, giving a runtime of around 4 hours. Plus, it would have drained the powerbank to nearly 50%. Obviously, the “4 light” capacity check isn’t brilliantly accurate, so maybe it did drain more power and a lot of it was lost to inefficiencies somewhere. Or maybe the camera is pulsing its consumption and the USB tester isn’t catching that.

Either way, I don’t think this USB power is particularly useful here. In my case I’ll just carry a spare internal battery, four hours total runtime will be fine.

If I did want more, the other way of approaching this to get a dummy internal battery and a PD based adaptor. I use something similar on my permanently mounted studio G80s and they work perfectly well. I’m not going to test this, but just on specs I’d expect one of these powerbanks to be equivalent to roughly four original batteries. Before I mains powered everything in the studio, I’d only ever need a maximum of two batteries to cover a session, and quicker artists would get done in one.

Side note: After about 3 hours recording when the G9 hit the 30m file limit it refused to restart due to high temperature. Interesting that it was OK to keep on recording, but then blocked afterwards. This is also the first and only time I’ve seen an overheating warning on a Panasonic camera.

Conclusions

Great on Zoom F8, definitely the way I’ll be running this way in the future. Pointless on the Panasonic G9, at least without using a dummy battery.

Of the two powerbanks themselves, I prefer the the Ugreen for the smaller size and weight, and the named cell manufacturer. I’d probably buy more of these if needed.