Continuous power for BLS powered cameras (in this case the EM10Mk2)

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Michael Meissner
Michael Meissner Forum Pro • Posts: 26,844
Re: Continuous power for BLS powered cameras (in this case the EM10Mk2)

You really need somebody who is an EE to answer these questions. As I've said before, I am a computer programmer by training but who at times dabbles in electronics. While I haven't smoked a camera, I always do realize I could.

But in general there are a couple of things to think about:

1. Are the plugs compatible, or do you need conversion cables?

In general there are two different sets of plugs: 5.5mm x 2.1mm (sometimes 5.5mm x 2.5mm) and 4.0mm x 1.7mm. The 5.5mm x 2.1mm tends to be the most standard. It is used by CCTV devices, and a lot of random electronics. The Tether Tools adapters use 5.5mm x 2.1mm, as does the European guy you bought adapters from.

The 4.0mm x 1.7mm plugs tend to be used by the smaller devices. In particular, they are used by Panasonic cameras.

And then you get into whether the adapter has a male plug or a female plug. In general, I tend to prefer the thing with the power be a male plug, and the thing getting the power (i.e. the dummy battery) be the female plug. But I've seen it the other way.

2. How much power do you need?

This is where I typically get into trouble, in trying to write about things I only marginally know. Assume if anybody grounded (pun intended) as an EE says otherwise, believe them, and not me.

A typical simplification of Ohm's law is that watts is the voltage times the amps. A common non-technical way to describe them is imagine a water pipe delivering water:

  • volts corresponds to the size of the pipe;
  • amps corresponds to the amount of pressure the water is under. Typically with amps, you want to use the worst case scenario of the max amps needed;
  • watts is the amount of water delivered through the pipe.

The typical 2 cell lithium-ion battery will deliver a nominal voltage of 7.2 volts, but if the battery is freshly charged, it is on the order of 8.4 volts.

Some newer formulations such as the BLN-1 batteries have slightly higher voltages. The BLN-1 has a nominal voltage of 7.6 volts. I don't remember what the voltage of the freshly charged BLN-1 is, but it is probably 8.8 volts.

For lithium-ion, the nominal charge tends to be the voltage put out during most of the discharge cycle. For non-rechargeable alkaline batteries, the voltage tends to vary over time.

The cameras are designed for the voltage range that they can expect from the batteries, with a little fudge factor. So a camera using a BLS-50 battery might run from 7.0 volts to 9.0 volts. Perhaps the cameras will run at a higher voltage, but I haven't dared check.

The cameras that support a battery grip with external power (E-m1 mark I/II/III, E-m5 mark I/II) or the camera that supports external power directly (E-m1x) need to support 9v input, since this is what the A/C adapter delivers.  Now, in theory the other cameras could limit things to 8.4v, but they don't seem to.

If the voltage is in the range that the batteries produce (i.e. 7.2 - 8.4v), Panasonic cameras tend to have a check whether the battery is supported. Thus if you are powering a Panasonic camera, you might want to get adapters that say 'decoded' -- this will allow you to use a bigger 2 cell battery, and the Panasonic voltage meter will give you the appropriate power indication. If the voltage is 8.5v or higher, Panasonic cameras tend to believe that the power source is coming from an A/C adapter, and they turn off the checks for Panasonic batteries and for low battery. As far as I can tell, Olympus does not do these checks, and you can feed it voltages down to the minimum.

Any time you are converting from one measurement base to another, there is always a loss in the conversion. For example, if you have a 5 volt power source that can deliver 2.1 amps/hour and you convert that to 9 volts at 90% efficiency, you will get roughly 1.05 amps/hour after the conversion. If the conversion did not involve a loss, you would get 1.17 amps/hour.

I haven't yet done measurements from the E-m5 mark III, and I can't find the measurements I did for the E-m1 mark I. For the G85, measuring USB voltage feeding into a 9v converter, it used up to 5v/1.7a (roughly 9w).

Now, whether the G9, E-m1 mark III/E-m1x use more power than that, I don't know. Also, user complaints of the Olympus 12-100mm f/4 lens sucking batteries dry, probably also means if you use that lens, you will need more power.

But for 'normal' cameras, if you are looking for an A/C adapter, you probably want one that converts A/C into 9v power, with at least 1 amp, preferably more. Note, that manufacturers do sometimes pad the numbers, so be sure to read the reviews.

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