Portable power supply?

[Rafael Lopes]

Hi guys,

Now that I´ve got the H4N along with the NTG3 I´m looking for some good options regarding portable power supply for the H4N (I´ve heard its´ phantom power drains it pretty fast). I´ve checked the duracell usb power supply that isn´t the most powerful (1150 mAh) but it´s pretty small. Do you think this would be enough to get me through one day of shooting? What other small alternatives are there?

[Greg Miller]

The H4n manual says a set of AA alkaline cells will list roughly 6 hours "in general use" or 11 hours in "stamina mode." Stamina mode allows recording only with 44.1kHz sample rate, so presumably we can eliminate that from our discussion.

I don't know what "general use" means but let's make some calculations based on the assumption that "general use" includes continuous recording. This may be wrong! Also, the manual does not mention whether "general use" includes generating 48v phantom power.

AA alkaline cells vary in capacity from about 2,000 to 3,000 mAh. We'll take the worst case and assume you need 3,000 mAh cells to get the full 6 hours. In that case, we can say that you need about 500 mAh capacity for an hour of "general use."

If your "one day of shooting" is eight hours of "general use" then you need a power source with a capacity of at least 4,000 mAh. However, that does not take into account any inefficiency in the H4n's power supply, when converting from the 5V input to the actual power used by the recorder. So you may actually need somewhat more than 4,000 mAh.

OR...

We can take a more conservative look at things. According to the manual, the AC adapter provides 5 volts at 1 amp. This presumably handles any load that the H4n might provide, even including the phantom power supply.

In that case, if you want to operate for eight hours, you need a 5 volt power supply with a capacity of 8,000 mAh.

NOTE that these are just calculations based on various published numbers and assumptions. I have not empirically determined any of these figures. YMMV.

To be more accurate, you'd need to operate the recorder from the specified power supply, configure it exactly the way you intend to use it (at the bitrate you intend to use, phantom turned on, mics actually connected, in record mode, driving headphones to realistic level). Use a DC milliammeter in series with the power supply to measure actual current flow, then multiply that by the intended number of hours, to calculate the actual capacity for your desired portable power supply.

[Richard Crowley]

Sure there are options. Much depends on exactly what "one day of shooting" means? Do you have access to mains power? Do you have an equipment cart? Do you need something you can clip to your belt? Do you need something that attaches to the recorder that you are holding in your hand? Do you need a solution where you can get a quick replenishment by using primary (throw-away) cells? Or do you want to use secondary (rechargeable) batteries? etc. etc....

[Nicholas de Kock]

I use a Tekkeon myPower ALL Plus MP3450i Battery (58Wh) along with a USB to H4n power cable I found on Amazon. Runs for days.

[Rafael Lopes]

Sorry, I should have been more specific. By a days´shoot I´m talking about an 8 hour shoot using phantom power and recording at maximum quality.

[Brian P. Reynolds]

So how many camera battery / camera card changes would you need to make in that 8 hrs?
With the H4n why not just change the batteries 1/2 way through a shoot like you would do for a radio mic? Nobody has ever got stressesd with radio mic batteries lasting less than 8 hrs...

[Rafael Lopes]

Originally Posted by Brian P. Reynolds

So how many camera battery / camera card changes would you need to make in that 8 hrs?
With the H4n why not just change the batteries 1/2 way through a shoot like you would do for a radio mic? Nobody has ever got stressesd with radio mic batteries lasting less than 8 hrs...

I´m talking about external shots where I don´t have access to power. If I was shooting indoors I would use an outlet all the way through the shoot.