It’s a question popping up about every week on the various groups and forums online: ‘How do I power my field recorder?’ or, ‘What are the best 12v+ batteries out there?’. Followed by loads of reactions, based on personal preferences, what the person is used to, or what the ‘hot new kid on the block’ is at the moment.
But what is often neglected is the pure technical background of DC power. the crux of most of the questions boils down to not completely understanding the basic essence of what’s needed to get your gear running throughout the day.

Therefore, this guide, including recommendations for the various bits and pieces.

This is part one of a series of articles, split up as follows:

Batteries: A Battery is a battery, is a battery

An electric battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars. – Wikipedia

I don’t want to bore you to sleep with a lecture on what a battery is, but a tiny bit of technical background info is always good to carry with you.
Every battery has a positive and negative connection (the positive is the cathode, the negative is the anode), a given (charged) voltage (electric pressure) a rated current (amperage or amps per hour) and the potential power output (wattage, or wattage per hour). Arguably the most important spec for our equipment is the voltage. Let’s take a look at a simple rechargeable AA battery packaging sleeve and the print on a NP1-style battery:

aa

idx

As I circled out, the AA Battery has a voltage of 1.2 and an amperage per hour rating of 2.5 (2500 milli amp hours). No wattage is given on the package, but Watt’s law thought us V(oltage) * A(mperage) = W(attage), thus 1.2 * 2.5 = 3 Watt (Hours). With this info we can calculate run time for example, lets say we use this battery for a device that is using 1 watt per hour, thus we know 1 battery will run for about 3 hours.
The IDX NP1 Battery shows everything, 14.8V * 4.6A = 68 Wh. Now in theory, the device I used as an example for the AA, would last for 68 hours with the NP1. BUT: remember I wrote: Arguably the most important spec for our equipment is the voltage. We can’t just give a piece of gear 1.2V, when it’s expecting 12v. We can’t give it 48v either. So or we get a battery with a voltage in the spec range of the equipment, or we take a battery and step up/down the voltage in various ways to get it in range (more on the latter in the next chapter about BDS).

Now lets focus on what we need for a recorder. A Sound Devices 633 states that the external input accepts everything from 10 to 18 Volts. A Zoom F8 wants between 9 to 16 Volts. There are a couple of reasons input is given in a range instead of an absolute number. One reason is that certain battery chemistries are fluctuating when the battery is charged or discharged. the (Lithium Ion) IDX battery in the example above will give a 16.8v rating when charged for example. If you followed along, you can see that’s a tad bit too high for the Zoom F8, which gives a maximum input of 16. Over pressurizing a power input continuously can damage the device, so this is something to take serious when selecting a battery solution. On the other hand, if you under-pressure an input, not much harm can be done, it just won’t power up.
Now very quickly back to the AA batteries: most recorders have the option to run on a couple of AA batteries, but aren’t those just 1.2 volts (up to 1.6v for Alkaline)? Yes, so we can introduce a new ‘law’ to remember: Serial circuits.

seriesexample

As you can see in the image, if you ‘butt’ the batteries to each other from plus to minus, you add the voltages up. so in case of the Sound Devices 633, which accepts 6 AA batteries, you get 7.2v of power (this also gives away that the AA compartment of this device accepts a lower total voltage vs. the 10-18 volts of the external power input). In case of the Zoom f8, which accepts 8 batteries, the formula is 8*1.2 = 9.6v for charged recyclable NiMh.
‘Serial circuits law’ dictates that the amperage stays the same. so if we have 6 2.5A AA batteries, they stay 2.5, but we can multiply that with the new created voltage. So in case of the SD 633 that will be 7.2 * 2.5 = 18 watt, in case of the Zoom F8 9.6 * 2.5 = 24 watt.

So how big a battery do I need?

To answer this question you need to know the power consumption (Wattage) your device needs over a given time. Most manufactures give a conservative estimation in the manual, in this matter, conservative means if you use all the bells and whistles of the device, like using Phantom on all the inputs, cranking up the headphones to maximum, etcetera. So in real world situations you will use most likely less, but it’s always good to base your needs on the conservative number.
Let’s continue with the two examples we use in this article, the SD 663 and the Zoom F8:
about 5.5 W for the 633 and 12W for the F8. Online reports show the real world usage of the F8 is more around 6W with phantom power on for all 8 inputs, so since that is way off from the specs in the manual, we will use that number from now on.
Now we do some math again, let’s say we want it running for about 10 hours before we need to swap or charge the battery, the simple calculation shows us 5.5 * 10 = 55 watt for the SD 663, and 6 * 10 = 60 watt for the F8. Again, these are sort of ‘worst-case numbers’, In the real world it probably will be better. But my advise is to calculate conservative, to not be surprised during a shooting day.
So for our two examples, a 60 Watt(h) battery will be good for a full day of shooting. That is, if we only power the recorder with it. In part 2 of this guide we will go in full detail about battery distribution to all potential other equipment in your bag. But we have to mention it here in the battery-chapter as well. Logically, the more devices you want to power, the bigger the power consumption will be, so a bigger battery-capacity you will need, or you need to be willing to swap the battery more often per day.
So if you want a good estimate of how ‘big’ of a battery you need, more calculation needs to be done. Look at these examples:

Bag power consuption examplea

I used a small but typical bag-based scenario to illustrate a real world example, a recorder with 2 or 3 receivers and a transmitter for IFB purposes. It shows us we need around 80 watts of power to get easily a full day of shooting. Again, most likely you will get more out of it, since you are not continuously running all the tracks, nor all the receivers all the time.

What are the options?

A Battery is a battery, is a battery, is how I titled this chapter. All will work, if the Voltage, Amperage, thus Wattage can provide the power needed for your demands. We do have a couple of options though, let’s go trough them.

Professional AV targeted batteries

Go to an online/offline vendor and you will see a variety of batteries directly offered for camera and audio use. The come in a lot of flavours: V-mount, AB-Gold mount, BPU mount, NP1 Style, NP-F style, etc. All different cradles to nest the batteries in. Under the hood most of them are the same: A number of 3.7 lithium ion cells wired in series, to create a 7.4/11.1/14.8v nominal battery. Basically the same way as I described above, how the AA batteries are being handled inside a recorder.

probatteries

For us sound recordists, the 11.1v and 14.8v (for the previously mentioned point, the range of input voltage accepted) are directly useful. 11.1v is not a very common one in this category though, about all brands are focused on 7.4v or 14.8v. The Zoom F4 and F8 are the only pro audio recorders not accepting a charged 14.8v (16.8v) very well, but the just announced F8n is updated with a wider input range. 7.4v needs a step up converter, or 2 of those can be wired in series to get the 14.8v nominal. In our next chapter about battery distribution systems, we’ll go into detail about that.
A couple of benefits of these AV targeted batteries:

  • Cradles/mounts/docking stations
    The Battery comes with a mount and simply slides into a cradle, permanently attached to the recorder’s input. this means no fiddling with cables. Most are of the locking kind, although the still most popular one for location sound (NP1 style) doesn’t. You can buy chargers with the same docking mount.
  • Widely used
    V-mount and AB Gold-mount are industry standards for pro camera’s. The BPU and NP-F batteries are Sony’s standard for the handheld camera range. So in case of emergency you could use one from the camera department, or charge them on their stations.
  • Quality control and extra features
    Because the target audience/usage of these batteries are known to be expensive camera or audio equipment, most vendors are building in extra circuitry in the newer lines of batteries. Like short-circuit protection, intelligent cycle counters, temperature checkers etc. You can also be sure that the specs written on the case actually are met.

But… Like all products specifically targeted towards pro AV use, this comes at a price, literally the price. These batteries tend to be expensive. Although nowadays there are a lot of good quality Chinese knock of brands competing, so in recent years the pricing has come down, they are still more expensive than other solutions we will point out later in the article. Also, most of them are bigger than needed. Due to all the previous mentioned extra features and the fact they have to conform to a specific standard size wise, they are often bigger than needed. Weight wise they are not that much heavier though.

Specifically for location sound, there is a relatively new mount/style on the market: the eSMART mount. It is a friction fit mount and the batteries has a lot of fancy micro-controlling going on to keep the batteries healthy as long as possible. Also, the casing is just as big as it needs to be, just a tad bit bigger than the cells within. Brands offering the batteries are AudioRoot, Remote Audio and Inspired Energy. Inspired Energy is the manufacturer of all of them by the way.

esmart

Generic rechargeable battery packs

Believe it or not, but other industries need batteries too. Think about surveillance cameras, bicycle lights, drones/quad-copters, emergency laptop chargers etc.
Here on WavReport we talked about the Talentcell battery before. It’s an inexpensive battery (100Wh) with a 12v output (ideal for the Zoom F4/F8, but also good for all the other brands out there). With unknown/new battery brands you have to be aware of the fact that lots and lots of manufacturers over state the capacity. A high-capacity battery with a low price tag often are what your gut tells you; too good to be true. Fortunately loads of people tested the Talentcells with results very close to spec. Because the target audience isn’t the AV-professional, the price is way below the mentioned AV-specific brands. Downside is they just come with a generic 2.5 mm output jack, not locking and with an annoying switch. So you might want to consider swapping that out for one of the locking kind (although a strong rubber band holding the cable tight against the casing also will work) and get rid of the switch. Talentcell, pros: cheap, proven capacity, small form factor. Cons: Not locking or ‘dockable’, the switch.

talentcell

Besides the Talentcell there are plenty other options out there. Keep in mind the chemistry though. Loads of so-called emergency laptop battery banks, or the famous blue wrapped CCTV back up batteries, are packed with lithium polymer (LiPo) cells. Although they will work, they are more fragile than the Lithium Ion cells used in all the previous ‘approved’ batteries. Remember the exploding Samsung phones? That was a LiPo cell. And be careful with smart phone/USB battery banks, besides the fact they just give 5v that you need to step up (more in chapter 2 of this series about that), most also can not deliver more than 10 Watt of output maximum, meaning you are really stretching out the battery, generally not a good thing to do with batteries.

About all these generic battery solutions need some form of rewiring/jumper cable to make them suitable for our purpose. In a later post we will go over the options.

DIY Route

Most likely you are not reading this post if you are that tech-savvy already to roll out your own batteries. But in case you are, remember what I said, a battery is a battery is a battery, you might as well make your own pack. Most commercial packs have 18650 cells in them, they are rated 3.7v nominal, so you need 3 to 4 to get it up to 11.1 to 14.8v nominal. double or even triple that in parallel to get the capacity up. Read our post about the DIY Pelican Battery for details. The tutorial is about mounting it inside a Pelican case, but just scale the amount down and you can use the same details for a smaller form factor pack. Also check out this video by YouTuber GreatScott! how he made a neat small battery as well as the housing.

Extra tip: AA Batteries

And I don’t mean putting them into all the devices separately, but in a so-called 10/12 slot battery holders first. To get back to the math at the beginning of the post, 10 * 2.5A = 25 watt, 12 * 2.5A = 30 watt nominal, based on 1.2V 2500mah rechargeable AA cells, like the IKEA ones reviewed here on this site. Most likely this will not give you all the juice to get throughout the whole day, but this might be one of those things to have as a backup in your arsenal, in case of emergency. AA’s can be bought anywhere in the world, and if shit hits the fan, like a broken charger for your fancy eSMART system, you got yourself covered.
It’s also very inexpensive, for example this one at BangGood. Do keep in mind: Alkaline batteries, the non rechargeable ones sold at every gas station, are 1.5v+ when charged. so a 10 slot holder might be a better bet, considering the range of acceptance voltage of the recorder.

Screen Shot 2018-04-28 at 21.18.48

To wrap things up

I know, this was a long read but we had a lot to cover and we are not there yet. Next posts will be about battery distribution system (BDS), mounts, cabling, connectors, Charging and various accessories.

If you have any questions or remarks, please leave a comment. Also please share your preferred battery solution!


This is part one of a series of articles, split up as follows:

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