Saturday, August 06, 2016

Zoom F8: Powering the recorder

This is the third article on the Zoom F8 multitrack audio recorder, which started with an overview of features and continued with my suggestions for firmware improvements. Here I will discuss a few power options and discuss batteries.

The latest generation of hand-held recorders, like the excellent Olympus LS-11, last an incredible time on only two AA batteries. With a life of 18 to 22 hours, I often forget that they need recharging. It's easy to take this small miracle of power management for granted. Thank you, electrical engineers!

The move to a larger recorder like the Zoom F8 can be a shock (no pun intended). These circuits are power hungry, not only because they provide phantom power. Finding the "right" power source can be a challenge, though not because solutions don't exist. The film industry worked all this out years ago, but their tools can be overly expensive. On the other hand, customised battery packs sourced from eBay parts might be cheap, but they raise safety and reliability concerns. Somewhere in between there must be a happy medium.

First, a quick explanation of key terms. Every device requires a certain voltage (AKA potential), measured in Volts, abbreviated V. Every device also uses a certain amount of current, measured in Amps, abbreviated A. You multiply these together to get power, measured in Watts, abbreviated W.

If you look at spec sheet for the Zoom F8, you will see that it is rated for 12 V and the power consumption is 12 W. That means it is drawing 1 A. The AC adapter actually provides "DC12V 2A", which means it provides exactly the correct voltage and exceeds the rated current draw. That is a good thing; there is no problem in providing more current than a device might use. But to exceed the voltage risks frying the components. This is important!

When hooked up to the wall, we don't usually need to worry about the juice running out. But when hooked up to a battery, we need to have some good idea of how long that current source will last. The current capacity of a battery is measured in amp-hours (Ah), though you will quite often see this specified instead in milliamp-hours. Maybe because the numbers look more impressive!

Take a typical AA battery that is rated at 2000 mAh. Those of us not in marketing would just say 2 Ah. This battery can supply the nominal 1.2 V at 1 Amp for 2 hours. Or if it needs to supply 2 Amps, it can do so for 1 hour. Or 4 Amps for half an hour. And so on.

Similarly, we can talk about the power capacity of a battery. This is the rated voltage multiplied by the current capacity. So that same AA has a power capacity of 2.4 Wh (1.2 V multiplied by 2 Ah).

Flight Limitations
This last value is important when travelling by air, because regulations exist to govern the transport of batteries, all of which are potentially dangerous, especially in a confined space. Though rules differ, to be safe you should not pack any batteries in your checked luggage. In truth, batteries within mobile phones and similar devices are likely OK, but I would not risk the letter of the law.

In your carry-on, no single battery should have a higher capacity than 100 Wh. And the total you can carry is 300 Wh. Anything more than that, you need to fill out lots of forms and adhere to stringent packaging and handling constraints.

You should also be aware that all powered devices should be ready to turn on. Otherwise, you risk confiscation. Do not fly with dead batteries in your laptop!

Armed with these facts, we can return to the topic at hand. The Zoom F8 is flexible in having three power sources: DC power inlet, Hirose inlet, and AA battery sled. They can all be hooked up and working. The unit will automatically switch from one to another with no break in recording, using the priority sequence as listed. Having this redundancy on hand is fantastic!

Now I will consider each of the three power sources in turn.

AA battery sled

The plastic sled is cleverly made of light plastic. It has hinged doors on each side that you can also pop right off. Each side holds four AA batteries, of whichever chemical formulation you wish. You can specify Alkaline, Lithium, or NiMH in the recorder's menu, though I believe that all this does is allow the F8 to estimate the remaining battery life. The sled slides into a cuboid space from the back of the unit, and is secured with a door and thumb screw. It's a nice design.

If you wish, you can buy extra sleds for $25. Then you can have sets of batteries on hand, ready to just pop in. The sled is 70 x 60 x 34mm and only 20g. A set of batteries weighs 240g. At home I have a proper conditioning charger, but when travelling I use a smaller Uniross Fast Charger, pictured above (110 x 63 x 38mm, 100g).

By the way, I am mentioning all of the dimensions and weight since I wish to minimise both values. The figures will be used in my next article.

For environmental reasons I refuse to use disposable batteries. For years I have standardised on the 1900 mAh Eneloop NiMH, which work just fine in portable recorders, cameras, flash-lights, and other devices. However these are somewhat underpowered for a large piece of equipment like the F8. The 2500 mAh Eneloop Pro last over 30% longer.

DC Port

The DC Port is located on the back of the unit, which is not necessarily handy if the recorder is in a bag. This input expects 12V and is configured in the standard fashion, with the centre pin positive and the ring negative. You should note that not all DC ports are physically the same. This one has a 5.5mm outer diameter (OD) and 2.1 mm inner diameter (ID), which I have found to be the most common type. Apparently it's called "Type M", though this terminology is not often used and is hence of limited utility.

The Zoom comes with a universal AC adapter as already mentioned. It has a long cable and weighs 150g. There is a solid connection between the jack and socket, which is very nice to find. You don't want the cable falling out accidentally.

The DC port can be used with other power sources, including battery packs and powerbanks. These days most powerbanks are made for mobile phones and tablets, and so only have USB outputs. But it is still possible to find models capable of supplying voltages suitable for laptop computers (anywhere up to 20V) and these have DC jacks. Just be sure the powerbank has 12V and you can use the one source for your Zoom F8 and laptop as needed. That is surely convenient.

What is a powerbank? Really it's only a set of Lithium-ion or Lithium-Polymer battery cells with integrated circuits to ensure safe operation, plus the correct electronics to convert the voltage. The distinction between a "battery cell", "battery pack", and "powerbank" should be clear, but grey zones exist, as we will see.

Hirose Port
The 4-pin Hirose port is located on the side of the recorder. This form factor will not be familiar to you unless you have used other professional film and audio gear. It's wired with pin 4 positive, pin 1 negative (which is the standard). The port is specified for 9 to 16V, but in fact has been confirmed to accept up to 17V.

I would recommend using the DC port for the supplied AC adapter or a powerbank specifically designed to emulate such an adapter. For other power sources, it is preferable to use the Hirose port, given its wider operating range. This might well mean buying a converter cable, or wiring one up yourself.

It's great that Zoom has adopted a standard already well known to video and audio pros. Many existing power solutions can be used with the F8 with no change. The next sections will consider some popular options.

One of the most popular battery formats is NP-1, a Lithium ion formulation rated at 14.4 V. Unlike NiCad or NiMH batteries, Lithium ion have no memory effect and very low self-discharge, so they can be kept on the shelf for extended periods.

The Swit brand has produced these batteries for the film sector for about fifteen years now. They sell a kit containing a dual battery charger and two 73 Wh batteries. Each battery is 185 x 72 x 25mm and weighs 690g. The charger is huge (215 x 155 x 55mm, 850g).

Then you need a way to connect the battery to the Hirose connector. Thanks perhaps to Sound Devices, this simple plastic box is known as a "battery cup". Their own XL-NPH is exorbitant in Europe, but Hawkwoods sells a similar unit more reasonably (75 x 30 x 37mm, 75g).

Sony BP
The Sony BP format was originally designed for video camcorders. It is also a Lithium ion formulation, rated at 14.4 V. On eBay one can source the various parts one needs to make this work with the Zoom: a battery tray that terminates in a DC jack, a DC to Hirose connector, and two 64 Wh batteries.

It's also quite easy to jury rig other systems, using battery formats meant for other established gear, for example Canon camera cells. If you don't mind doing a bit of soldering the package can be relatively inexpensive, but I wouldn't want to explain what I am carrying when checking in for a flight.

Lithium Polymer
LiPo batteries are commonly used in hobbies such as remote control (RC) vehicles. These batteries are light-weight compared to their large capacity, and can be made in almost any shape and size. Their flat discharge rate ensures even operation, but they can also handle sudden power requirements due to a high peak discharge rate. On the downside, LiPo batteries have particular requirements for charging and discharging to ensure their safety and durability. If using raw RC batteries, you need to take special care and monitor them at all times.

Tracer sell high-performance batteries for astronomy, emergency services, construction, and other industries. Their LiPo range incorporate power conditioning electronics, safety features, and a charge indicator with super-bright LEDs. In fact, these are powerbanks in all but name. They don't even look like batteries, which is a comfort to security inspectors. I find their industrial design most appealing!

Operating at 12V, the Tracer LiPo series starts with a small 4Ah 48Wh unit that is only 115 x 76 x 32 mm and 360g. Each battery comes packaged with a universal AC wall charger (95 x 50 x 40mm, 205g), car charger, and belt pack. The charger even has multiple prongs for different locations. While this completeness is reassuring, it is also rather wasteful when buying more than one unit. (I inquired, but the company has no plans to offer alternative packaging.)

Purchase adapter cables separately, or request a custom fitting. I bought the appropriate DC connector and, for redundancy, a "bare wire" connector to make my own Hirose hookup. (Once I stop writing articles, I might have the time!)

Tracer also offer a higher capacity 8Ah 96Wh battery (152 x 80 x 38 mm, 600g). Actually, they have quite a few others, up to 264 Wh, but this model slides right under the airline regulations.


These are certainly not all of the power solutions, just some typical examples. In my next article I will compare them in terms of size, price, and capacity. I've run some real-world tests using the F8 and the results surprised me.

In the meantime, for general technical background check out the extensive information at Battery University. Or learn about LiPo cells from the hobby perspective.

Finally, here's an in-depth video that demonstrates the Zoom options.



Noiz Boy said...

A minor correction. In the US anyway battery restrictions are only for lithium batteries. None of the other chemistries really poses a risk, they don't burst into flames or blow up like lithium batteries have done on occasion. So maybe all batteries are restricted in the UK/EU, but not in the US. TSA is a different issue and carrying on a lot of batteries might get you a closer look? Honestly I have traveled a fair amount and never had an issue. A friend though had an issue many years ago with a pair of fairly large gel cel batteries that security wanted to keep. The good old days when the "light weight" battery was 3lbs!

robin said...

Sure, I am talking about rechargeable batteries here, those with various Lithium chemistries. And I am not really interested in only those rules that apply to the USA, since most people live somewhere else!

I have based my advice on the actual technical rules I have read, which are detailed and contradictory. In fact, there is a rule on the books with many airlines that Lithium batteries in carry-on are strictly forbidden. But they don't actually enforce this. One day they might decide to! Likely the day after an attack somewhere.

Airlines change their battery rules regularly. Just this last week we saw new announcements regarding battery safety. It's best to play it safe and conservatively. Because having something confiscated really sucks!

Anonymous said...

Center pin of F8 power supply is 2.5mm not 2.1mm

robin said...

That contradicts the information I have from my source that makes power cables. I don't have calipers handy. What is your source?

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