I have been asked frequently about my smart battery system which includes the Audioroot power distribution units and the Inspired Energy batteries. What people seem to like the most or are the most impressed by is the very cool battery telemetry that my power distro unit is able to provide, along with the incredibly small-sized shape, yet high capacity the battery provides for location sound use. Considering there are a few options available in the market, I thought I’d write up the following buying guide for those who are interesting in investing into the smart battery systems.

First Things First, What Makes a Smart Battery Smart?

smart battery, unlike regular batteries, has a micro-controller in a single-wire or two-wire system, which is able to provide state-of-charge (SoC) information about the battery. If capable, other devices being powered by said batteries can in turn read and interpret this SoC information to provide highly accurate battery information and telemetry. The key difference between the single-wire and two-wire systems (also known as System Management Bus or SMBus), is that SMBus moves the charge-control from the charger to the battery, so that the battery can dictate what the correct charging algorithm is to the charger. This can be beneficial as each smart battery can tell the same charger what their optimal charging procedure is.

These smart (SMBus) batteries have existed for over two decades, and are heavily used in the medical, military and industrial fields, for example, but they hadn’t been used in location sound specifically until Audioroot, a French company that makes unique power solutions for location sound, came up with their eSMART line of batteries and power distribution systems some years ago. Since then, Aaton Digital and Sonosax have joined the wave, and have started to utilize the smart battery as the power source for their newest recorders, the Aaton Digital CantarX3 and the Sonosax SX-R4+. Remote Audio has also joined the wave with the introduction of their MEON HI-Q battery system.

All of these portable smart battery systems made by Audioroot, Aaton Digital, Remote Audio and Sonosax are using what is called the “205x” range smart battery, originally designed and developed back in the mid 2000s by Inspired Energy, one of the leading manufacturers of SMBus smart batteries in the United States.

205x Range Smart Battery

What are the current 205x smart batteries available in the market, you ask? Here you go (in ascending alphabetical order):

Brand Model Nominal Voltage (V) Capacity (Ah) Energy (Wh) Estimated Price (ea) *
Aaton Digital ND2054AA 14.4 3.4 49 USD$170
Audioroot eSMART Li-49Wh 14.4 3.4 49 USD$145
Audioroot eSMART Li-98Wh 14.4 6.8 98 USD$217
Inspired Energy ND2054HD34 14.4 3.4 49 USD$108
Inspired Energy NH2054HD34 14.4 6.8 98 USD$164
Remote Audio MEON HI-Q 49 14.4 3.4 49 USD$105
Remote Audio MEON HI-Q 98 14.4 6.8 98 USD$160
RRC RRC 2054 15 3.2 48 USD$120

While there may be a few more available options in the 205x range of batteries not listed here, these offerings listed above are ideal for portable / bag solutions, as they supply the required DC voltage to power most devices (9VDC – 18VDC), and they meet the International Air Transport Association (IATA) and TSA travel guidelines for lithium batteries. These guidelines state that you can carry-on without restriction, lithium batteries that have less than 8 grams of lithium content or 100Wh per battery. And at 98Wh, these are the highest capacity batteries available in the market at their size and weight, still coming in smaller than the widely used, standard NP-1 style battery, which also has substantially lower capacity than the offerings above.

One thing you may have noticed is that the Aaton Digital ND2054AA, the Audioroot eSMART Li-49Wh, the Inspired Energy ND2054HD34, and the Remote Audio MEON HI-Q 49 (and similarly the RRC 2054) all have the same nominal voltage, capacity and energy; and look to be the exactly the same. The Audioroot eSMART Li-98Wh, the Inspired NH2054HD34, and the Remote Audio MEON HI-Q 98 do as well. So what is the difference between them? Physically, not very much. They all have the same physical components and are Smart Battery Data Specification (SBDS) compliant. The only thing that differs them physically is the label printed on them. However, the one huge, more subtle difference between them is the firmware loaded into each battery. Each manufacturer loads a proprietary firmware with a unique manufacturer identifier and data into their batteries. Currently this doesn’t mean much, as for the most part, these batteries seem to be completely open to work with any SMBus-compatible device. But in the future, it can mean that if Audioroot decides to do so, their chargers and power distribution systems will only work with their branded batteries. 

205x Smart Battery Chargers

Talking about chargers, you’ll be needing one if you want to be able to reuse any of these smart batteries. Here are your options (in ascending alphabetical order):

Brand Model Time to Charge 1 Battery (hrs) ** Time to Charge 2 Batteries (hrs) ** Estimated Price (ea) *
Single Bay Chargers
Audioroot eLC-SMB 3 N/A USD$130
Audioroot eSMART Mono Charger 3 N/A USD$220
Inspired Energy CH4000 Single Charger 3.5 N/A USD$118
Inspired Energy CH5000 Single Charger + Calibrator 3.5 N/A USD$139
Inspired Energy CH7000 Single Charger 3.5 N/A USD$140
Dual Bay Chargers
Aaton Digital Cantar X3 Dual Smart Battery Charger 3.5 3.5 USD$1,111
Audioroot eSMART Dual Charger 3 3 USD$300
Inspired Energy CH4040 Dual Charger 3.5 3.5 – 6 USD$236
Inspired Energy CH5050 Dual Charger + Calibrator 3.5 3.5 – 6 USD$278

So, let’s break this down a little. All these chargers are able to charge either a single 49Wh or a 98Wh smart battery in about 3 to 3.5 hours. All the dual bay chargers do simultaneous charging to both bays, and will charge two 49Wh batteries in about 3 to 3.5 hours total, however, if you are charging two 98Wh batteries, the Inspired Energy dual bay offerings will increase the total charging time for both batteries to a little less than double, about 6 hours. The Audioroot eSMART Dual Charger claims that it will charge both batteries, either 49Wh or 98Wh in 3 hours.

In addition, you will notice that Inspired Energy offers a single-bay and a dual-bay option with and without a calibration feature. A smart battery has a highly accurate on board fuel gauge, but when the battery is not fully drained and charged (or run through a full cycle), the gauge begins to drift and lose accuracy. The smart battery’s microcontroller will keep a log of this, and when plugged into one of the Inspired Energy chargers with integrated calibrators, the charging LED will flash red, indicating that the battery requires recalibration. All you need to do is press the button on the charger to re-calibrate the battery. All the other brands in this list offer integrated and automatic calibration, so that when you plug in a smart battery that requires recalibration, it will automatically do it. Recalibration adds about 30 minutes to the charging time. I highly recommend getting a charger with a calibrator.

The Inspired Energy CH7000 can operate from any DC voltage between 10 and 25V. This makes it ideal for use with a vehicle cigarette-lighter socket or 12V solar panel. All Inspired Energy chargers have a cooling fan that turns on whenever you plug in a battery. The fan is not quiet, but it isn’t annoyingly loud either. The Audioroot eSMART chargers remove the fans for silent operation. The Audioroot eSMART chargers also offer a very cool OLED screen which provides all kinds of useful battery telemetry: current state of charge (%), battery voltage, charging current, estimated time to end of charge, battery pack temperature, and the number of battery cycles.

Lastly, Inspired Energy offers their chargers in a few international variants:

  • CHX0X0A: US/North American AC plug
  • CHX0X0E: European 2-pin AC Plug
  • CHX0X0U: UK 3 Pin AC Plug
  • CHX0X0X: No AC cable

Now, how do I connect these batteries to my gear?

Well, this is where we can get creative. At a very basic level, you will need a molded battery connector or a “battery cup”, as it is more commonly known in our industry, that can connect to the smart battery’s terminals on one end and to the power input of your device on the other end. Here are your off-the-shelf options (in ascending alphabetical order):

Brand Model Termination Estimated Price (ea) *
Audioroot eCON-OUT (5-Wire Straight Cable) N/A USD$30
Audioroot eCOIL-OUT (2-Wire Coiled Cable) N/A USD$39
Inspired Energy 629028 (5-Wire Straight Cable) N/A USD$20
Inspired Energy 629030 (2-Wire Coiled Cable) N/A USD$20
Audioroot eXLR4-OUT XLR4F USD$46
Audioroot eHRS4-OUT Hirose 4-Pin USD$46
Audioroot eHRS4RA-OUT RA Hirose 4-Pin USD$46
Audioroot eZAXRX-OUT Switchcraft 761K USD$40
Audioroot eSRARX-OUT Switchcraft S760K USD$40

The key difference between the Inspired Energy and Audioroot cups is that the Audioroot cup locks into the battery, whereas the Inspired Energy cup simply slides. Now the Inspired Energy cup doesn’t easily slide out, however, I highly recommend getting a locking Audioroot cup instead, as there is no possible way for cup to accidentally disconnect from the smart battery. It is well worth the higher price for the added peace of mind.

The straight cable unterminated cups come with a 5-wire pigtail that can be terminated to any desired connector for use with any SMBus-compatible device, and the coiled cable unterminated cups come with a 2-wire pigtail that can be terminated to any desired connector for use with any non-SMBus-compatible device. The terminals on the 205x smart battery and the leads on the straight cable unterminated cups are as follows: [1] (+) positive end of battery, [2] (C) SMBus Clock, [3] (D) SMBus Data, [4] (T), and [5] (-) negative end of battery. To power any regular device, all you require are leads [1] (+) and [5] (-). To power an SMBus capable device, you will require leads [1] (+) and [5] (-) for power, and leads [2] (C), [3] (D) for SMBus communication. Lead [4] (T) is not used in the terminated connector. On the terminated end, the order of the pinout for the connector is reversed so that pin [1] is (-), pin [2] is (D), pin [3] is (C), and pin [4] is (+).

Please be careful to not use SMBus-compatible cables with non-SMBus-compatible devices, as this may cause damage to the battery, the device, or both.

Audioroot eHRS4-OUT-4Wire

Audioroot eHRS4-OUT-4Wire

Since the Audioroot eZAXRX-OUT and the eSRARX-OUT are terminated to Switchcraft connectors with only two leads, these cups are for use with non-SMBus-compatible devices; in this specific case, with Zaxcom and Lectrosonics wireless receivers, respectively. These are great for powering wireless receivers on cameras for example. The rest of the Audioroot cups are terminated to connectors with 4 pins, and as such, are for use with SMBus-compatible devices. Please note that Audioroot sells non-SMBus versions of these cups, only utilizing pins [1] (-) and [4] (+) on the output connector, and unless specified, these will be the versions you receive when you purchase them. I suspect they do this to make sure you don’t damage any gear. You must request the “4Wire” version to receive the SMBus-compatible versions of these cups. Audioroot labels these as eHRS4-OUT-4Wire and eHRS4RA-OUT-4Wire for example.

Before moving on, I’ll also add these options from Inspired Energy into the pot:

Brand Model Compatibility Output Cable + Connector Estimated Price (ea) *
Inspired Energy MP20503 Small Belt-pack ND2054 Straight 5-wire + Unterminated USD$35
Inspired Energy MC20501 Small Belt-pack & Charger ND2054 Coiled 2-wire + 5.5x2.1mm USD$110
Inspired Energy MPL205-5BV01 Large Belt-pack NH2054 Straight 5-wire + Unterminated USD$39

These are “belt-packs”, or battery holsters with a belt clip that can be used to power devices (typically used in the medical field). They come in two different versions: the MP which is only used for powering devices, and the MC which can be used for powering devices and/or charging the battery. They also come in two different sizes, the MP20503 and MC20501 fit the smaller ND2054, eSMART Li-49Wh, ND2054AA and RRC 2054 batteries, and the MPL205 fits the larger NH2054 and eSMART Li-98Wh batteries. There is no belt-pack with integrated charger available for these batteries. The MP and MPL units come with a straigh 5-wire unterminated cable, which can be terminated to the 4-pin connector of your choice for use with SMBus-compatible devices. The unit with an integrated charger comes with a 2-wire coiled cable terminated to a 5.5x2.1mm plug. The cool thing about these belt-packs is that you can remove the belt-clips, and essentially create a sliding battery holster that securely slides in and holds the entire battery.

Now, how to power multiple devices at once?

This is where the fun begins. You can take any of the batteries and cups listed above, and plug them into any power or battery distribution system, which then in turn power all the devices in your bag. The Remote Audio BDSv4, Sound Guys Solutions MD-6u, or the Cable Techniques Battery Bud II could work with many of the options above, for example. All you need to do is make sure that the cup is terminated to the appropriate input connector compatible with the distro, and that only pins [1] (-) and [4] (+) are wired on the output connector of the cup, as these distros are not SMBus-compatible. Although you will not get current SoC information from the battery using these distros, these batteries can still benefit your overall workflow as you will be getting the highest capacity batteries available at their size and weight to power your bags, if for nothing else.

Audioroot also makes power distros that will interface with these batteries, as well as other non-smart batteries. Where Audioroot really shines, though, is in their SMBus-compatible power distros. Here’s a full list of the Audioroot distros:

Brand Model I/O Estimated Price (ea) *
Audioroot vmDBOX Switchcraft 760K USD$160
Audioroot vmDBOX-HRS Hirose 4-Pin USD$170
Audioroot eSMART BPA  Switchcraft 760K USD$129
Audioroot eSMART BG-DH MKII Integrated Cup + Hirose 4-Pin USD$220
Audioroot eSMART BG-DU Hirose 4-Pin USD$291
Audioroot eSMART BG-DU-REG Hirose 4-Pin USD$460

First let us get the non-SMBus-compatible distros out of the way. Both vmDBOX‘s feature a voltmeter with six power outputs and a single locking toggle switch, which is quite ingenious as it requires you to pull the switch up before you can toggle it. The main difference between these units is that one features Switchcraft 760K connectors for its I/O, and the other features Hirose 4-Pin connectors instead. You can use them with any battery and cup in the market. If you use them with a smart battery, then remember to use a cup with only a 2-wire configuration for its connector.

The rest of the distros are SMBus-compatible, which means that they can receive SoC information from the smart battery. The eSMART BPA is both a cup and power distro built into one. It will only fit the 205x smart battery. It has 4 power outputs on two small switches, so you can power two sets of devices independently. This particular unit also features a serial output which can be connected to an external fuel gauge display. The eSMART BG-DH MKII is the exact same size as the vmDBOX, but it has a locking audioroot cup for 205x range batteries wired for its input, which means it will only work with the 205x smart battery. It features a beautiful OLED screen fuel gauge displaying all sorts of useful SoC information, including remaining capacity (%), estimated running time left, battery voltage, current consumption, battery pack temperature, and the number of battery cycles (charge/discharge). It has 6 outputs on Hirose 4-pin connectors; the first four outputs are on one locking toggle switch, and the other two are on a second locking toggle switch. ‡

The eSMART BG-DU and the eSMART BG-DU-REG are very similar to the BG-DH MKII; they add two extra Hirose 4-pin outputs on an additional locking toggle switch for a total of 8 outputs and 3 locking toggle switches. These differ from the BG-DH MKII, however, in that they do not have a cup wired to them, but instead have a Hirose 4-pin input. This means that you’ll need a battery cup along with your smart battery to plug it into either of these distros. It also means that they are capable of connecting to non-SMBus batteries as well. As a matter of fact, both units feature a coulomb counter and calibration routine that is able to measure non-SMBus batteries and store their SoC in the distro itself, as well as display all pertinent battery telemetry as though it was a smart battery. The biggest disadvantage is that it assumes non-SMBus batteries are fully charged when connected, and they have to be calibrated frequently to maintain accurate SoC data.‡

Both BG-DU distros are essentially the same, with the BG-DU-REG differing only in its offering of power regulation on some of its outputs. The BG-DU-REG has two 12V/12W regulated outputs and two 9V/18W regulated outputs. The former are good for troublehsooting ground loop issues, and the latter are good for wireless receivers, which tend to be less power hungry. The addition of power regulation also increases the depth of the BG-DU-REG quite substantially, almost twice a deep as the BG-DU. In my opinion, the BG-DU-REG may not be as necessary in a bag as it would in a cart, where you would be powering many more components.

Okay, anything else?

Yes! If you buy into the 205x range smart battery, look at the following accessories, which can be handy:

Brand Model Description Estimated Price (ea) *
Inspired Energy 936186 Dust / Travel Cap for 205x Batteries USD$1
Inspired Energy 936143 Battery Mounting Guide Block USD$1

The dust / travel caps are very useful for covering the terminals in your battery, and protect them from any dust. They are essentially a must for travel, as the IATA and TSA require that spare batteries have their terminals insulated to prevent any short circuits. These do the job exceptionally well for an incredibly low cost. The mounting guide blocks can be useful for DIY battery mounting solutions.

What about us cart users?

Glad you asked! Don’t think that you’re out of the smart battery circle. You can use many of the products listed above in your cart, but there are a few other SMBus-compatible options that may serve you better for cart usage. Audioroot has the following:

Brand Model Description Estimated Price (ea) *
Audioroot eSMART LiFe-115Wh 12.8V / 9Ah / 115Wh lithium-iron phosphate SMBus battery. N/A
Audioroot eSMART LiFe-256Wh 12.8V / 20Ah / 256Wh lithium-iron phosphate SMBus battery in Pelican case. N/A
Audioroot eSMART LiFe-576Wh 12.8V / 30Ah / 576Wh lithium-iron phosphate SMBus battery in Pelican case. N/A
Audioroot eLC-PO4 Smart charger for 4Ah or higher capacity batteries USD$100
Audioroot eLC-PO10 Smart charger for 20Ah or higher capacity batteries USD$110
Battery Output Cables
Audioroot eXLR4-XLR4 XLR4M to XLR4F cable to plug in LiFe battery to power distribution system. USD$40
Power Distribution
Audioroot eSMART K-ART  Cart power distribution system USD$800

The Audioroot LiFePo4 batteries also have microcontrollers for SMBus communication, so they will pass on all the same SoC data as the smaller 205x range batteries. Because of their higher capacity, these batteries lend themselves better for cart work, however, because of their high capacity they are also not allowed for air travel. The UN & DOT requires Lithium batteries greater than 100Wh to be shipped as class 9 hazardous goods. You may transport up to 2 batteries with a capacity higher than 100Wh but no higher than 160Wh in your carry-on with explicit consent from the airline. That means that you could potentially carry-on two of the eSMART LiFe-115Wh batteries, but the eSMART LiFe-256Wh and the eSMART LiFe-576Wh batteries cannot be transported by air.

The eLC-PO4 charger is good for the eSMART LiFe-115Wh and eSMART LiFe-256Wh, and the eLC-PO10 is ideal for the eSMART LiFe-256Wh and the eSMART LiFe-576Wh, as it will charge them faster. The Audioroot eXLR4-XLR4 cable doesn’t have anything special; it’s just a regular XLR4M to XLR4F cable, so you can get this one or buy any other off-the-shelf brand.

The Audioroot eSMART K-ART is a highly sophisticated power distribution system for the cart, with two simultaneous power inputs, like the eSMART BG-DU, capable of receiving any type of battery and displaying accurate battery telemetry on two fuel gauges, one for each battery. Of course, if you use SMBus batteries, the battery telemetry will be automatic and will not need to be measured by the distro. It has 16 power outputs (4 XLR4 and 12 Hirose 4-pin) grouped into 10 switchable power paths, as well as 4 USB ports. This should truly cover any and all powering needs in the cart.

Having shown all the Audioroot offerings for cart users, it is important to note that the LiFePo4 are not available for sale in the United States as they cannot be shipped via air. Currently Audioroot does not have any ocean freight shipping available for their products. However, do not lose hope yet! There are other LiFePo4 SMBus-compatible batteries available in the market. In Australia, there are the Drypower LiFePo4 SMBus-compatible batteries (IFM12-90E3IFM12-200E3 and IFM12-450E3). In the U.S., there is the IronWorks LiFePo4 SMBus-compatible battery. ‡

However, if you wish to have an SMBus-compatible powering solution with a much higher capacity not bound by the regulations established by the UN, DOT, IATA and TSA, consider creating a custom smart battery array which utilizes the same 205x range smart batteries. By wiring two or more of the 205x range batteries in parallel, you can produce a battery array that has the same output voltage as a single battery, but you will have increased the total capacity by the sum of the capacity of all the batteries in the array. For example, two NH2054HD32 batteries wired in parallel will produce the same nominal voltage as a single battery (14.4V), but will have double its capacity to 13.6Ah (2x 6.8Ah). Three of these batteries will have tripled the total capacity to 20.4Ah. And so on. The main benefit here is that an array will allow for hot swapping of individual battery packs. The remaining batteries just need to be able to handle the total load. The SMBus can be polled from all the batteries in the array to give the overall fuel gauge for the entire array.

Where can I buy all of this?

You can most likely go to any reputable location sound dealer for the Aaton Digital and Audioroot stuff. The Aaton Digital charger and batteries are included in the purchase of the Cantar X3, currently the only Aaton Digital device that uses these batteries, so you may not need to purchase these if you are already purchasing the X3. For the Audioroot items, your preferred dealer can give you accurate pricing for each item based on your locale. For the Remote Audio MEON HI-Q batteries, any Remote Audio dealer should be able to take care of you.

For anything Inspired Energy, you will need to contact them directly. Currently, they do not have any means for purchasing their products online; you may get quotes via email, but you will need to call them to place an order. It helps to know the part numbers for all the items you wish to purchase. They build to order, which means that when you place an order with them for any batteries or chargers, it will take them about 3-5 business days to fulfill the order and ship it from Florida. For anything RRC, you will also need to contact them directly as well. They have locations in many countries around the world. For the larger LiFePo4 batteries, you will have to do a bit of your own research to figure out locations near you where you could potentially buy them.

What Does the Future Hold?

I’m a firm believer that the SMBus batteries are the future. There are just too many benefits to neglect. Currently, there are a few remarkable options in the market that are great for location sound use, and luckily for us, they all seem to work well with each other. Unfortunately, this could change, as manufacturers can select to lock the usage of their SMBus-compatible devices with their batteries only. While I understand the reasoning for this, I would hope that SMBus-compatibility would continue to be open instead. I see it being something like DANTE, where multiple products can adopt the technology and easily interface with each other, and the choice is ultimately left to the users.


That’s it! If you are interested in investing into smart battery systems for location sound use, I hope this guide was useful. Please feel free to drop any questions or comments in the section below.



‡ Aaton Digital, Audioroot, Remote Audio and RRC batteries each have custom proprietary firmware that is unique to them, and which differs from the standard Inspired Energy batteries. Any of these batteries may work with some, but not all Aaton Digital, Audioroot, Inspired Energy, Sonosax, Remote Audio, RRC or other devices; they may work with all Aaton Digital, Audioroot, Inspired Energy, Sonosax, Remote Audio, RRC or other devices; or the may work with some Aaton Digital, Audioroot, Inspired Energy, Sonosax, Remote Audio, RRC, or other devices up to a certain date or product revision. Any functionality between these batteries and devices from other manufacturers is a fortunate coincidence or intentional choice by the manufacturer of said devices. As such, if you choose to operate any particular branded battery with a different branded device, you do so at your own risk, and you cannot hold any of the mentioned manufacturers, suppliers, distributors, dealers or Mixelius Inc. responsible.

* These prices serve only as approximations as of October 8th, 2015, in USD when purchasing in the U.S. They may be converted approximations from other currencies if the product is manufactured outside of the U.S., as it is in the case of Aaton Digital and Audioroot products, for example. They represent the price per unit when buying less than 10 units.

** These charging times are approximations only, as provided by each manufacturer.