Best Thunderbolt docks 2022: Extend your laptop’s capabilities

With Thunderbolt ports becoming more common in laptops, a Thunderbolt dock can be a critical accessory. Think of the Thunderbolt dock as a more powerful, high-speed alternative to a USB-C hub, adding I/O expansion to your laptop in the form of extra ports for mice, keyboards, external drives, SD cards, and, most importantly, displays. It can even charge your laptop and smartphone!

Simply put, laptops are slimming down. And in the quest for a “cleaner” look, many laptop makers are forgoing the legacy ports (particularly in the premium models), leaving those duties to external devices.

The biggest difference between Thunderbolt docks and USB-C hubs are price and bandwidth. USB-C hubs or dongles are far cheaper, but they offer far less bandwidth. That primarily matters where display connectivity is concerned, but can also affect the number and type of external hard drives, SSDs, and other peripherals that your PC can connect to. While a USB-C hub can support a single 4K display, often at an eye-wearying 30Hz refresh rate, Thunderbolt docks can support up to two 4K displays at a comfortable 60Hz. You can also use Thunderbolt 3 to enable an external GPU for your PC. (There’s nothing stopping you from using a USB-C hub with a Thunderbolt dock, either.)

If your laptop includes a Thunderbolt port, chances are it supports the Thunderbolt 3 or Thunderbolt 4 standard, both of which provide 40Gbps. Intel helped launch the updated Thunderbolt 4 specification in July 2020 as part of its 11th-gen “Tiger Lake” Core laptops, and the specification has become more popular on productivity laptops. The bandwidth of Thunderbolt 4 is enough to drive high-resolution displays and shuttle data back and forth between peripherals without causing your display to flicker or your video stream to stutter.

What’s the difference between Thunderbolt 3, Thunderbolt 4, and USB4? The simple answer is that they’re all extremely similar. The longer answer, explaining the differences, may be found within our Thunderbolt buying guide below our recommendations. If you want to learn more about the benefits of a Thunderbolt dock, what to look for when buying one, or how to know whether your laptop will support one, you can find that in our buying guide, too.

We define a Thunderbolt dock as one that supplies the ports you need for legacy devices, like USB-A and HDMI. We define a Thunderbolt hub as Thunderbolt-in, Thunderbolt-out. The latter is useful if you’re among the small number of those who own dedicated Thunderbolt displays. (If you don’t have one, that’s fine—just buy a Thunderbolt dock instead.)

We define the “best” Thunderbolt docks as much by availability as performance. If a dock goes out of stock, it may be pulled from our listings. Why you can’t buy a Thunderbolt dock may be as much to do with the simple (in)availability of components as anything else. The founder of dock maker Plugable explains this in more detail in our story.

The best Thunderbolt docks

We lead off with our picks for best budget docks, which typically boast a compact form factor and just two display outputs. They’re usually bus-powered, meaning they’ll require an external charger for power and to power any connected phones.

Most of the “full-featured” Thunderbolt docks ship with the sort of sizeable power bricks normally associated with gaming laptops. Unlike our budget options, these docks are truly desk-bound. Expect the 40Gbps bandwidth common to all Thunderbolt 3 docks to be shared among a surfeit of ports, including multiple USB-A ports, a USB-C port or two, SD card slots, and more. Audio jacks are common, and you may even find an external Thunderbolt 3 port as well for daisy-chaining additional devices. All of those ports take up space, so a model that can be positioned on its edge or vertically is better for cramped work surfaces.

IOGear Quantum Dual Mode Thunderbolt 3 Dock Pro (GTD737) – Best budget Thunderbolt dock

Pros

• Great mix of features
• Budget price
• 60W of passthrough charging power

Cons

• Two DisplayPort ports limit display I/O options
• Might be difficult to find in stores

About the only knock against IOgear’s GTD737 is its use of two DisplayPort 1.2 ports on the rear of the dock, which serve as the only dedicated display outputs. (We suspect HDMI is more popular.) In our testing, an HDMI-to-DisplayPort adapter didn’t work, either, which means that you’ll have to own a display with this port connection.

Otherwise, this dock is excellent, providing almost all the features you’ll want at an affordable price: a 10Gbps USB-A port on the front for 7.5W smartphone charging; on the rear, two 5Gbps USB-A ports for legacy mice and keyboards and two 10Gbps USB-C ports for further expansion. There’s also a gigabit ethernet port and a headphone jack. The 2.3-foot Thunderbolt 3 cable supplies 60W for your laptop via the associated 135W power brick.

The performance was a little less than we expected, dropping 1 percent of the frames in our 4K YouTube test—a bit of jitter that was noticeable, though not annoying. The dock warmed under load, but never got hot. On one occasion, one of the USB-C ports didn’t recognize our test SSD, but powering the dock off and on solved the problem.

If the DisplayPort issue isn’t a concern and you don’t mind a power brick, this IOgear dock is a very good budget choice. It’s actually our preferred Thunderbolt dock, though supply shortages and out-of-stock notifications have pushed prices sky-high — temporarily, we hope.

Belkin Thunderbolt 3 Dock Core – Best budget Thunderbolt dock runner-up

Pros

• Compact
• HDMI 2.0 + DisplayPort 1.4 port covers two displays

Cons

• Unlabeled USB-A ports look identical
• Bus-powered

Belkin’s Thunderbolt 3 Dock Core arrived in bare-bones packaging, and the product is equally unadorned: It’s a smartly designed “powered” Thunderbolt 3 travel dock, and an inexpensive one as well.

At a nearly square 5.2 x 6.5 x 1.5 inches, the Thunderbolt Dock Core black doesn’t take up much room, and the included 8-inch Thunderbolt 3 cord provides ample length for flexibility. Ports are adequately spaced out around the flat, black plastic cube, with HDMI 2.0 and DisplayPort 1.4 ports providing a stable 4K/60Hz experience to both of my 4K displays. There’s gigabit ethernet and a 3.5mm audio jack, but good luck telling the USB 3.1 and USB 2.0 Type A ports apart—they’re not labeled.

Save for the irritating lack of labels on the USB-A ports, the Dock Core worked as expected, with solid performance. The plastic shell never warmed to worrisome levels.

There’s one catch: The additional USB-C port on the Dock is a vanilla USB-C port that needs to be connected to a 60W charger to power the dock—which isn’t supplied. That’s fine if your laptop charges with a USB-C charger; if it doesn’t, you’ll need to buy one. That means extra expense and something else to carry. Otherwise, the lack of a charger certainly saves space while on the go.

Plugable TBT3-UDZ Thunderbolt 3 Docking Station – Best overall Thunderbolt dock

Pros

• Tons of ports
• Space-saving vertical stand

Plugable’s TBT3-UDZ is simply one of the best Thunderbolt 3 docks we’ve tested, though it’s also one of the most expensive, too. With a boatload of ports, including options for using DisplayPort or HDMI for both displays, the TBT3-UDZ offers flexibility and then some. There’s even a sturdy stand to mount it vertically on your desk.

On the front, the TBT3-UDZ includes a 10Gbps USB-C and a 10Gbps USB-A (USB 3.1) port, microSD and SD card slots, plus a headphone jack. On the rear, five USB-A (USB 3.0 ports) and gigabit ethernet complement a pair of DisplayPort 1.4 ports and HDMI 2.0 ports. (It’s all based on Intel’s Titan Ridge chipset.) A 29-inch 40Gbps Thunderbolt 3 cable connects the dock to your laptop, and is capable of delivering 96W of power over a 2.6-foot Thunderbolt 3 cable. Naturally, this is a powered dock, with a hefty 170W (!) charger.

Performance was excellent, driving both 4K displays at 60Hz, and transferring our test file at close to peak speeds while simultaneously playing back two 4K/60Hz videos on both displays over ethernet. The attractive gun-metal chassis never warmed uncomfortably, though it’s a whopping 4.1 pounds—probably heavier than the laptops it’s driving. The extra weight, plus the chassis stand, keeps the TBT3-UDZ rock-solid while in its vertical, space-saving orientation. It measures about 8 inches long/high by 3.75 inches wide, and an inch thick.

A two-year warranty covering limited parts and labor is included.

Plugable TBT3-UDC3 Thunderbolt Dock – Best overall Thunderbolt dock runner-up

Pros

• A less expensive version of the Plugable TBT3-UDZ
• Supplies 96W of power

Cons

• Just two display ports, but an adapter dongle is included

Plugable’s TBT3-UDC3 is a smaller, less-expensive version of the TBT3-UDZ, with less I/O flexibility but more focus. The dock includes a pair of USB-A 5Gbps ports on the front for a mouse and keyboard, and then a second USB-A (10Gbps) port on the back. A pair of two 10Gbps USB-C ports sit alongside it for further expansion. There’s gigabit ethernet, too. Smartly, Plugable includes one HDMI 2.0 port and a DisplayPort 1.4 port for display connections, plus an HDMI-to-DisplayPort dongle in the box in case you own two HDMI displays.

A 2.6-foot Thunderbolt 3 cable supplies 96W of power to a laptop, which is excellent.

Performance was on par with the TBT-UDC3, with very little heat emitted from the dock. On one occasion the dock stopped working, but resumed working a second time when we plugged it in a week or so later. This seems like an otherwise excellent dock, but we’ve slightly lowered the rating because of this. Plugable includes a two-year warranty in case you receive a bad unit.

HP Thunderbolt Dock 120W G4 (4J0A2AA) – Best Thunderbolt dock for business

Pros

• Ports aplenty, plus charging
• Solid performance
• No thermal concerns

HP sells two versions of this Thunderbolt dock: the 4J0A2AA (this model) and the 4J0G4AA, which we haven’t tested. The difference is that the 4J0G4AA includes a “combo cable” that supplies up to 280W of power via the combination of a Thunderbolt 4 cable plus a barrel charger, for HP workstations. The 4J0A2AA supplies up to 100W to the host laptop via the Thunderbolt cable—still among the highest we’ve seen. Even then, there were no thermal issues at all.

This squat little plastic cube feels a lot more solid than its rated 1.68lb would indicate, and sprouts ports to all sides: a 10Gbps USB-C port capable of 15W charging on the front, a 5Gbps USB-A port on either side plus two more on the back, all capable of 7.5W out. The back also houses two DisplayPort 1.4 ports, an HDMI 2.0 port, and a USB-C 3.2 Gen 1 port designed for video. We only tested this dock with two 4K/60 external displays, but it’s capable of driving three 4K/60 displays provided you have a DisplayPort 1.4-capable laptop with Display Stream Compression, or DSC.

There’s also an ethernet port capable of 2.5Gbps as well as another Thunderbolt 4 port outlet. The ports are crammed together with barely enough space for DisplayPort cables or USB keys, but a couple of the outside ports are slightly skewed outwards to provide more room, a nice touch.

This business-oriented dock includes vPro support and the power button/LED can be used to turn itself on and off —but only when connected to supported HP notebooks. The throughput is excellent, meeting expectations on all of the ports. The front USB-C port delivered 15W of power, as the HP’s manual says it should—although, weirdly, the dock lost connection with the displays for a few seconds when a smartphone was connected. We expect a firmware upgrade could solve these issues, and we don’t consider them dealbreakers because of the charging capabilities of the other ports. When notified of our findings, HP reps said they couldn’t reproduce our results.

Kensington SD5700T Thunderbolt 4 Docking Station – Best Thunderbolt 4 dock

Pros

• Meets the more aggressive Thunderbolt 4 specification
• 90W of charging power

Cons

• The priciest dock we’ve tested

We really liked the build of the SD5700T, but the price is a little daunting given the strong competition.

Do you need to buy a Thunderbolt 4 dock over a Thunderbolt 3 dock? No, not really. As we explain in our buyer’s guide below, the capabilities of both are largely identical. But this is the best Thunderbolt 4 dock we’ve seen, if the spec matters to you.

The Kensington SD5700T Thunderbolt 4 Docking Station has one upstream Thunderbolt 4/USB4 port to connect to your computer, and three downstream Thunderbolt 4/USB4 ports to connect other devices, including external displays. In addition, the dock supplies three USB-A ports (10Gbps, charging at 4.5W) and a single USB-A port (480Mbps) that can charge at 7.5W. In addition, the SD5700T provides gigabit ethernet, a UHS-II SD card reader, and a 3.5mm audio jack. The dock is powered by a quite powerful 180W power supply, among the highest we’ve tested. This should provide plenty of power (90W) for connected devices.

We also love the lights that show power and connectivity status, plus the On/Off button that will relieve strain on your connected laptop’s battery.

Plugable 5-in-1 Thunderbolt Hub (USB4-HUB3A) – Best Thunderbolt 4 hub

Pros

• Incredibly compact
• USB-C to HDMI adapter included
• 15W/60W of charging power to phones/PCs

Cons

• Limited ports
• Best for Thunderbolt-attached displays

The Mac world tends to emphasize Thunderbolt-connected displays far more than the Windows world, so this might be a niche product for most of you. But this thing is tiny (4.75 x 2.88 x 0.5in.) even if, unfortunately, the associated power brick isn’t. It will send 15W of power via the Thunderbolt/USB-C connections to charge smartphones, and 60W to the host PC.

We lack Thunderbolt-connected displays among our test bed, so we can’t fully test this. But the box does include a USB-C to HDMI adapter, so you can certainly connect one display natively out of the box, then attach a USB-C hub to connect another. There’s a standalone 10Gbps USB-A port, as well. Sure, connecting a second device sounds like a hassle—but for Plugable’s price $180 or so, you might end up trading saving some cash for a bit of extra clutter.

Again, we couldn’t test this dock to its full capabilities. But in terms of charging power and throughput, it lived up to its specifications. The hub did get a bit warm, but its metal construction dissipates heat effectively.

Anker Apex 12-in-1 Thunderbolt 4 Dock – Best Thunderbolt dock for HDMI displays

Pros

• Two HDMI ports
• An extra 40Gbps downstream Thunderbolt 4 port
• Power button

The Apex Thunderbolt 4 Dock features one 40Gbps upstream TB4 port (that connects to the computer with the included Thunderbolt 4 cable) and one 40Gbps downstream TB4 port for other devices, such as a fast SSD storage drive. The upstream Thunderbolt port can supply up to 90W of power to your laptop, while the downstream port can charge other devices at 15W.

Anker’s inclusion of two HDMI ports means you don’t need any adapters to connect displays, provided you own two with HDMI connections. In total, the dock supports the two Thunderbolt 4 ports, two USB-A ports (10Gbps, 4.5W of power), another two USB-A ports (480Mbps, 4.5W), and a USB-C port (10Gbps, 20W) alongside gigabit ethernet, a UHS-II SD card reader, and a 3.5mm headphone jack. The dock is powered, with a 120W power supply.

An extra plus is a power button on the front so that your laptop isn’t receiving a potential charge when it’s not needed, and can keep the dock’s temperature down at night.

We think the Anker Apex as well as the Plugable TBT3-UDC both make excellent alternatives to our overall pick for the best Thunderbolt dock.

CalDigit Thunderbolt Station 3 Plus (CalDigit TS3 Plus) – Most flexible Thunderbolt dock for I/O

Pros

• Ports, ports, ports
• Vertical orientation, no stand necessary

Cons

• Only a single DisplayPort port

CalDigit’s Thunderbolt Station 3 Plus is one of the most popular Thunderbolt 3 docks available, and it’s easy to see why: a space-saving vertical orientation, 87W charging, gobs of available ports, and even niceties like a S/PDIF optical connection and an external Thunderbolt jack for daisy-chaining devices.

The TS3 Plus measures 5.15 x 3.87 x 1.57 inches, and weighs 1.04 pounds. Though it lacks a supporting stand, it rested easily in a vertical position. CalDigit includes small rubber feet for positioning the aluminum dock in an horizontal orientation.

Port selection includes: two Thunderbolt 3 ports (one from the laptop, and one for an external connection), and a single DisplayPort 1.2 port. That’s ideal for a single 4K display, but awkward for two. The TS3 Plus includes one full-sized SD (SD 4.0 UHS-II) card reader, the S/PDIF port, gigabit ethernet, and two 3.5mm audio jacks—one in, one out. Five USB Type A ports are also included (all 5Gbps USB 3.1 Gen 1) and two USB-C ports (one 5Gbps port, and one 10Gbps port).

To enable two 4K/60 displays, you’ll need a second USB-C dongle running off either the Thunderbolt or USB-C dock—or a forward-looking display with a built-in Thunderbolt/USB-C connector. These are still rare in the Windows world.

Daisy-chaining the Thunderbolt port to enable a second monitor worked fine, though the connection dropped momentarily on both displays when playing back video on both displays and transferring files. Otherwise, high-bandwidth video playback went completely smoothly. The external audio jack also didn’t work initially, but did on a subsequent retry. CalDigit’s TS3 Plus barely warmed under load.

Thunderbolt dock buyer’s guide

If you’re on the fence about whether a Thunderbolt dock is right for you, knowing the answers to the following questions could help you.

How do I know if my laptop has Thunderbolt?

The short answer: Look at the laptop’s published specifications to be sure. A Thunderbolt port may look indistinguishable from a USB-C port, since they both use the same physical USB-C connection. Put another way, all Thunderbolt ports are USB-C, but not all USB-C ports are Thunderbolt-equipped.

Thunderbolt ports are supposed to have a small lightning-bolt icon to identify them. But some laptop makers use a similar lightning-bolt icon to indicate that a USB-C port can be used for charging your phone, and not for Thunderbolt. Laptop makers sometimes don’t want to clutter the clean lines of their products by adding additional logos, it seems. 

Adding to the confusion, you may also see USB-C hubs marketed as “Thunderbolt compatible.” That’s true. You can plug a Thunderbolt dock into a non-Thunderbolt, generic USB-C port. But it will be limited by the available bandwidth that the port provides, so it’s somewhat deceptive in that regard. 

How fast is Thunderbolt?

Most USB-C ports are built on the second-generation USB 3.1 data-transfer standard, which transfers data at 10Gbps. Most Thunderbolt 3 ports, the most common standard, transfer data at up to 40Gbps. Thunderbolt 4 differs slightly in that it supports a theoretical maximum of 32Gbps where data transfers are concerned, specifically for external storage devices.

There are somewhat rare exceptions: A new USB 3.2 Gen 2×2 spec can pair two 10Gbps channels together, creating an aggregate 20Gbps hub. And while the vast majority of Thunderbolt 3-equipped laptops are designed with four PCIe lanes for a total of 40Gbps, some laptops only ship with two PCIe lanes for a total of 20Gbps. (A Dell support page, for example, details its four-lane and two-lane laptops.) Essentially, a 20Gbps connection should be enough for a single 4K monitor running at 60Hz, with a bit of extra bandwidth for other data transfers among connected peripherals.

What’s the difference between Thunderbolt 3, Thunderbolt 4, and USB4?

The short answer: Not that much, and we consider Thunderbolt 3 docks and Thunderbolt 4 docks to be functionally equivalent for most users. The longer answer, which we’ll describe below, is that there are differences, and parsing the nuances can be confusing. Think of Thunderbolt 4 as the more restrictive version of Thunderbolt 3, with little room for any gotchas.

Essentially, Thunderbolt 3 and Thunderbolt 4 allow up to 40Gbps maximum bandwidth, enough for two 4K/60 displays. “Up to” is the key phrase: Thunderbolt 3 is only required to support a 10Gbps connection, allowing for a single external 4K display (a 16 Gbps PCIe connection, paired with USB3.2). Most manufacturers go beyond this, however, and our recommended docks support the full specification (and two 4K displays) unless noted. Thunderbolt 3 also supports a slower (16Gbps) PCIe connection for connecting to external storage. Unless you’re editing video or using an external GPU, this probably won’t matter.

Thunderbolt 4 doesn’t allow for any leeway—you’re getting a full-fledged 40Gbps connection (32 Gbps PCIe + USB 3.2), no questions asked. For external storage, Thunderbolt 4 supports 32 Gbps of data transfer — again, this really only matters for video, external GPU connections, or possibly games. Thunderbolt 4 supports “wake on sleep” from an external keyboard or mouse, which allows you to tap your external keyboard or wiggle your mouse to wake your PC up, which is handy. Thunderbolt 4 allows for longer cables and more Thunderbolt ports on laptops, too.

USB4 is essentially a subset of Thunderbolt 4, mainly designed as an an I/O specification. USB4 can only support one display, and manufacturers can choose whether it supports a 20Gbps connection or a 40Gbps connection, according to Thunderbolt dock designer Plugable. As a subset of Thunderbolt 4, a USB4 device will run just fine plugged into a Thunderbolt 4 port. But a Thunderbolt 4 device may not work as expected when plugged into what is specifically a USB4 port. Don’t worry about this too much, as it’s rare to see a USB4 hub. Instead, most hubs and docks are marketed as Thunderbolt 4, while most devices (like an external SSD) are designed around USB4.

Note that Thunderbolt 3 and 4 require at least 15W to power devices plugged into the Thunderbolt port, such as a bus-powered hard drive. USB4 requires just half that.

Device maker Anker has a nice summary of all of the technical features associated with Thunderbolt 3, Thunderbolt 4, and USB4, if you really want to get into the fine distinctions.

Anker

Virtually every Thunderbolt device will ship with its own cable. We’d recommend that you use Thunderbolt 3 cables with Thunderbolt 3 products, and Thunderbolt 4 cables with Thunderbolt 4 products.

What to look for in a Thunderbolt dock

Ports, cables, peripherals: Those are the three major considerations when buying a Thunderbolt dock. 

We’re beginning to see the Thunderbolt dock market break down into a few different ways. First, there’s the budget versus full-featured docks we’ve highlighted above. But you also may see something similar to the USB hubs of old, too: Devices that take Thunderbolt in and then provide several USB-C (including Thunderbolt) ports out. There are a small number of displays with Thunderbolt inputs, which can be plugged directly into these hubs. Do you have an existing cheap USB-C dongle? You can certainly plug that in into a Thunderbolt dock and add even more I/O functionality.

Basically, consider what you’ll want to plug into the dock as a guide for buying one. We prefer devices with ports built in (such as HDMI, USB-A, and so on) as the USB-C device ecosystem is still in its infancy. But ask yourself some questions. Do you want a basic Thunderbolt dock, with just a pair of HDMI ports for connecting two displays? Does an SD card slot matter? How many USB Type A peripherals do you plan to attach? Do you want to use the Thunderbolt cable to charge your laptop, too?

Cables can be an unexpectedly important consideration, too. Virtually every dock ships with a Thunderbolt cable. But consider the displays you own (typically HDMI or DisplayPort) and consider whether the dock will accommodate them.

Check your laptop’s power supply. Does it plug into your laptop via USB-C? If so, a Thunderbolt dock will likely power it. You’ll need to understand how the dock supplies power, though. Check your laptop’s charger to learn how much power it supplies, and how much the dock will need to supply to replace it. If your laptop or devices aren’t receiving enough power, you may see a warning pop up.

A “bus-powered” dock won’t come with an external charger in the package, saving some cost, space, and power concerns. A dock with “power delivery” will supply its own power and charge your laptop and/or a phone via your laptop’s existing USB-C charger. (Chances are that it won’t offer the quick-charging capabilities premium smartphones offer, though.) The more power your dock supplies, the greater the ability to charge your laptop and any bus-powered devices. This is a gotcha most people don’t think about, so if you plan to connect several bus-powered hard drives or SSDs, buy a dock with a hefty power supply. (USB keys, on the other hand, require tiny amounts of power. Don’t worry about these.)

There’s one more consideration: the length of the Thunderbolt cable between your laptop and the dock itself. You may have noticed or heard about USB-C ports wearing out on smartphones; a loose or wobbly connector on Thunderbolt docks can cause monitors to unexpectedly flicker or lose connection. Consider how much tension will be put on a cable. A Thunderbolt dock that’s dangling from a Thunderbolt port will stress the physical connector. You don’t want that!

If you’re a Mac user who has stumbled across this article, welcome. But please be aware that early Apple MacBook Pros powered by Intel silicon supported up to two 4K displays. The first MacBook Pros powered by the Apple M1 chip only support a single 4K display. Many Mac users have recently left negative reviews on Thunderbolt docks on shopping sites because of this. Buy a PC!

How we tested

We’re working from the premise that you’re buying a Thunderbolt dock for its unique ability to connect to two 4K monitors at 60Hz. Lower resolutions should be much easier to run successfully. Our first test simply connected each dock to a pair of 4K/60Hz displays, each of which could accept DisplayPort and HDMI cabling, and made sure there were no visual artifacts at 60Hz resolution.

Second, we checked to see whether the available ports delivered the bandwidth we’d expect, connecting them to an external SSD and transferring a collection of test files over the Thunderbolt cable and port. We also used AJA’s System Test tool to double-check our numbers and test whether read and write speeds were consistent. 

Finally, we spot-checked the available power draw of the hubs and ports with a USB power meter, as well as simply connecting them to bus-powered devices to see if they could deliver enough power to allow them to operate. Here, we discovered that one of our testing laptops didn’t supply enough power running on battery to power a bus-powered Thunderbolt dock, so we enlisted a second, different laptop as a backup.