Setup guide
DNT Hydra Battery Life, 18650s and First-Night Setup
You've bought a couple of spare 18650s for your DNT Hydra, and the battery cap won't screw down. The usual cause is length: the Hydra takes flat-top 18650 cells 65 mm long, and many 18650s sold with a built-in protection board run to 68–69 mm. Get the right cell, carry a spare, and a full night out is straightforward.
This guide covers the battery first, then the setup steps worth doing before your first night with the scope.
The battery the Hydra takes
DNT specifies a flat-top 18650 measuring 65 × 18 mm. Some 18650s include a small protection circuit at one end, which adds length; DNT says those 68–69 mm cells won't fit inside the device. The diagram below shows the difference to scale.
When you buy spares, check the listed length as well as the 18650 label, and make sure it's a flat-top cell. The Hydra-Mini HS210M also runs on flat-top 18650s.
The battery goes in positive end first: twist the battery cap anticlockwise to remove it, slide the cell in, and twist the cap clockwise until it's fully tight. The USB-C port can power the Hydra, but it won't charge a battery sitting inside, so charge your cells in an external 18650 charger.
How long one battery lasts
The Hydra holds one battery at a time, and DNT's run-time ratings range from up to 4 hours on the 640 models to 5.5 hours on the HS225. The Hydra-Mini HS210M is rated at up to 7 hours per battery. The chart below sets those against a long night out.
This is the Hydra's main trade-off: on a long session, you'll be swapping batteries at least once. Plan the swap rather than waiting for the screen to die, ideally during a quiet spell between sightings.
Say it's a frosty June night and you're sitting on a fence line waiting for foxes to come in to the whistle. Lithium-ion cells deliver less in the cold, so the rated hours shrink. Keep the spare battery in an inside pocket where your body heat keeps it warm, and swap it in when the first one drops. DNT rates the Hydra to work down to −20 °C, so the scope copes with the cold; the battery is what tires first.
Two settings stretch a battery further. A short press of the power button puts the Hydra into standby, which blanks the screen between sightings. Auto power off then shuts it down after 10, 20 or 30 minutes in standby, so a forgotten scope won't sit there draining. On a long night you can also run the Hydra from a 5 V USB-C supply such as a power bank.
Before your first night out
A few minutes of setup at home saves fiddling with menus in the dark. The order below follows DNT's user manual, and none of it takes long.
Set the ocular first, by turning the eyepiece until the screen looks sharp to your eye. It works independently of the target, so you can do it with the lens cap still on, and once it's set it stays set. The focus ring on the objective lens is different: it sharpens the scene itself, and you'll adjust it as targets move closer or further away.
For zeroing as a standalone scope, DNT recommends 50 yards, about 46 m. Fire a shot at your point of aim, press the power button briefly to freeze the image, then move the reticle onto the point of impact using the X and Y values and save. The Hydra stores 10 zeroing profiles, so you can keep one for each rifle or load. If you also use the Hydra as a clip-on, see using the DNT Hydra as a scope, clip-on or handheld.
The DNT app is optional. Turn on the Hydra's Wi-Fi in the menu, then connect your phone to the network it shows, using the password listed in the manual. We'd leave Wi-Fi switched off when you're not using the app.
Our advice: buy at least one extra flat-top 18650 of the right length when you buy the scope, and charge everything the day before. Which Hydra to choose is covered in our DNT Hydra review, and the Hydra-Mini's longer battery rating in DNT Hydra-Mini HS210M: who needs a 4-in-1 thermal.
Need batteries or a mount for your Hydra?
Ask us which flat-top 18650s and chargers suit the Hydra, or see the quick-detach mounts.
DNT QDM150 mount DNT QDS150 mountDNT Hydra battery and setup FAQ
What 18650 battery fits the DNT Hydra?
The DNT Hydra takes a flat-top 18650 measuring 65 × 18 mm. Check the listed length before you buy spares, because many 18650s with a built-in protection board are 68–69 mm long, and DNT says those won't fit inside the device. The Hydra-Mini HS210M also uses flat-top 18650s. Ask us if you're unsure which cells suit.
Why won't my 18650 battery fit in the DNT Hydra?
It's almost certainly too long. The DNT Hydra is built for 65 mm flat-top 18650 cells, while protected 18650s carry a small circuit board that stretches them to 68–69 mm, so the battery cap won't close. Swap to a 65 mm flat-top 18650 and it will fit.
Can I charge the DNT Hydra battery through the USB-C port?
No. DNT's manual says the USB-C port on the DNT Hydra can't charge the 18650 battery inside it, so charge your cells in an external 18650 charger. The port can still power the scope from a 5 V USB-C supply and transfer files to a computer. Charge your spare battery the day before you head out.
How many batteries do I need for a night with a DNT Hydra?
For most nights, two. DNT rates the 3-in-1 Hydra models at up to 4–5.5 hours on one battery, so anything longer means a swap. On cold winter nights, the rated hours shrink, so a third battery is cheap insurance on a long session. The Hydra-Mini HS210M is rated at up to 7 hours per battery.
Can I run the DNT Hydra from a power bank?
Yes. The DNT Hydra accepts 5 V USB-C external power, so a USB-C power bank can keep it running on a long night or a stationary sit. A cable trailing from the scope is awkward when you're moving or shooting, so it suits glassing from a fixed spot better than stalking. The power bank won't charge the battery inside.
Does cold weather drain the DNT Hydra battery faster?
Yes, as it does for any lithium-ion battery. DNT rates the DNT Hydra to operate down to −20 °C, but the 18650 cell delivers fewer hours as it gets colder. On frosty nights, carry the spare in an inside pocket to keep it warm, use standby between sightings, and expect to swap earlier than the rated run time suggests.
How do I zero the DNT Hydra as a standalone scope?
DNT recommends zeroing the DNT Hydra at 50 yards, about 46 m. Open Zeroing in the menu and pick a profile, aim at the target and fire a shot, then press the power button briefly to freeze the image. Move the reticle onto the point of impact with the X and Y values, and save. Confirm with another shot.
How many zeroing profiles does the DNT Hydra have?
The DNT Hydra stores 10 zeroing profiles, and each one keeps its own zero, reticle style and reticle colour. That lets you set up a profile for each rifle or load and switch in the menu rather than re-zeroing. Write down which profile number belongs to which rifle, so you pick the right one in the dark.
How do I stop the DNT Hydra draining its battery when I'm not using it?
Use standby and auto power off. A short press of the power button puts the DNT Hydra into standby, which turns the screen off between sightings; another short press wakes it. Auto power off, set in Function Settings, then shuts the scope down after 10, 20 or 30 minutes in standby. Switch Wi-Fi off when you're not using the app.
How do I connect the DNT Hydra to the DNT app?
Turn on Wi-Fi in the DNT Hydra's Connections menu, then open your phone's Wi-Fi settings and join the network named after your Hydra model, using the password given in the user manual. Then open the DNT app to view a live feed from the scope and manage your recordings on your phone. Turn Wi-Fi off again afterwards to save battery.
This guide is based on DNT's published Hydra specifications, battery FAQ and user manual.