Battery guide
Pulsar Thermion 3 Battery Life: Dual Batteries, Charging and Cold Nights
The battery icon on your Pulsar Thermion 3 starts flashing well before the rated hours are up, usually on a cold night. That's expected: Pulsar's run-time figures are measured at 22 °C, and lithium batteries give less as they cool. The fix is simple. Charge both batteries before every trip, carry a charged spare APS5 for long sessions, and use the scope's display-off features between sightings.
This guide covers both the Thermion 3 LRF XR60 and the Thermion 3 LRF XT60, following Pulsar's user manual.
How the dual battery system works
The Thermion 3 carries two 4,900 mAh APS5 batteries: one built in, and one removable. The diagram below shows how they share the load.
The scope draws from the removable battery first, then switches to the built-in one when the removable battery runs low. You can swap the removable battery with the scope switched on, so a fresh spare keeps you going without a restart. The battery icon in the status bar flashes when charge is low.
How long it lasts
Pulsar rates the XR60 at up to 14 hours and the XT60 at up to 8.5 hours, both at 22 °C with both batteries. The XT60's 1280×1024 sensor needs more processing power, which is why it runs shorter. The chart below sets both against a long winter night.
For a typical evening of spotlighting, either model has plenty in hand. On an all-night session, the XT60 will need a fresh APS5 or a power bank partway through, and the XR60 may too once the cold sets in. If you're still choosing between the two, battery life is one of the trade-offs we cover in Thermion 3 XR60 or XT60: is the 1280 sensor worth it.
Cold nights
Say it's a frosty June night, you're sitting on a fence line calling foxes, and the temperature has dropped below zero by midnight. The scope itself is rated to work down to −25 °C, so it copes. What drops is battery capacity: Pulsar's manual notes it falls below freezing, as it does for any lithium battery.
Carry the spare APS5 under your jacket, close to your body, and swap it in as soon as the icon starts flashing. Because the scope switches to its built-in battery on its own, the swap never leaves you in the dark mid-sit.
Two settings help. With the proximity sensor on, the display switches off when you lift your eye from the eyepiece and back on when you return. If the scope sits in display-off mode for 30 minutes, the no-use shutdown turns it off, so a forgotten scope won't drain overnight.
Charging and power banks
You can charge through the scope's USB-C port or in Pulsar's APS5 charger, which holds two batteries. The chart below sums up the charging rules from Pulsar's manual.
Pulsar sets a charging range of 0 °C to 45 °C. After a cold night, let the batteries sit indoors for 30–40 minutes before you charge them. For storage between trips, keep them at 50–80% rather than full or flat.
For long sits, the Thermion 3 runs from a USB-C power bank that supports 5 V or 9 V Power Delivery. Pulsar recommends connecting it after the scope has been running for a few minutes. A short cable and a power bank in a jacket pocket suit a fixed stand or a vehicle rest better than stalking on foot.
Our advice: buy a spare APS5 with the scope if you hunt past midnight, and treat it as part of the kit. For setting up the rest of the scope, see mounting and zeroing the Pulsar Thermion 3, and for the full model rundown, our Pulsar Thermion 3 LRF review.
Need a spare APS5?
Ask us about APS5 batteries and the APS5 charger, or check the current price of each Thermion 3.
Thermion 3 LRF XR60 Thermion 3 LRF XT60Pulsar Thermion 3 battery FAQ
Can I run the Pulsar Thermion 3 from a power bank?
Yes. The Pulsar Thermion 3 LRF accepts external power through its USB-C port from a power bank that supports 5 V or 9 V USB Power Delivery. Pulsar's manual recommends connecting it after the scope has been running for a few minutes. A power bank in a jacket pocket suits a fixed stand or vehicle rest, where a cable won't get in the way.
How do I charge the Pulsar Thermion 3 built-in battery?
Charge the Pulsar Thermion 3 LRF through its USB-C port, which Pulsar's manual lists as one of two charging options. The other is the APS5 charger, which takes two removable batteries. Charge fully before first use, use the supplied or an approved charger, and only charge between 0 °C and 45 °C. An LED on the battery cover shows charge when the scope is off.
Which battery does the Pulsar Thermion 3 use first?
The removable APS5. According to Pulsar's manual, the Thermion 3 LRF draws from the removable battery first and switches to the built-in APS5 when the removable one runs low. That means you can swap in a fresh removable battery while the scope keeps running on its built-in battery, with no restart and no lost settings.
Does cold weather reduce Pulsar Thermion 3 battery life?
Yes. Pulsar rates the Thermion 3 LRF's run time at 22 °C, and its manual notes that battery capacity drops below freezing, as with any lithium battery. The scope itself works down to −25 °C. On frosty nights, carry a spare APS5 under your jacket and expect to swap sooner than the 14-hour XR60 or 8.5-hour XT60 rating suggests.
Can I swap the Thermion 3 battery while it's switched on?
Yes. Pulsar's manual says you can change the removable APS5 battery on the Pulsar Thermion 3 LRF while the scope is on. The built-in battery keeps it running during the swap, so you won't need to restart or re-find your target. Make sure the battery cover is fully closed and turned to lock afterwards.
Can I charge Thermion 3 batteries when they're cold?
No. Pulsar's manual allows charging only between 0 °C and 45 °C. If a Pulsar Thermion 3 LRF battery has come in from a cold night, let it sit indoors for 30–40 minutes before charging. Wait until it has warmed up before plugging the scope into a vehicle charger on a frosty morning.
How should I store Pulsar Thermion 3 batteries?
Pulsar's manual recommends storing APS5 batteries at 50–80% charge rather than full or flat, in a cool, dry place. Before your next trip with the Pulsar Thermion 3 LRF, charge both batteries fully the day before, so the built-in and removable APS5 start the night full.
How do I save battery on the Pulsar Thermion 3?
Turn on the proximity sensor, which switches the Pulsar Thermion 3 LRF's display off when you lift your eye away and back on when you return. If the display stays off for 30 minutes, no-use shutdown turns the scope off. You can also dim the display brightness and turn Wi-Fi off when you're not using the Stream Vision 2 app.
This guide follows Pulsar's Thermion 3 LRF user manual and published US specifications.