Most modern red dots run on a coin cell: a CR2032 in most rifle sights and many Trijicon and SIG sights, a CR1632 in most Holosun open pistol sights, and a CR1620 in Holosun's enclosed EPS family. Larger rifle sights often use a CR123A or a AAA, and Holosun's SCS range has a built-in rechargeable cell. The chart below lists the battery for each optic we stock, checked against the manufacturer's own specifications.
The codes are not interchangeable, so match the exact cell. If your model is not listed, or the manual for your optic differs from this chart, the manual wins, because makers do revise designs.
Key takeaways
- Holosun's 407C, 507C, 507K, 508T and 509T use a CR1632; the EPS, EPS Carry and EPS CORE use a CR1620; and the HS510C, HE512T and most AEMS sights use a CR2032.
- Trijicon's RMR Type 2, RMR HD, SRO and RCR all use a CR2032.
- SIG's ROMEO5 Gen II and ROMEO4T take a CR2032, the ROMEO-X and ROMEO1PRO a CR1632, the ROMEO5XDR Gen II and ROMEO4XT-PRO a AAA, and the ROMEO8 family a CR123A.
- EOTech holographic sights run on a CR123 and quote about 1,000 hours, far less than an LED dot, because a holographic sight is laser-driven.
- In a coin cell code, the first two digits are the diameter in millimetres and the last two the thickness in tenths of a millimetre, so a CR2032 is 20 mm across and 3.2 mm thick.
Holosun battery chart
Holosun generally quotes battery life at brightness setting 6. Its current red dots load the battery from a side tray, which lets you change the cell without removing the sight; the SCS is the exception, with no user-replaceable cell at all.
| Optic | Battery | Holosun's quoted life |
|---|---|---|
| 507C X2, 407C X2 | CR1632 | 50,000 hours |
| 507C X3, 407C X3 | CR1632 | 100,000 hours |
| 507K X2, 407K X2 | CR1632 | 50,000 hours |
| 507COMP, 407COMP, RONIN 507COMP, 507 ProMax | CR1632 | 50,000 hours |
| HE508T X2, HE509T X2 | CR1632 | 50,000 hours |
| EPS, EPS Carry, EPS CORE, RONIN EPS Carry | CR1620 | 50,000 hours |
| HS510C, HE512T, HS403C | CR2032 | 50,000 hours |
| AEMS CORE X2, AEMS PRO X2 | CR2032 | 50,000 hours |
| AEMS EVO | CR2032 | 100,000 hours |
| AEMS Micro | CR1620 | 100,000 hours |
| AEMS Macro | CR1632 | 100,000 hours |
| ARO EVO 2 MOA | CR2032 | 50,000 hours |
| AEMS EVO Dual, ARO EVO Dual | CR123A | 300,000 hours for the dot; 12 hours for the green laser and 50 hours for the IR laser |
| SCS range (MOS, Carry, 320, PDP, P10, VP9, MP2) | Internal rechargeable, not user-replaceable | Up to 20,000 hours of reserve, recharged by the solar panel |
| MP3X prism | CR2032 | Up to 50,000 hours, depending on brightness |
The EPS and the AEMS Micro use the thinner CR1620, and the AEMS Macro uses a CR1632, even though most AEMS models take a CR2032. These are the easiest cells to get wrong. If you are not sure which Holosun you have, our Holosun model numbers guide decodes the name on the box.
Trijicon battery chart
| Optic | Battery | Access | Quoted life |
|---|---|---|---|
| RMR Type 2 Adjustable LED (RM06, RM07, RM09) | CR2032 | Underneath the sight | 4+ years of continuous use at setting 4 of 8 |
| RMR Type 2 RM01 | CR2032 | Underneath the sight | See Trijicon's manual |
| RMR HD | CR2032 | Top-loading | At least 3 years at setting 5 |
| SRO | CR2032 | Top-loading | 3 years at setting 4 of 8 |
| RCR | CR2032 | Top-loading | At least 3 years at setting 5 |
The RMR Type 2 figures come from Trijicon's spec sheet and the SRO figure from Trijicon's launch release. The RMR HD and RCR figures are from Trijicon's launch information as published in the shooting press. More on the range is in our Trijicon buyer's guide.
SIG Sauer battery chart
| Optic | Battery | SIG's quoted runtime |
|---|---|---|
| ROMEO5 Gen II | CR2032 | 40,000 hours with MOTAC |
| ROMEO5XDR Gen II | AAA | 50,000 hours |
| ROMEO4T | CR2032 plus solar | Over 100,000 hours with solar and battery |
| ROMEO4T-PRO | CR2032 | 50,000 hours with MOTAC |
| ROMEO4XT-PRO | AAA | 50,000 hours |
| ROMEO8H | CR123 | 50,000 hours |
| ROMEO8T | CR123A, side-loading | 100,000+ hours |
| ROMEO8T-AMR | CR123 | 50,000 hours with MOTAC |
| ROMEO-X Pro, ROMEO-X Compact | CR1632, side-loading | 20,000 hours |
| ROMEO1PRO | CR1632 | 20,000+ hours |
The differences between these families are explained in our SIG ROMEO range guide.
EOTech and Primary Arms
| Optic | Battery | Quoted life |
|---|---|---|
| EOTech XPS2, XPS3 | CR123 | 1,000 hours at setting 12 at room temperature (600 hours for the green XPS2) |
| EOTech EXPS3, EXPS2 | CR123 | 1,000 hours at setting 12 at room temperature (EXPS3) |
| EOTech EFLX | CR2032, top-loading | About 25,000 hours (3 MOA) or 20,000 hours (6 MOA) at level 5 |
| Primary Arms SLx 1X MicroPrismT | CR2032 | 25,001 to 50,000 hours |
| Primary Arms SLx 3X MicroPrism | CR2032 | Up to 29,000 hours on a medium setting |
| Primary Arms SLx 5X MicroPrism | CR2032 | 25,001 to 50,000 hours |
| Primary Arms GLx 1X MicroPrism | CR2032 | 14,925 hours at setting 5 |
The holographic sights stand out. A holographic sight projects its reticle with a laser diode rather than an LED, which is why EOTech quotes hundreds or about a thousand hours rather than tens of thousands.
Don't confuse the coin cells
A coin cell's code tells you its size. The first two digits are the diameter in millimetres, and the last two are the thickness in tenths of a millimetre.
| Cell | Diameter | Thickness | Typical capacity (Energizer) |
|---|---|---|---|
| CR2032 | 20 mm | 3.2 mm | 235 mAh |
| CR1632 | 16 mm | 3.2 mm | 130 mAh |
| CR1620 | 16 mm | 2.0 mm | 81 mAh |
A CR2032 will not fit a CR1632 tray, because it is 4 mm wider. A CR1620 will physically fit a CR1632 slot but is 1.2 mm thinner, so contact is unreliable and it holds well under two-thirds of the capacity. Treat the codes as non-interchangeable. Capacities are from Energizer's published datasheets, which rate all three cells for use from -30°C to 60°C.
Expert tip
The hours on the box are measured at one stated brightness, in the warm. Brighter settings, bigger reticles and cold mornings all cut into them: EOTech's own EFLX figures drop from about 25,000 hours with the 3 MOA dot to 20,000 with the 6 MOA dot. On an optic you rely on, change the cell once a year on a fixed date, write the date on a piece of tape in the case, and keep a spare of the exact code in the rifle bag.
Getting the most from a battery
- Let motion sleep do its job. Holosun's Shake Awake, SIG's MOTAC and Primary Arms' AutoLive power the dot down when the gun is still. Holosun notes that if you switch the sight off manually, Shake Awake will not wake it.
- Know what solar does. On Holosun Solar Failsafe models, Auto mode runs the reticle on light, and the battery takes over in manual mode. It extends the battery's life but does not replace it.
- Prefer side or top loading. On an RMR Type 2 you remove the sight to reach the cell, so confirm your zero afterwards.
- Buy branded cells from a reputable seller, and store spares somewhere cool and dry.
How motion activation and solar backup behave in practice is covered in Shake Awake, Solar Failsafe and 50,000-hour batteries.
Frequently asked questions
What battery does the Holosun 507C use?
A CR1632, in a side tray, on both the 507C X2 and X3. The 507K X2 also uses a CR1632, while the EPS Carry uses the thinner CR1620.
What battery does the Trijicon RMR use?
The RMR Type 2 uses a CR2032, fitted from underneath the sight. The RMR HD, SRO and RCR also use a CR2032 but load it from the top.
Can I use a CR2032 instead of a CR1632?
No. A CR2032 is 20 mm across and a CR1632 is 16 mm, so it will not fit. Always match the exact code on the manufacturer's spec sheet.
How often should I change my red dot battery?
Quoted figures run to years, but they are measured at one moderate setting in the warm. On an optic you rely on, a fixed annual change is cheap insurance.
Shop this guide
- Red Dot Sights — every dot we stock, with battery type on each product page
- Pistol Dot Sights — the CR1632, CR1620 and CR2032 mini reflex sights
- Holosun Optics — solar, Shake Awake and side-tray models
- SIG Sauer ROMEO Red Dot Sights — including the AAA-powered ROMEO5XDR and ROMEO4XT-PRO
