Caliber Corner stickers are here!
Seiko Caliber 7x52a

Seiko Caliber 7X52

Seiko Caliber 7x52

Brand Seiko
Caliber Number 7X52, 7X52A
Movement Type Quartz, Solar Powered
Jewels 10
Crystal Oscillator Frequency
32,768 Hz (cycles per second)
Driving System
Step motor
CLB2016 (3.7V)
Functions Automatic GPS time setting, date, dual-time, in-flight mode
Country of Manufacture Japan
Known Models SAST005, SAST007, SAST015

The Seiko caliber 7x52A is found in the first generation of Astron watches.

Detailed Features:

  • GPS controlled time and time zone adjustment
  • Perpetual calendar correct to February 2100
  • Signal reception result indication
  • World time function (39 Time Zones)
  • Daylight Saving Time function
  • Power save function


Seiko claim the accuracy of the 7X52 in normal conditions is +/- 15 seconds per month.

Charging Time

The Seiko caliber 7X52 requires more energy than other solar watches because of the GPS signal reception. The charging time depends on the light source and how how much light is emitted, measured in LUX. The higher the LUX the faster the charge. For example, charging in the sunlight will be faster than using a standard light bulb.

  • 3,000 LUX florescent bulb takes ~530 hours to fully charge
  • Daylight on a cloudy day takes ~135 hours to fully charge
  • Sunlight on a sunny day takes ~65 hours to fully charge

Power Reserve

It literally takes days to charge the Astron, however, when fully charged the caliber 7X52A has a power reserve of about 6 months.

Note: when charging your watch in the sunlight, make sure that the temperature is not too hot or it can damage the dial, solar cell, or other parts of the watch. Always keep the watch temp below 60 C.

Can you wear it while charging?

You can wear your watch while it has low power or while it is charging, however, it may slow down the charging time if your watch is under your sleeve or not in direct light.

Can you overcharge it?

The Seiko caliber 7X52 has an overcharge prevention function to make sure your watch will not be over charged.

Low Power Indicator

The Seiko 7X52 has several series of low power warnings:

  • Second hand ticks every 2 seconds: The watch will still tell the time, but the GPS automatic time setting will not work until it is charged.
  • Second hand ticks every 5 seconds: The watch will stop telling the time and the GPS will not function until it is charged.

From Seiko

While the watch is being charged, the second hand moves at “ 5-second Intervals.” During the “5-second Interval Movement,” neither the buttons nor the crown can be operated.

2 Power Save functions

Please allow us to interrupt your gear turning and caliber learning to say thank you. Thank you for being here! Now, back to the movement..

The second hand has stopped at the 15 seconds mark: Power Save 1 function has been activated. The time display will stop and the time cannot be set until the watch is charged. This Power Save setting can be initiated with as little as 72 hours without a sufficient light source.

The second hand is pointing to the 45 seconds mark: Power Save 2 has been activated. The time will stop and the date will display 1. The time cannot be set until the watch is charged. This Power Save setting is initiated when the watch is in storage or without a light source for a long period of time.

Rechargeable Capacitor

The capacitor (secondary battery) that is installed from the factory is a 3.7V rechargeable cell. The number is CLB2016. Also stamped on the cell is 12 and 63M. This oem part is manufactured by Maxwell in Japan, however, similar cells from other manufacturers will work fine.

Seiko Caliber 7x52 Clb2016 Capacitor

Replacing the Capacitor

Capactitors do not last forever. Sometimes they will need changed. According to the notice on the battery cover, when replacing the cell you must “short AC and + of the battery”. Do not try to fit a standard battery.

Seiko Caliber 7x52a Battery

From Seiko

The battery used in this watch is a special secondary battery, which is different from ordinary batteries. Unlike an ordinary silver oxide battery, the secondary battery does not require periodic replacement. The capacity or charging efficiency may gradually lower due to long-term use or operating environment. In addition, long-term use may shorten the charge duration due to wear, contamination, lubricant deterioration of mechanical parts, etc. Request repair when the performance lowers.

Examples of watches with this movement

Seiko Astron Sast007 7x52Seiko Astron Sse060 7x52Seiko Astron Sast009 7x52

Additional Resources


Is the Seiko Caliber 7X52 any good? Share your opinions, experiences and watches below... Keep comments respectful and follow our community guidelines.

Leave a Reply

newest oldest most voted
Notify of

Hi guys, I’m confused by this one. Is it quartz or solar powered? Love the site by the way!


Where can I find a battery for this model?

PD Mathur
PD Mathur

I was able to get an LIR2016 to work in place of the original battery (able to get from Amazon for $7/2 pcs). I have posted instructions on Still on full charge after 5 days. I am waiting to see how long it takes to discharge to normal and recharge again. Will post results.

Gabriel Lantos
Gabriel Lantos


Gabriel Lantos
Gabriel Lantos

Hello Mr. PD Mathur with I could not find your instruction posted on to change the batteries(capacitor) on the SEIKO ASTRON GPS SOLAR watch. Would you kindly provide me with your instruction how do it!
Thank you in advance

PD Mathur
PD Mathur

This website appears to be buggy. I posted a response; it showed posted and now it is gone.

PD Mathur
PD Mathur

Looks like links are not allowed here. I used a pair of forceps to peel off stickers gently, a pair of scissors taped open to unscrew the back (open with firm pressure so you don’t slip and scratch the back), and the smallest flat head screw driver from a set of jeweler’s screw drivers to open the two tiny screws inside the watch and to put the flat head between the clip and the battery and gently break open the two spot welds. No incidents on my end, but please be careful and gentle. Once the existing battery is dinged,… Read more »

Seiko Caliber 8B43 Watch Movement |

[…] The Seiko Astron models feature similar functionality, check out the caliber 7X52 here. […]

Benny D
Benny D

I have an Astron that I bought when it first came out but it has been in my drawer for the past 8 months and lost all power. It would not move at all until I put it on the window for a week. Does anyone know of a faster way to charge these?


Sun during day, led lamp at night


The LED lamp I used barely has an effect. Do you know if some LED work better than others?


I used the led lamp of my aquarium. It’s perfect because it’s powerful (1000lx measured with free apps on my phone) , cold and flat so I could place it half an inch from the watch 24/7 without the watch getting even warm. Took 2 weeks from E to F


Edit, measurement was 10,000 lx

PD Mathur
PD Mathur

I had the same issue and Google searches returned nothing useful. As of tonight, here is what I have done. – Bought a couple of LIR2016 rechargeable batteries from Amazon. – Opened the watch. Using a small flat head screw driver, removed the plate that holds the battery down. Gently peeled off the white sticker (need later). – Using the head of the small screw driver and applying counter pressure from the other side using my fingers, gently broke free the two small spot welds. – Removed the reddish ring sticker and transferred to the new cell. – Put… Read more »


Update: It took a few more days than I thought for the needle to return to the middle. Happened on July 16 after I initiated the full GPS synch. I have not taken any special measures to charge it back. Will leave by a window for a few days and see what happens.

Eddie M.
Eddie M.

These Astrons take about a month to properly charge. It’s way too long imho, but it will last forever on a full charge. I just wish they would make the capacitor available for the general public.

PD Matbur
PD Matbur

Some sad news about my experiment folks: the replacement battery does not appear to be charging unless the watch ia exposed to very bright light. At that level it is taking a lot longer than the manual suggests, but it does eventually charge from E to middle with 14 days under a lamp (like the old battery did). I believe this is indicating a solar cell or chargin circuit issue (as another poster on another forum had mentioned). Oh well. … I am dissapointed. Thats not what I would have expected to fail in such a nice watch otherwise.