Citizen Caliber J810

The Citizen caliber J810 is a solar powered (Eco-Drive) quartz watch movement with a day-date calendar complication. The official documentation for the J8 family of Eco-Drive movements is shared with the J7 series as well.

Solor Powered Watch:

In Citizen’s own words:

“Your Eco Drive watch does not operate on a conventional battery. It is powered by light that is converted to energy that is stored in a special cell. This cell provides a reserve of power that is used when the watch is not receiving light sufficient for operation and charging.” –source

J810 VS J800:

There is a similar caliber J800 with the main difference being that the J810 has a date and the J800 has a day-date.

Accuracy Rating:

Citizen claims that the accuracy of the J810 is within +/- 15 seconds per month when the watch is in normal operating temperatures of +5C to +35C (41F to 95F).

J810 Charging Time:

The fastest way to fully charge your J810 powered watch is to expose the dial side of the watch to clear and bright sunlight for about 30 hours. When doing this, be careful that the sunlight is not too hot or else it can damage the dial and solar cell. You can try to place your watch on a windowsill which gets full sunlight, in an air conditioned room. Periodically check to make sure the dial is ok and that the watch is not getting too warm. Just bear in mind, that using the windowsill method takes longer:

“Optimal charging is achieved with direct outdoor sunlight (not through a window). Sunlight through a window provides less energy than direct outdoor light due to glass filtering and coatings. If charging under this condition, double the specification for outdoor light on a cloudy day.” -Citizen Eco Drive Recharge Guide

If you attempt the same as above but on a cloudy day, it can take up to 120 hours. Fully charging under a fluorescent lamp can take 240 hours (at a 6″ distance).

Overcharging:

Don’t worry, the Citizen J810 has an overcharging prevention function and cannot be overcharged.

Power Reserve:

The J810 holds a power reserve of up to 8 months (about 240 days) on a full charge when the capacitor/rechargeable cell (lithium button cell) is storing energy correctly.

Note: There are some reports online that the J810 caliber watches do not hold as much power reserve as similar Eco-Drive timepieces. However, looking at the data, it appears that the power reserve specs are not lower, but rather the time it takes to fully charge a J810 may be longer. If true, this would explain why some J810 powered watch collectors are experiencing lower power reserve, possibly because they are not charging it for a long enough time – 30 hours of sunshine takes days to achieve.

Low Battery Indicator:

The J810 features a built-in Insufficient Charge Warning function. When the watch does not have sufficient energy to operate correctly, the seconds hand will jump in a two-second interval for about 5 days. When your watch starts skipping like this, refer to the charging information above to get it back to full charge. If you feel that you have done the appropriate steps to fully charge your watch but the seconds hand is still skipping/jumping, then perhaps your capacitor/battery cell needs replaced.

Replacement Capacitor/Rechargeable Cell:

The part number for the rechargeable battery cell in the calibre J810 is 295-5100 (sometimes written as 295-51). The price usually ranges from around $15 USD to $25 USD. You can find it here (your purchase supports this site).

Video: Time setting instructions

Additional Resources:

• Official Citizen J7/J8 series instruction manual (pdf)
• J810 recharging guide