Watch Capacitors Accumulators

Watch Capacitors

Watch Capacitors Accumulators Square

What is a Watch Capacitor or Accumulator?

Watch capacitors (also referred to as accumulators) are battery-like cells that store power in solar or kinetic watches. Unlike a mechanical watch which gets energy from a mainspring, or quartz watches that are powered by stored energy in a battery, solar watches get their energy from the sun or other light sources. Remember solar powered calculators we used in school? They would only work when under an adequate light source, and covering the small solar panel on the calculator with your finger would cut the power and shut it off. A solar powered watch is similar, except that it needs to be able to stay “on” even when the light source is unavailable (at night or when your sleeve covers the watch) in order to keep the time. This is where the capacitor comes in. The energy from the light source is transferred to the capacitor, and as it accumulates energy, it continuously powers the watch.

A kinetic watch is similar, except that instead of garnering its energy from the sun, the energy comes from a rotor that spins while on your wrist. This concept is like an automatic movement, but instead of the energy from the spinning rotor accumulating in a mainspring, it goes to the capacitor which keeps the watch powered even after you take it off at night.

Watch Capacitors Note

The note above came on a small piece of paper from a watch parts supplier I ordered capacitors from before. Not sure which one it was, the source will be updated if found.

“Capacitor Information: Capacitors are storage devices and do not necessarily come already charged. The customer needs to charge the watch after inserting the capacitor. Seiko capacitors are charged either by oscillating motion or a Seiko Kinetic Recharger. Citizen capacitors are solar cells, using sunlight or an artificial UV light source to recharge. Capacitors should not be tested. A battery tester will not give an accurate reading. Most of the time, the capacitor itself is not defective. Sometimes the brass connector may not be attached perfectly and may be the problem. If the watch does not run after fully charging the new capacitor, do not assume the capacitor is defective. There may be an unrelated problem with the movement. Returns for capacitors are not accepted without prior authorization.” -Unknown source

How to Replace a Capacitor in a Watch?

Replacing the capacitor in a solar or kinetic watch is much like replacing the battery in a quartz watch. Typically instead of a battery strap holding the battery cell in place, there will be screws holding tabs or prongs that are welded onto the capacitor cell. There are many different styles of capacitors, so the replacement process will vary depending on the caliber in your watch.

What is MT920 or MTxxx?

Each capacitor is typically stamped with a cell number such as MT920 or CTL621. This is the manufacturer’s capacitor number and is not the part number for your watch. The cell number indicates the type of battery and its specs. For example, an MT920 is 9.5mm in diameter, can last for up to 2500 hours with a voltage between 1.2v-1.5v, and withstands up to 500 discharge cycles.

Common brands or manufacturers of the capacitors are Panasonic, Sony, FDK, Sanyo, Maxell, etc. Do not be alarmed if your capacitor is stamped with one of these brand names and not Seiko, Citizen or Casio.

Pro Tip: A common mistake when ordering a new capacitor for your watch is to select the part based on the cell number. MT920 refers to the type of cell itself, whereas the Seiko part number is necessary for the correct configuration of prongs and tabs on the cell. In other words, even if the original capacitor in your Seiko Kinetic is stamped MT920, it is important to remember that not all MT920 will fit in your timepiece. For this reason, it is important to figure out the correct part number for your watch based on the caliber number of the movement.

Seiko Capacitor List:

Note: The following capacitor chart is a work in progress and is meant to be used for information only and not guaranteed. The data may be incorrect, if you spot something, please share in the comments below.

Seiko # Type Calibers
3023.24D, 302324D MT920
3023.24L, 302324L MT920 5D22A, 5D44 Seiko 3023 24l Capacitor
3023.24M, 302324M MY920
3023.24P, 302324P MT920 5Y75A, V121A, V122A
3023.24R, 302324R MT920 7M12A, 7M22A, 7M42A, 4M45A, V12
3023.24T, 302324T MT920 Seiko 3023 24t Capacitor
3023.24X, 302324X MT920 Seiko 302324x Capacitor
3023.24Y, 302324Y MT920
3023.34R, 302334R TS920E
3023.34T, 302334T TS920
3023.5MY, 30235MY TC920
3026.24X, 302624X MT621
3027.26T, 302726T MT516F
3027.26Y, 302726Y MT516
3027.26Z, 302726Z MT516F
3027.29N, 302729N MT616
3027.29R, 302729R MT616
3027.29Y, 302729Y MT616
3027.23MY, 302723MY MT616
3023.5MZ, 30235MZ MT616
3027.4MZ, 30274MZ MT616
3027V1Z, 3027V1Z MT516F
PA16001H, PA16001H MT621

Citizen Capacitor List:

Note: The following capacitor chart is a work in progress and is meant to be used for information only and not guaranteed. The data may be incorrect, if you spot something, please share in the comments below.

Citizen # Type
295-28 (295-2800, 295.28, 29528, 2952800) MT616 8510A, 8627A Citizen 295 28 Capacitor
295-29 (295-2900, 295.29, 29529, 2952900) MT920 0850A, 0855A, 0870A, 0875A Citizen 295 2900 Capacitor
295-31 MT1620
295-34 MT920
295-38 MT920
295-39 MT920
295-41 MT616
295-44 MT1620
295-51 (295-5100, 295.51, 29551, 2955100) MT621 B110M, B117M, E000M, E001M, E010M, E011M, E030M, E031M, E068M, E100M, E101M, E110M, E111M, E168M, E410G, G430M, G431M, G530G, H500M, H501M, H570M, H571M Citizen 295 51 Capacitor
295-53 US2025
295-55 MT621
295-56 (295-5600, 295.56, 29556, 2955600) MT920 7821A, 7828A, 7871A, 7873A, 7876A, 7878A, 7879A, A710G, A715G, A730G, A735G, A780G, A784G, A786G, B510Z, B515Z, B910M, C651, C660, E510G, E511G, E710M, E711M, E712M, E715M, E716M, E717M, E760M, E760N, E761N, E765M, E766M, E767M, E768M, E810M, E811M, E812M, E816M, E817M, E860M, E865M, E870M, H410M, H411M, H412M, H430M, H460M, H461M Citizen 295 56 Capacitor
295-60 MT621
295-65 MT1620
295-66 MT616
295-67 MT416
295-69 CTL920
295-753 CTL621
295-758 CTL920
295-76 (295-7600, 295.76, 29576, 2957600) MT516F B020, B023, J015 Citizen 295 76 Capacitor
295-7630 MT516
Caliber Corner is the world's most popular resource for watch movement pics, specs, mods and DIY repairs. Be sure to check out the member's forum and follow @calibercorner on Twitter, Instagram and YouTube (NOT Facebook). Join our mission to spread movement awareness! Login/Sign-up

Community Reviews & Questions:

  • Keep comments respectful and follow our community guidelines.
  • Keep comments on the topic of Watch Capacitors

For off topic or general watch questions, post in the Caliber Corner Forum.


newest most voted
Inline Feedbacks
View all comments
Does Seiko Still Make Kinetic Watches – Watches Of Today
3 years ago

[…] watch capacitor is used to store power in battery-like cells. Kinetic, as well as solar watches, used […]

Prakash Patel
Prakash Patel
3 years ago

What are the difference between MT621 & CTL621f capacitors? Can they be switched if one type is not easily available? Thx

Seiko Caliber 9T82 Watch Movement | Caliber Corner
1 year ago

[…] the capacitor for the caliber 9t82 is not available for sale. Unlike most kinetic watch capacitors which can be purchased on Amazon, the 9T82 apparently uses a special capacitor which Seiko does not […]

William C Allen
William C Allen
1 year ago

What is the capacitance of these capacitors in farads, microfarads, picofarads or whatever units apply?

Seagull Caliber St19

Join our mission to spread movement awareness!

Members Online

  • admin keepthetime echadden

Recent Forum Posts

Trending Comments


Miyota Caliber 2115

El casio marlin duro mvd 106 usa el miyota 2115. Cuando busco el repuesto aparecer…


Seiko Caliber 5M82

I have a cal. 5m83 in a watch that was bought for me, by my…


Ronda Caliber 515

It looks like a very good and cheap caliber. I have it in Roamer Power…


Sellita Caliber SW280-1

They rotate in phase with the lunar cycle. Which is 29 days, 12 hours, 44…


Miyota Caliber 2035

Why not just use another Seiko Y121? My cheap "George" Walmart $8.88 watch has one,…


Would love your thoughts, please comment.x