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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.

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 #TypeCalibers
Example
3023.24D, 302324DMT920
3023.24L, 302324LMT9205D22A, 5D44Seiko 3023 24l Capacitor
3023.24M, 302324MMY920
3023.24P, 302324PMT9205Y75A, V121A, V122A
3023.24R, 302324RMT9207M12A, 7M22A, 7M42A, 4M45A, V12
3023.24T, 302324TMT920Seiko 3023 24t Capacitor
3023.24X, 302324XMT920Seiko 302324x Capacitor
3023.24Y, 302324YMT920
3023.34R, 302334RTS920E
3023.34T, 302334TTS920
3023.5MY, 30235MYTC920
3026.24X, 302624XMT621
3027.26T, 302726TMT516F
3027.26Y, 302726YMT516
3027.26Z, 302726ZMT516F
3027.29N, 302729NMT616
3027.29R, 302729RMT616
3027.29Y, 302729YMT616
3027.23MY, 302723MYMT616
3023.5MZ, 30235MZMT616
3027.4MZ, 30274MZMT616
3027V1Z, 3027V1ZMT516F
PA16001H, PA16001HMT621

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
Calibers
Example
295-28 (295-2800, 295.28, 29528, 2952800)MT6168510A, 8627ACitizen 295 28 Capacitor
295-29 (295-2900, 295.29, 29529, 2952900)MT9200850A, 0855A, 0870A, 0875ACitizen 295 2900 Capacitor
295-31MT1620
295-34MT920
295-38MT920
295-39MT920
295-41MT616
295-44MT1620
295-51 (295-5100, 295.51, 29551, 2955100)MT621B110M, B117M, E000M, E001M, E010M, E011M, E030M, E031M, E068M, E100M, E101M, E110M, E111M, E168M, E410G, G430M, G431M, G530G, H500M, H501M, H570M, H571MCitizen 295 51 Capacitor
295-53US2025
295-55MT621
295-56 (295-5600, 295.56, 29556, 2955600)MT9207821A, 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, H461MCitizen 295 56 Capacitor
295-60MT621
295-65MT1620
295-66MT616
295-67MT416
295-69CTL920
295-753CTL621
295-758CTL920
295-76 (295-7600, 295.76, 29576, 2957600)MT516FB020, B023, J015Citizen 295 76 Capacitor
295-7630MT516
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