Cartier Tank Must Solarbeat: owner reviews and feedback

The Cartier Tank Must SolarBeat, launched in 2021, transfers one of Cartier’s most traditional silhouettes to almost completely invisible photovoltaic technology. Introduced during the revival of the Tank Must, it retains the rectangular proportions, parallel brancards, Roman numerals, railway minute track, blued sword-shaped hands and beaded crown set with a blue synthetic spinel that immediately define a Tank.

The difference lies behind the dial: tiny perforations allow light to reach a photovoltaic cell that charges an energy-storage battery. Cartier states that the system can operate for at least sixteen years before this battery needs replacing. The first versions are available as a 29.5 x 22 mm small model and a 33.7 x 25.5 mm large model, both measuring only 6.6 mm thick. From November 2024, the system evolves through a fully micro-perforated dial and autonomy reaching approximately twenty-four months from a complete charge. The Tank Must SolarBeat nevertheless remains a simple two-hand watch without seconds or date.

Design and legibility: a classical Tank whose technology disappears behind the Roman numerals

The main aesthetic appeal of the SolarBeat comes precisely from the fact that it does not look like a solar-powered watch. Cartier retains an extremely traditional silvered dial, large black Roman numerals, a rectangular railway minute track, blued sword-shaped hands and the small secret Cartier signature hidden within one of the numerals. On the first generation, selected areas of the Roman numerals are micro-perforated so that light can reach the photovoltaic cells beneath them. On the generation sold after November 2024, this micro-perforation is extended across the complete dial. The almost invisible transformation of the Roman numerals and later the complete dial into a light-capturing surface forms the essential distinguishing feature of the Tank Must SolarBeat. At normal viewing distance, the watch therefore retains the appearance of a conventional Tank Must. The dial needs to be examined very closely before its role in powering the movement becomes apparent. This discretion allows technology to serve the design rather than become its dominant visual element.

The relationship with the Tank created by Louis Cartier in 1917 remains particularly strong. Its two parallel vertical brancards visually extend the sides of the dial towards the strap and allow the watch to move geometrically from a rectangular time display to an almost continuous wrist construction. The dial remains highly legible despite the absence of luminous material because Cartier relies mainly on contrast between the silver background, black numerals and blued hands. The SolarBeat prioritises contrast-based reading rather than the nighttime visibility of a sports watch. It has no central seconds, date or displayed power reserve, allowing the dial to remain almost identical to that of a conventional Tank. This simplicity also has a practical advantage: no additional display visually reveals the photovoltaic movement and the absence of a seconds hand prevents the one-second stepping action typical of quartz from becoming noticeable.

Case, bracelet and comfort: 6.6 mm thick in two historical formats

The Tank Must SolarBeat is offered in two principal dimensions. The small model measures 29.5 mm high by 22 mm wide and the large model 33.7 x 25.5 mm. Both retain an especially slim thickness of 6.6 mm. These figures need to be interpreted differently from those of a round watch: a Tank is measured in two axes and its comparatively narrow width forms part of its traditional balance. The thickness of only 6.6 mm is one of the principal practical advantages of the SolarBeat. The watch easily disappears beneath a cuff and its flat back sits naturally against the wrist. The case is stainless steel and its polished finishing emphasises the vertical lines of the brancards. Its beaded crown is set with a cabochon-shaped blue synthetic spinel, a typically Cartier visual element. The documented modern versions use sapphire crystal.

Water resistance is limited to 3 bar, or approximately 30 metres. This figure corresponds to the purpose of a dress watch and should be understood as protection against accidental contact with water rather than an invitation to swim. The Tank Must SolarBeat has neither a screw-down crown nor construction specifically designed for aquatic activity. The 30-metre water-resistance rating means that the SolarBeat should be treated as a city watch rather than a sports watch. Its slim construction and polished case are also far better suited to the office, travel or dressier clothing than to activities regularly exposing it to impacts and water. On an older or pre-owned example, water-resistance testing remains advisable if the watch will frequently be worn in humid conditions.

The first SolarBeat watches are paired with straps containing no animal-origin material and approximately 40% plant matter produced partly from apple waste. Cartier developed this solution within the same general approach as the photovoltaic movement, using European manufacturing and stating lower resource consumption than for a conventional calfskin strap. Black, blue and light-green straps appear at launch. More recent generations also use black calfskin and, importantly, a stainless-steel bracelet. The steel bracelet substantially changes the character of the SolarBeat by giving it greater presence and everyday versatility. A flexible strap remains closer to traditional Tank elegance and further reduces perceived mass. The choice therefore depends less on technology than use: flexible strap for thinness and dress wear, steel for a more versatile everyday watch.

SolarBeat movement: natural or artificial light and very long service life

SolarBeat is a Swiss quartz movement powered by photovoltaic energy. Natural or artificial light passes through the micro-perforations in the dial, reaches a photovoltaic cell and is converted into electrical energy stored in a rechargeable battery. Unlike a solar watch with visibly exposed cells on its dial, Cartier seeks to make this system almost impossible to distinguish from a conventional dial. The SolarBeat movement retains the accuracy and simplicity of quartz while avoiding the regular battery replacements required by a traditional movement. Cartier estimates that it can function for at least sixteen years without battery replacement, compared with approximately eight years for its high-autonomy quartz movement and around three years for conventional quartz according to the Maison’s own comparison. This period does not mean that the watch can run for sixteen years in darkness: regular exposure to light is still required to maintain its charge.

The first generation offers several months of operation when its battery is completely charged. The version documented for watches sold after 1 November 2024 significantly increases this capability, with Cartier stating approximately twenty-four months of autonomy from a full charge. Its dial simultaneously becomes completely micro-perforated to improve light capture. The 2024 evolution primarily changes the duration between meaningful exposures to light without altering the overall appearance of the Tank. When a completely depleted watch stops, Cartier recommends positioning the dial towards a light source and allowing it sufficient time to recharge before use. Charging works under both natural and artificial light, although its speed naturally varies with source intensity. This architecture makes the watch especially straightforward for an owner who wears it regularly.

SolarBeat powers hours and minutes only. This limitation may appear extremely simple beside a complicated mechanical watch, but it corresponds perfectly to the historical vocabulary of the Tank. The lack of a seconds hand notably prevents the one-second stepping action of the quartz mechanism from being observed and preserves an almost motionless visual impression. The two-hand display allows Cartier to integrate modern technology without changing the traditional visual experience of a Tank. There is no winding, displayed power reserve or date to correct after several weeks without wear. As long as the battery contains energy, the watch simply continues to display the time. This simplicity is one of its principal advantages over a mechanical Tank for someone wanting to pick up the watch again after days or weeks without performing extensive setting.

Chronological milestones and main models (1917–2025)

(1917) Cartier Tank Creation of the Foundational Design:

Louis Cartier designs in 1917 the watch that creates one of the most enduring silhouettes in watchmaking. The Cartier Tank reference not communicated uses two parallel vertical brancards framing the dial and extending towards the strap, a construction geometrically connecting the central square with the rectangle formed by the complete watch. A first prototype is presented to General John Pershing before commercialisation of the Tank begins in 1919. The earliest examples use precious metals, manually wound mechanical movements and leather straps. Dimensions vary according to execution and cannot be summarised by a single figure. Water resistance in the contemporary sense is not communicated. Roman numerals, the railway minute track and blued hands gradually become emblematic codes. More than a century later, the SolarBeat retains this general architecture almost intact, demonstrating that photovoltaic technology can be inserted into a much older historical design.

(1977) Must de Cartier Democratisation of the Tank Language:

During the 1970s, Cartier develops the Must de Cartier world in order to make some of its aesthetic codes accessible to a broader audience. The Must de Cartier Tank reference not communicated reproduces the rectangular silhouette of the Tank Louis Cartier using more accessible materials and configurations, notably vermeil cases and a broad variety of dials. Monochromatic red, blue or black versions become especially characteristic of this period alongside classical Roman-numeral dials. Quartz and mechanical movements exist depending on reference. Dimensions, crystal, water resistance and calibre need to be checked watch by watch and cannot be generalised across the entire family. This approach is essential to understanding the modern Tank Must: when Cartier revives the Must name in 2021, the logic remains similar. The objective is not simply to copy a gold Tank Louis but to preserve the major Cartier design codes in a technically more accessible steel watch.

(2021) Cartier Tank Must SolarBeat Large Black First Large SolarBeat:

The first large-format SolarBeat transfers photovoltaic technology into the now-classical proportions of the contemporary Tank Must. The Cartier Tank Must SolarBeat WSTA0059 has a 33.7 x 25.5 mm stainless-steel case measuring only 6.6 mm thick. Its silvered dial uses black Roman numerals, a railway minute track and blued-steel sword-shaped hands. The beaded crown receives a blue synthetic spinel and the crystal is sapphire. Water resistance reaches 3 bar, or approximately 30 metres. The photovoltaic SolarBeat movement powers hours and minutes only; light passes through micro-perforations incorporated into the Roman numerals to feed the cell positioned beneath the dial. Cartier states at least sixteen years before replacement of the rechargeable battery. This reference is originally delivered with a black strap containing no animal-origin material and manufactured partly from plant-based components. It represents the most classical large-model launch configuration.

(2021) Cartier Tank Must SolarBeat Small Black First Small SolarBeat:

The compact version offers exactly the same concept in proportions closer to smaller historical Tank watches. The Cartier Tank Must SolarBeat WSTA0060 measures 29.5 x 22 mm and retains the same 6.6 mm thickness as the large model. Its case is polished stainless steel, the crystal sapphire and the beaded crown receives a blue synthetic spinel. The silvered dial displays hours and minutes through two blued sword-shaped hands and retains the traditional combination of Roman numerals and railway track. Water resistance is limited to 30 metres. The photovoltaic SolarBeat receives energy through perforations within the numeral design and charges a battery engineered for an extremely long service interval. Its original black strap contains no animal-origin material and incorporates a significant proportion of plant-based matter produced partly from apple waste. At only 22 mm wide, this reference creates a particularly traditional presence and is highly suited to smaller wrists.

(2021) Cartier Tank Must SolarBeat Small Green Light-Green Plant-Based Strap:

Cartier also uses straps to give the new technology more personality without altering the historical dial. The Cartier Tank Must SolarBeat WSTA0061 retains the small 29.5 x 22 mm steel case, 6.6 mm thickness, sapphire crystal and 30 metres of water resistance. The dial remains silvered with black Roman numerals, railway minute track and blued sword-shaped hands; the photovoltaic SolarBeat movement continues to charge through light passing through openings in the dial. The principal difference is its light-green strap manufactured from the animal-free material developed for this generation. Production of this material uses approximately 40% plant-derived components originating notably from apple waste, allowing Cartier to associate a long-life movement with broader consideration of the strap. Its pale colour gives this small Tank a considerably more casual appearance than the black version.

(2021) Cartier Tank Must SolarBeat Large Blue Contemporary Blue Strap:

The fourth notable launch configuration combines the large case with a strap colour directly connected with one of Cartier’s historical visual codes. The Cartier Tank Must SolarBeat WSTA0062 measures 33.7 x 25.5 mm and 6.6 mm thick and has a stainless-steel case, sapphire crystal, beaded crown with blue synthetic spinel and 30 metres of water resistance. Its silvered dial follows the same principle as the WSTA0059, with two blued-steel sword-shaped hands, black Roman numerals and a railway minute track. The SolarBeat movement receives energy through the dial micro-perforations and uses a rechargeable battery stated to operate for at least sixteen years before replacement. Its blue animal-free strap is the principal visual difference. The complete watch is more colourful than the black version while remaining highly coherent with the blue hands and crown cabochon. It offers the SolarBeat technology in a less formal configuration without changing the actual watch design.

(2024) Cartier Tank Must SolarBeat Small Steel Second Generation on Bracelet:

From late 2024, Cartier evolves the photovoltaic system while notably introducing a version on a metal bracelet. The Cartier Tank Must SolarBeat WSTA0121 has a 29.5 x 22 mm stainless-steel case measuring 6.6 mm thick, silvered dial, blued sword-shaped hands, a beaded crown set with a synthetic spinel and a stainless-steel bracelet with folding clasp. Water resistance remains 3 bar. The most important technical change concerns light capture: the complete dial is now micro-perforated to feed the photovoltaic cell beneath it. Cartier states that this generation can operate for at least sixteen years without battery replacement and that a complete charge provides approximately twenty-four months of autonomy. Charging works under natural or artificial light. The steel bracelet increases mass and presence compared with the original plant-based straps but turns the small SolarBeat into a substantially more versatile everyday watch.

(2024) Cartier Tank Must SolarBeat Large Steel Large Model with Extended Autonomy:

The large model receives the same technical evolution and metal bracelet. The Cartier Tank Must SolarBeat WSTA0122 measures 33.7 x 25.5 mm and only 6.6 mm thick. Its case and bracelet are stainless steel, the dial silvered, its sword-shaped hands blued steel and the beaded crown set with a synthetic spinel cabochon. Water resistance remains limited to approximately 30 metres. The fully micro-perforated dial allows natural or artificial light to reach the photovoltaic cell and rechargeable battery. Once fully charged, it can provide approximately twenty-four months of autonomy while being designed to operate for at least sixteen years before replacement. The steel bracelet closes with a folding clasp and gives this version a more structured presentation than the first SolarBeat watches on flexible straps. It nevertheless preserves the same extreme thinness and is probably the most versatile configuration for someone wanting to wear a Tank regularly without managing either mechanical winding or frequent battery replacement.

Choosing the right version: small or large, first or new generation and strap choice

The first choice concerns proportions. The 29.5 x 22 mm small model closely respects the traditional idea of a discreet Tank and works on a very broad range of wrists. The 33.7 x 25.5 mm large model remains compact beside a modern round watch but has greater presence. The large model is generally easier to adopt for someone coming from 38 to 40 mm round watches. The small model better suits someone seeking historical elegance and accepting that a Tank is deliberately less substantial than a sports watch.

The original 2021 generation is interesting for its inaugural character and animal-free straps. Models sold after November 2024 instead benefit from a substantial increase in autonomy from a full charge and a completely micro-perforated dial. Visually, the difference remains highly discreet. The recent generation is the more practical choice when autonomy in darkness or extended rotation between several watches genuinely matters. A first-generation watch remains perfectly logical when it is worn regularly and therefore frequently exposed to light.

The choice between a flexible strap and stainless steel substantially changes the personality of the watch. Black provides the most classical Tank interpretation, the earlier blue and light-green alternatives add a more casual touch and the steel bracelet moves the SolarBeat towards a visually more robust everyday watch. A flexible strap remains the best choice for fully enjoying the 6.6 mm thickness and dress-watch character of the Tank. Steel better suits someone wanting to wear the watch in a broader range of situations without worrying about the ageing of leather or plant-based material.

Exposure to light normally requires no particular discipline when a SolarBeat is regularly worn. Both outdoor and artificial light contribute to charging, although stronger illumination naturally charges it more quickly. If the watch stops after an extended period in darkness, its dial needs to be oriented towards a light source for sufficient time. The SolarBeat is particularly appropriate for someone wanting quartz simplicity without organising regular battery changes. A completely closed watch box used for very long storage periods is less naturally suited to its operating principle than storage allowing occasional exposure to light.

Finally, this Tank remains a 30-metre dress watch. Its photovoltaic technology does not make it more sporting than a conventional quartz Tank Must. Sapphire provides effective dial protection, but its polished case can mark and water should remain an occasional constraint. A water-resistance check is advisable on a pre-owned SolarBeat before regularly exposing it to heavy rain or splashes. For normal everyday use, its principal advantage lies precisely in combining the thinness of a traditional Tank with an energy source requiring very little intervention. Other customers’ opinions are essential.

Conclusion

The Cartier Tank Must SolarBeat is aimed at someone wanting the almost unchanged design of a Tank while prioritising the simplicity and very long service interval of photovoltaic technology. The 2021 references have the interest of being Cartier’s first SolarBeat watches and are notably distinguished by their animal-free straps, while generations sold after November 2024 substantially improve autonomy from a complete charge. The small model prioritises historically faithful presence and the large model makes the transition from larger contemporary watches easier. Steel-bracelet versions finally add greater versatility without changing the 6.6 mm thickness. In every case, the essential achievement lies in the technology almost completely disappearing behind Cartier’s Roman numerals and dial.

To compare comfort, accuracy, charging behaviour and strap ageing with extended real-world ownership, Dialicious customer reviews provide a particularly useful complement.

(Updated August 2026)