A new era for silver–zinc batteries
By the 1950s, silver–zinc batteries were established specialised power sources. Lighter and more compact than lead–acid batteries, they delivered high current with a relatively stable discharge voltage. Their advantages became particularly important in the 1960s, as the space race, rocket development and a renewed search for alternatives to petrol cars advanced together.
Silver's cost often became secondary. For spacecraft, rockets, torpedoes or experimental cars, saving mass and volume could be decisive. Silver–zinc batteries were neither cheap nor long-lived, but offered performance unavailable from most contemporary alternatives.
Why space programmes chose silver and zinc
Spacecraft needed power for communications, automatic controls, attitude instruments, life support and re-entry equipment. Every extra kilogram increased launch-vehicle requirements. Silver–zinc cells offered high specific energy and power, while limited cycle life mattered less for short missions or expendable vehicles.
That explains their use on both sides of the space race. The United States and Soviet Union independently reached a similar engineering choice: an expensive metal was justified where failure was unacceptable and the battery had one time-limited task to perform reliably.
Silver–zinc batteries in NASA programmes
In Gemini, silver–zinc batteries provided part of the power during launch, all power during particular flight phases, and power during re-entry and after splashdown. In January 1963, NASA, McDonnell and Eagle-Picher discussed five main batteries and three separate high-power batteries for relays and actuators. Delays in fuel-cell development made silver–zinc batteries a ready alternative for the first Gemini spacecraft.
Apollo's command and service module obtained most of its energy from hydrogen–oxygen fuel cells, but silver–zinc batteries remained critical. They powered the command module, including during re-entry after separation from the service module and its fuel cells. NASA explicitly identifies Apollo's command module among early spacecraft using silver–zinc batteries.
The system also served robotic spacecraft. Surveyor lunar landers received a main silver–zinc battery that passed qualification, thermal-vacuum and simulation tests before flight. In the mid-1960s, NASA also investigated silver–zinc sources for Atmosphere Explorer satellites and interplanetary spacecraft.
NASA simultaneously sought longer life for rechargeable versions. Researchers studied separators, sealing, shock and radiation resistance, and heat sterilisation. Results improved, but deep cycling still rapidly damaged electrodes. In space, the technology was consequently valued mainly as a light, reliable source for a limited number of discharges rather than years of rechargeability.
The USSR: from Vostok to early Soyuz
The Soviet space programme also made extensive use of silver–zinc batteries. Vostok carried a main battery in the instrument compartment and an additional battery in the descent module to power descent and landing. This arrangement supported the first crewed flights, including Yuri Gagarin's spacecraft in 1961.
Voskhod, derived from Vostok, belonged to the same engineering lineage. Public sources describe Vostok's batteries in the most detail, while continuity of the design illustrates how deeply silver–zinc systems were embedded in early Soviet crewed spaceflight.
On early Soyuz spacecraft, first flown in 1967, silver–zinc batteries operated alongside solar arrays. The Gagarin Cosmonaut Training Center's official description gives a 300 Ah main buffer battery and a 75 Ah reserve. Solar panels recharged the buffer battery, while the batteries stabilised power as illumination changed and during critical mission stages.
Both NASA and Soviet designers therefore treated silver–zinc batteries as important elements of early space power systems. Spacecraft architectures and combinations of sources differed, but the rationale was similar: high energy and power for low mass.
Continuing military development
The space race did not displace military applications; both sectors developed the technology in parallel. Aviation considered silver–zinc batteries a lighter alternative to lead–acid backup batteries. An ARINC report in 1965 noted the mass, volume and power advantages that new alkaline systems brought to military and specialised aviation.
Primary reserve batteries continued to serve missiles, control systems and equipment that needed long storage followed by immediate high current. Electrolyte could remain separate until activation, limiting self-discharge and allowing years of dormant storage.
Marine applications remained important, including torpedoes, submersibles and deep-ocean systems. A 1969 SAE paper described silver–zinc batteries as an operational power source for deep-ocean vehicles. Cost was again an acceptable trade-off for compactness, power and the ability to locate battery packs outside the pressure hull.
How space technology reached the road
By the mid-1960s, automotive engineers were revisiting electric propulsion. Motors could provide quiet operation and good acceleration, while power electronics were becoming smaller. Batteries remained the main obstacle: conventional lead–acid packs were too heavy for a passenger car with acceptable speed and range.
Silver–zinc appeared to offer a ready answer. It had demonstrated its capabilities in aviation and space, and General Motors had battery research experience, including NASA contracts. A technology associated with costly government programmes consequently found its way into an otherwise ordinary-looking Chevrolet Corvair.
Electrovair I: General Motors' first experiment
GM's research organisation built the first Electrovair in 1964 using a Chevrolet Corvair. Electric propulsion replaced the petrol engine and transmission. GM reports that the project developed a roughly 450 V silver–zinc battery. Its purpose was to test powerful electric propulsion in a full-size passenger car, rather than prepare a production model.
Electrovair I demonstrated that a car of this size could run on electricity, but its performance did not satisfy the engineers. It was a mobile laboratory for the motor, inverter, controls and battery installation. GM used the experience to build a substantially redesigned second car.
Electrovair II: an experimental car with serious performance
Electrovair II appeared in 1966, based on the second-generation Corvair. Its approximately 532 V silver–zinc pack occupied the front luggage compartment and former engine bay. It supplied a three-phase induction motor rated at about 115 hp, comparable with the petrol Corvair.
Performance was impressive for an experimental vehicle: around 80 mph (129 km/h) and an estimated range of 40–80 miles (64–129 km), depending on driving conditions. Electrovair II approached ordinary production-car performance rather than that of a slow urban runabout.
Silver–zinc made this possible without an entirely prohibitive battery mass. Electrovair II was still about 800 lb (360 kg) heavier than a conventional Corvair. Its developers estimated that an equivalent lead–acid pack would have weighed almost as much as the entire standard car.
The limitations were equally clear. Range was insufficient to replace a petrol car fully, the battery lasted only around a hundred cycles, and the silver pack made production uneconomic. In their SAE paper, GM engineers concluded cautiously that a modern high-performance electric car was technically possible but required a substantially better and cheaper energy source.
EM-0466: a Soviet silver–zinc electric van
A similar line of work emerged in the USSR around the turn of the 1970s. The All-Union Research Institute of Electric Transport in Kaliningrad and electrical-industry enterprises built two experimental EM-0466 urban vans. Publications date the project to either 1970 or 1971, so it is best treated as a development spanning the two decades.
The EM-0466 differed from the American Electrovair. It was a compact delivery van with a payload of about 500 kg, rather than a fast passenger sedan. It used silver–zinc batteries, an AC motor and thyristor controls. Some accounts also mention regenerative braking, an advanced feature for the early 1970s.
Later sources disagree on its specifications. Common figures are a top speed of roughly 40–50 km/h and a range of 80–100 km. Such a vehicle could suit predictable urban routes for mail, goods or industrial services. An expensive, heavy battery, limited life and no economic advantage over petrol vans prevented series production.
Were there other silver–zinc electric cars?
Reference works mention earlier European experiments, including an electric Dyna-Panhard in the 1950s and some Renault Dauphine conversions. Silver–zinc batteries are attributed to them, but documentation is much thinner than for GM's programme. They are better treated as background than placed on the same evidential footing as Electrovair.
Not every 1960s electric car belonged to the silver–zinc line. The 1967 AMC Amitron, for example, combined nickel–cadmium and experimental lithium–nickel-fluoride batteries. Other projects used lead–acid batteries or fuel cells. Silver was a visible but far from exclusive branch of development.
The best-known vehicle continuation of the space programme was the Lunar Roving Vehicle, first driven on the Moon in 1971. It used two non-rechargeable 36 V silver–zinc batteries. Although it belongs to the next period, the lunar rover strongly symbolises the meeting of spaceflight and electric transport.
Why silver–zinc cars did not fill the streets in the 1970s
In space and military equipment, a costly battery could be justified if it saved mass and reliably completed a critical task. The automotive market demanded hundreds or thousands of deep cycles, convenient charging, low cost and production in millions of units.
The silver–zinc systems of the 1960s did not fit that economic model. Deep cycling changed the zinc electrode's shape, damaged the separator and shortened service life. Enlarging the battery increased both mass and the quantity of expensive silver. Impressive prototypes therefore did not become viable production vehicles.
The legacy of the 1960s and early 1970s
Within a decade, silver–zinc batteries served US and Soviet crewed spacecraft, robotic lunar missions, aviation and marine equipment, and experimental cars on both sides of the Atlantic. They offered a particularly clear illustration of the connection between space technology and future ground transport.
Electrovair II and the EM-0466 were not direct ancestors of today's production EVs. But they demonstrated the industry's central problem early: building a fast electric car was possible; building a battery that was light, durable and affordable at the same time was much harder. This lesson shaped the next decade of oil crises, government programmes and renewed attempts to bring electric cars to the road.
Sources and notes
- NASA: silver–zinc battery research history
- NASA: Gemini chronology and battery development
- NASA: Apollo Experience Report — Battery Subsystem
- NASA/JPL: Surveyor silver–zinc batteries
- NASA: Atmosphere Explorer-B batteries
- Gagarin Cosmonaut Training Center: early Soyuz electrical power system (in Russian)
- V. Bobkov and V. Syromyatnikov: Vostok's electrical power system (in Russian)
- ARINC, 1965: silver–zinc batteries in aviation
- SAE, 1969: silver–zinc battery power for deep-ocean vehicles
- General Motors: the Electrovair project
- SAE, 1967: Electrovair — A Battery Electric Car
- Za Rulyom magazine archive: electric-transport institute developments (in Russian)
- The EM-0466 and Soviet experimental electric vehicles (in Russian)