Rebels in Syria are designing rechargeable batteries for shoulder-fired antiaircraft missiles, a development that could make them more lethal against Syrian warplanes but that also carries potential risks to civilian aircraft, according to a rebel behind the new design and to Western analysts who have assessed his work.

The batteries are matched to the SA-7b missile system, or Strela-2, an early variant of heat-seeking missile that originated in a Soviet design bureau in the late 1960s and has been reproduced in several countries, including China, North Korea and Pakistan.

A weapon of a class often colloquially called Stingers, as the best-known American model is known, Strelas have for decades been the most commonly seen antiaircraft missiles among rebel and terrorist groups. But the limited availability and short life span of their batteries, which are attached to the exterior of the tube that contains the missile, has meant that nonstate groups often struggle with power supply, posing limits on the Strela’s use.

Improvised batteries have been documented in the Syrian conflict, and a missile system powered by one apparently was used to shoot down a helicopter last year. The designer of the rechargeable battery, Abu al-Baraa, said he was a Syrian Air Force major until defecting to the rebels in 2012. Abu al-Baraa, who asked that his full name not be used because of concern for the safety of his relatives, said rebels in Syria could now overcome the problem of possessing many more missiles than batteries, and of high rates of battery consumption in marginally trained ranks when using SA-7s, which the Syrians call Cobras.