energy capacitor (E-CAP)
A mega particle cannon like those installed in space warships requires a large electrical power source, a steady supply of energy in the form of Minovsky particles, and a massive energy condensor to compress the latter into mega particles prior to firing. Therefore, it initially seems impossible to install these weapons in mobile suits. These issues are addressed with the development of the energy capacitor, which makes it possible to create compact beam weapons with greatly reduced power and energy requirements.
The E-CAP stores Minovsky particles in a compressed, high-energy state, just short of fusing into mega particles. The power output of a mobile suit's generator, although far lower than that of a warship, is sufficient to complete this process and form mega particles. However, the mobile suit is unable to replenish the supply of Minovsky particles inside the E-CAP, and once this energy supply is exhausted the weapon must be returned to a base or carrier vessel for recharging.
energy pack (E-pack)
A removable external energy capacitor (E-CAP), which can be replaced in combat just like a rifle magazine. By the time of the Gryps Conflict, most beam rifles use these interchangeable energy packs, giving them a far greater energy supply than the weapons used during the One Year War. [Gundam 0083, Zeta Gundam, Gundam F91]
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I only quoted the E-Cap definition just as a refresher. Now on the E-pac definition, it states that MOST beam rifles by the time of Gryps use E-pac technology. If so...then why are the only gundams to use them are the Zeta, MK II, and the GP Gundams? Then it skips a large gap into F91, and only used by the F91 and the Vigna Ghina's beam launcher.
What happened to the good o'l e-pacs? They seemed to be the greatest innovation to the beam rifle made post-OYW.
Are the MAHQ stats slightly wrong/out of date, or is gundam official exaggerating?