BA-53635/PLMD
From Halopedia, the Halo wiki
The BA-53635/PLMD the a United Nations Space Command integrated non-replaceable battery for the Weapon/Anti-Vehicle Model 6 Grindell/Galileian Nonlinear Rifle (W/AV M6 G/GNR) "Spartan Laser" weapon.
It powers the Spartan Laser's blood red laser beams, which are incredibly vast in power and can destroy any enemy, infantry or vehicle, typically upon a single impact (except for heavy vehicles such as Wraiths, unless the exposed vehicle operator is directly shot[1] or the vulnerable circular vent on the rear is hit). However, the energy consumption for the M6 G/GNR is expectedly extreme, and the BA-53635/PLMD battery is drained in five laser shots.
It is unclear whether or not this battery can be recharged. If it could, the generator required would be too large to carry on the battlefield.