See \gamemodes\terrortown\readme.txt or the SVN copy of the readme. CTRL+F on "battery":

ttt_voice_drain (def. 0):
Enables the voicechat battery feature. Voicechatting reduces a battery meter,
when it's empty the player can't voicechat and must wait a few seconds for it to
recharge.

ttt_voice_drain_normal (def. 0.2):
Battery drain per tick of voicechat for non-admin players.

ttt_voice_drain_admin (def. 0.05):
Battery drain per tick of voicechat for admins. Set to 0 to allow infinite mic
usage.

ttt_voice_drain_recharge (def. 0.05):
Battery recharge rate per tick of not voicechatting.

L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\gamemode\shared.lua:1] unexpected symbol near '4'
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\gamemode\init.lua:4] ERROR PARSING CLIENTSIDE FILE: 'terrortown\gamemode/shared.lua'
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\gamemode\shared.lua:1] unexpected symbol near '4'
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\gamemode\gamemsg.lua:237] table index is nil
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\gamemode\player_ext_shd.lua:34] table index is nil
L 11/23/2010 - 20:59:57: Load Gamemode: 'terrortown'
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\weapons\weapon_tttbase\shared.lua:137] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\weapons\weapon_tttbasegrenade\shared.lua:57] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\weapons\weapon_ttt_phammer\shared.lua:51] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\weapons\weapon_ttt_push\shared.lua:50] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\weapons\weapon_ttt_wtester\shared.lua:71] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\entities\ttt_basegrenade_proj\shared.lua:14] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:57: Lua Error: [gamemodes\terrortown\entities\entities\ttt_c4\shared.lua:39] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:58: Lua Error: [gamemodes\terrortown\entities\entities\ttt_flame\shared.lua:14] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:58: Lua Error: [gamemodes\terrortown\entities\entities\ttt_hat_deerstalker\shared.lua:11] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:58: Lua Error: [gamemodes\terrortown\entities\entities\ttt_health_station\shared.lua:29] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:58: Lua Error: [gamemodes\terrortown\entities\entities\ttt_traitor_button\shared.lua:7] attempt to call global 'AccessorFuncDT' (a nil value)
L 11/23/2010 - 20:59:58: Lua Error: [gamemodes\terrortown\gamemode\init.lua:136] table index is nil(Hook: Initialize)
L 11/23/2010 - 20:59:58: server_cvar: "mp_friendlyfire" "1"
L 11/23/2010 - 20:59:59: Lua Error: [gamemodes\terrortown\entities\entities\ttt_map_settings\init.lua:26] attempt to call global 'Dev' (a nil value)
L 11/23/2010 - 20:59:59: Lua Error: [gamemodes\terrortown\entities\entities\ttt_map_settings\init.lua:18] attempt to call global 'Dev' (a nil value)
L 11/23/2010 - 20:59:59: Lua Error: [gamemodes\terrortown\entities\entities\ttt_map_settings\init.lua:23] attempt to call global 'Dev' (a nil value)
L 11/23/2010 - 21:00:00: Lua Error: [@gamemodes\terrortown\gamemode\weaponry.lua:489] bad argument #1 to 'pairs' (table expected, got nil)(Hook: InitPostEntity)