Two ways ...

1) Add a 0 to the last LCDOUT ...
Code:
    lcdout $1F,0
2) You can make the battery icon 1 pixel taller ...
Code:
            ELSE
                BattLevel = (Volts - MinBat +1) * 15 / (MaxBat - MinBat +1)
            ENDIF
        ENDIF
        GOSUB ShowBattery
    ENDIF
RETURN

;----[Show Battery Icon  0 - 15, 0=Empty  15=Full]--------------------------
ShowBattery:
    lcdout $FE,$C0,1,$FE,$48,$0A,$1F
    for y = 5 to 1 step -1
        if BattLevel >= (y * 3) then
            Char = $1F
        else
            if BattLevel >= (y * 3 - 1) then
                Char = $17
            else
                if BattLevel >= (y * 3 - 2) then
                    Char = $13
                else
                    Char = $11
                endif
            endif
        endif
        lcdout Char
    next y
    lcdout $1F
return