Modifier la ligne de status d'EMACS

Bonjour

je voudrai ajouter le niveau de la baterie à la ligne de status

;; display the line-number and column-number in status line
(setq column-number-mode t)
(setq line-number-mode t)
;; display the size of file in status line
(setq size-indication-mode t)
;; display time in status line
(setq display-time t)

;; use setq-default to set it for /all/ modes
(setq-default mode-line-format
  (list
    ;; the buffer name; the file name as a tool tip
    '(:eval (propertize "%b " 'face 'font-lock-keyword-face
        'help-echo (buffer-file-name)))

    ;; line and column
    "(" ;; '%02' to set to 2 chars at least; prevents flickering
      (if line-number-mode
        (propertize "lin:%02l" 'face 'font-lock-type-face)
      )
      (if (and line-number-mode column-number-mode)
        " ; "
      )
      (if column-number-mode
        (propertize "col:%02c" 'face 'font-lock-type-face)
      )
    ") "

    ;; relative position, size of file
    (if size-indication-mode
      (concat
        "["
        (propertize "%p" 'face 'font-lock-constant-face) ;; % above top
        "/"
        (propertize "%I" 'face 'font-lock-constant-face) ;; size
        "] "
      )
    )
    ;; the current major mode for the buffer.
    "["

    '(:eval (propertize "%m" 'face 'font-lock-string-face
              'help-echo buffer-file-coding-system))
    "] "


    "[" ;; insert vs overwrite mode, input-method in a tooltip
    '(:eval (propertize (if overwrite-mode "Ovr" "Ins")
              'face 'font-lock-preprocessor-face
              'help-echo (concat "Buffer is in "
                           (if overwrite-mode "overwrite" "insert") " mode")))

    ;; was this buffer modified since the last save?
    '(:eval (when (buffer-modified-p)
              (concat ","  (propertize "Mod"
                             'face 'font-lock-warning-face
                             'help-echo "Buffer has been modified"))))

    ;; is this buffer read-only?
    '(:eval (when buffer-read-only
              (concat ","  (propertize "RO"
                             'face 'font-lock-type-face
                             'help-echo "Buffer is read-only"))))
    "] "

    ;; add the time, with the date and the emacs uptime in the tooltip
    (if display-time
      '(:eval (propertize (format-time-string "%H:%M")
              'help-echo
              (concat (format-time-string "%c; ")
                      (emacs-uptime "Uptime:%hh"))))
    )

    " --"
    ;; i don't want to see minor-modes; but if you want, uncomment this:
    minor-mode-alist  ;; list of minor modes
    "%-" ;; fill with '-'
    ))

que doit je ajouter à ce code
Merci