wmbattery: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/wmbattery - from package: wmbattery

You may install the required package with command apt-get install {package}

Error in other languages:
wmbattery: bevel nie gevind nie
wmbattery: comandă negăsită
wmbattery: comando não encontrado
wmbattery: commande introuvable
wmbattery: command not found
wmbattery: käsku ei ole
wmbattery: không tìm thấy lệnh
wmbattery: komanda nerasta
wmbattery: Kommando nicht gefunden.
wmbattery: kommandot finns inte
wmbattery: komut yok
wmbattery: nie znaleziono polecenia
wmbattery: níor aimsíodh an t-ordú
wmbattery: no se encontró la orden
wmbattery: no s'ha trobat l'ordre
wmbattery: opdracht niet gevonden
wmbattery: parancs nem található
wmbattery: perintah tidak ditemukan
wmbattery: príkaz nenájdený
wmbattery: příkaz nenalezen
wmbattery: команда не найдена
wmbattery: командата не е открита
wmbattery: 命令找不到
wmbattery: コマンドが見つかりません