This shellscript will show the "battery health" of most Mac laptops.

#!/bin/bash

#ioreg -w0 -l | grep Capacity
run=`ioreg -w0 -l | grep "MaxCapacity\" = " -c`
if [ $run -ne 0 ]; then
  cur=`ioreg -w0 -l | grep "CurrentCapacity\" = " | awk -F" = " '{print $2}'`
  des=`ioreg -w0 -l | grep "DesignCapacity\" = " | awk -F" = " '{print $2}'`
  desRun=`ioreg -w0 -l | grep "DesignCapacity\" = " -c`
  max=`ioreg -w0 -l | grep "MaxCapacity\" = " | awk -F" = " '{print $2}'`

  perc=$((($cur*100)/$max))
  if [ $desRun -ne 0 ]; then
    health=$((($max*100)/$des))

    if [ $health -gt 100 ]; then
     health=100
    fi

    echo "Health: ${health}% (${perc}% charged)"
  else
    echo "Health: unknown (${perc}% charged)"
  fi
else
  echo "No battery found"
fi