i have one and AFAIK they dont display your remaining balance. Usually I manually reload 500 sa toll booth.
I do a weekly visits in my in-laws at marilao bulacan, kaya 90 pesos two way ang nagagastos ko sa toll.
Minsan i lost track kung naka ilan gamit na ako sa ec-tag ko since the day i reloaded.
Kaya pag nag dilaw na nag aalangan na ako pumasok ulit sa ec-tag lane.

Sana they display the exact remaining balance.