Android 4.4 dead at recovery mode dm

[Swastik Singh]

At the time of installing custom rom my galaxy s duos 3 goes off due to low battery and now it's dead,it not responding on any key,first i charged it for about 1 hour but its shows nothing on screen while charging and not responding to any set of key either its power key or recovery mode key combination. As it not goes on recovery mode so i cant reinstall it firmware. Please suggest me some way to repair it...

 

[smvim]

Sounds like you bricked your phone while flashing that custom ROM, hopefully it's just soft-bricked and not a full on hard brick.
Your model has a user-removable battery so try removing the battery and leave it out for several minutes. Put it back in and try to boot up, if it's still dead maybe try getting a 'jig'. You can make your own, or buy one on Amazon, they're only a few bucks.
USB JIG to Give Life to Your Bricked Mobile: 8 Steps
If using a jig works it should boot your phone up into its Download Mode, and be sure to charge your battery BEFORE you start the flashing process, or do it while plugged into a power source (USB port or adapter).
Samsung Galaxy S Duos 3 - Full phone specifications