Easter
happy that you did not give up - one more EPLUS user.
Pity I am in Canada, Alberta so far away.
when you said "batteries suddenly showed dead...." what was display showing ?
normally before EPLUS shut down because battery near dead will give blinking warning , no sudden shut off just like that.
so first:
last bar blinks, next all battery symbol blinks
is it what you had? - this is what is normal.
it is highly unlikely electronics, whatever electronics would fail just like that during ride on DRY day,
cables , wires, connectors yes, but not electronics.