As per my experience its due to battery, there is just 1 battery under the hood.
I have Mira eiS, 2013 model, getting a new battery is the only solution.
Ordinary battery will not do, you have to get imported battery meant for "Idle Off" cars.
I have same problem as yours, I tried 2 different batteries and the problem reoccurs after some time.
I am now trying to get Panasonic battery..
"The battery of the idling stop car is different from the normal battery, both fast charge, discharge, and capacity.
The car side is also equipped with a rapid charging system for batteries for idling stop cars.
It can not be said that there is no danger of short-lived or ignited when repeating rapid charging and discharging to a normal battery . "
We need battery type "M-42"