My car is a Camry 99 with i4 engined only electrical fix I ve done on it was a few months back when I had alternator issues, I replaced d alternator and d auto electrician did start d car, removed d battery and switched on full light and it was bright without d battery and he told me this is how to test if an alternator is working properly.
Now if I dont use d car for about 24hrs d battery won't start d car, if I leave same battery in another car for 3days without starting d car it wld still start when I need to. Am tired of swapping batteries as d other car is not even mine and not always available.
What could possibly be wrong in my car?
Thanks.

Nothing is wrong with your car. Take good care of it and it will serve you well. I suspect the alternator to be the culprit. Was the one you bought last time a used one or brand new? I have learnt not to patronize used car parts (at least some of them) because one can never tell what life they have left before going bad again.

Get a reliable re-wire to look into your alternator and if need be, please get a new one.

Is the battery almost dead? As they get old they loose capacity, and only have enough for maybe one start.

Otherwise you need a meter to measure the current draw from the battery. Then pull fuses one at a time until you find what is using the power.

@Autosbay and siena thanks a lot.
The replaced alternator was tokunboh, I would try as suggested. I have a multi tester and I know how to use it on electronic components but is there anyway I can use it to check for what could possibly be causing d battery drain?
Thanks again.