How do I fix my car battery that keeps draining after some hrs of usage

Probably something draining the battery overnight. Interior light left on? The regulator in the alternator could be bad and keeping the ignition energized draining the battery. If your jump start it drive to work get off work and it starts after 8-9 hrs you have a system voltage leak some where. If nothing is left on overnight have the voltage regulator tested in the alternator.

Do you see a brake light on while driving? That could be a bad alternator.

Ask your garage to perform a parasitic draw test - you could do this with a multimeter, as well; it sounds like something is draining your battery while off - it could be any fuse and not obvious like with lights on/etc.

I would 95% positively guess this is the issue due to time frame. If the garage doesn't know what this is, take her somewhere that does. Shouldn't be costly, either.

then you need to start doing the process of elimination. you can either pull out fuses and see if it stops the drain.pull out 2 or 3 at the time to save time. if it stops the drain. reinsert one at the time till the drain starts again. then you will know approximately where the drain is .. or you may also use a measuring device to see how much amperage is passing through the fuses... you are looking for around 9 or 10 amp drain if you loose a battery in 5-6 hrs .

i reccomend using a measuring device (multimeter or voltmeter) as it is a much better way to locate where the drain is.

youtuube videos are useful source for info about checking for the drains for first timers

you have a short somewhere try taking one fuse out at a time until you find the right circuit

It could be many things, like a faulty ignition switch, a burned circuit on your dash panel board, any kind of a slow drain (poor ground) in the wiring, but I'd go with the ignition switch if it was me.

Hi suggest check this procedure about How to Do a Battery Parasitic Drain Test.

Find the battery drain. Disconnect negative cable from battery. Place test light between pattery negative post and disconnected negative cable. If light is bright while no accessories are on, there is a drain. While keeping the test light in this configuration, pull each fuse out and replace on at a time while watching test light. If the light dims or goes out when a particular fuse is out, that identifies which circuit has the drain. Use that information to track down what is on or draining.

a serious drain you have going there, use a ohm meter and measure between the chassis and the reciving end of the fuse,(not the side connected to the + of the battery, ) if the resistance is very low on one, you have a short in that cirquit, look for anything close to or below 1.2 ohm (equals 10A, or approx 5 hrs on a fully charged new 60 Ah battery)

Not an expert, but I expereinced a similar problem in my 1991 Econoline and it was the voltage regulator.

Usually if the battery is draining that means there's a problem with the alternator.