problem with starting the car

i can not start the car even roll down the window. i seems that the battery does not have enough high voltage, i wait one hour and tried again, it took me some effort to started the car including push gas pedal during ignition. I drove for a while to charge the battery and had no problem srating the car when i went home that night but the same problem occured next morning. there is no problem when i driving the car. i measured the voltage and it is not stable, after i start the car, sometimes the voltage was 13.2, sometimes about 14. my friend told me maybe the connection between alternator and battery is bad and the alternator cannot charge the battery all the time. is there any way that i can check this problem?

It would help to post what year, model, engine size and mileage.

it's a 01 GP GTP. and from the experience last night, it is more likely that the battery is losing voltage. when i started the car and drive for a while, then turned off the engine, there was no problem if i strated again, i tried several times and the ignition went smooth. i let battery charge for a while and went to sleep, but this morning the starting was again difficult unless i gave more gas to the engine during ignition

Do you have the original AC Delco battery? Best to get the battery and the charging system (alternator) tested. Places like Autozone will do it for free.

When you first tried starting it was it cranking normal or slow before you gave it gas?

you mean this morning? it was slow and even won't start if i do not give it gas and the clock will change to 1:00. if i successfully start the car i can then shut off it and start again with no problem. only when i park it for longer time, this strating problem will occur

Yup! Classic battery issue. Not holding a charge due to a bad cell or low specific gravity.

so i need to change a new battery, right?

I would but you can get it tested first just to be sure. Do you have Autozones in your area? If so, take it there. It will be free.

all right, there is autozone nearby. do i need to take some tools like wrench and sockets to take off the battery and test it in the shop or they will do it?

It is up to you. Your can remove the battery yourself and take it in the store for testing or many AZs have a tester they can bring out to the car which can also test the alternator or complete charging system. For the battery terminals all you need is an 8mm socket or wrench. For the retainer block holding the battery to the tray a 13mm socket, extension and 3/8" drive ratchet. Good luck!

just from my experience, if u have an aftermarket stereo system and somehow the power wire is touching the remote wire, it will keep ur amp on while ur car is off, thus draining power. happend to me once on accident... just an idea