Depends on the make, model, & year of the car, who installs the alternator & battery, and the type battery you buy. Most auto parts stores will install a battery for free. Batteries cost from $60 to $250. Alternators cost from $65 - Up. Labor to install an alternator can be from $75 to $225 or more.
You have a bad alternator.
If you install a new battery & new alternator and the battery runs down overnight then you have something pulling power from the battery. Look for any light on the vehicle that is on or a relay that is stuck.
battery tests good, alternator tests good, new voltage regulator installed and still no charge to battery from altanator .
Alternator not charging battery due to a bad fusable link?
check the alternator
is your battery Low or poor?? Charge your battery on slow charge for 8hrs to give it a good deep charge, Installing an alternator on a low or dead battery will ruin it and also not charge your battery properly.. An alternator is not a battery charger its a battery maintainer!!
Fusable Link?
you need to have your charging system tested. also check the battery it may be bad.
I suggest you buy a new car battery replacement in http://www.laptops-battery.co.uk/.
If your question is what may be a problem with a car that you have to change the battery after a new battery was installed a month ago? Then the alternator may be suspect and or a draw from the electrical system.
You need a new belt, it has nothing to do with the battery, but rather the new alternator. The belt is probably old, dry and cracked so it is slipping during the acceleration period due to the load from the engine.
Alternator is sending to much volts to battery. Suppose to turn itself off when battery gets to around 13 volts. May need new alternator.