battery wont charge

Dont really drve the car much and just put a new battery and alternator. Two weeks ago put in a sound system and this week the problem begins. The car sits about 5 days straight in the cold with no starting or nothing. The car started up last week with no problems but this was before the system install. I have a box and amp with the remote wire hooked up for the amp from the radio. However i have a small odyssey battery that dies with the slightest mistake fast. The body shop man didnt put a trickle charger on it when he charged it and im thinkin it has internal damage. I drove the car about two times then it is just dead. Here is the setup: i put in a high amp alternator that was refurbished. I turn the key and no dash lights or anything comes on. When i try to jump it the lights come on and as soon as i take the cables off no more lights. I hooked up a voltmeter and the battery went from10 to 3v with the key still in the off position. I cant even get the engine to turn over. Does anybody have a experience with this or any other advise? Im definately getting a bigger battery but dont want to change the alternator in the cold lol. So im hoping its not the alternator.

the only real way is to get a new battery and the check alternator output but it sounds like the battery is most definetly shot and those small oddesey batteries usually have just enough amps to start the car. Sorry to here they messed up your batt though.

Sounds like the batt. When the car runs and you remove the batt cables does the car shut off?

get a OPTIMA BATTERY if that battery dies out and you read lower than 12.6 volts …it could be parasitic drain…whoever installed the system did something wrong…

I installed the system myself and i made sure to hook up the remote wire to the amp. This week i will tackle the problem with a new battery, starter, and a kill switch so when i dont drive i can cut the power just incase there is a parasitic draw. Actually i will check for that also if i have time but no more small oddyssey batteries. It sure looked nice tucked on the frame but now im relocating a bigger battery probably from Sears to the trunk. I think its better anyway so if the battery goes out again i dont have to order a special battery because not to many people sell oddyssey batteries in store. Also the battery wont charge past 10v so i think there is a dead cell. The oddyssey batteries are probably good but you have to be careful of charging them the wrong way and i really dont think jump starts are healthy for that type of battery.