Hi Guys, having an issue with my battery, it drains overnight.

Background info:

This all started over a few weeks ago, woke up to my car completely dead and the battery drained.
Finally after 30 minutes with it hooked up to another car I got it started. Went to Advanced Auto parts and was told my alternator was not giving it enough juice to charge it while it was running.
Replaced the alternator and the issue continued. Went to two different battery places and was told that my battery (not even a year old) is in good shape and my alternator was doing its job but that battery just needed a full charge.
The next morning my car was dead again. Took the battery out of the car and up to advanced auto to have them charge it for the day. He ran a test and said it had a bad cell, warrantied it out for me so I thought I was good to go... Nope. My car was not driven this last weekend and, again, it was drained. Spent an hour trying to jump start it and although it was getting charged i couldn't get it to completely turn over. Within minutes i noticed the battery was completely drained again when I went to use the key fob to lock it, nothing happened.

More info:

-The HFL was disconnected a few years ago by the dealership when a similar issue, like I'm having now, occurred. I doubled checked that it was last night.

-I have always had an amp and sub in my car but recently had to replace the amp because the power and ground were touching (I believe) and fried and melted the connection leads to the amp.

-My radar detector and dashcam are wired in with the ignition switch but have been since I first bought the car and have never given me issues.

-There is an iSimple that was professionally installed for awhile so I don't think that is causing the issue. I'm not even sure what I would test to see if that is malfunctioning and creating a draw.

I have a multimeter but I'm afraid if I start pulling fuses that other issues could arise. Does anyone know if there are other common draw issues that the 2008 TL have that are easy to check?
Any info or help is greatly appreciated.

 

I'm pretty sure that jumping a car is best only when it's slightly low. If it's completely dead, it's best to trickle charge it back to life or you can kill the battery really quick. Investing in a charger will pay for itself in spades.

Using the multi-meter, you can just do a quick voltage test across the battery terminals.

• With the car off, 12.75 V or higher would be considered "full" while 11.9 or lower is low or dead.
• With the car running, a proper alternator will show somewhere between 13.5V and 14.5V when charging (depending on RPMs). Any less than that, and your alternator's dying - if it's showing less voltage running than the when the car is off, then the alternator is dead.
• A bad cell can be shown by having the battery at normal voltage while off, but it will drop below 12V while you try to crank it (I had one show 8V). You'll need 2nd hands for this one.

I had the HFL issue over the weekend (just got the car) and my battery was fully dead and only read 7.6V. Trickle charged it overnight (6amp charger) and got it back to a healthy 13.5. Another guy on the forum had his HFL "reconnect" during the installation. Even though unplugged, the connector sat just right to make connections. I put electrical tape over mine just to make sure it never connected.

I can't tell you of other electrical issues, but how easy is it to disconnect all of your accessories? Electrical issues are a pain to diagnose and connection corrode all the time. The low hanging fruit's easiest to eliminate what it could be. Personally, I would start with the new amp. Disconnect everything, and check the voltage drain on a daily basis. Make sure nothing's draining and then reconnect things one at a time. Recheck voltage, repeat and work backwards until you find the culprit.