An improper installation or a defective piece of equipment can cause a constant drain on your battery, even when the vehicle is off. This is known as a parasitic draw and results in a dead battery... like every day. Not only is this a huge annoyance but it will damage a battery over time. Allyn and Brendan talk about different factors that could cause a battery to continually drain, and how to perform a parasitic draw test using a digital multimeter (DMM). While your vehicle is in the off position you should see less than 25 - 30 milliamps (.025 - .030 amps) of current. If your test reveals a number higher than this you should systematically disconnect equipment to narrow down and find the source of the problem. How to perform Parasitic Draw Test: Disconnect the positive (or negative) battery terminal, wait a moment for all electrical activity to stop. Set your DMM to read Direct Current (DC) Amperes and connect probes between the removed terminal connection and the corresponding battery terminal . Make sure all interior lights are off. the reading on the DMM may fluctuate when the connection is first made, after a moment the number will settle to a more constant number, this should be your reading. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Sonic Electronix always strives to be the premiere online shopping destination for car electronics and other consumer electronics. Our slogan is "The X-Factor When Shopping for Electronics" and it is our goal to be just that. We're here to help you find solutions and great prices without sacrificing service. Our Store: http://www.sonicelectronix.com/ Our Facebook: https://www.facebook.com/sonicelectronix Our Twitter: https://twitter.com/SonicElectronix Our Instagram: http://instagram.com/sonicelectronix