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parasitic battery drain

36904 Views 22 Replies 12 Participants Last post by  Skelly
For the last several years, my 2010 3.5 Altima has surprised me every few months by draining the battery from 12.6 volts to 8 or 9 volts overnight.

Replaced battery - same problem. Check voltage after driving an hour, shut down engine - voltage is over 12. Next morning, voltage can be 7, 8, or 9 volts. Have to jump the battery to start; charging system checks out fine.

So today I decided to check battery drain. Disconnect battery negative cable, put ammeter leads between battery negative post and car's negative cable.

Drain is around 200 mA. That's *way* too high - should be closer to 20-40 mA. Pulling each fuse (under hood and under dash) one at a time, drain remains around 200 mA - except the second "Meter" fuse removal lower drain from 200 mA to 120 mA. Still way too high.

Something's pulling over 100 mA 24/7. If car sits overnight, *sometimes* voltage is almost cut in half.

Has anyone had a similar problem with "phantom battery drain"? Is there a system which can go on by itself, or one that may not show an "active" light on the dash panel?

EDIT: car has a Bose sound system. I've heard from several Nissan forums that some Bose systems can draw power 24/7, whether in use or not.

Tom M.
2010 Nissan Altima 3.5 sedan
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Gen4/gen5 Altimas all have a "smart" charging system that's entirely dependent on the Battery Current Sensor (located on the main ground cable next to the battery). If the sensor goes bad or the ground cable has high resistance, it can cause the smart system to get stupid and chronically over- or under-charge the battery. That results in the car "eating batteries" one after another, either from boiled plates if it's overcharging or repeated deep cycles if it's undercharging. Unfortunately, the diagnostics Nissan gives us techs for the current sensor are pitiful, and the BCM (which monitors the sensor) doesn't have the tools to detect a lying sensor, only a flatlined one. So the best diagnostic approach is usually to disconnect the sensor, replace the battery if it's weak, and see if that solves the problem. I wouldn't trust Nissan's "standard" battery testers either, or the ones typically used in a parts store. I've seen all of them call batteries "good" which were dead 20 minutes later from a simple ignition load. Nissan does have a new tester called the DCA-8000 which takes a bit more time and setup, but actually works right and gives trustworthy results. Ask the dealer to test your battery with that and not the "quickie" testers.
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Drains in the alternator will usually show up in the field circuit and not the main terminal, so you have to check both individually. Pull the 3-pin connector, then reconnect that and disconnect the main. Keep in mind, no draw test means anything until the car has spent 30 minutes with no electrical activity, ignition off, fobs removed from the car, doors closed (or door switches disabled). Readings before that point are essentially meaningless.
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