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Vehicle has not been used in 6 weeks. Will a charger work if the battery is completely dead and the charger "sees" no current?

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    Welcome to Motor Vehicle Maintenance & Repair! You can try to put the battery by itself on a slow charger (2A). The battery might recover. Thing is, though, if the battery is too low of juice, the charger might not recognize it as a battery and not charge it. To help it see, you might need a second battery (known good) to put in parallel with it. It wouldn't have to be a car battery, but almost any chargeable battery which is 12vdc rated. I use a battery I have from a battery backup (garage door opener) which was no longer serviceable for doing the garage door thing. – Pᴀᴜʟsᴛᴇʀ2 Jan 11 at 0:55
  • How old is the battery? If more than four years, just replace it. – DavidSupportsMonica Feb 15 at 15:30
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Most modern chargers have a feature where they will not put current into a battery that has too low of voltage. This is a safety feature to avoid cooking a bad battery which leads to bad things.

As Paulster2 mentioned in the comments a common way around this is to hook up another battery of the same voltage (12V for your car battery) in parallel (positive to positive, negative to negative) with the discharged battery. This will cause the charger to read a high enough voltage to start putting current into the battery. If the battery is just discharged without any other issues, it could charge it back up without a problem. Once the discharged battery's voltage is high enough, you can remove the second battery and charge normally.

Another solution is to get a charger with a manual mode that puts current into the battery regardless of the battery's voltage. Doing so on a low setting for an extended period of time can bring your battery back to life. However, because this charging mode isn't monitoring the batteries voltage you need to monitor the battery periodically to make sure it isn't overheating, spewing acid, etc.

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