# 1998 Mercedes-Benz C-Class - how to keep battery from draining?

**URL:** <https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952>\
**Category:** Maintenance/Repairs\
**Tags:** c-class, mercedes-benz\
**Created:** [December 3, 2020, 6:42pm UTC](https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952 "2020-12-03T18:42:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![MikeBateman](https://avatars.discourse-cdn.com/v4/letter/m/8baadc/32.png) [@MikeBateman](https://community.cartalk.com/u/MikeBateman)\
**Post date:** [December 3, 2020, 6:42pm UTC](https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952/1 "2020-12-03T18:42:59Z")

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Newer car battery dies below starting level while parked for a month at airport. Have 1+ amp solar panel glued to trunk attached to battery. (Same panel model keeps my boat battery charged, but not car.) Computer draw is less than 1/4 amp. How do I return to my car without needing a jump?

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**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\
**Post date:** [December 3, 2020, 10:51pm UTC](https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952/2 "2020-12-03T22:51:39Z")

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A quarter of an amp is way too much draw when off. 50 **milliamperes** , (0.05 amps). yours is drawing 0.25 amps.

Most vehicles **draw** some battery **current** when the key **is off** , thanks to the clock and the internal memory of engine computers, body-control modules, and radio presets. Altogether, they **draw** a very small amount of **current**. Fifty milliamps would be a safe upper limit for this, though many vehicles will **draw** less.

Your solar panel only produces power during periods of sunlight. I think it can not keep up with the excess power drain.

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**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\
**Post date:** [December 6, 2020, 8:47pm UTC](https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952/3 "2020-12-06T20:47:43Z")

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Indeed, the 250 milliamp draw is excessive so you are going to have to track down the source of the problem. Once that problem is eliminated I think your solar panel will do fine to keep a charge up on the battery. Here is a link you can refer to that will help you find the problem.

> **[Diagnosing A Car Battery That Runs Down](https://www.aa1car.com/library/battery_runs_down.htm)**

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [December 6, 2020, 8:56pm UTC](https://community.cartalk.com/t/1998-mercedes-benz-c-class-how-to-keep-battery-from-draining/172952/4 "2020-12-06T20:56:25Z")

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By chance, you don’t have anything plugged into your cigarette lighter, do you?

I’m asking because your cigarette lighter is always hot, so anything plugged in could drain the battery

Even a charger with nothing attached . . . those little LEDs draw current

Do you have an aftermarket alarm or sound system?