Need advice about power draw

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kellyscallywag

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i am looking for advice finding the power draw on my 2010 jeep wrangler unlimited.
my buddy unplugged everything from the battery, removed all the fuses, tested the alternator and let it sit for well over an hour unplugged from everything to drain the power out of the computer. it's still got a 10.2v draining the battery and we can't figure out where it's coming from. the battery is only a year old.
 
I'm not sure what you mean when you say "it's still got a 10.2v draining the battery"... do you mean with everything disconnected and sitting, the battery voltage is reading 10.2V?

~10.2-10.5 is (historically) a classic example of a damaged cell (lead acid batteries have 6 cells at 2V each, for 12V total). With a bad cell, you will also see a really large voltage drop under load (turn you lights on and see how low the voltage goes!).

While we wouldn't expect a 1 year old battery to have damage, it could have been to a number of reasons. If you can, throw the battery on a charger and see if you can get it to 12V. If so, let it sit overnight and check voltage again, or bring it to an autoparts store to have it load tested. They can quickly tell if something internally is a problem.

With any luck, the place you bought it from has a warranty on it and should be covered...
 
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If it is not your battery you can take a knife switch made for attaching to a battery and use it to find the draw. If you open the knife switch and then place a volt meter across it set for the current mode, you can verify any draw. In the past I have had alternators draw current even though they had output when running. Good Luck!

Meter Measurement R.webp
 
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Baja-D said:
If it is not your battery you can take a knife switch made for attaching to a battery and use it to find the draw. If you open the knife switch and then place a volt meter across it set for the current mode, you can verify any draw. In the past I have had alternators draw current even though they had output when running. Good Luck!
Click to expand...
You don't even typically need the knife switch; most multimeters have a fused "high-amperage" port for measuring current, allowing you to run the leads in series to see what the measured draw is.
 
I have a clamp on AC/DC amp meter. More expensive than a typical multi meter but it’s quicker to measure current than a multi meter
 
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One thing I like about a knife switch is that you can isolate the battery real easy to keep it from running down. Either by the drain issue or for long term storage. Unfortunately even new batteries can be internally damaged if they are allow to sit discharged for any length of time.
 
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