Big Time Poster
battery check and OBC 9 test reading question, please
Hi,
I checked my battery with DMM it shows 12.20V and also I took a OBC test 9 reading and it says 11.79 UB.
Shouldn't those be identical? If, yes then where do I loose that voltage?
Thanks guys
Super Moderator
What kind of dmm do you use.. If its a real cheapo then your
margin of error might be that much or your obc margin of error could be that much. Or if your battery terminals have any corrosion at all on them the resistance increase could be enough that the obc would read off... assuming that you stuck your leads from your dmm directly on the battery posts
Originally Posted by nariusb
Major Contributor
Bill, could there possibly be more drain on the battery when you perform TEST #9 versus using the DMM on the battery posts?
Let's see, using the OBC (TEST #9), the door may be open and interior lights on, and when you turn the ignition to position 1...what else has powered up and drawing power from the battery (since the engine isn't running...thus not recharging the battery). This may account for the different reading...just a thought.
Q
95 525iT / 97 740iL
Big Time Poster
where is this OBC testing point
Where does OBC look at the DC exactly? I can't get a reading that way above 12v ever. Does this mean the battery is dying? I do get a battery light ON for a second at the startup and cranking could be shorter too. I wonder if that's related at all.
Super Moderator
Q, i figured that he was checking it at the back seat which meant that the
door would be open and the lights on, but i didn't consider any other draws when the key is on such as the ventilation system fan or anything else that gets energized.. thats a good possibility. He could also check it up front at the jumper cable contacts and see if its lower there than directly at the battery which would imply resistance in the battery cables somewhere.
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