mmunster

I have been dealing with a starting issue for most of the time I've owned my 97 maxima se (which is a very long story I'll possibly write up another thread on). It seems something electrical, though I have new (less than 2 years) battery (has zero corrosion), alternator, and starter, and have cleaned all ground connections. When my car sits for more than a few days, the battery is completely dead. I charged the batter out of the car and after two weeks it was still charged enough to start the car (although it still starts rough... Again, a separate post someday), so I'm looking for a parasitic drain.

I opened the circuit with a fully charged battery by disconnecting the negative terminal and completed it with the multimeter set to 20 amps, and worked my way down to mA. These are the tips I found everywhere on the internet. The current was steady at 0.2 mA, which I understand to be normal and not enough to drain the battery so quickly.

note: I have a basic understanding of electrical currents, but very little practical experience, so it is possible that I am misreading where the correct decimal placing will be, but I am fairly confident, as even if it were 2 mA rather than 0.2 it would still be within normal range... Correct me if I am wrong.

my question is this: I used the negative terminal as that is what the write-ups I've found suggest. Since many circuits on the car are grounded on the chassis and not directly to the negative terminal, and current takes the path of least resistance, could I be missing drain on certain circuits? Would it be more accurate to test on the positive terminal, since all circuits must flow through the hot side? Or am I completely misunderstanding the physics of DC current?

obviously I could just do the same test on the positive terminal and compare results, which I plan to do today, but I'm hoping someone smarter than me can help me understand.

thanks in advance,
Matt
**long time reader, first post woohoo**

ac max 92

iTrader: (13)

Have you tried swapping the battery with a known good one to make sure it's not the battery itself?

mmunster

I do not have a known good battery to test with. I charged the battery out of the car and let it sit for about two weeks. I then put it back in the car, and it seemed to still be fully charged. I hoped that would be evidence enough that the battery itself can hold a charge. Perhaps that was not an accurate enough test? Thoughts?
note: while fixing the problem is the ultimate goal, I am sort of hoping explanation to my theory on testing positive vs negative terminals. Any electrical engineers out there? Of course I am happy for any help/info/discussion related to the issue

njmaxseltd

iTrader: (19)

Any terminal will work, as long as the meter is in series.

Climaxx

iTrader: (4)

The negative(ground) cable connects directly to the chassis under the battery tray. And then to the engine. So you were correct.

DennisMik

iTrader: (2)

It doesn't matter whether you use the positive or negative terminal for measuring current draw.

There is a slight difference between the battery sitting out of the car and being installed in the car. It is the current drain. Batteries will eventually loose the ability to produce the amp hours it is made for and will discharge quickly. Take the battery to a place that will test with a load tester and see what that shows.

mmunster

So the amps will always be the same on both terminals, as I learned by experimenting before looking back on here. For some reason I thought some circuits might lose power before navigating back to the negative terminal. In hindsight I feel a bit foolish; of course its the same because if the current wasn't able to make it all the way around it would not be a circuit, by definition. I blame a brain fart, as it seems obvious now.

Dennis, you are saying that just because the battery held a charge outside of the car doesn't mean it is a good battery, and may be unable to hold charge under slight load. This makes sense... I imagine oreillys can test the battery... Does community experience show that these tests are accurate? I'm weary trusting the workers at those stores

thanks.

DennisMik

iTrader: (2)

I don't know what kind of tester O'Reilly has. A load test will suck maybe 350 or so amps out of the battery. When this is happening, the battery voltage should not drop below 10 volts (I think).

As far as not having any faith in O'Reilly's, it is hit or miss with any auto parts store. The O'Reilly's by me have knowledgeable people. But that is just one store. You could always go to several stores and see how the results match. Just make sure you give the battery time to re-charge in between tests.

mmunster

"faith in OReillys" is not what I have. They mostly are clerks who do hobbyist repairs and mods. I guarantee I take any advice from retail shops with a whole bottle of salt. I have Chilton, fsm, and this excellent forum to refer too, and I do listen to the clerks (see earlier salt ref.) because 10% of the time there's a cool dude who knows what he's talking about. I stay AWAY from AZ and Advance, as they have always talked me into the reman starter then later an alternator w/ lifetime warranty, but they are super sketchy and I gotta rule them out before moving on with any further tests on the issue. Oreilys has been the most consistent for me, though I usually only go there for heavy parts that are less efficient to source online.

Nopike

iTrader: (2)

I checked my 98 SE which works normally and does not have this problem. I opened my hood and checked current with everything else off and closed. The draw was approximately 0.1 Amps = to 100 milliamps. If I depress the switch that senses if the hood is closed after about 30-60 seconds the current draw goes down to about 0.01 Amps or 10 milliamps. This is the sleep mode kicking in. That is quite a difference.

Your Maxima needs to go into sleep mode otherwise you will probably have issues with the battery not holding a charge.

Regardless what/how you are reading the meter, current draw should drop 90% once the vehicle goes into sleep mode.


http://forums.maxima.org/4th-generat...rain-help.html