Infiniti G37 dead battery again.

[aczlan]

Thanks for the continued good advice guys. We have had the battery tested at AutoZone (or Advance, I don't remember). Both times they indicated that the battery needed to be replaced. On one of those they pro-rated the price since the battery was still under warranty. I have no idea if they tested the alternator.

I ordered the multimeter. It should be here in a few days and will test as you guys have described. May also take it back over to AutoZone and see what they say about the alternator. The problem is that it is usually my wife who has to do this so I'm never there.

With the initial diagnostic steps that you guys have described I'm not sure why the dealership didn't want to do the work. It is a Nissan dealership and the car is an Infiniti but Infiniti is just a Nissan brand and share many if not all major components.
Another possibly stupid question: Wouldn't an alternator issue throw a code? I have a code reader and it is clear.

Autozone should be able to give her a printout of the results if she asks for it (they have to do that when they warranty a bad battery). An alternator issue may or may not throw a code, it depends on the car, what is bad and how bad it is.
Usually an alternator that has a voltage that its too high or too low will throw a code, but it will not trip the check engine light (and sometimes it will set a OEM code that basic code readers cannot see).

Aaron Z

 

[dodge man]

I just went through this with my sons car. As I recall it was drawing around 5 milliamperes with the car off which checked good. The battery load tested good and the alternator checked good. The ingnition key was staying on sometimes and the radio was draining it. Most of the time you would catch this by hearing music but he was playing music with his phone so the radio was on but no sound. It would only do this once in a while so it was hard to catch. 2004 GTO so different car.

 

[N80]

Update: Got my multimeter today so I'm going to tell you guys what I did and what I figured out and probably open myself up to more ridicule, so here goes:

Car has been on trickle charger for several days. Trickle charger indicates full charge. Yesterday it would start but only barely even with indication of full charge.

This afternoon I set the multimeter to DCV and put probes on positive and negative battery terminals. It reads between 12 and 13 volts. (I'm assuming that is normal.)

While holding probes in place I have my wife crank the car. Starter turns over a few times and voltage drops to about 10.5 while cranking (which I am also assuming is about normal) but car will not crank. Voltage returns to 12+ when she stops trying to crank it.

So I now assume that the battery itself is okay but not delivering full capacity to the starter. The terminals look clean but the negative battery post looks odd. So I remove the post clamp and there is one of those spacer things in place and the inside of it is fairly corroded looking. I'm assuming this was left from the last battery that I had to use the spacer on because the terminals were too small. So, I remove it and clean the post and the connector.

Before I hooked that back up I changed the multimeter to DC mA (correct setting???), turn everything in car off and connect the positive probe to the positive terminal and the negative probe to the negative battery cable. The reading is 13mA. So now I assume that there is nothing drawing on the battery.

I went ahead and cleaned the positive post and connector as well. I applied dielectric grease to posts and clamps.

Car starts up like normal.

From all this am I safe to assume that 1) Battery is generally healthy? 2) There is no parasitic draw on the battery? 3) The whole problem was probably a corroded post/clamp spacer?

There is also the possibility that I did all the diagnostics wrong but still got the right answer......even a blind squirrel.........

Will drive the car tomorrow and see how it shakes out. Also ordered one of those spare/battery things to keep in the trunk. Not a bad thing to have anyway.

Finally, was it okay to use dielectric grease here?

 

[LD1]

Corrosion can indeed be the problem. Time will tell.

10.5 while cranking is in the right ballpark.
Taking that cranking measurement, but at the starter would have answered if corrosion was the issue.

Good juice at the battery doesn't mean good juice at starter. Resistance via corrosion is like a kink in a garden hose. Good pressure at the spigot (battery) doesn't mean good pressure at nozzle (starter)

Lastly. When reading A battery 12-13 volts doesn't suffice. Gotta read tenths or hundredths. 12.6-12.7 is full charge. 12.0-12.2 is dead. 12.4 is 50%

 

[N80]

Lastly. When reading A battery 12-13 volts doesn't suffice. Gotta read tenths or hundredths. 12.6-12.7 is full charge. 12.0-12.2 is dead. 12.4 is 50%

Good to know. It was mostly up around 13 but I couldn't quote tenths.

 

[LD1]

When testing battery condition, it is also important to let it rest for about 15 min after charging or running the car.

If you check it immediately after charging or shutting car off, it will likely read over 13v. Which is a false reading.

Any thing north of 12.5 v ( after a rest period) should start a car. Below that is gonna be noticably slower than normal cranking. Get down to 12.2-12.3 at rest, and it's likely not gonna start

 

[N80]

When testing battery condition, it is also important to let it rest for about 15 min after charging or running the car.

If you check it immediately after charging or shutting car off, it will likely read over 13v. Which is a false reading

I did check it right after charging and right after it was running for a few minutes. I'll check it again today after it has been sitting for a while. However, wife drove it all day today with no issues so hopefully problem is solved.

 

[LouNY]

A battery needing to be replaced means to me that there is something wrong with the charging system: alternator, voltage regulator (usually self contained). Here's what I do:

Park car in a garage and wait for complete darkness. That's where you can see the single mirror light on by mistake. Same for other lights: under-hood, trunk, glove box, driving lights.

Then start the car and disconnect one battery terminal. Car runs OK or not?

The connect the ammeter across the disconnected cable, key off and measure any residual current. When cable is reconnected, and motor running, measure charging voltage (should be over 13v.

Anything plugged into the lighter socket (Garmin, camera, phone charger ?) On my truck, the socket is always hot. On one of my cars, the socket is dead with key off, on the other the socket is also hot all the time.

Any builtin radio sources present (On-Star, etc?) On my truck, On-Star is always reporting mileage and service needs whether truck is running or not. Kills my battery after a month of non-use. My insurance company (State Farm) is also always checking mileage because I'm getting a low mileage premium 'discount'. I think they check Average Speed per miles interval, too (Yes On-Star can do that), plus many other secret features (like turn on the microphone to listen for sounds: we used to use this feature at work (GM) to locate snow covered cars in storage lots. We blow our horn and On-Star tells us when we are close to the vehicle we are looking for).

I also recommend pulling the key out after use. When I leave the key in (switch 'Off', my battery will be down after a week. Something's enabled with the key fully inserted. Same for our car. Now we pull the keys and no more problems (except for the On-Star snitch).

Do not remove a battery cable with the car running, you are almost guaranteed to screw up something, with all the computers in the car one of them is likely to get spiked.

 

[milkman]

After reading all the thread, it's been mentioned a couple of times, alternator. That would be my bet, bad diode will cause your symptoms.

 

[bunyip]

A faulty earth somewhere can also create some interesting problems.