This may sound crazy, but what is your other car? Swap the battery out and see if the problem happens with the other car. If you tell me your other car, I can tell you if it will fit. Heat is tough on batteries, you may have a hydration short in the battery that is causing the issue

Just a thought.

 

my gf's car…2014 vw jetta se

 

This was all the checks, at all the locations listed? You need to check all the locations to weed out a battery cable connection problem.

Also with car off, was the check with the tender still attached, and what tender are you using (what is it max voltage that it will charge the battery to before it times out).

As for battery if your tender is shutting off at a lower battery charge voltage, easy one to check.

Off the tender, push the run/star button for about 10 seonds without touching the brake or clutch pedal . This will put the car into run mode without the car started. Now turn the head lights off, then turn them back on again. Your looking for only about only a .5V drop in voltage on the DIC when the lights are on with the car in run mode if the battery is still good.

So DIC should be reading around 12.6 volt with the light off with the voltage you show, and around 12.1 with the lights on***. If the voltage drops below 12 volts on the DIC, you have a battery going south problem (if you have already weeded out for a cable connection problem). If the drop in voltage is only around .5V for the light test, then the battle starts to be come fun, and time to find the voltage drain problem when the car is in sleep mode instead.

This could anything from a crack in the positive wire that runs behind the engine block slightly grounding out to the engine block due to a split in the loom/cable shelding, a sticking relay in one of the modules or relays in the fuse blocks, to On Star pulling it voltage drain mystery checks when the car is supposed to be in sleep mode instead.

And yes, even if you don't have on star service activated, it still pulls this check. So if you have OnStar in the car, and not using the service/blue tooth feature of it on the newer models, just pull the connectors to the VCIM, and jump out the GM lan bus wires on the one VCIM connector.




*** again, normal for the DIC to show slightly lower voltage of around .3V than what a multimeter is showing at the actual battery/alternator terminals instead.

 

it was only at the alternator points you had listed, so probably 1/3rd of what you had listed….since its my dd, its not the easiest to work on it without concerns of having to drive the next day …only way i'll be able to do the full checks is being home the full weekend, like this one coming up…will try to head out of work a little earlier to get started on the rest of the list you had mentioned

this is the battery tender i have:

http://www.batterytender.com/Automot...12V-0-75A.html

with the car off, the tests were done after i removed the battery tender from the battery posts.

 

sla07, no worries, but with the larger difference in voltage between the capacitor and the battery with the car running (14.7 to 15.1), does lead me to believe that you have a wire connection problems somewhere in the system. The battery will act like a capacitor in line for the alternator, so you should not be having the wide difference between the battery and the alternator voltage since they are looped together.

So add this to the check list, pull a ground from the battery negative terminal wire connector with the multimeter negative probe instead of the alternator body during the car running alternator running voltage tests, and see what voltage you get.

This will limit the the cable checks to the negative path back to the alternator body, to check to see if the problem is in either the cable to motor, or motor and bracket back to the alternator housing instead.

If you have a major drop in voltage of over say .1 volt out of the alternator voltage from the 15.1V to the battery ground wire, then probe to first the alternator bracket to see if you have a drop in voltage, then motor metal farther away from the alternator bracket next. This will weed out the negative awire from battery to bolted to the side of the motor path as well as if there is a bad ground from the alternator body to the bracket.

If you have 15 volt from the battery wire to the back post on the alternator, then your ground loop is good, and the problem is in the positive wires side instead.

 

Not sure the year of your car, but her battery is 30mm longer and 15mm high than the T5 that will fit every year battery tray.

 

So it looks like 2.15 v/cell. If you have two cells short together you'll see the battery voltage drop below 11 volts. The issue is, how long would it take for the battery voltage to drop? As long as the other cells are charged to keep the battery voltage up, it'll stay up. If there is something external discharging the battery, that would leave you to a possible mistake thinking the battery is at fault when something is discharging the battery. Hence, the desire to leave the battery disconnected overnight before measuring. If it's bad, it'll be bad in the morning.

I expect measuring charging voltage to be a bit higher at the alternator than at the battery. There a going to be losses between the battery and the alternator. It looks like a 4% loss, not bad as a lot of circuits are designed for 5% to 10%.

 

sorry for the very late post on all of this, but the issue is resolved as of today…have not had any time to do anything but thats a separate issue…passed by a recommended mechanic of a local corvette group here and i mentioned the issue to him…took him about 30 seconds to find out what was wrong while the car was on the lift…looks like the shop that replaced the starter didnt tighten up the connectors on the starter very well…they were loose and moved when the mechanic touched them…loose enough where the cable was sitting on the starter and triggered a spark and a little bit of a "minor flame" to brew up when the mechanic touched it…luckily nothing serious and nothing damaged…he checked the connections, put some solid heat shrink on there and re tightened the bolts to sit how its supposed to…once done with that and started the car up, it started right up like it used to…

he also found a bad job from that shop as well unfortunately…they messed up the alignment of my exhaust all the way back so the passenger side exhaust is clunking on the fuel tank tray causing a thumping sound whenever i hit a bump or something…so going to have to loosen up bolts, line it all up, and re-tighten the bolts again with the pipes lined up straight...

and last but not least hes going to drop my fuel tank and see if he can fix the gas fume issue ive been having (gas fumes with 1/2 tank of gas or more, appears to be fuel pump related like other posts/threads with no visible leaks or anything else etc)...

 

Another happy ending!

 

thank you all for the tips and suggestions…awesome information in this thread

 

Sounds like you found a good shop that will pay attention to detail. So many of them don't these days.

 

Glad to hear you got it fixed. But for future reference if you have a standard battery I would highly recommend spending $5 for an hydrometer. After fully charging a battery a hydrometer will test each cell independently. If good each cell will float 4 or 5 *****, if one or more cells float less ***** you have a weak or dead cell.

I had this issue on my 2008 and even though testing systems at the Dealer, AAA, and AutoZone said the 2 year old Delco battery was fine. After about a week of multiple dead battery incidents the hydrometer found that 2 cells that were extremely low. New battery in 4/2014 and no more issues.

A battery tender is good to maintain a fully charged battery and should be used anytime the car is parked for more than 3 or 4 days. It is not however intended to charge a discharged battery. You really need more power to charge a fully discharged battery.

A volt meter is a good indication of whether or not the charging system is working but often may not indicate a dead cell, hydrometers do not lie.

One other thing to note is that I have had extremely bad luck with Optima Red tops on my 69. It stays connected to the special Battery minder for AGM batteries but over 6 years it has taken 3 batteries, fortunately 2 were under warranty. Warranty is only 3 years now so next time it will be an Interstate standard battery.

 

I am also having some battery issues and will do some of these checks and report back what I find to help others.