I know this is beating a dead horse, but I am having a no start issue. Optima yellow top 27 months old. I've fully charged the battery and at rest it is reading 12.56 volts. I did a draw test and after about 1 hour rest, the draw is reading 46 milli amps. I did a capacitance test on the battery and the meter reads the battery is good. And as I understand it any draw 50 milli amps or less I am in the clear.
But if I let the car rest for 2-3 days, no crank ( or very slow crank ), no start.
I also checked for a draw at every fuse and only the 11 fuse in the passenger footwell was drawing like 200+ milli amps, all the rest were basically 0 milliamps, so I pulled the fuse. Still the problem persists. Even if the alternator is not charging , I charged the battery with a battery charger and still the issue persists.
starter????

I should let everyone know I recently upgraded my radio with a touch screen and installed a back up camera. It was necessary to use an Axxess interface between the radio and the factory wiring. But if those components were causing a draw, wouldn't that be covered by the draw test I did at the battery???

I have had the battery on the charger for the last 2 days, IT started up right away and I drove 8 miles to work. After about an hour I tested the battery voltage and it was 12.56 volts. The voltage draw at the negative battery cable was .46 milli amps. So if there is no excessive draw, and the battery charges to full capacity and test good, what is draining my battery?

 

When you are getting very slow crank what is the battery voltage at that time?
Was this happening before the radio/camera upgrade?
There are a lot of videos on how to diagnose a parasitic drain. C5 Diag has a particular one he recommends but I forget which one.

 

Your right, I don't know what the voltage is at the time of the no/slow crank. And no I did not have the problem before I installed the radio/back up camera. I had a difficult time with the wiring for the radio and the back up camera, and both units are Alpine which I purchased through Crutchfield. I have been on the phone with Crutchfield and Alpine many times and I finally understood where all the wires had to go so I think I have a good handle as to where the wires for the radio and the camera are to go, and I think I have a better chance finding the problem some where else for now.

 

A fully charged AGM battery is 13.0 volts…12.56 is around 80% so if you can’t charge over this I would buy a new battery and then check for a draw…pulling fuses is not the best way to do a draw test…voltage drop is…video below…also disconnect the alternator B+ as a faulty diode can cause a draw…20 milliamps is the magic number on a C5….the Reserve Capacity of the battery divided by 4 is an acceptable draw…if all this started after the radio install I would focus there.

 

 

OK, disconnected the alternator and the draw is the same, 43-45 milli. Voltage is now 12.50, down 6 hundredths from this morning.

 

Good luck. I've been down this road before and it's usually the last work you did before the issue started happening.
C5 Diag gives great advice.

 

Moved to C5 Tech.

 

OK, so when I got home from work, I put the battery charger on it over night. This morning I disconnected the charger and checked the battery voltage, 12.58. My guess at this point is the battery is not accepting a full charge.

My plan now is to drive the vette until it wont start and then check the battery voltage and to note how long it take's from this mornings 12.58 charge to no crank and to check the voltage at the no crank time.

So C5's Diag is a great video. I wish it was that simple for me. I wish one of the fuses showed a high draw, but all the fuses, engine compartment and passenger footwell show no draw.

I think I am dealing with a marginal battery here.

 

I went down that rabbit hole years ago convinced I had a excessive current drain, but it was the battery which was not holding a charge. Your cars 43-45 millamps is almost double what it should be, I had to wait 20 minutes before my car entered sleep mode.

 

Optima is not the great battery that it used to be years and years ago.. I would pick about any other battery besides one of them

 

Battery charger ....or ....battery maintainer? Was it connected stand alone, or with the vehicle battery cables connected?

 

So the battery was connected to the car, not stand alone. I use the Battery Tender. 1.25 amps. I thought it was a charger until the battery was fully charged and then reverts to a maintainer.

My C6 buddy has indicated he reads many blogs indicating Batteries in general are not what they use to be. I chose the Optima Yellow top as I thought it represented the best of the best. I have not heard Optima is not what they use to be but judging from my experience that very well could be the case.

I now have the battery on a better charger and will see if it will put in or the battery will accept more charge. I think I will know in about 2-3 hours.

 

Just to establish a baseline, I would disconnect the battery cables from the battery, and hook up a battery charger ......NOT ....maintainer ....and see what result you get. If takes a full charge stand alone, I would have it load tested.

 

I like the idea of disconnecting the battery from the pos/neg cables.

I have learned that load testing is kind of out of fashion as it hurts the battery. I did a capacitance test, and the result of that indicated the battery was good.

 

If it were me I would pull the radio fuse for a day or so and see what happens....

 

That's a good idea but a pain in the but to get too. or are you suggesting the radio fuse in one of the fuse boxes?

 

I see. Sounds like you have advanced knowledge.
Good luck.

 

Ok another test. I charged the battery up while I was at work. 12.58 V. Drove home 8 miles and checked the voltage, 12.78v. did not charge the battery over night and left the cables attached. In the morning I was at 12.18 v. Started right up. Drive to work 8 miles. tested battery, 12.56v. drove car into shop and charged up battery. At 8am, I was at 12.55volts battery charger off and not connected any more. At 10am I was at 12.58 volts.

So it would look like when the battery cables are connected, no charger, the battery is being drained. But when the cables are disconnected there is no drain.
An videos which involve charging up a yellow or red top Optima, everyone seems to be able to get 13+ volts. But my battery has never seen ( in the past week ) anymore then 12.6ish volts. One blogger indicates that 12.6 is only 80% of the charge. Yet when I test for draw and the negative battery cable, it is only drawing 40 mil.
I know still a bit much . And when I check all the fuses no draw at all.

 

Is your charger or maintainer or whatever you’re using capable of being used for an AGM battery ??…you can’t use just any type and a you don’t need to look at a video…you need the correct maintainer and or new battery…your car came from the factory with a lead acid battery…you should stick to that kind since the charging rates are different between the two.