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I got some strange voltage drops while driving (to 9.6 V) and I'm currently searching for a cause. I bought this car with already relocated battery. It seems pretty large, and as far as I know its not normal size for this car. What is strange is when I measure voltage on it (car is shut down) I got only 12.05 V while turbo timer shows 11.84 V. Then when I start the car it goes to 14+ V but as I said before sometimes it drop to 9.6 V.
This is the picture of my battery:
I had some conversation with manufacturer of my ECU considering those voltage drops:
The log can only tell us that voltage drops and not really why they drop. We can see that it drops under load when you crank. So it is either the battery that is dying ( showing the voltage being ok but can't handle the load anymore) or from what you are saying especially if the battery has been relocated, I would check the wiring. Do you have a cable that is starting to break, a bad joint connection somewhere? Bad earth, ECU ground, etc.
Do you think this battery has correct size and parameters for my car? Does it need to be replaced?
Hard to say. I did have one battery with some weird behavior and it "felt" like something inside broke since I always disconnect the terminal after every use. I got 5 years out of that PC680, but several others including myself got new ones that wont hold a charge and we think it got dropped during shipping. I dont know but maybe yours broke inside too
It could be a bad battery, a bad alternator, or bad wiring between alternator and battery or battery and ground. Do the following to check:
1. Disconnect the battery and test the voltage between positive and negative terminals with a voltmeter. It should be between 12 and 13.2V when fully charged. If not, it is probably bad and must be replaced.
2. Reconnect the battery and run the engine at 2k RPM. Turn on all the loads (blower on high, headlights on, rear defrost on, and so forth). Measure the charging voltage across the battery terminals, and between the big battery alternator terminal and alternator case. There are two things that you are looking for. The charging voltage across the battery should be between 13.9 to 14.4V. The voltage at the battery and the voltage at the alternator should be within 0.5V of each other. If the voltage at the battery and alternator don't match, for example the battery reads 12V and alternator reads 14V, this means that there is an issue with wiring. If the voltage at the alternator is less than 14V then you have a bad alternator.
3. While applying the same conditions as (2) above, put the black multimeter probe on the negative battery terminal (if possible dig it into the battery post, not the terminal). Put the red probe on the alternator case. You're looking for the voltage to be below about 0.5v. If the voltage is higher than that, examine all the negative cabling for problems. Preform the same test with the positive side. Place the red lead on the positive battery terminal (if possible dig it into the battery post, not the terminal). Place the black lead on the battery post of the alternator. Same thing as above, if the voltage is above 0.5v then examine the positive cabling for problems.
