smitty37g

So i have been noticing that when I start my car and for the first 2 mins, the battery voltage is about 14.1.
After the 2 mins it drops to 13.2 - 12.8. Now under normal circumstances this is probably fine. But I am running aftermarket amps. And the voltage never rises.
Is there a way to have the computer reprogrammed to run the volts closer to 13.5- 13.9???? I dont have a problem with the battery yet... but its also only 6 months old... maybe a bigger battery negative cable even??
I did a grounding kit on my car, but I did not do the battery do to the voltage sensor.
Am I being paranoid???
Thanks

slartibartfast

iTrader: (7)

The computer has nothing to do with the alternator. The alternator has an internal voltage regulator, that's what has to be changed. Or, replace the alternator with a unit putting out more volts.

[edit] I have since learned that the ECU can indeed manipulate alternator output to reduce load while at part-throttle. Not sure about other operating regimes.

smitty37g

Well if the computer does not control the output of the alternator, why is there a voltage sensor on the negative cable??

telcoman

If your battery is fully charged then the voltage you are reading is entirely normal.

Yes!

Telcoman

smitty37g

Thanks and thanks.. lol

SonicVQ

The sensor on the negative battery cable is a current sensor that tells the ECU the electrical demand. The ECU then determines how much power the alternator should generate. (CHG-9 in the FSM) This is done to reduce fuel consumption.

Your grounding kit provides an additional electrical path and basically removes the current sensor. Then the ECU assumes the power demands is LESS than what it actually is and the alternator output is REDUCED.

Remove the grounding kit and the alternator should increases the voltage output to meet demand it can now see.

smitty37g

So even though I didnt do the battery ground wire??
Ill try it. It cant hurt..
Thanks

Surfnazi

Did you check water level in battery? If cells are empty or low battery won't function right. You also may see white buildup on the terminals since OEM battery is acid cell nit sealed

smitty37g

It is only 5-6 months old, it is a maintenance free, no white build up on it..

I checked the battery at work and it checked out ok..

jdog78

Removing the ground cable solved the issue for me. Thanks SonicVQ!

SonicVQ

I just re-read this thread and saw your question that I missed. Better late than never

If you added a ground from the body to the engine, that should be ok as the battery current sensor is still being used.
But, if you added a ground from the battery negative terminal to the body or engine that bypasses the current sensor any may cause issues.

Surfnazi

Even new batteries can go bad