I don't understand how I'd fix it. My car is running steady on Volts, I check it every other day and while running. But if that does seem to happen and I'm not noticing it, how do I fix it?

 

This is basically what mine does with the current sensor in service. You didn't state when you are reading the radar detector. I am not really sure how much I would trust it but then at least you have a reference. I use an OBD for my readings which I have compared against my true rms DMM and they are very close.

When I first start the car fully loaded it will go up to about 14 volts even. After running for a couple of minutes it will drop down to about 12.9 - 13.0 and stay around that level. If the lights are on after the start it will drop to maybe about 12.6 (after the intial 14) before working its way back up to 12.9 to 13.0 .

If it doesn't change from a high point immediated after a start to a lower value that would mean to me that the current sensor is not in the picture (therefore the battery state is not being determined by current draw) and the alternator ic is operating at its default setpoint.

As far as current draw on the negative battery lead what I see is a fairly high value immediately after a start which doesn't last long at all (up to about 30 or so if I remember correctly). It then rapidly drops to about 5 amps and then after a couple of minutes drops to some value less than 2 amps which at that point my meter is no longer accurate. The positive leads at the same time with everything on will register about 41 amps.

 

Hmm, my radar is accurate I believe, when I first turn my car on it reads 14.7V, then 14.5V, A/C and radio turn on it drops to 13.8V then steady 13.5 I've never seen it drop below that. But if that is the case I can go to the dealer and ask them to test it and see if that's true otherwise I think it may just be an issue with your car. Butttttt you could also be right about mine ^_^

 

The common number I usually here quoted for a stock 07 and up after it is warmed up is about 13 volts even. I know the OBD is correct based on the comparison with the other meter (which I actually have used two). Also this is taken at the battery terminals which may be part of the difference since it is before any drop in cable runs. I have a battery operated detector in the Infiniti but do have one in my other car that plugs in and also has a voltage read out so I could take it out and see what it would read at the outlet instead of the batter.

I find your numbers interesting in ways if they are correct. If I remember the write up of the current sensor correctly it controls in I think 1/2 volt increments although I tended to think if the current sensor was out of the picture it would control a little bit low.

Now consider if your aftermarket negative lead was exactly the same size as the stock lead. With it in place initially the current sensor would see about 1/2 the current flow to the battery if we were simply using it for taking a reading. However it is used for charging purposes so the current sensor will only see have the current flow and tell the alternator ic that the battery is in a different state then it actually is. After the car is up and running for awhile and the battery charges up at some point the alternator should go into what I would consider a maintenance mode for the battery to maintain it at whatever level it is designed for. With the bypass on the negative lead I would then conclude that it drops into this mode early and holds it at that level.

Note while I reference that I measure at the battery terminals I have measured on the positive terminal to engine ground with the same values within .1 volts since the reference for the alternator ic I believe is the alternator ground point.

If you have a digital meter compare it to the the radar detector taking your reading at the battery leads.

 

I can always stop by my infiniti dealership, they all seem to know me because I am the only kid that stops there with a 07 G35 Sedan ^_^ Plus they're in their mid 30's so they're cool about this kind of stuff and interested in doing stuff to the cars.