VT 304 Battery in boot not charging

[vc commodore]

The above pic is my temperature with fans disconnected...It's a 6cyl VC running a EF/EL falcon alternator, with a relocated battery...I had the car running 30 minutes from work to home, sitting home for 10 minutes and another 5 minutes idling with the fans disconnected to get this temperature reading

Here is the running output at the alternator

Here is the battery input car running after it goes through an isolator switch

Would you like to see where my earths are? Like a measurement for my alternator charge wire? That goes from the alternator to the isolator switch at the back of the car

Judge whether it's a temperature related issue?

 

[nes138]

There is the standard VT 5L earth straps and I added a 0 gauge strap from the engine head to the body. I also put a second earth strap on the -ve battery to body. Earth points everywhere!!
Is there a temp sensor for the battery / alternator in the VT S1?

Like I said I am getting above 14v cold then at or below 13v after driving half an hour (hot).

 

[Immortality]

There is the standard VT 5L earth straps and I added a 0 gauge strap from the engine head to the body. I also put a second earth strap on the -ve battery to body. Earth points everywhere!!
Is there a temp sensor for the battery / alternator in the VT S1?

Like I said I am getting above 14v cold then at or below 13v after driving half an hour (hot).

Where are you measuring the voltage?

View attachment 272406

The above pic is my temperature with fans disconnected...It's a 6cyl VC running a EF/EL falcon alternator, with a relocated battery...I had the car running 30 minutes from work to home, sitting home for 10 minutes and another 5 minutes idling with the fans disconnected to get this temperature reading

View attachment 272404

Here is the running output at the alternator

View attachment 272405
Here is the battery input car running after it goes through an isolator switch

Would you like to see where my earths are? Like a measurement for my alternator charge wire? That goes from the alternator to the isolator switch at the back of the car

Judge whether it's a temperature related issue?

I was talking about the temperature of the conductors (cables), not so much the actual engine temp. It really depends on how/where the cables are routed and their size.

 

[nes138]

I am measuring it from the Alternator positive and the engine / body and the battery and the body.

Pos cable runs through boot inside car up passenger fire wall then along back of dash into the existing loom to the alternator. except fo the last metre, it is all 0 gauge and what is on the back of the alternator is standard VT size wiring

 

[chrisp]

I am measuring it from the Alternator positive and the engine / body and the battery and the body.

Pos cable runs through boot inside car up passenger fire wall then along back of dash into the existing loom to the alternator. except fo the last metre, it is all 0 gauge and what is on the back of the alternator is standard VT size wiring

I suspect that it might be an alternator issue is the voltage is dropping when hot. It could be a faulty diode pack, regulator, or whatever.

After the car is started and has been running for a short time, the electrical load for the car is entirely from the alternator, so the battety current is relatively low - and the wiring impedance to the battery plays very little in the whole scheme of things. (As an aside, if the wiring to the battery, or it’s ground return, was the issue, you’d struggle to start the car).

Regarding the temperature coefficient, a lead-acid battery has a coefficient of about -3mV per degree Celsius per cell coefficient. So, an alternator that has a 14.7V regulator (at 25 degrees) will output less at higher temperatures. For example, at 65 degrees it’ll output 14.7V - (65 - 25) x 3mV x 6 cells = 13.98 V. An alternator with a 14.3V regulator will output 13.58V at that temperature.

If you are seeing deviations in the voltage at the alternator way beyond those figures, then look at the alternator.

 

[vc commodore]

I was talking about the temperature of the conductors (cables), not so much the actual engine temp. It really depends on how/where the cables are routed and their size.

Can measure the size of my positive and earth cables if required. From memory, the motor earth is a thinner cable than the battery earth cable

My positive cable and charge wire run down the left side of the car, across to the trans tunnel, then to the right hand side at the back, to where the battery is located.

Cables are over 10 years old too if that helps with diagnosis...That includes charge cable from alternator

 

[Immortality]

I am measuring it from the Alternator positive and the engine / body and the battery and the body.

Pos cable runs through boot inside car up passenger fire wall then along back of dash into the existing loom to the alternator. except fo the last metre, it is all 0 gauge and what is on the back of the alternator is standard VT size wiring

Measure between the alternator positive output and the alternator body to get the true alternator voltage output reading. Then you can see if there is a drop in your wiring or just the alternator itself.