Thread: Separate Alternator cable for D3

Why wouldn't you fit a Schottky diode in the circuit to prevent back voltage.

I recall that I used some high amp diodes when I fitted an electric fan switch to my RRC to prevent the back voltage from switching the aircon on.

https://www.futureelectronics.com/en...ky-diodes.aspx

The voltage drop should be compensated for by the ECU regulation of the battery voltage.
This is probably a stupid comment as I have no electronic qualifications , but I have used a diode to prevent back voltage successfully.

Regards Philip A

If would be simple to determine if these alternators require battery voltage on the B+ cable for initial excitation. It would be feasible to also have a diode in the reverse direction with an in-line low current fuse if initial reverse feed was required. The high-current diode would need some form of cooling to dissipate a possible 100-125W. The voltage effect of inserting a diode could be measured at the battery if comparable conditions could be established, perhaps more difficult with the more sophisticated charging algorithms of D4s.

I fitted a 70 amp waterproof resettable circuit breaker today in place of the fuse that I had installed. ( The 80 amp fuse was lasting about 6 weeks before it would blow ) , so will see what happens and keep an eye on it , I also found the 2 battery voltage monitor that I had in my D2 on the canning stock route trip , which is alarmed for 11.8 volts on each battery from memory so will also look at installing that, I may just use it on trips away, but will see how it looks and fits the D3.


Will update if it turns out that 70amp is not enough.


Cheers Ean

I am having my doubts about 70 amp being enough , it has tripped 3 times since being installed , I will try a couple of things first but its 10 amps less than the fuse I had used.


Will see how things go over the next couple of days.


Cheers Ean

A few years back, I was looking at developing some specialised gear for motor home electrics.

While in the development stage, I purchased some high side current monitoring ICs.

I opted not to use them because they had a constant 35ma current draw and this was too much wasted power for the intended application.

But their power consumption is not a concern when they would only need to be operational while the motor was running, which would be the case for monitoring the operation of an alternator.

The Chips had two very useful features. The first was that they give a measurement in both directions, in this case, charging and discharging.

The other feature was that they did not contact the circuit being monitored.

In theory these chips, which are that small you could fit about 10 to 15 on your thumb nail, could be mounted on a thin strip of printed circuit board and secured to the alternator cable with a couple of small cable ties.

A small micro could then monitor the current flow and direction and give a warning in the cab.

The problem is that you still need a simple way to disconnect the alternator if a problem arose.

Just thinking out loud

Originally Posted by Ean Austral

I am having my doubts about 70 amp being enough , it has tripped 3 times since being installed

The 120A CB that I fitted to the 3.0 D4's alternator hasn't tripped yet. Perhaps you might try a 100A.

Originally Posted by Graeme

The 120A CB that I fitted to the 3.0 D4's alternator hasn't tripped yet. Perhaps you might try a 100A.

I had an 80amp fuse Graeme that lasted ok , , they never had any 80amp C/B in stock so I opted for 70 but I may have stuffed up.


Did you rubber mount yours ?


Cheers Ean

I don't wish to hijack this but what sort of Kim's are the alternator's failing?