D4 Alternator

**drivesafe** · 12th February 2012, 05:16 PM

Originally Posted by DM Disco

Hi all,
A friend of mine has done a bit of research on my problem with the alternator and found the D4 3ltr diesel has a " voltage sensing, charge on demand alternator". Which means that when a second battery is connected via a dual battery controller that direct connects batteries the electronics seen the voltage of the second battery and can confuse the #*%# out itself.

Hi David and I’d guessing your mate is a mechanic, or a plumber, or an accountant.

He sure as hell wouldn’t want to be passing himself off as an auto electrician.

For a starter, unless the auxiliary battery’s negative terminal is connected directly to the D4’s cranking battery’s negative terminal, ( which is a NO-NO anyway ) there is absolutely no way the D4 can tell if the auxiliary battery is at a higher or lower State of Charge ( SoC ).

Now the reason for this is that there is a device fitted to the negative cable of the cranking battery, between the battery’s negative terminal and the earth stud on the side of the guard.

This device is used to monitor the cranking battery, so again unless the auxiliary battery’s negative is connected directly to the cranking battery’s negative terminal, the SoC of the auxiliary battery will have no effect on the way the D4’s electronics works regarding the charging of the cranking battery.

Next, I am so fed up with this crap that when an auxiliary/house battery is connected to a vehicles electrical system that the alternator knows this is happening.

This is nothing but TOTAL FANTASY.

The load created when connecting an auxiliary/house battery to a vehicle’s electrical system is no different to the load a set of driving lights will cause when they are turned on and turning your driving lights on has no effect on the D4’s ECU.

NOTE, this is very similar to how these set ups work in most vehicles, not just D4s.

Now to prove my point that the auxiliary battery does not effect the way D3 and D4s work, I have well over a thousand D3s world wide with my gear in them with no FANTASY problems and now with a few hundred D4s fitted up and with the exception of one vehicle which is playing whether the is a dual battery system connect or disconnect, the same thing, no FANTASY problems.

This info relates only to my isolators, as I know some other brands are causing problems.

**DM Disco** · 12th February 2012, 06:36 PM

Hi Graeme, I have disconnected the DB controller and all seems to be charging propperly.

No more FANTASY problems as some suggested. Don't know about anyone elses system, and I'm not an expert
(fyi friend has degrees in computer sciences/electronics),
All I know is that when the DB Controller in connected I am having trouble.
Sorry to waste everone elses time.

Regards
David

**discotwinturbo** · 12th February 2012, 07:00 PM

Originally Posted by DM Disco

Hi Disotwinturbo, where did you mount your unit, I have my optima AGM mounted in front of the main battery so there's not a lot of space left.
The Piraha controller is on a vertical bracket in front of the Optima battery.

Regards

David

I actually have my agm mounted behind the passenger rear seat in front of the fridge. Charger next to it.
Regular Agms (not optima agms) dont appreciate excessive heat, and although the D4 spot in front of the main battery would be a good spot (cooler in that location than most cars .... Used a monitor to see what temps it hit), I chose to keep it in the back. Fridge runs longer due to less voltage drop....I always use big cable anyway.

**drivesafe** · 12th February 2012, 07:24 PM

Hi David and sorry mate, I don’t care what your mate’s credentials are, he knows nothing about how the D4 works and is just pointing you in the wrong direction.

If your alternator is constantly running below 13.0v, even when coasting, you need to talk to your dealer.

BTW folks, there is an upgrade coming supposedly to fix a number of D4s with this low operating voltage.

Apparently some do not rise back above 13+v when coasting and this is a problem.

Check out the UKD3 forum for more info.

**Graeme** · 13th February 2012, 06:59 AM

Originally Posted by DM Disco

I have disconnected the DB controller and all seems to be charging propperly.

I assume you have checked voltages in arriving at this conclusion. What did you disconnect?

I can only assume there is something incorrect in the connection of your DB controller that is causing the load monitor on the negative terminal of the main battery to give incorrect readings that is upsetting the charging logic. Are you sure there is no direct connection to the main battery negative terminal?

Edit: It might be worth testing voltages with the DB sense wire connected directly to the main battery positive rather than to a switched source.

**CSBrisie** · 13th February 2012, 12:26 PM

drivesafe, can you tell me which section of disco3.co.uk?

**drivesafe** · 13th February 2012, 12:30 PM

Hi Stornoway and when I get a chance I’ll find the threads and post links to them.

Are you having low voltage problems?

The problem is not with every D4, it seems to only be occurring in a very small percentage but I have not come across anything that indicates which specific vehicles are effected and which are not.

PS if you are on the UKD3 site, keep an eye out for any posts by Wiggs, he is right into this and is a wealth of info.

**CSBrisie** · 13th February 2012, 02:00 PM

Yes, I am (classic "low battery - start engine" warning) but I am going to trickle charge the main battery for a day or so first as the car has had limited use (and a period of non use for two and a bit weeks when it was shipped up from Adeliade to Brisbane in December).

**drivesafe** · 13th February 2012, 02:35 PM

Hi again Stornoway, can I make a suggestion.

If your battery charger has a setting for Calcium/Calcium ( Ca/Ca ) batteries or if it has a “Boost” or Equalisation “ cycle, run your charger on this cycle and once the battery is charged, remove or turn the charger off, to allow the charge to rest, then repeat this cycle as many times as is convenient.

A single boost cycle is just not enough the fully charge a Ca/Ca cranking battery.

If your second battery is an Optima or another Ca/Ca battery, you can leave them connected while you charge.

**CSBrisie** · 13th February 2012, 02:46 PM

Thanks drivesafe, will do!

cheers

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