D3 voltage levels.

**DiscoDB** · 19th July 2023, 11:42 AM

Out of interest, went back over 3 years of data - which picked up the lockdown periods.

This is prior to adding solar, but during the lockdowns my battery voltage regularly dropped below 12v as the car was parked up for many many weeks at a time.

Even on a cold morning start with the battery below 12v (as low as 11.7-11.8v), the BM2 only logged a peak of 14.1-14.2v after restarting. Actual peak may be higher but this is not seen on the daily trend graphs.

The graph above was the day before the start of a 2 week lockdown. I did a trip out of Melbourne but had to be back that evening when the lockdown started. Was just a typical short snap lockdown that lasted many weeks.

From what I have read, the only real time the generator will ramp up the voltage is for very low temperature operation where I have seen reports of >15v being observed.

So having a high voltage cut off setting for cold climate use to suit a lithium auxiliary battery sounds like a great idea.

And no - the battery did not survive the lockdowns (not quite true - it was replaced but still does light duties in the garage).

Edit: I should add - the example above does not show the auxiliary battery which was fully isolated with the engine off, but holding 12.9v at the time even after extended periods of no use. As soon as the USI-160 did energise, I am sure there would have been some good current flow from the auxiliary to the cranking battery.

**shack** · 21st July 2023, 12:09 PM

Hope this helps.

Running 75 litre dual zone fridge freezer which is responsible for the discharge.

**drivesafe** · 21st July 2023, 12:22 PM

Hi Shack and thanks for those graphs.

Where are you located?

And is this a D3 or D4?

**simonmelb** · 21st July 2023, 12:42 PM

Hi Tim,

Confirming D2a max voltage I have seen is 14.61V.

This is measured using my Victron MPPT 75/15 solar controller connected to my AGM battery in the rear of my D2a. It has a new OEM Denso alternator which feeds the rear battery via an SC80 and fully thick cable as per your recommended setup.

Originally Posted by drivesafe

Hi and No, I have been testing charging of lithium batteries with a non SMART alternator operation.

While D3s have a SMART alternator, so far I have not come across one that charged at less than 13.5v.

This makes them ideal for charging lithium batteries.

BUT, I am aware of D3s overseas, have charging voltages as high as 15.4v and this is an absolute No-No for lithium batteries.

The Traxide DT90 and new UST-175 isolators have an Over-voltage safety shut down of 15.1v, but this again is still too high.

As I posted above, I have a few customers with Defenders, charging lithium auxiliary batteries with no problems.

But D1s, D2s ( I am not sure about the D2a ) Series, Defenders and Pumas do not operate above 14.7v

I am considering adding a customer selectable Over-Voltage shut down of 14.7v, to be set when ever someone is charging a lithium auxiliary in a D3.

I would still like to know the maximum voltage reached with Australian D3s and more importantly, how long they operate at the highest voltages.

**shack** · 21st July 2023, 01:19 PM

Originally Posted by drivesafe

Hi Shack and thanks for those graphs.

Where are you located?

And is this a D3 or D4?

D3, and I think it was at or near Innamincka.

**drivesafe** · 21st July 2023, 03:52 PM

Originally Posted by shack

D3, and I think it was at or near Innamincka.

Thanks and do you remember the outside temperature, in the morning?

**shack** · 21st July 2023, 04:02 PM

Originally Posted by drivesafe

Thanks and do you remember the outside temperature, in the morning?

Wasn't terribly cold, maybe 3-5°.

**drivesafe** · 21st July 2023, 05:15 PM

Originally Posted by shack

Wasn't terribly cold, maybe 3-5°.

Thanks again Shack, and between the low temperature and the fact you were running your fridge 24/7, the SMART alternator operation is well within what I would expect.

That is a great bit of info Shack and it confirms the need for an over-voltage shutdown function to be added to my isolators, allowing them to be used safely when charging a lithium auxiliary battery.

Thanks to everyone for your info and it will be of great assistance while doing my latest upgrade.

Nothing like first-hand info and great feedback.

Only on AULRO!

**SeanC** · 22nd July 2023, 04:59 PM

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2008 TDV6

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