Thread: Alternator SDV6, anyone upgraded for larger than stock 150A??

The TowPro diagnostics indicated that the flashing red is related to the earth return from the trailer brakes or trailer battery earth back to the tow vehicle, not a 12V supply problem.

Originally Posted by imaz

Here are some notes on my vehicle 1.


When the towpro elite is flashing red.

1. Starting battery 13.63v
2. In-house aux 40a dcdc in “Absorbing state” and aux battery 14.46v
3. Camper dcdc 25a is in “boost state” and Battery 13.98v
4. Tow pro elite circuit breaker at ~13.30v


When the towpro elite is stable normal condition:

1. Starting battery 14.42v
2. In-house aux 40a dcdc in “absorbing state” and battery 14.44v
3. Camper dcdc 25a is in “absorbing state” and battery 14.50v
4. Tow pro elite circuit breaker at 14.36v

I’m sorry imaz, the info is just not sufficient to gain any real idea of what is happening.

You obviously took the voltage measurements while the motor was idling.

This means you had a maximum available charge current of about 60, may 70 amps, but more likely 45 to 50 amps, coming from your alternator.

Your D4’s own electrics would be using 30 to 40 amps, so at a VERY rough guess, you have somewhere between 15 to 30 amps available and again, my guess, judging by your voltage readings, its closer to 15.

Next, you need to know how much current your brakes are drawing.

The fact that when the voltage was higher, and that both reading were while the 40 amp DC/DC was in absorption stage, the battery was near, if not fully charged.

And the battery connected to your 25 amp DC/DC charger was in a similar state of charge.

One last point, because of the voltage differences at the starting battery, between the first and second readings, in the first reading, you were probably drawing more current than your alternator can produce “AT IDLE”. This would be the reason for the lower voltage reading, the first time.



Also note, and this may be the reason for the Tow-Pro’s different indications, there will always be voltage drop in both the positive ( + ) and negative ( - ) circuits and may be worse in one than the other. Usually the positive, but not always.

A poor earth connection anywhere in the circuit, could easily cause a voltage drop in the earth circuit, while under load, but not there when there is very little load, and this could be the reason for the different RED LED indications.

So thats something else you need to investigate.

Originally Posted by Graeme

The TowPro diagnostics indicated that the flashing red is related to the earth return from the trailer brakes or trailer battery earth back to the tow vehicle, not a 12V supply problem.

I’ll need to recheck what this exactly means, since the tow pro returns to normal when the trailer battery is full!

And not to forget, it happens on all three camper/caravans...

Must be a Landrover thing.

I think drivesafe is likely on the money - when idling, amp output seems to be restricted. So if charging everything at once, the smarts of the brake controller are detecting a limitation.

Does it also stop flashing when you start driving?

Originally Posted by imaz

I’ll need to recheck what this exactly means, since the tow pro returns to normal when the trailer battery is full!

And not to forget, it happens on all three camper/caravans...

Must be a Landrover thing.

And yet believe it or not we also have Land Rovers (Not Landrovers) with Tow Pro Elite’s and multiple batteries with no issue????

Originally Posted by imaz

I’ll need to recheck what this exactly means, since the tow pro returns to normal when the trailer battery is full!

And not to forget, it happens on all three camper/caravans...

Must be a Landrover thing.

Do any of you own an IID TOOL so we can get some useful info such a what the BMS is doing, what the alternator is up to etc?

What’s common about you all? Same installer? Something is super odd that you’re the only people having this issue and you all somehow know each other?

Seems odd.. Something isn't up to spec in the wiring on the connections back to vehicle from the trailers being pulled.

I currently run:

Primary > DcDc 50a > 2x 60ah AGM > Victron DcDc 30a > 2x 115ah AGM
Tow Pro Elite
50a of Driving Lights
16a of Light Bar

Never seen these errors regardless of the state of house batteries or vehicle batteries.

The Tow Pro is reporting poor earth return from the brakes with those error signals.

Check the vans/campers wiring set ups. I'm thinking the Earth return is insufficient to maintain the system. Or the wiring used is under-rated.
On the vans/campers what's the earth set up like?

Originally Posted by imaz

And not to forget, it happens on all three camper/caravans...

Must be a Landrover thing.

I think you risk not finding the problem with your installation (and your friends cars) if you dismiss it as a Land Rover thing. I, like others on the forum run 2 x auxiliary batteries under the bonnet and I have two in the camper with a Redarc Manager 30. I have a tow pro also. I don't have any faults and often run with all 4 aux batteries taking charge.