Alternator

autostaretx

Erratic Member
. I note in another thread a person fitted a bigger 200A alternator for good charging then fitted a 40A DC-DC charger ??? Money down the drain for what purpose :dance:
I can't say why they sprung for the 200 amps, but the 40-40 could well have been to limit the charging current to some whacko battery's specified limitations. (Gel, for example).

--dick
 

Skippy and Emu

Active member
MB''s usual placement is to the center rear of the seat pedestal. See previous post's photo.

lThe "D+" signal automates the "manual switching". That's its job. It goes high when the Sprinter's Alternator is producing power, and that's when you want the isolation relay to operate. That's how MB's auxiliary battery option does it.

--dick
I am curious as to the actual output of the D+ terminal when the signal is being supplied by a "smart" alternator.
I do not have a "smart" alternator, so am not able to verify the output myself.

Assuming the D+ terminal output is fed via a relay which is controlled by the Instrument Cluster, via the alternator.
My questions are :

Is the output a fixed value voltage, regardless of the actual alternator output ?
Is the output "smoothed" to cater for regenerative braking, and when engine "stop - start" features are engaged etc. ?
Will the D+ output remain constant during the entirety of the journey, even when the full suite of the alternators "smartness" capabilities ,
are activated / deactivated ?
 

autostaretx

Erratic Member
I am curious as to the actual output of the D+ terminal when the signal is being supplied by a "smart" alternator.
I do not have a "smart" alternator, so am not able to verify the output myself.

Assuming the D+ terminal output is fed via a relay which is controlled by the Instrument Cluster, via the alternator.
My questions are :

Is the output a fixed value voltage, regardless of the actual alternator output ?
Is the output "smoothed" to cater for regenerative braking, and when engine "stop - start" features are engaged etc. ?
Will the D+ output remain constant during the entirety of the journey, even when the full suite of the alternators "smartness" capabilities , are activated / deactivated ?
First, the "D+" has only two states: on (+12v) and off (0v).
I do not know how it changes time-wise when the alternator is being "smart".
The EK1 post is connected to relay contacts, and thence to normal power.

But .... the "smart" alternator merely means that it has a bi-directional communication path (the LINbus) with the rest of the Sprinter. It's the Sprinter that commands the alternator, not the other way 'round. So the Sprinter certainly has the power/knowledge to turn D+ on and off as it's having the alternator do strange things.

From an "old school logic" point of view, (ignoring D+) ... the alternator (at maximum smart mode) will be commanded to be in one of four states:
(a) immediately after starting, charge the starter battery at a fairly high "recovery" rate.
(b) after not-too-long a while, drop the charge to a "medium" rate.
(c) an unknown (to me) time later, once the battery is above 80% state-of-charge, tell the alternator to stop charging.
this maximizes MPG by removing the 4 horsepower alternator load (at full 220 amp output).
(d) at times when additional engine braking force is desired, resume charging the battery to put that 4 hp load on the belt.
(this is why the "80%" of (c) ... it leaves "room" to cram more current into the battery when wished)

As someone above mentioned, the Sprinter monitors the charging current reaching the battery (and voltage levels) so it has some idea of what state-of-charge the battery has reached.

Midwestdrifter's idea of simply watching the voltage level with a plug-in meter is quite good. S**t-simple.
My (totally dumb) T1N would show 14.2 for (a), and 13.6 to 13.8 for (b), loads depending (lights, AC, fans).
I use my ScanGauge as my "plug-in" voltmeter.

If the D+ was purely following (chasing?) the alternator's function, i would expect (a)(b) and (d) to be "on".
If you buy MB's charging-rig option (the isolation relay, etc) they (might) "obviously" would tell the control system to perhaps forgo (c).

In the 2007-2013 NCV3 Sprinters, the 4-cylinder engine made use of "smarts" ... the 6-cylinder didn't seem to.

--dick
 
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Skippy and Emu

Active member
But .... the "smart" alternator merely means that it has a bi-directional communication path (the LINbus) with the rest of the Sprinter. It's the Sprinter that commands the alternator, not the other way 'round. So the Sprinter certainly has the power/knowledge to turn D+ on and off as it's having the alternator do strange things.
Thank you, for another of your excellent, well laid out explanations !
Still curious if the full blown smart system would / could actually turn off the D+ output, at any stage whilst travelling from A to B.
 

Batz

Member
Thank you, for another of your excellent, well laid out explanations !
Still curious if the full blown smart system would / could actually turn off the D+ output, at any stage whilst travelling from A to B.
Well...ill let you know. As i'm going to give the D+ method a go. But surely Eric and co would not be so adamant that it works if the above was an issue??
 

autostaretx

Erratic Member
I think their "won't work" is a short way of saying "may not put anywhere near enough charge into the house battery" since the Smart Alternator will be in state (c) (no charge) for most of the drive-time. So it's not a win.
Folks have reported the VS30 D+ signal coming "on" when the key is turned to "position 2" ... in other words, it did NOT wait for the engine to actually be running.
Looking at the 2007 NCV3 wiring diagram, the EK1's "ignition on" and "D+" posts are driven by separate relays ... so the *hardware* certainly exists to allow "separate (intelligent) lives". Whether the ECM programming makes use of it (and the option mixes weren't clearly specified in the "comes on" post (i.e. did they have an MB isolation relay and Aux Battery?).

I believe a number of 6-cylinder NCV3 owners have successfully used the D+ for their house charging.
I don't recall hearing unhappy 4 cylinder folks, but they may have gone VSR (which will stop charging in state (c))

--dick
 

Eric Experience

Well-known member
Dick.
D+ is always on when the engine is running, never on if the engine is not. it has many other functions, it is not just for the alternator, D+ has been on European vehicles for over 100 years. hence its name comes from Dynamo positive. The alternator control gives a strong charge until the current starts to drop then the voltage drops to protect the battery from drying out, that is why the system works so well. The more batteries you connect in to the system the longer and harder it charges. All important vehicles are designed by engineers to work reliably, that is why this system is used on Ambos, fire trucks, police cars, army vehicles, ETC The loads in a motor home are small compared to the government vehicles. Eric.
 

Skippy and Emu

Active member
Folks have reported the VS30 D+ signal coming "on" when the key is turned to "position 2" ... in other words, it did NOT wait for the engine to actually be running.

--dick
JACKPOT !
Exactly the type of info I was looking for.
Can anybody, either confirm or deny, that this event can take place. ( bearing in mind, any conflicting options the vehicle may be loaded with, or coincinding events )
 

autostaretx

Erratic Member
Member jaahn posted:

... very interesting (and i should'a recalled) about turning on the headlights forcing the alternator into (a) (high charge)
... i've seen other (older: 1995) cars increase their idle speed when electrical loads were turned on (the service manuals even recommended it for analyzing charging issues).

I have no doubt that the air conditioner would cause a high-charge state, too.

Obviously my list should've included:
(e) engage charging if significant electric load (headlights, AC) is turned on

--dick
 

Batz

Member
Hi Eric & Dick,

So here is an update. I did as Eric advised and fitted a simple relay to the D+ terminal which after startup the relay closes and the house battery seems to be charging. This was done back in July. Obviously I have been driving the van since. Drove to the snow in August staying a couple of nights in accomm at Thredbo, then in Canberra staying in the van. No issues with the battery losing voltage with the Fridge on the whole time etc etc.

Basically the fridge is on the whole time. (24/7). While the van is parked in my driveway, every few days I plug in a 240v charger to give the house battery a top up. I hadn't been on any decent trips away since the snow. So this weekend I drove from Newcastle up to Forster, then Taree and then to Port Macquarie, stayed a couple of nights in the van overall before driving back from Port to Newcastle.

I would have thought all that driving would have kept the house battery topped up ??? ...however after returning home yesterday I notice that the House battery was sitting at 12.2 when the fridge compressor kicked in. In my mind that's too low and that's when I would normally plug in my 240v charger to top it up. But I would have thought that the amount of driving to Port Macquarie and back to Newcastle, mainly doing 115kms for 2 hours would have topped the house battery sufficiently to last a few days when I got home?

Do you think there may be something wrong with the Smart Alternator?. Would having headlights and also aircon most of the time while driving affect the charging of the battery?

cheers for any advice. Its appreciated.
 

Eric Experience

Well-known member
Batz.
How old is your battery? You could have a faulty crimp on the battery cable. To resolve the question measure the battery voltage with and without the engine running. Should be 14.2 and 12.6 . when the engine is running the voltage on the terminal on the alternator should be only a fraction higher than the battery terminal. The alternator should handle the lights and air con no problems. Eric
 

Batz

Member
Batz.
How old is your battery? You could have a faulty crimp on the battery cable. To resolve the question measure the battery voltage with and without the engine running. Should be 14.2 and 12.6 . when the engine is running the voltage on the terminal on the alternator should be only a fraction higher than the battery terminal. The alternator should handle the lights and air con no problems. Eric
The House Battery? New as of June this year. 190ah AGM. The start battery, I have no idea.

The voltage is as you say. When the relay first kicks in after the engine starts, it reads 14.6. Ends up dropping to around 13.2 while driving. With the engine off, it depends on how charged the battery was beforehand and if I've had 240 charger on overnight. But like I said, when I came back from Port Macquarie yesterday after driving for 2 hours, after the engine was off the charge was sitting at 12.4 with no load and then 12.2 when the fridge compressor kicked in. I would have thought, after that length of time driving that the house battery would have been fully charged (12.8 resting and 12.6 under load)

I've always felt funny about using the style of sensor relay that I've got, that basically joins both batteries together when engine is running. As Eric if you remember you said the alternator can sense both batteries and adjust accordingly?

All terminals are secure by the way.

cheers
 

Eric Experience

Well-known member
Batz.
Voltage sensing relays are no good with smart alternators. After driving for a few minutes the voltage drops and your relay drops out. Best to change to the Bosch system using D+ to connect your battery to the alternator. You may be able to remove the voltage sensing cct and just connect D+ directly to the relay. Eric.
 

Batz

Member
Batz.
Voltage sensing relays are no good with smart alternators. After driving for a few minutes the voltage drops and your relay drops out. Best to change to the Bosch system using D+ to connect your battery to the alternator. You may be able to remove the voltage sensing cct and just connect D+ directly to the relay. Eric.
Hi Eric,
Sorry i think I've confused you. We have already had this convo back in June. I followed your advice by using the D+ setup as per below
1606039963895.png
 

Eric Experience

Well-known member
Batz.
NO NO that is the wrong set up, that will not work if connected to D+ because D+ drops with the alternator voltage. You must use a straight relay. The words in the first part are correct but the words about ignition 12 volt are wrong. Eric.
 

Batz

Member
Sorry Eric, probably a bad example using that picture. That was more to describe the type of relay I'm using. The "Ignition 12V+" lead is, as you suggested back in June, connected to my D+ terminal.
 

Batz

Member
Batz.
NO NO that is the wrong set up, that will not work if connected to D+ because D+ drops with the alternator voltage. You must use a straight relay. The words in the first part are correct but the words about ignition 12 volt are wrong. Eric.
OK, I just read your above response again. You are saying the above WONT work if connected to the D+ terminal???....ok now I'm confused. These are the instructions I followed from an earlier post, which you agreed was correct.

First, you need an "isolation relay" (such as a Cole Hersee unit).
The isolation relay will have 3 or 4 terminals.
Two really BIG studs, and one or two much smaller ones.

Each one of the BIG studs goes to the positive posts of the two batteries (one to one, the second to the other) with thick wires.

The D+ signal goes to one of the smaller studs. If there's a 2nd smaller stud, it goes to frame ground (or starter battery negative).
If there is not a 2nd smaller stud, the metal of the relay case itself is the "ground" and needs to be screwed to metal with decent connectivity (that will not be carrying much current).

When the alternator is running, D+ is turned "on" by the Sprinter (via a relay) and presents 12v to its wire.
That 12v (and the ground connection) cause the isolation relay to "pull in" and join the two batteries.
Charging current flows through the BIG studs (and thick wires).
The D+ is just a dinky signal to tell the isolation relay to act.
 

Midwestdrifter

Engineer In Residence
Nothing wrong with the setup you describe. You need to be aware of its limitations. The alternator won't stay at the higher voltage for very long, which limits charge speed, especially for the last 20%.
 

Batz

Member
Nothing wrong with the setup you describe. You need to be aware of its limitations. The alternator won't stay at the higher voltage for very long, which limits charge speed, especially for the last 20%.
Thanks Midwest....if it has limitations, then is it the best way to have it setup?

As I said in my earlier post, i confused why the house battery wasn't fully charged after driving back from Port Macquarie to Newcastle?
 

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