D40 STX550 Battery management

[JLA]

I have had a look through this forum but can't specifically find the information, perhaps someone can comment. I have had my Spanish D40 for nearly three years and notice that the main battery is never fully charged often only around 30% even after a run. It always starts fine and I would never know there was a problem unless I had a digital battery tester that tells me CCA, charge state, battery health, internal resistance etc.
The problem is flooded lead acid batteries sulphate up if they are not kept at full charge which shortens their life. Occasionally I connect up the Projecta charger for a top-up and it immediately goes into auto-de-sulphate mode.
I'm don't know what difference this make to battery life, I assume it takes off a couple of years.
I know about the ECU control and the green wire mod. I have not enabled that as yet.
I assume there is a shunt in the lead between chassis earth and the earth pole of the battery and this is where it gets interesting. This is normally where the ECU detects charging requirements and sets the green wire to a voltage to the alternator so it charges more as the load increases. Then the ECU drops the charge to minimum probably to lessen engine load & pollution.
The Ford Ranger has a shunt in the battery negative lead also. The ECU management can be disabled via software but not on the D40's according to my dealer.
THE PROBLEM WORSENS: IF a winch is installed where does the negative terminal of the winch go to. Remember the negative cable on the winch is connected to the metal case of the winch.
1/ Directly to chassis - woops the 500A's that the winch pulls just burnt out the shunt.
2/ Directly to the negative of the battery - woops I just shorted out the ECU sensing shunt. The ECU will never increase the charge voltage because the voltage across the shunt is always shorted out.

What about other accessories that you add-on. Well they all have to have their meatal parts go to the vehicle chassis and not to the battery negative pole and this is vital.
Starter motor - This must have a balanced input i.e. neither the positive or negative terminal on the starter motor is connected to the metal parts of the starter motor. The starter motor connects directly to the battery as it would burn up the shunt resistor otherwise. It does not short out the shunt resistor like the winch does because the starter's metal body does not connect to the starter's negative lead.

It does not seem possible to add a winch to my Navara without it disabling the ECU charge management.

The Green Wire Mod: Would it not be great if this was supported by Nissan but they seem happy to leave us like shags on a rock. They told me, "sorry can't help, see an auto elec or ARB".

I wonder how many people have been caught by connecting back to the battery negative rather than back to the vehicle chassis?

Assumptions I have made:
I have not verified that the Navara's starter motor has balanced input.
I have not found a shunt resistor in the negative battery lead.
In the Ford Ranger the shunt is obvious. In the Navara it could even use the resistance of the lead between the chassis and negayive battery terminal rather than a shunt?
Would be interested to hear any feedback on this issue.

 

[JLA]

I now have a workshop manual for the Frontier (2012) and the V9X engine.
It says that there is a current sensor in the negative battery lead and there is a connector on the current shunt that goes to the computer. (I have not found either as yet, but not had an exhaustive look either).
The alternator is branded Nissan, has a one way drive clutch and has a three pin connector with low current wires (as well it has a heavy charge wire).
The manual shows the three wires going to the alternator fault light, the battery (Sense) and the computer (IPDM E/R).
The alternator has an internal regulator fitted but is also controlled by the input from the computer.

To check the alternator the manual tells you to either set the computer to disable the computer's alternator input (using special test gear) OR to remove the plug from the current sensor.
Then I assume the alternator charge is controlled soley by it's internal regulator? But will it work normally? Will it produce a fault condition?

Not sure if finding the current sense plug and removing it is a fix or not as yet, perhaps someone knows?

From Googling and discussions with auto elecs it seems like todays alternators are not setup to aggressivly charge a battery perhaps only ever getting it to 80% charge.
Those in the know put on a 240V charger once a month to top up the battery and perhaps desulphate, making the battery last longer.
The average dumb bumb buys new batteries every three years or so. The upside of a poor charging system is marginally better fuel consumption.

The half hearted attempt at charging the main battery is not good news for 4wd's who demand lots of power from their aux battery etc.

My next step would be to find that current sensor, remove the wire from the computer and measure the charge voltage over time.
Alternately I can just put the charger on the main battery every week or two and hope for the best.

Would appreciate input from anyone who can add something.

 

[Old.Tony]

The "shunt" could just be the multistrand wire between battery negative and the block. A shunt is used to measure the amount of current by monitoring the precise voltage on both sides, knowing that there's a specific resistance in the shunt, which will give a very precise voltage drop depending on the amount of current going through the shunt. This means that all I really need to know to create a shunt is the resistance of the wire then measure the voltage at both ends to get the current flowing through it.

Taking power directly from the negative battery post will not damage a shunt, so connect your winch and don't worry. All that will happen is the ECU will be unaware of how much power is being drawn from the battery.

You're absolutely right about the charge level affecting battery life. Removing the green wire stops the "smart" process and will allow the alternator to charge the battery more, but generally not much beyond the 75% mark anyway (here's a good read about that).

At the moment the only real choices for charging the aux battery are to remove that green wire or use a LV DC-DC charger. The only choice for the starter is to remove that green wire.

 

[JLA]

Some good stuff in the battery charging refence, thanks for that.

I have sent Varta querying the type of battery used in the Navara D40 V9X engine.
The part number: 595 103 085 is not a model on their web site.
I am expecting either Silver/Calcium or standard Lead Acid, low maintenence.

I take your point about the shunt it could be anything even the chassis bonding lead and the earth starter lead in parallel.

I'll chase that green wire and try to understand it before I disable it.
It may well be the wire joining the alternator to the ECU, and once it is removed will allow the alternator to do its own thing.

The charging systems just don't seem to be smart enough to correctly manage modern batteries.
A smart alternator simply helps with fuel economy, not battery management. The task is complex because its not just sitting on a shelf being charged, loads are being turned on and off all the time, so how can an alternator decide whether its in bulk, absorption or float charging phase?

What mods could be made:
1/ Remove the green wire - will help but still a "rough as guts" charging system - seems worthwhile though.
2/ Replace the main battery with an AGM type as they seem to require slightly less voltage to charge, in fact they float down to 13.2v The 14.2 across a fully charged AGM that can only take 13.2v will destroy it eventually.
3/ Add a diode in the sense lead so the alternator raises the charge voltage by 0.6 volt to 14.8v Once the (Calcium) battery charges this may be a bit high. Also what is the upper limit of voltage that the computers can tolerate?
4/ Remove the internal reglulator from the alternator and use a better external regulator. One that can be set to the correct battery chemistry, and alters its charge according to load and the state of the battery charge.

Or just do the green wire and put the charger on each month or so. This is why I paid $65,000 for this vehicle.

 

[Old.Tony]

Don't feel too bad about the price tag. Owners of the F40 (anywhere from marginally below $400K to $900K) were greeted with a piece of rope to open the car from the inside.

Standard AGM and "normal" (starter) lead acid batteries should enjoy the same charging voltage, AGMs should be able to handle similar (or higher) charging currents as well - gel batteries are the odd ones out, but that's not because the lead plates are sensitive - it's because you cannot (ever) risk fizzing the electrolyte in the battery, because it's a gel - and once a bubble forms, it's there forever.

Re the choices:

1) Brings the car in line with "traditional" charging systems. Cranker battery will last as long as it would in any older car, and dual battery systems will function as they used to without the need for specialist charging devices. We (all of us) need to bear in mind that this new charging method is the way things are moving towards - our next car will likely have this sort of system in it. Either we accept and embrace it, or perpetually have to find a way to defeat it. And once the alternators themselves start doing this making it impossible to defeat, we'll all need to move forward.

2) Shouldn't change the charging capability but will increase the cost. Both "normal" batteries and AGMs float at 13.2V when they're fully charged, but in a motor vehicle that fully charged state happens very rarely so holding the voltage at the nominal 14.1V or more won't negatively impact the battery in normal operation. In extended use (very long trips) either battery will approach full charge and either will suffer from the higher voltage.

3) This is a solution already offered by some (can't remember if it's Piranha or Projecta). It raises the voltage a little higher than I'd like, increasing the likelihood of gassing and venting by a normal flooded cell battery. The ECU should have its own voltage regulator (high-current 13V Zener on the input, perhaps?).

4) If you're going to bypass the regulator you need something that can handle the entire output of the alternator (130A). I've not seen a DC-DC charger rated that high. The C-Tek D250S handles 20A. Pretty sure there's a Redarc unit that can handle 40A. Both fall far short of what's needed but both are excellent battery managers.

It's not all about battery management, though. Once the car's been started, your starter battery can be removed - the alternator will (is supposed to) provide all of the electrical power needed by the car for the various control units, instrumentation and lighting. Ideally, you'd have the battery provide starting power, then disconnect and a DC-DC charger manage the recharging. That's a 600A switch/relay needed there! Higher to be safe.

Another option (I'm going to do this when I get my act into gear) is to add a small solar panel to the roof of the car and feed power via a relay to the starter battery (ignition off = panel connected). The low power of the solar panel shouldn't be able to overcharge the starter battery but will bring it up near full SOC. This should negate the drain of the standby systems (NATS, remote entry) so it should be possible to leave the car off for weeks at a time rather than the current max of 4-5 days.

That doesn't achieve your goal of an auxiliary battery system though - but as noted in 1) above, every car is moving in the "smart alternator" direction (with ever-more-restrictive emission standards to meet) so finding some charging method that works using the new alternators is a good step forward for everyone.

 

[JLA]

4) I should clarify what I meant with this option. The internal regulator of the alternator controls a small current through it's brushes/rotor which may be a maximum of say 5 amps.
So when 5 amps is flowing in the rotor the alternator gives out 140amps. By regulating that rotor current from 0 to 5 amps we correspondingly regulate the alternator from 0 to 140amps or perhaps 12 to 15 volts.
These days the 0 to 5 amps is controlled by pulse width modulation (PWM), which means the current through the rotor is rapidly turned fully on and fully off.
More charge happens if you turn increase the on time compared with the off time. The on/off switches many times per second (400Hz I saw somewhere).
Transistors do not get hot if they switch fully on or off. If they have to hold the current at say a constant 2 amps then they will get hot - hence we use PWM then everything is smaller.

BUT The internal regulator is a dumb device it has no knowledge of the battery condition, it just responds to different total loads.
To make the alternator use an external regulator (to control the small rotor current) we just remove the internal regulator and run a wire out from each brush to an external regulator.
By controlling the current throught the brushes we control the alternator's output.
External regulators are not a new thing they were used in the past. The point of using one is that because you can get at it, it can be parameterisable.

The vehicles computer should be doing this stuff but (sigh) it doesn't, it only wants to up fuel economy.
An external regulator could have the following features: (They may even exist with these already - who knows)
1/ Have an external switch to set to the current battery chemistry/construction ie. Flooded, AGM, Calcium, Gel, Lithium etc.
2/ Have a couple of option switches like auxiliary battery connected (so it can aggressively charge).
3/ Sets the alternator charge based on battery chemistry, battery state of charge, temperature of battery and load.
4/ It really needs to know whether the load is the battery being charged or vehicle power requirement, hence the current shunt.

On a long trip other options are possible like battery desulphation if needed.

What a pity that the vehicles computer has not been programmed to do these tasks.

So again I suppose it's green wire off and manually charge the main battery once or twice per month.
But if someone made a sensible regulator that could control the Nissan alternator I believe I would fit it.

Re the solar panels. Sounds like a good maintenance charger.

 

[Old.Tony]

I can't disagree with anything there. An external regulator of the kind you've described with those features would be awesome. Especially if it could handle the full current of a car's alternator. You'd have to split it into two power output streams:

1) Steady 12+V at about 50A peak to handle ECU, BCM, interior and exterior lights plus trailer lights, radio, interior power sockets.

2) Boosted output to provide power to starter battery for recharge then aux battery for constant supply/recharge.

Develop something like that and you might find a market for it, particularly if you can modify someone's existing "smart" alternator and provide those features at a reduced cost.

 

[JLA]

I submitted a query to Varta Batteries in Europe to find out what type of battery (model 595 103 085) is originally fitted to the D40 STX550 V9X engine . They answered "The model 595 103 085 was a standard flooded lead acid 12 volt battery."
The battery case is black which indicates it is Varta's basic range.