Current sensing Variable Voltage alternators in NW...

[likatiger]

Hi Pauld & Skiz05,

This issue seems to be getting more complex, especially to people like me, who get turned off by the technicalities.

Anyway Paul, my Piranha Dual Battery Management System is the DBE 180S model.

It worked perfectly in the NP so I hope it will be OK for the NW, what do you think?

Thanks for any advice and sorry to be a nuisance.
Larry

[pauld]

That unit whilst having some extra functionality is essentially just an isolator, it does not control the current or voltage to the Aux battery it just connects the 2 batteries together after the car reaches a certain voltage. It therefore cannot ensure that the main battery is charged before it charges the auxillary.

http://piranhaoffroad.com.au/index.php/default/isolators/dbe180s-plus.html?SID=39lh3op96guqr511qo98e4lik6

So, what happens is, as the car starts the isolator is open (disconnected batteries). When the engine runs for a short period (usually seconds) the voltage will come up to 13.4 or more and then the isolator will sense this and join the batteries together, they will then be charged as essentially 1 large battery. If the voltage falls below 11.5V (according to the instructions - I think this might be a misprint and should be 12.5V) then the isolator will turn off. The idea is that whenever the engine is running the isolator will keep the batteries joined & charging. When you turn the car off the load off the Aux battery (fridge etc) will actually draw from both batteries until the voltage dips below 12.5? then the isolator will disconnect so as not to over discharge your main battery, your load continues to run for the Aux.
This is the same functionality as say a Redarc or other isolator, it's just that the Piranha has other functionality for monitoring etc.
With the NW it would appear that the voltage that normally sits up around 14V is going to fluctuate as you come on and off the gas. At start up it should go above 13.4 to engage your isolator. The system should stay above 12.5 whenever the engine is running so the isolator will remained joined despite the voltage fluctuation.
It would appear to me that the only real potential problem is that it will take longer to charge, which may be especially noticable if you have heavily discharged the Aux.......
If I was in your situation I would give it a go, monitor it with a voltmeter connected to the Aux in your cab and see how it goes. If neccessary then go spend more money.

[likatiger]

Thank you so much Paul, your articulate explanation helps me understand what is happening in the black magic world of car dual batter systems.

I will continue with the install and try the voltmeter monitoring. Strangely, I have a voltmeter but have never really been shown how to use it correctly.

Where did you gain the knowledge, it is obviously great to have.

At least now I know what to expect.

Thanks again.
Larry

[pauld]

No worries Larry, I have personally got heaps out of this forum in regards to good mods, advice that has saved me money etc so it's good to give back where you can. I have just been collecting information on here about a roof rack that I might buy, other people have already done the hard yards and worked out the good & the bad. I had some help from a forum member earlier in the week with regard to a suspension decision I was trying to make. So it works well.

I have a background in electronics & RF.

A unit like this is good to have to keep an eye on your battery when camped

http://www.ebay.com.au/itm/7-5V-20V-Blue-LCD-Digital-Voltmeter-Volt-Panel-Meter-/250894831268?pt=AU_B_I_Electrical_Test_Equipment&hash=item3a6a7f4ea4

I assume your voltmeter is a multimeter - turn to VDC and hook up the leads pretty much. I guess you will need to get some cables into the cab to do this but I assume you are doing that anyway as part of your install.

Perhaps leave some slack in your cables where you might ultimately install a DC-DC if required, I think some of those units can be installed under the bonnet...

[reformedjeeper]

WOW!! that's a lot of very technical and extremely helpful information.
i have just finished installing my "dual" battery system with 2 auxilary batteries with a Redarc SBI-12 isolator and thought all was going well - till I read all your posts

I will take the previous advice and get out the multimeter again and have a good hard look at what happens, thank you all for the information

[skwiz05]

An article from AAEN 23 Aug 12.... (http://www.redarc.com.au/images/uploads/files/aaen_aug-sept_2012.pdf)
New Vehicle Technology Can Affect Dual Battery
System?s Charging Performance
Australia is following the trend occurring in the rest of the world regarding reducing pollution from new vehicles and from next year they must meet even tighter exhaust emission standards. New cars sold in Australia from 2013 must meet ?Euro 5? exhaust emissions standards and the tougher ?Euro 6? standard around 2017. As the standards have been becoming progressively tighter over recent years car manufacturers in their quest to meet the new standards have had to introduce new technology. They have designed the ECU to interconnect with the alternator
and monitor electrical load. The ECU can control important engine functions via the CANbus including injection duration and timing to better control emissions as loads vary. The ECU can even shut off the alternator in certain circumstances, adjust the alternator output voltage, and preload the alternator when the load changes as occurs when you turn on your vehicle air conditioning. We refer to these alternators as ECU Controlled Variable Voltage Alternators.
For the most part, the changes made by vehicle manufacturers are aimed at increasing fuel efficiency, whilst reducing engine emissions. They can also frustrate the 4WD enthusiast however, particularly when faced with the ugly prospect of drinking warm beer from their fridge connected to their flattened auxiliary battery. The new engine and alternator control technology we are experiencing however is nothing new. It is widely known that temperature compensating alternators have been used primarily in the Toyota range of vehicles fitted with D4D common rail diesels since early 2000?s. It is also present in 2010 Toyota Kluger Petrol, BF Falcon and the subsequent models just to name a few.
The rollout of this technology will render the common Voltage Sensitive Relay (VSR) virtually useless as was commonly used over the last fifteen years or so when adding a second or auxiliary battery to your 4WD vehicle. A smarter product is therefore required to ensure the auxiliary battery is 100% charged whilst coping with the fluctuations in voltage. It is important to note that current sensing in the vehicle?s electrical system means that all additional electrical accessories must be grounded to the vehicle chassis or body, not to the main battery negative terminal.
REDARC, has developed a patented charging solution. They have released a family of In-Vehicle Battery Chargers
known as the ?BCDC? to charge auxiliary or house battery banks to 100% state of charge whilst on the move. They feature a multi stage DC-DC battery charger that is designed for installing in any 12 or 24 volt passenger car, 4WD, truck, bus or marine electrical system. Another key feature of the BCDC In-Vehicle Battery Chargers is the voltage inverter technology that overcomes voltage drop when the auxiliary or house batteries are a considerable distance from the charging source as experienced in caravans and camper trailers, trucks and buses. Most critically though, to avoid the warm beer conundrum, they boost the low output voltages provided from ECU Controlled Temperature Compensating Alternators to your auxiliary or house battery.
The BCDC in-vehicle charger utilizes voltage sensing technology of the main battery to determine when to charge the auxiliary battery and when to isolate the vehicle start battery so as to ensure the vehicle will not be stranded due to a flat start battery. These voltages are researched by REDARC Design Engineers and have been selected to suit a wide range of vehicles, and for this reason there is the need to have a range of BCDC products to best suit all vehicle
manufacturer charging system variations. The standard BCDC range will operate on voltage sensing alone in vehicles where the alternator voltages do not regulate lower than 12.7V at any time, such as standard Fixed Voltage Alternators and ECU Controlled Temperature Compensating Alternators. The wider range of BCDC variants are
applied in vehicles fitted with ECU Controlled Variable Voltage Alternators. The turn on and off voltages are sensed
at different levels along with an ignition input to the charger, ensuring that the BCDC will charge the auxiliary battery to 100% while effectively protecting the main battery from over-discharge. The BCDC In- Vehicle battery chargers are available in 6 Amp, 20 Amp, 25 Amp and 40 Amp outputs. These current output options ensure
there is a BCDC for all common load and battery charging requirements. The BCDC products incorporate specific battery charging algorithms to suit Lead acid, Gel, AGM and Calcium batteries. The BCDC1225 and BCDC1240
models also feature a MPPT Solar Regulator, which can be used to charge your auxiliary batteries from solar panels whilst camping. The MPPT Solar charging algorithm extracts the maximum available power from your solar
panels at any given time. A common question is which model of BCDC do we need to use for the alternator technology in our vehicle? Typically vehicles released from late 2011 onwards with common rail diesel motors
are fitted with ECU Controlled Variable Voltage Alternators such as the Nissan Pathfinder, Nissan Navara, Ford Ranger, BMW X5 2010 onwards, Ford Ranger 2011 onwards, Mitsubishi Pajero 2012 onwards, Mazda Spirit, VE Commodore onwards, Mazda BT50 and various Range Rovers. Practically, the best way to determine your alternator?s characteristics is to go for a drive with a voltmeter on the main battery. Run the vehicle through
varied driving conditions and record the minimum voltage found. The driving condition variations should include:
? Engine temperature (test
whilst the engine is cold and
again whilst at operating
temperature)
? Vary engine load (accelerate up
an incline)
? Vary electrical load (turn on
the airconditioner).
It is important to ensure that the correct BCDC is selected for your vehicle, application, and battery charging requirements. REDARC have developed a growing database of vehicles that determines the correct BCDC model to use for each vehicle. If you have any questions or require help choosing the right BCDC for your vehicle, please
contact the REDARC technical helpline, [email protected]. au or call the friendly REDARC technicians for free assistance on (08) 8322 4848.

[pauld]

I am guessing with 2 Aux batts you have them in the back, that is a case to consider the DC-DC units due to the voltage drop, especially with this 'smart' alternator, hope you put some big cable in. I have 1 normal lead acid Aux battery under the bonnet just for backup starting (already had the tray etc) which is charging via an isolator, I then have 2 AGM batteries under the rear floor but these are charged via a DC-DC. But I have a dumb alternator which is good.

[cranky]

OK checked my battery voltages yesterday, this is what i have concluded.
i have a dual battery setup using a piranha DBI 140S isolator.

1/ With the engine hot and at idle in park.
Start battery reading above 14 volts
Aux battery reading above 14 volts

2/ With the engine hot and RPM varying between 2000-3000 rpm
Start battery reading above 14 volts
Aux battery reading above 14 volts

I am not sure if these voltages would change if the engine was in a drive
condition Auto transmission in drive could not replicate as i don't have
a volt meter indicator fitted in the vehicle to monitor.

My conclusion, In a warm engine scenario and auto in drive start battery
above 12.8 volts and the Alternator does cut back voltage or stops charging
the start battery because it senses its full and does not require further charging, if the Piranha DBI 140S isolator senses the Aux battery requires charging due to a load on the Aux battery this would allow the Piranha isolator to close and connect the two batteries together and the start battery at some predetermined voltage point fall bellow its full charge point because it is now connected to a load with the Aux battery the alternators trigger point would then sense that the start battery requires charging which would also charge the Aux battery. and then the whole process would start again.

1/ The start battery would go above 12.8 volts
2/ The Alternator would stop charging the start battery
3/ The Aux battery falls bellow 12.8 volts due to load
4/ The isolator would close and reconnect the two batteries
5/ The Aux battery gets charged.

Sorry for the long post i am not suggesting my conclusions or my assumptions are correct but just my understanding and limited knowledge of how the isolator works.
I am hoping to install a Volt meter in the coming weeks to see if my assumptions are correct.

Let the experts examine.

Regards cranky

[pauld]

Nope, the alternator can't sense how charged the battery is and the isolator is dumb, just switches at voltage points as described above

[cranky]

G'day pauld,
So if the Alternator is Dumb and does not sense Start Battery Voltage what does, in the old days it was a regulator, does not make sense that once the start battery is charge the alternator does not provide charge to it anymore what if you did not have a dual battery system and you ran some load off the start battery say like an engel fridge & a caravan fridge if connected.

You may be correct just trying to understand how it works, time will tell after i install a volt meter to monitor real time voltages.

Regards
Cranky

[reformedjeeper]

Thanks for all your efforts Cranky - logic tells me you're on the mark

[skwiz05]

Just spoke to A Redarc rep at the Melb 4x4 show, hes going to email me some info about the 1220-IGN and LV models, says theres some adjustments made now to make them work better with smart alternators... will share once Ive heard in a day or so.....
Apparently I was the only bloke whom asked him a few intelligent questions about how those specific features worked with the new alternators, and being an engineer, he was happy to chat a bit of the lingo. Cant ask for better customer service I say.....

[pauld]

Alternator does cut back voltage or stops charging
the start battery because it senses its full and does not require further charging

A standard alternator / regulator or a Smart alternator / regulator does not do this. It does not sense when the battery is charged. It simply puts out a voltage & tries to maintain that. When a load (battery or other) draws current at that voltage the regulator further excites the alternator to generate enough current to allow it to maintain the the preset or ECU controlled voltage.
These Smart alternators do not reduce their voltage because the battery is charged, they reduce it to reduce load on the engine which will save fuel & reduce emissions by very, very small %s.
Their calculations on typical driving / starting will ensure a primary battery typically gets enough charging during deceleraton, idle etc. They are not allowing for an Aux battery that may be near flat from running the fridge for the last 2 days.

if the Piranha DBI 140S isolator senses the Aux battery requires charging due to a load on the Aux battery this would allow the Piranha isolator to close and connect the two batteries together

You have assumed the Pirhana is way smarter than it is. In my post above I have decribed how an isolator works & this one is no different. It will connect just after you start the car and will disconnect after you turn the car off and the voltage falls below X (or when you next crank the car).

Thus, smart alternator or not, your primary and aux batteries will be connect in parallel and will draw what they draw from the alternator based on the voltage presented to them and their internal resistance (which varies with charge state).

[Dion]

A standard alternator / regulator or a Smart alternator / regulator does not do this. It does not sense when the battery is charged. It simply puts out a voltage & tries to maintain that. When a load (battery or other) draws current at that voltage the regulator further excites the alternator to generate enough current to allow it to maintain the the preset or ECU controlled voltage.

What pauld has said above is correct. Alternators just attempt to hold a voltage in order to charge the battery. A heavily depleted battery may mean the alternator can't put out 13.8V or whatever it is programmed to, as the load is too high. Once the load drops off (battery gains some charge) the voltage will rise.

This is the concept behind dual battery isolators. They achieve a 'priority' by not linking the two batteries until the alternator voltage (which is the voltage in all devices on the vehicle) is above a certain point. So if your start battery was heavily depleted the alternator voltage will be low initially so the isolator will not link. Once the voltage "comes up" they will link the batteries as it is assumed the start battery has been charged "enough" as it is not drawing such a heavy load anymore.

These Smart alternators do not reduce their voltage because the battery is charged, they reduce it to reduce load on the engine which will save fuel & reduce emissions by very, very small %s.
Their calculations on typical driving / starting will ensure a primary battery typically gets enough charging during deceleraton, idle etc. They are not allowing for an Aux battery that may be near flat from running the fridge for the last 2 days.

Yep. Remember all a battery has to do is start a car. For "x" milliseconds there is a current draw from the starter and then that's it, the alternator runs the car load. As manufacturers have gotten more relentless in chasing fuel economy, they have decided that having the alternator putting out 13.8V all the time is pointless, so they've worked out to only charge it at certain times by varying the altnerator voltage.

They 'could' do some smarts by looking at the current flow into the battery as a way to determine charge. I've noticed the inductive loop around the negative on my NT Pajero, I should look up and see what it is there for ...

[Morville]

I've noticed the inductive loop around the negative on my NT Pajero, I should look up and see what it is there for ...

I wonder what it is for on my NW too. If the auxiliary battery is earthed straight to the chassis it may negate the action of the inductive loop and whatever it is meant to do.
Peter