Alternator Voltage Booster

Hi Mainey, only because the vehicle charging sytem never seems to get the battery higher than 12.55v. When I am on a powered site, I just top them up with my smart charger, they then seem to get to 12.75 (after a rest period).
Just wondered if it was a good idea or do Toyota have a good reason electronically, to keep maximum charging voltages down, temperature controlled or what?
I have two 100amp aux. batteries isolated from the cranking one by a Red-Arc unit. Should be plenty to run our car fridge on freeze mode for a few days. I also have a portable solar panel but not been able to give it a good test as yet.
Time will tell,

Cheers again, Col

Col,
12.55v is not even the charged rate of a 12v battery, so there is a problem somewhere and to find and rectify that problem may fix everything for you.
A charged 12v battery is rated as 12.66v.

Maybe recheck the voltages after a run of at least 10 mins and see what the voltages are in the Cranking and Aux battery is when engine still running, then when turned off after a few minutes and also after 3 hours, they should all be different numbers.
Use the same earth for each test.

Maîneÿ . . .

I thought a 12 volt battery had 2.2 volts per cell Eg 13.2 volt for a fully charged good condition battery at rest.

Try another volt meter! Or your battery is losing a cell, and needs to be replaced.

Cheers.

Theres plenty of info regarding this device on pradopoint if you look there.

Colcam42 when you say the voltage never gets above 12.55V, is that with the engine running, if so as Mainey says there is something wrong.

If it is when the engine is off, do you have accessories on the aux at the time.

I also have a D4D V8 ( 200) and it will charge at about 14.2V for about 10 - 15 mins when cold then backs off to about 13.8 - 13.9V when warm.

If you have 2 batteries with an isolator, with the engine running check the battery on the passengers side. This should be the main battery. It should be 13.8V plus.

If that is not the case then something is wrong.

a) disconnect the second battery & test main one again.

If it is still low then you have a problem, either incorrect aftermarket wiring, the wiring from the alternator or something wrong with the alternator.

From memory it is a 160A alternator ( in the 200, not sure about the 70) so it should have plenty of grunt.

Is your redarc the one with the clear plastic or solid? The soliod ones have a lower cut out voltage and draw power from the main battery to a lower voltage. Again disconnect the aux battery ( at the isolator) and see if you still have a problem.

Hi Boobook, yes the alternator is the 160 amp, as you say plenty of power. The 12.55v reading is with a digital VM connected permanently to the aux. batteries. Several writers on different forums confirm that few, if any vehicle alternators can fully charge the batteries. This I understand, but wondered about the advert for the booster. I am sure that there is nothing wrong with the systema as is, just a design issue. This has been around for many years hence the reason why some people use DC-DC chargers on their RV to get a fully charged set of batteries. As I have said to Col below, not sure which Red-Arc I have but from your description, I might be able to ID it.
Thanks for this,
Cheers, Col

Col,
As Boobook has stated you have a problem, he has the same vehicle as you (I believe) and is getting a much higher voltage.

Now you have to ascertain where you get your problem, first thing is to check with a voltage meter (multimeter) at the Cranking battery with engine running, then each side of the battery isolator, then at the Aux battery.

I get 14.4v max at my *Aux battery* with a 55 Amp alternator, take that as an example and work towards getting somewhere in that area, as I say check all connections and see where the loss occurs, then will be easy to fix the problem when you know exactly where it is.

Maîneÿ . . .

"Several writers on different forums confirm that few, if any vehicle alternators can fully charge the batteries. "

They're wrong. They've been sucked in by the "You MUST buy our expensive accessory to charge your batteries fully" websites.

A Lead Acid battery charged less than 100% will NOT last a year.

I totally agree with mike, generators and alternators where designed to do one with and one thing well, charge lead acid batteries and the have done so for the past 60 years.

A lead acid battery will fully charge from any voltage source as long as a charging voltage greater than its terminal voltage is applied, this is pure chemistry nothing else. The only that will change with a lower charge voltage is the time it takes to reach 100 SOC.

Bottom line is more volts and low impedance power source such as an alternator will charge multi batteries faster then any charger ever will unless it has the same current capacity as a Alternator has, in the case of modern vehicles some 60 ~ 100A. Its only with recent manufacturer changes that have reduced the Alternator output voltage to meet upcoming overseas anti emission requirements has a problem occurred. It has nothing to do with maximising cranking battery life in fact it will have the opposite effect if anything.

So bottom line is if your Alternator is putting out around 14.2 volts it will do the job better than any charger will.

Cheers

Leigh

My experience of my V8 79 series trayback is very similar to what Boobook has posted above.

I have an ARB dual battery setup and the initial voltage is around 14.2 then tapers off a little. This is more than adequate to reach 100% charge in a short time especially with spiral wound AGM batteries.

I have also noticed on quite a few batteries warnings about charging above 14.1 volts.

Be very cautious of the advice given by many that higher voltages are needed to charge dual batteries. It seems they are much more "expert" than the vehicle and battery manufacturers.

This is not to say there is not a place for DC DC chargers and other charging devices that may use higher voltages for short times but I doubt there is any need to boost the alternator battery in a properly functioning system.

May as well comment on the assertion made elsewhere on this thread "you can't charge past 70% using an alternator" - this is total bunk and is completely discredited. This 70% corresponds to a rest reading of 12.32 volts. Unfortunately this misinformation continues to float around the internet as if it is fact. Both my batteries sit on 100% charge and have not been charged by anything other than the alternator. After running the fridge/freezer overnight the dual battery is usually around 12.3 to 12.4 volts as would be expected. It got that extra 30% it used out of the alternator.

Flynnie

Flynnie,
Yes I also fully agree with your statement "May as well comment on the assertion made elsewhere on this thread 'you can't charge past 70% using an alternator' - this is total bunk and is completely discredited"

Same as some who falsley believe a solar panel only delivers 70% too

Maîneÿ . . .

That's ok if you have 14.1V to charge the battery, unfortunately some of the newer models are lucky to charge at 13.2V when engine bay is hot hence the need for some of these devices unless your happy to wait for a week for the battery to charge.

LeighW

Leigh,
sure the newer alternators are operating at lower Voltages, but their Amperes are still high, some as high as 100 amps, and as it's Amps that charge a 12v battery.
The lower voltage is not such a major problem as it's made to sound, as long as the charging voltage is higher than the Aux battery it's charging it will charge the Aux battery.

Maîneÿ . . .

Leigh

It is CORRECT for the alternator to cut back the voltage when the engine bay is hot. This saves destroying the battery.

I have had no problem with the dual battery charging correctly in temperatures from -9 to 43 degrees. My charging system appears to be functioning correctly.

A dual battery used in hot climates is probably better located away from the engine bay. That has been covered by other people at other times on this forum. If I lived in the Northern Territory I would likely have the second battery under the tray but I don't live there and under the bonnet location has been fine.

Flynnie

Flynnie,

Just to clarify a couple of points, yes your charging system is doing what it is designed to. Car alternators are temperature compensated and correct the charge voltage as the battery heats up and so prevent over charging.

Even the old relay type regulators had temperature compensation.

However, in some of the latest models the charging voltage has been reduced much more than the accepted norm of around 3mv / C. Toyota for example is one of the manufactures that has significantly reduced the charge voltages on some of their recent models to meet upcoming anti emission requirements for overseas markets.

The reduction has nothing to do with maximising cranking battery life in fact it will most likely have the opposite affect but as long as the majority of cranking batteries survive the warranty period the manufactures don't care.

In the case of the current D4D, the ECU maintains ~14.3V for several minutes until what is assumed a reasonable amount of charge has been put into the cranking battery to recover the battery drain during starting and then it reduces the charging voltage to around 13.2V or lower though some temperature compensation control is still retained.

This would equate to a under bonnet temperature rise of around 366 Celcius obviously this is not the case.

The change is purely for overseas anti emission requirements, future changes planned are to stop the charging altogether at idle and other certain conditions and to turn of aircon and power steering etc to reduce the load on the engine at idle.

Charging a second battery is not considered by any manufacturer and we have been lucky to get away without modifications to this point in time.

Yes you can charge a battery at 13.2V assuming you have that ie no other accessories running, but if you expect to charge a 100A aux that's been discharged to around 70% SOC and also charge the cranking battery back to 100SOC in a five hour run it is just not going to happen at 13.2V

Cheers

LeighW

Leigh

Just a final comment to clarify.

Nowhere did I suggest charging at 13.2 volts. I did say in a few different ways that a correctly functioning system does not need a voltage boost to the alternator.

You mention that figure of 13.2 volts at least twice in your posts and refer to allegedly what happens in a current D4D. Well it does not happen in my 2009 D4D cruiser and presumably not in a 2007 D4D cruiser which is the subject of the thread. Mine backs of the voltage as per Boobooks post as I have previously said.

Those newer vehicles that drop to 13.2 volts quickly may be in need of a modification but as the old saying goes "If it ain't broke don't fix it."

Flynnie

Fylnnie,

No argument with "If it ain't broke don't fix it."that.

Cheers

LeighW

Flynnie and Leigh, seems like my simple question at the beginning of this thread has raised a whole heap of other issues. However, getting back to my position, and I agree with Leigh, it is a driving-time issue that is the real problem.
I understand that the amount of current that can flow into a battery is dependent upon the differences in terminal voltages, It really doesn't matter if the alternator can deliver 100amps to all of the vehicle electrics, there is no way the amperage at this level will be going to the battery.
Therfore as Leigh says, if the Alternator is down on terminal volts at the batery, it will take longer to charge said battery. Hence, in my case, when the fridge uses 3amps from the aux, battery, for several hours, it figures that the charge cycle is having to replace this usage. If the driving time is insufficient to do this at a given voltage, the batteries cannot be fully charged.
This is the truth behind the fact that most vehicles driven on a daily basis for short commutes, never charge the battery completely. And I defy anyone to refute this.

cheers again, Col

Col

I agree. (I want to finish a blog I am working on too and stop jumping backwards and forwards on the site.)

To charge a battery a vehicle must be driven for a while. My driving is usually more than a half hour each time. Those who do short trips and have fridges etc could look at the suggestions that have already been posted elsewhere on the forum or look at the articles on Power and Electrics and also maybe the Business members of Exploroz and the products they sell.

Flynnie

"You mention that figure of 13.2 volts at least twice in your posts and refer to allegedly what happens in a current D4D. Well it does not happen in my 2009 D4D cruiser"

Flynnie - what voltages do you get at the battery.

I can see that if someone measured at the rear compartment lighter socket, while the fridge compressor was running, that they could get 13.2 volt. I got 12.0 volts drawing 10 amps with the original Pajero wiring.

Mike, you say; "I can see that if someone measured at the rear compartment lighter socket, while the fridge compressor was running, that they could get 13.2 volt.
I got 12.0 volts drawing 10 amps with the original Pajero wiring"

Mike, it would be totally *impossible* to get 13.2v at "rear compartment lighter socket, while the fridge compressor was running"

Your 12v is a more accurate and correct number under the conditions you state.
0bviously it's a 'typo' ??

Maîneÿ . . .

Mike

When the batteries are at rest and no load, that is not powering anything, they come in at 12.7 volts. When I had the dual battery installed I checked this for a few months. I usually checked before going to work and after work before driving home so the batteries would have settled down. Powering anything, even a mobile phone charger will drop the voltage and make the reading invalid.

The cruiser usually starts off about 14.2 volts when running and tapers off to about 13.8 or 13.9. This morning it held around 14.0 volts. It was a cold morning. I have used my "Battery Spy" to give me a continuous reading while driving. When I did some testing earlier in the year it sometimes took about 15 minutes before the isolator would allow the fridge battery to start charging. I do recall the voltage dropping lower while driving around the warmer parts of Western Australia recently but I did not take much notice of the readings.

The Subaru I drove today started at about 14.8 volts and then tapered off but always was higher than the cruiser. I will be using it for a few days so will keep an eye on it to see how it goes. It should be exposed to some real cool conditions and I expect its voltage readings will be higher than usual.

Flynnie

Hmmm . . . so you have to wonder where "D4Ds only charge batteries to 13.2" came from ?

Mike,
No, you have said; "I can see that if someone measured at the rear compartment lighter socket, while the fridge compressor was RUNNING, that they could get *13.2* volt"

I don't think it's possible to get 13.2v at "rear compartment lighter socket, while the fridge compressor was running" after all, the fridge compressor is drawing ~0.5v to start with.

You have said your Paj has only registered 12v under the same situation ?

Maîneÿ . . .

Hahaha how true Robin. That might be a bit of an exageration though. You may have to pay 3 or even 4cents for one off quantities.

Hi Robin,
what type of diode would you place in this circuit?
And which way around?

I thought a resistor of a certain value would be what is required, to reduce the voltage to the alt, so it thinks it needs more.

Would like to try this at home, so any info on the type of diode would be much appreciated.

Thanks

Trains

Hi Trains

I don't have specific details / circuit of that alternator so I could not say, but I don't mind experimenting with things.

The principle though is well known and used in ordinary alternators as per the how to do it link below.
A resistor cannot be used as a reference because the voltage across it changes with current , hence a diode(s) with a fixed drop (0.6)

The secret is to change the reference voltage and the alternator re-regulates itself to the new reference.

The link below does it in a slightly different but more universal way and requires heavier diodes , 10amp 400v.


http://www.smartgauge.co.uk/alt_mod.html

Thanks Robin Miller

Makes sence now.
I got a diode, and tried both supplies to the alternator, but being internally regulated, it didnt make a difference :(

Might have a word to my auto elecy and see what can be done for the 2.8 diesel hilux.

T

Hi Col, thanks for this, you confirm that the Toyota has lower charging voltages and as I understand it, it is now the Engine Management CPU that controls the regulator of the alternator.
Not sure about the Red-Arc, it was fitted before I bought the bus and as I had read about this issue with Toyotas, I asked the previous owner. He didn't know, just had the Smartstart/ auxiliary system fitted. One day when I get under the bonnet, I will try to see if there is any figures on the relay so as I can compare it with Red-Arcs data. (It is hidden under the second battery). I also understand from the 12v specialist shop that Red Arc no longer make this lower voltage unit for Toyota Diesels. This came up when I bought one for my older Pajero where they asked me if it was for a diesel. Explaining that I had a diesel Toyota in mind, the recommended a different brand.
I understand that the voltages that I get, subject of course to meter accuracy, are typical for Aux. batteries being charged from the car alternator.
I do have access to an auto-elec so when back home, discuss this a bit more with him. I will also have a look at the link to lcool.org
Thanks again,
Col too!

Hi Phil, now that would be the way to go then, just have the increased voltage to the Aux. batteries, What cost I wonder?

I re-tested the alternator charge voltage this AM, just so I could let the above posters know. Run for about 20mins to the dump and back, so warmed up a bit. At fast idle 14.2 volts. As I have said, it must be that when I am driving with the fridge running, the alternator is not keeping up to it, hence the 12.55v reading (engine STOPPED!), after a run.

All as I wanted to know, is would the Voltage Booster gadget be useful or not, I guess not!

Lovely day here at Copi Hollow

Cheers all, Col

Col,
Just read some of your other replies.
Your Redarc is most likely the problem. The solenoid remains powered after you turn the motor off until the starting battery has dropped to 12.5V. That is the way they make them.

The simple fix is to install a relay into the Redarc's earth wire so that the relay cuts power to the Redarc when IGN is turned off. A source of IGN power to run this relay is usually taken from the wiper motor.

Your charging voltage is completely normal.

Cheers
Phil