navara d22 dual battery decision!

so do you think that the under tray battery would be better so I could have a bigger one?

Big is better, the more you discharge a battery the shorter the life.

If you have a 100ah battery and you discharge it 75% compared to. 200ah battery that you only discharge the same amount of amps relating to 35% of the capacity...... Your doing less damage to the 200ah battery.

I've already bought a redarc 100amp dual battery isolator, so all I need to do is get a heavier gauge cable and that should suffice do you think? I really appreciate the help

There are a number of threads on this and other fora explaining why you won't get a truly full charge to the second battery using straight alternator charging.
I suggest a bit of reading for some education on the subject.

There are various opinions on this. I will declare my bias straight up - I lean strongly towards a dc-dc charger, for a number of reasons:

1 It readily makes up for cable losses between the power source and the target battery (within reason).

2 If your alternator has low voltage output by design, it makes up for that. The Nissan forum mentioned elsewhere can help you with that. Or posters here.

3 It can tailor the charging profile to better suit your aux battery.

4 Some have a solar input and can integrate and/or automatically switch between alternator input and solar input.

5 They act as an isolator themselves, so you don't need a VSR or "smart relay".

To answer your question in your follow-up, "so all I need to do is get a heavier gauge cable and that should suffice do you think?"...

If your alternator output is up around the 14.2 to 14.4V then YES, it will suffice but in my opinion not be ideal.

If your alternator is temperature-regulated or controlled by the ECU then it is likely to be low output, in which case my answer is NO, big cabling will not fix the issue, a dc-dc charger would be the better approach. There are plenty of threads on this, it's worth doing some research. And have a look at the articles in Power add Electrics here on ExplorOz.

Cheers

Brian01,

Can you please explain why an alternator can't full charge a battery a why a DCDC charger can?

As mentioned previously, if you do a search you will find all your answers.
Sorry if I appear rude or a bit short, but this topic has been done to death. The truth is already out there.

I'm at a loss to why you even bother posting John.
Dave.

Because some people are either stupid or lazy, and need to decide which. And it's Regina.

David M
If you are as pedantic as someone else you, according to his reply have to include it as:

John and it's Regina.

Oh, bugger,
Both he and me forgot the BIG M

Smack on hand!

Into the corner for you Ross M. :)
Dave.

Leigh you know too well why an alternator cant charge a battery 100% and stop acting dumb trying to get someone to bite so you can tell them about your over priced diode fuse you sell.

Aah, the overpriced DCDC charger pusher returns.

Please fell free to actually provide some hard data and not sales spiel to support your statement.

I'll be providing some real time data recordings of the the performance of a basic vsr versus DCDC charger in the near future, how about providing some of your own instead of hot air for a change?

Sure if you gave Anthony Kittle from Redarc a call he would love to talk to you are provide the data you request.

Oh and overpriced.....yes i suppose they are but i am pretty sure they don't make a 5000% markup as some do!

Im not the one trying to sell on here.

olcoolone,

You know dam well that Redarc will not provide any information regarding the performance of their DCDC chargers compared to alternator charging in an under bonnet situation. I they would and it supported your claims you would have plaster it all over this forum long ago to support your claims.

They always to refer to modern vehicle charging systems high compensated alternators and sytems used on vehicles such as the BT50.

Ahhh thank you olcoolone.
Now I know why he pushes direct alternator charging so vehemently.
A bit like DS and his ulterior commercial motives on other forums.
I couldn't understand the closed mindedness, now it all becomes clear.

olcoolone,

Another of your totally untrue and unsubstantiated claims, you have know idea what my production costs are, and having what would appear to be little real technical knowledge never will.

I would suggest you stop making rash claims and leave the technical work to your staff who hopefully know what their doing.

I also notice you don't attack ABR who has similar pricing to me yet his unit is manufactured in China and not Australia?

Brian,

It clearly shows on my posts;

Classifieds Alternator Voltage Booster!

Yes I support my product as well as other Australian made goods when they deserve it.

My unit as well as ABR's are used in thousands of vehicles by their happy owners both here and internationally.

Also Brain,

As I asked olcoolone, rather than quoting glossies and saying all this has been covered, how about providing some hard data to support your claims regarding DCDC charger superiority, Redarc won't maybe you or olcoolone will back up your claims?

At least Derrick from ABR Sidewinder doesn't rubbish other manufactures proven products nor try and sell his own over someone else's.

He gives true unbiased advice and i praise him for that...... Top guy.

Its no secret I sell, fit and service many product including Redarc along with many other products a 4x4er would use but i'm not here to sell or make money from forum users nor sway them from one brand to another....... My market is heavy vehicle, earthmoving, mining and large fleet.

I have a simple outlook, supply the best and don't compromise, why supply something that does 75% we i can supply something 100 % and be proud to put my name to.

Leigh you have to understand your product does not work to 100% but a DC-DC charger will. And you also have to understand people have different view points and you have to accept the..... Offering unbiased advise would also go a long way.

I think i could honestly say Redarc and the other DC-DC manufactures would of spent 100's of thousands of dollars testing and developing their products...... And you.

Your the one who can on here attacking Brians and Franks advice saying how wrong they were and trying to throw doubt in the mix to get a sale........ Maybe next time you should not say anything.

True, everyone has a right to their view point so why is it every time I point out a simple VSR will do just as good as job or better you so vehemently attack my opinion?

By the way Derek also found when testing his 150 setup that a simple VSR and booster diode worked as well as a DCDC charger under bonnet which is why I assume he is still marketing them.

I did not attack Brian, I just asked him to provide some hard data to justify his DCDC charger claims, as I have asked you, you obviosly have the resources to do some on road testing and data logging and I would have imagined you would have done so before selling these devices to your customers but you seem adverse to supply any, same as Redarc.

I have once again asked redarc to supply some information regarding recharge times, SOC achieved etc of their standard VSR comapred to their 20A DCDC charger when connected to a standard alternator.

If they ever respond I'll post their response.

I am not even going to dispute your claims. yes your product is far superior and I can not understand why anyone would spend 10 times more than your product if it delivers 100% the same results.

Same goes for a old fashioned battery charger, why do people spend their hard earned money on multi stage 240v smart chargers when the older type just does the same and the same can be said for MMPT solar regs over conventional.

It has nothing to do with charge times but a DC-DC charger will achieve 95-100% SOC..... its about giving you battery the best you can.

People spend $50,000+ on a 4x4, another $15,000 on accessories, $40,000+ on a caravan or camper, $600+ for a dual battery system but the don't want to spend another $300 on a DC-DC charger....... most spend more on beer and smokes in a month.

Its like most things in life; many are looking for the 5,10,15% improvements and are willing to spend the coin......a few aren't.

So your device will provide the exact same 100% results everytimes as a DC-DC charger for 1/12 the money?

ocoolone,

A redarc basic VSR when used in conjunction with a standard alternator or boosted one in the vast majority or under bonnet, in car or trailer installs will give either superior or similar results to that that can be obtained with a 20A charger.

I as already wrote if you have a large caravan then you would need to look at that on an individual basis.

When I able to contact Redarc I will have an in depth discussion with their technical expert regarding the same and post the results as I have already written.

I will also ask them to comment on your one stop solution suits all policy and if that is also the policy of Redarc.

Cheers
Leigh

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Yes your right John, some people are just stupid or lazy

I don't mean to insult anybody in particular, but this

Can't Charge fully aregument is all over the place and sorry......most of the argument is complete and utter rubbish.

The battery manufacturers data sheets and application notes simply do not support the notion.

Anybody who is interested can go and look up a battery data sheet.

look for charging voltage....most will specify a wide range of charging voltages.

Typically they ( those that publihs good sheets) will have two charging voltage specs....cyclic or boost charging and float charging.

I am yet to see a lead acid family battery that does not specify somewhere arround 13.8 volts and a float charge voltage, most will specify a cyclic charging voltage in the reigon of 14.2 to somewhere under 15 volts.

Yoi can and will fully charge a battery on the specified float charge voltage...but it may take some time.

in general flooded unsealed batteries where limited to 13.8 volts as a long term charge voltage because higher than that would result in excessive fluid loss.

Modern sealed batteries will tolerate higher long term charge voltages with out fluid loss because they have changed chemistry..and they are sealed and work on recombinant electrolite systems.


Many crude old chargers had a high low charge switch..on low they where arround 13.8 volts...maybe a bit more, on the high charge they where arround 14.5 to 15 volts....but off load the voltage creaps.

nothing new here...this is 40 year old battery chargers.

The major reason we increasecharge voltage is to increase the rate of charge...pure and simple.

The second reason we do so in sealed batteries is because SOME exhibit charge resistance when over discharged or left idle....they require higher voltage to over come this....but this is a different issue to "wont fully charge".

more soon

As for why there are and whay people buy multistage chargers, DC to DC chargers and the like.

Predominantly they buy, because they have been SOLD, not because they realy know any better or understand.....for good or bad they buy because they have been SOLD.

There are very good reasons to use multistange chargers....and they ALL revolve arround charge rate.
The single overriding reason for multistage chargers is to charge the battery as fast as is safe and good for the battery, without boiling its innards out.

The multistange charger charges as hard as it can, until the battery reaches a certain stage of charge ( this varies) then is drops the charge voltage back to a safe long term voltage.

There may be other tricks....but the above is the overriding reason...and it is as simple as that.

more soon

oh you lovely Batman, there is after all an almighty!

You can now take the barrage and i can duck into the trenches for a rest!

Now where the rubber meets the road.

If you have a dc to dc charger with a maximum chaging voltage of 14.5 volts and a current limit of 20 amps
.
AND
.
You have an alternator with a maximum charging voltage of 14.5 volts and capable of delivering 80 amps total.

Assuing the wiring is adequate and the battery will accept high charge rates and tolerate the charging voltage long term.

The alternator will charge the battery faster and will produce exactly the same state of charge as the DC to DC charger.

That is simple physics..and "Ya cana change the laws of physics JIM".

There are very good reasons to buy a DC to DC charger, but none of them are because you can not fully charge a battery from a car alternator.

Good reason to buy a DC to DC charger.
#1 because you want to use it to merge multiple charging sources automatically

#2 because the battery you have chosen has a limited maximum charge rate and the DC to DC charger acts as a current limiter.

#3 because you have an installation with inadequate cabling and voltage drop is an issue.

#4 because the DC to Dc charger may provide other features such as monitoring facilities or pulse desulphation.


the main reasons why people fail to fully charge their batteries are.

Failure to allow sufficient time...very common.

Failure to wire is sufficiently heavy wire...it does not need to be rediculously heavy...again very common

Failure to have sufficient battery capacity and be constantly hammering into deep discharge....yet again very common.

but mostly combinations of the three.

All too often people do not want to hear the simple truth, they will much prefeer to believe it is not their fault and that there original choices where not the problem............and be told they should be using AGM batteries and DC to DC chargers.
Both of which as high margein items suitable for mail order.

cheers

I have to say Leigh that I hadn't been back to this thread since my last post, but your rant on the pedantics thread caused me to have a look at what you were talking about.

You don't think for a minute that Mathew from Redarc was just blowing you off, as some of those answers are in direct contravention to both Redarc's stated policy and established fact.

As long as you and your customers are happy with the way you do things, then once again I'll leave it at that.
I got a headache from the brick wall last time.

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The Ctek 250s dual is fine provided the alternstor input does not fall below 12.7v as that device can't handle voltages lower than that. For most newer voltage controlled alternator vehicles, you would do better to get a different DCDC charger, and if you want an integrated solar controller as well, then the Redarc would be a better choice.

There is either a 250S update or a workaround for the low voltage alternators.
The 250S has a solar panel input and regulator which works well.

There is Ron.
It involves a relay to connect the alternator to the solar input when the motor is running and to connect the solar to that input when the motor is not running.
The minimum input voltage is still very restricted as compared to other DCDC chargers available.

oh beauty I didn't think there was one! thanks mate

athdaddy
Now you have the aux battery fitment decided, make sure you mount the battery so it has a cushion pad to sit on and the clamping arrangement used also has some "give" of cushioning to it too. Not squashed hard into it's mounting.

That is so any sudden movement, vibration or road shocks experienced by the vehicle is not then hammering the insides of your battery to pieces.
Also, the "give" tries to absorb forces which are the cause fracturing of spot welds and bracketry on inner guards in an engine bay.

If mounted under the tray and the battery is not cushioned, it will be receiving the shocks the chassis is suffering.
The cushion may allow you to use the life of the battery instead of it failing internally by being physically destroyed.
Charging is one thing, a smooth ride is another.

Cheers
Ross M
PS Most people don't seem to cushion the battery for some unknown reason.

Leigh W
I also hold the same viewpoint, and while DC/DC chargers do work ok and are often recommended by many, they aren't necessarily the only way.
I added two series switchable diodes to my HJ61 which originally charged at 13.8v and switching in one diode raised it to 14.4v which is the 0.6 v extra created by the diode. With the two diodes series switched into alt sense wire the voltage ran at just under 15v if required to overcome voltage drop. Second wasn't used/needed.

With the main and then aux in the engine bay, and one in the back and also one via Anderson in the camper they all charged and ran at whatever the alt voltage was at the time. I never saw the batteries not charged, from the DC pump ie alternator at the front. The Aux system was around 300ah. All aux topped up by 200w of solar.
Cheers
Ross M

Hi Ross,

Yes as you, myself and many many more have found a DCDC is simply not required.

Yes they have their place but in a majority of installs just aren't required generally increasing recharge times considerably not reducing them as widely believed as the figures I quoted prove.

I have yet to see anyone provide any hard data, is is always I have been told, I believe or I read somewhere.

Cheers
LeighW

A couple of points to consider with what you guys are saying above.
1. Not sure where you get that first bit about a DCDC charger not reaching full output until the battery is 80% charged Leigh, that's about when they start to throttle back.

2. After starting the vehicle, the initial discharge will cause the alternator to up its output which will cause the main battery voltage to rise rapidly. This won't take hours but just minutes due to surface charge taking time to be absorbed.
So the DCDC device will turn on very soon after starting irrespective of the true Soc of the main battery, and for the same reason the battery will not accept a large charge current.

3. The alternator output responds to the voltage of the main battery, and as that will rise very quickly as stated in point 1, the output will drop back to just enough to run the electrics.
For more on this I suggest you research how an alternator/regulator combination really works.

4. While the alternator may be capable of outputting 14 or so volts, the computer will ultimately control this, and it may be considerably lower than that.
5. If you are determining that your batteries are fully charged at the end of a drive by voltage measurements alone, then you really have no idea where your true state of charge is.

After all of the above, if you are happy to continue with direct alternator charging then that's your choice.
There has been enough anecdotal evidence available to contradict that view and is the reason that so many manufacturers have spent many millions of dollars developing these DCDC devices.
If only they had known what you know. lol

G'day Brian 01
I don't know figures of DC/Dc chargers but do understand the concept.

With your point 2,

After the engine starts ie 150amps for 3 seconds, Not many AH there so the main battery will be charged shortly after as you said and yes a DC?DC will begin operation immediately, so will a VSR or same if manual
solenoid is switched on.

Point 3.
I agree the alternator reg reacts to the voltage of the battery system connected to it, however with a solenoid/VSR OR a DC/DC connected the voltage of the seen at the terminals of the main battery will decrease as soon as ANY load is seen there. Leaving equalizing flows out of the equation, the lower voltage will cause the alternator to be readily supplying ampere flow to try and return the voltage to the original value.
Since the main IS charged the lower SOC of the rest of the system is then absorbing the amp flow from the Alternator and possibly this will faster than a DC/DC if the alternator peak voltage is suitable.

Yes, you do have to understand how a Reg/Alt combination works.

Point 4. Not all vehicles have Computer controlled alternators and only IF they do is the DC/DC the thing which will positively charge the battery/ies to a decent level.

Point 5.
The batteries will charge up and if it is by Alt or DC/DC the voltage measured by anyone at any time will see what the system voltage level is. No one will really know what the SOC is.

if the SOC is being measured by a sophisticated AH IN/OUT register then that may be more effective to determine SOC. Again and extra cost and the DC/DC is a cost in itself.

I like DC/DC chargers and what they can do but they are promoted as though they are the only thing, and being the tech society we are, now everyone just blindly accepts they are the only way to go and nothing else is any good.
How did all the people who have used battery systems before DC/DC chargers ever survive?

I agree manufacturers have spent $$$$$$$ on development of the systems, yes to prolong battery life and have a good charge in some situations but also to sell the gear to make money too. Always have to include the profit factor.

Often, less well healed, 4wd users have spent most of their available budget on actually owning a 4wd and would still like a cold beer or frozen/cooler tucker.
Therefore, it doesn't really matter if manufacturers had known or not known what you claim we think we know, and that issue often is mentioned when someone still has a slightly differing to what is being promoted.

For the price of a DC/DC charger, One can buy suitable cabling, solenoid, and batteries and some solar and keep their fridge cold too.

When I have extra cash and the batteries are not lasting or flat all the time, somehow, I might buy a DC/DC unit too. They are good kit no doubt.
There are more systems out there without DC/DC units than there are with them but with current (no pun intended) thinking it will change.

Cheers
Ross M

Brian,

I would suggest you actually research your facts before commenting,

Point1 a DCDC current limits its output ot protect itself from overloading, this means its output voltage starts out low and gradually rises to its maximum output voltage at around 80% SOC then it reverts to constant voltage charging same as used by the alternator, ie it sits on 14.4V.

Point2 Starting a car does not cause a normal alternator to up its voltage, its output voltage is purely dependent on temperature unless it is an engine management system controlled type and very few are. As I alreadt wrote the alternator output voltage will rise to its maximum with seconds of the motor starting not sure what your on about.

Point 3 is incorrect for 99.9% of vehicles it only applies to the engine management controlled types, ie the Madza BT50 and a couiple of other models, certainly no Toyota, Nissan 4x4 use this system. I suggest you actually do some research, all standard alternators are temperature modulated only, ie its output voltage will be around 14.4V @ 22C and will vary slightly up and down as the temperature changes in line with its temperature compensation profile.

Point 4, again only applies to the very few ECU controlled models.

Please actual to some real research before making brash claims.

Even Redarc will tell you you don't need a DCDC device if you have a standard alternator.

Cheers
Leigh

Leigh, at the risk of going through it all again I will make some comments on the points which you dispute.

1. The DCDC will only limit its output voltage in the early stages due to over temperature, its first charge parameter is bulk with constant current where it attempts to input as much current as the battery can take. The only way to do this is with a high voltage which it will supply within its design limitations.
Its output voltage is there from the start.
In the case of the Redarc unit which you mentioned, it does not have a soft start feature, it stops its output every 100 seconds to see what the battery voltage has risen to and will only reduce that when it goes to the next stage or due to temperature.

2. Starting the car takes quite a bit of energy from the battery, which depresses its terminal voltage a few points. The regulator sees this and causes the alternator to output extra current to bring the voltage back up.
An alternator's output is not purely dependent on temperature at all. Whilst that has an effect in some vehicles, the primary control on all alternators' outputs is the regulator, (and that is controlled by the battery voltage) which still exists in some form or other even in computer controlled cars

3.Ever since alternators and regulators took over from generators the regulator has controlled the alternator output. It did this and still does in non computer situations purely by responding to the terminal voltage of the start battery.
Apply a load - battery voltage drops - regulator increases field current - alternator outputs more current - battery voltage rises.

4. Even in the most basic of electrical charge systems there are times when the alternator is outputting no voltage at all.

To your points Ross:-

3. You should get together with Leigh as he doesn't agree that the alternator output is controlled by the battery voltage.
With the 2nd battery directly connected to the first, surface charge on the first will cause the alternator to cut back its output and surface charge on the second will reduce the potential difference between the two batteries which will limit the transfer between the two. This has been the eternal bugbear of alternator charge systems.
4. For the reasons given above, the DCDC charger will always provide a superior charge.
5. Many DCDC chargers have LED indication to show which mode they are in. If it shows float then you can be pretty sure the battery is fully charged.
What indication do you get with direct alternator charging?

An auto elec friend and I did a test some time back the results of which I posted on another forum.
Basically, we connected a charged start battery and a partly discharged deep cycle together via a 6 metre circuit of 6AWG and hooked it all up to an alternator and regulator on his test rig.
The initial inrush current was impressive with roughly 45 amps going to the 2nd battery. However, in less than ten minutes that current had dropped back to just a couple of amps and remained that way for the rest of the time.
Voltage readings on the 2nd battery showed it to be at a constant 14.6 volts while the set was running but showed the same when the battery was disconnected, and only slowly dropped.
The reason was surface charge, and this is why the direct alternator can't do the job.
As I said before, if you're happy with your setup then stick with it there's no more that I can add here.

Brian,

I stage constant current charging, a severely depleted battery has a very low internal resistance, it will draw considerable more current than a 20A charger can supply and would destroy the charger. To overcome this the Redarc and others current limits their chargers output current for 20A chargers to 20A maximum output. If you have idea as to the charging requirement of a typical high capacity lead acid battery you would know that you only need to apply a charging voltage of .5V or so above the terminal voltage of a a "flat" battery to achieve recharge currents well in excess of 20A which is why the charger needs to protect its. Yes it will charge at 20A but it does not need a high output voltage to acheive this when the battery is low. As the battery charges its terminal voltage gradually rises at around 80% SOC, as shown in Redarc's own figures in their specs and graphs, I suggest that you you actaully go and have a look. They also show when the output voltage reaches 14.5V the charger switches to constant voltage charging. At no time will the voltage exceed 14.5V again their figures.

Current is determined by the applied voltage and and load resistance, a depleted battery has a very low internal resistance and not a lot of voltage is required for a large current to flow.

2/ The regulator does not see a flat battery and apply more current, you appear to not understand the difference between currently regulation and voltage regulation. An alternator voltage regulator regulates the voltage, it maintains the voltage at a set level, the battery takes whatever charge current it wants of the alternator, the alternator does not regulate the charge current to the battery only the applied voltage which is dependent on the ambient temperature.
The alternator has no idea as to how much current is flowing in the electrical system nor does it care, BT50 excluded.

I suggest you refer to the DCDC manufactures websites and read up on how their chargers actually work.

I also suggest that you refer to texts on how automotive alternator regulators work and the difference between current and voltage regulation.

As for the statement your friend measured the applied voltage to the battery at 14.6V due to the surface charge and this why you can't charge the battery is pure rubbish, did you actually read what you wrote?

As already pointed out, Redarc specify the max output voltage of their charger is 14.5V, certainly it is accepted that 14.2V to 14.5V is the ideal voltage to charge a battery and why both normal alternators and DCDC charge at this voltage. If 14.6V is applied to the battery it will fully charge given the required time be it off an alternator or a DCDC charger.

Yes if you connect the alternator for say to minutes it will force the batteries terminal voltage to 14.4V and yes the battery isn't fully charged as how could it in two minutes and yes the voltage will gradually decrease when applied voltage is removed, the exact same thing will happen with a 60A DCDC charger for example on a smaller capacity battery as it has the current capacity to force the batteries terminal voltage up. A 20A charger doesn't, and that's why a DCDC charger initially constant current charges to protect itself. An alternator will also current limit due to its design but as it generally has much more current than a DCDC charger it can force the batteries terminal voltage up to its float voltage it will only be apparent for a few seconds.

Leigh

I forgot to add,if you need a light to tell you when your batteries are charged how did you ever make the determination they weren't being fully charged by an alternator, let me guess the salesman at Redarc?

you do, drive till the fully charged lamp lights?

I have carefully engineered my system, it works very very well and not a DCDC device to be seen, do a need a light to tell me the batteries are charged, I know how much I take out of the batteries and I know how long I need to drive to recharge them. I do monitor the battery voltage to ensure the system is performing as expected and to monitor the battery capacity.

In most cases people never drive long enough to fully charge their
batteries if they actual use them and like most supplement with solar while camped for extended periods. Much prefer to spend my hard earned cash on batteries and solar panels than DCDC chargers that aren't required.

I will only answer a couple of your points there Leigh as the others are just going over old territory and I hate bashing my head against a brick wall, but contrary to what you say, a severely discharged battery actually has a high internal resistance.
This is because the acid in the electrolyte is gradually absorbed into the plates until at dead flat the electrolyte is pure water which has a very high resistance, plus the gradual build up of lead suphate on the plates acts as an insulator between the electrolyte and the active plate material.
I don't expect you to believe any of the above and normally don't resort to posting web links but you seem to need more proof, go to this link and see for yourself.
Have a look at the graph, you will note that internal resistance is highest at low Soc when charging first begins, here's another one, go to the heading "operation of lead acid cells".
Not quite what you are saying, but then perhaps they are both also wrong.
I'm sure you can google more of the same answers.

Calcium Calcium batteries are renowned for this where in some cases they will even refuse to accept a charge when very flat due to their high internal resistance at this Soc.

It's easy to tell that you aren't getting a full charge from an alternator simply comparing the available capacity to the rated capacity.

The surface charge "rubbish" that I posted is easily verified and an accepted fact with lead acid charge and discharge technology.

Brain,

Yes a flat battery has a higher internal impedance than a fully charged one, however what you seem to have missed is a battery is not a linear device, its internal impedance changes as the applied voltage changes ie

If we apply 14.4V to a fully charged battery is charging current will be around a couple of amps or less after a short duration.

If we apply 14.4V volts to a battery with an SOC of 0% the inrush current with be huge and again referring to Redarcs documentation the current is expected to be greater than 20A till the battery reaches 80% SOC or there abouts at 14.5V for an average battery.

Quite clearly to a charging voltage of 14.4V a battery has a lot lower effective internal impedance when it is discharged to what it has when its fully charged.

ie a fully charged battery connected to and alternator floating at 14.4V will draw about 2A, its effective internal impedance is therefore about 7.2 ohms.

A fully discharged battery at 14.4 volts will have a inrush current of around 100A, effectively its internal impedance is around .144 ohms with respect to the charging source.

A battery can't not be treated as a linear device its impedance is dynamic depending on the applied charge voltage and current or discharge current.

The rubbish is was referring to is claiming you can't charge a lead acid battery with 14.6V

Leigh W wrote in Followup 806475
"its [the alternator's] output voltage is purely dependent on temperature unless it is an engine management system controlled type and very few are."

The list below is from the TJM website. I don't think it's intended to be definitive.

However I think it represents more than a "very few" - it covers a good percentage of commonly used 4WD tourers, though the OP's D22 Navara seems to have escaped.

[Begin quote]
Temperature compensating Alternators

Some post 2000 model vehicles have temperature compensating alternators. Mainly vehicles fitted with common rail diesel engines utilise this style of alternator. The temperature compensationg alternator will charge at approx 14V when the engine is cold, and decreases to 13.4V when the engine reaches operating temperature. For this reason, the alternator may only charge a dual or multi auxiliary battery system to 60-70% state of charge at best, depending on the battery chemistry type used.

Known vehicles with this style of alternator - Toyota Hilux, Prado, LC200 LC7679 D4D Common Rail Diesel. Petrol Kluger 2010 on and BF Falcon

Variable Voltage Alternators

Some vehicles released in late 2010 onwards with common rail diesel and petrol engines have variable voltage alternators that are on the vehicle CANBUS. These alternators vary output based on driving conditions at the time. The range of voltage can be between 12.3V and 15V For this reason, the alternator may not charge a dual or multi auxilary battery bank at all times, and may apply too high a voltage for the auxliary battery chemistry type at other times.

Known vehicles with this style of alternator - Nissan Navara D40, R51 Pathfinder 2011 onwards V6 Diesel only. Hyundai Santa Fe 2010 +, Range Rover 4 2011 +, Ford Ranger 2011 +, Pajero 2012 +, Mazda BT-50 2011 + and Land Rover Disco 4, Isuzu D-Max 2012.
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If having an alternator on the CANBUS means it is ECU-controlled, then add D4D Prado 2007+ to the second list.

I do not wish to become involved in the technicalities of whether or not an alternator charges a battery better than a dc-dc charger or vice versa. But I do think that the list suggests that a dc-dc charger for a second battery might be the optimum charging solution for a wider range of vehicles than many people think.

Cheers

There currently three main types of charging systems employed:

Normally temperature compensated alternators.

High temperature compensated alternators.

ECU controlled alternators, ie controlled by the engine management ECU.

99.9% of vehicles in Australia use one or of the first two. The output voltage of these alternators is controlled by the alternator voltage regulator with modulates its output voltage on temperature.

The high compensation types, lower their output voltage more than a standard alternator in response to temperature to reduce vehicle emissions and fuel consumption. This can be simply corrected by use of a booster diode to restore voltage levels to normal.

Very few models are currently ECU controlled types as I already pointed out, these vehicle may or may not be controlled by the can buss, for instance when I checked the latest NAVARA service manual the alternator is controlled by the engine management system but not via the can buss. The can buss is simply used to connect to different items of equipment by use of common wiring rather the individual wiring each component. On some of these vehicles it may also be possible for the dealer to disable the smart charge function so I would suggest if you have one these vehicles talk to them.

As for fully charging a battery basic chemistry states that as long as the applied voltage is greater than the resting terminal voltage of the fully charged battery the battery will eventually fully charge, it will just take longer. As I have not seen a fully charged battery with a resting terminal voltage of 13.2V (full calcium excluded) any voltage in excess of that will eventually fully charge most batteries. Having a higher charge voltage is obviously desirable if possible to shorten reach time.

Alternators controlled by the can bus....... Please stop me from laughing and please learn what a can bus actually does and what it would be used for.

A can bus doesn't control anything in any vehicle and it never will.

olcoolone,

For such a self professed expert it would be nice if you actually new what you were talking about before commenting:

"Automotive

A modern automobile may have as many as 70 electronic control units (ECU) for various subsystems.[3] Typically the biggest processor is the engine control unit (also engine control module/ECM or Powertrain Control Module/PCM in automobiles); others are used for transmission, airbags, antilock braking/ABS, cruise control, electric power steering/EPS, audio systems, power windows, doors, mirror adjustment, battery and recharging systems for hybrid/electric cars, etc. Some of these form independent subsystems, but communications among others are essential. A subsystem may need to control actuators or receive feedback from sensors. The CAN standard was devised to fill this need.

The CAN bus may be used in vehicles to connect the engine control unit and transmission, or (on a different bus) to connect the door locks, climate control, seat control, etc. Today the CAN bus is also used as a fieldbus in general automation environments, primarily due to the low cost of some CAN controllers and processors."

Sounds like it can be used to control one or two things to me, and members seem to believe you actually know what your talking about, most of the time you don't!

Leigh a can bus does not control anything, it is only a pathway for communications between ecu's and in turn the ecu talks to the controller by either a simple on/off signal or a frequency divided signal, the controller as in a stepper motor may send a simple reference back to the ecu that the ecu can understand from a programmed map but it is not on a can bus.

Why do you need a high speed communications to open and close a door?

It's a basic logic device.

But the door locks may talk to the ecu by a simple output/input and the door lock ecu will send and receive simple signals from the door lock, the ecu that the door lock sends and receive the simple signal from may be on the can bus that will talk to other ecu's like the BCM.

Can bus is only used in applications where a lot of data is to be transferred between ecu's.

A controller and ecu can be combined in one unit for ease and the ecu may be on the can bus but internally the signal from the ecu to the controller is just a straight analogue signal.

A controller has to have an ecu to understand the can bus data.... The can bus does not control anything mechanical, the ecu that may be on the can bus that sends a basic signal to the controller that does the mechanical work.

The can bus has no energy to do anything other then provide a high speed data communication link.

A Computer USB cable is a Basic form of can bus, the computer sends data to an ecu. All printers have an ecu inside that interprets the data from the computer and sends it to the controller inside the printer that prints the image.

Like can bus the more data that is transferred need higher speed and band width to stop bottle necking hence why we have USB 3 on computers, automotive is no different.

Basic things in automotive don't need can bus.


And please don't make personnel attacks at me.

ocoolone,

Please I have worked with computers for 35 years, desk tops, mainframes, distributed processing.

Your the one that ridiculed the OP, it was quite clear the poster was indicating the alternator could be controlled via the can bus, and yes it could, as you wrote you only need an interface and some firmware and you could make a bum scratcher work over it. I believe a couple of companies have already released expansion units to allow adhoc devices to be connected.

I wrote an alternator could be controlled via the can bus same as a printer can be controlled over a usb connection and just about every other peripheral these days, seems like everyone else except you that read it understood what was meant. How about you minding your own business next time instead of jumping in ridiculing members.

By the way I seem to remember once mentioning to you in another forum if the vehicle manufactures thought smart charge functions were so good it would be a simply thing for them to implement them in their vehiclescharging systems, you ridiculed me at the time, funny thing isn't it that that is just what they have done on the BT50 for example, not because the battery needed it though but to reduce fuel consumption and pollution emissions instead.

I don't know what other way i can explain it....... A can bus does not control anything, can bus is just a high speed communications link between two or more computers allowing data flow back and forth.

If more then two computers are on the can bus it means the computers can communicate with each other instead of one computer telling another computer to tell another computer what to do, it gets rid of the middle man or it can broadcast and receive data to a group of computers.

A can bus is no different to a road where the car uses the road to get from one point to another....... The road doesn't control the car.

A ecu that controls the alternator can be on the can bus to communicate with other ecu's but it does not communicate to the alternator by can bus unless the alternator has an inbuilt computer that controls a controller that in turn controls the alternator by a basic analogue signal.

The data the alternator uses and sends is very very basic and does not need to be on the can bus....... Most of the time it is on or off, most ecu controlled alternators are frequency driven and frequency driving is a simple on and off signal.

Geez,

It is an expression, your grasp of English can't be that bad!!

Controlled via they can bus, the engine management system wants to command the alternator, it sends a request thorough its I/O via the can bus to the alternators can bus interface which then does whatever needs to be done to get the alternator to do it, maybe as simple as changing the voltage level on a wire that runs to the alternator.

It is an express, controlled by the can bus in difference to controlled by a hard wired circuit form the ECU to the alternator.

To answer previous question, why would one control the door locks via the can bus? the can bus was introduced to reduce the amount of wiring required in a modern vehicle, reducing wiring reduces weight and improves fuel consumption, within the next 10 - 20 years most of the vehicles wiring will disappear altogether, it will most likely be replaced by fibre optics and a power bus system.

Are you talking about multiplexing and nodes?

ocoolone,

I tire of this discussion, there was nothing wrong with what FrankP posted, you should have just let it go.

awesome information! I was going to go with a big battery now seeing as though I've decided on an under tray mount.

all I want to run is a 40 litre engel and a couple of lights here and there so i'll use the redarc isolator I already have and if any issues arise i'll rip it into an auto lec.

Thanks heaps mate

Now to some individual issues.

Having established that under the bonnet is possibly the worst place to have a battery, lets move onto issues.

Mounting
above all the battery must be firmly mounted and on a substantial bracket.
I bit of rubber is going to do not one single thing to absorb the sort of vibration involved.
Unless the battery carrier is fully suspended ...like an engine mount...rubber will do bugger all for vibration.

It is wise to fit a thin 2 to 3mm thichness of rubber under your battery from a traction and load restraint point of view.
With rubber it will require less downward pressure to stop the battery moving around....a little rubber under the battery strap may be of use for the same reason.

All too often the battery mounts..and I include the factory ones are not strong enough don't support the battery well and are not mounted to strong enough structures....THIS is where the excess vibration comes from.
I make a distinction between vibration and shock.

If a battery is well suported under its base and the tie down strap distributes it pressurte, batteries will take quite a bit of compressive force.

I have no beef with mounting a cattery to the chasis...if you are mounting a plastic box full of lead and acid that weighs 20 odd KG (the weight of a skinny girlfriend if it two batteries), you need the strongest thing you can find to mount to.

Select a batter that is specifically designed to cope with vibration...like a marine, earthmoving , minimg or 4wd battery.

more later
cheers

Having run a single 32litre fridge off an N70, I can tell you I will be building a bigger battery carrier and fitting two N70s or a T105 traction battery or some such as time permits.

That will give about 200AH.....which I think is enough without going silly.

On the matter of voltage drop.
We don;t have to go silly here.
#0 battery cable is just rediculous.

Unless you plan to winch or crank off the second battery 10mm2 solar twin will be plenty big enough to overcome the voltage drop issues when charging.

Most of the dual battery kits come with #8 which is close enough to 8mm2......just on the verge of being adequate.

You could run 25mm2 (#3 battery cable), but unless you are winching any bigger is way overkill.

cheers

Now choice of battery.
I have chosen to run marine cranking batteries in both starter and auxiluary positions.
Firstly because I want to winch off both batteries and secondly because it simplifies many things.

Sealed marine cranking batteries have many of the advantages of AGM and none of the drawacks.

One of the biggest issues is that I have two batteries that have the same charging requirements..I have no issues with dissimilar batteries.

The aux battery will also take as much as the alternator will stick at it.

Many of the AGM and deep cycle batteries have charge current limitations, that require a DC to DC charger or a current limiter to manage.

AND finally, marine cranking batteries cost half what a similar AGM spec will cost.
So I can either afford to buy twice as many and cycle them half as deep or replace them twice as often.

hope this helps.

cheers

Bantam wrote
"You could run 25mm2 (#3 battery cable), but unless you are winching any bigger is way overkill."

It was me who suggested larger cable. On reflection and considering the charging currents involved, I agree with you and accept the correction.

Cheers

I would recommend 3 B&S as a minimum, you can alway jumpstart from the aux battery and if you even had a winch you could alway bring in the aux battery to help take the load of the starter battery and alternator....... Plus the price difference in 8 B&S as opposed to 3 B&S only relates to about $50 more in the installation.

If someone is running certain AGM or deep cycle batteries, jump starting or winch assisting is out of the question.

For simply charging an aux battery 10mm2 should be plenty big enough for a battery under the tray.

25mm2 is not unreasonable.....but running #0 battery cable as was recommended is just rediculous.

cheers

A battery is a battery....... It is not advisable to use a deep cycle or AGM for long term high discharge applications as there are better cheaper solutions but for what I'm talking about the battery would not really care and would suffer no long term effects...... Same as everyday starter batteries don't like low discharge environments but many still use them with good results, ahhh only if it was a ideal world!

Yes 0 B&S is overkill and if anything it would be more of a installation hassle the anything.