Dual battery setup

Hi

Is the screw top fluid battery the ones with the 6 screw caps??. I bought a new DMax and that is the type of battery supplied.

Until a few years back it was the norm for charging systems to run 14.4V@25C, all car batteries back then were screw tops and not as good modern batteries using ultra pure lead in that they were more prone to gas, yet how often did you need to top up the battery?

I have been marketing my booster for over 7 years and never had anyone complain of excess water use in there batteries. I have also seen many screw tops go for over 6 years before being replaced and they have never needed to have water added.

Yes if you live in a hot enviroment you may need to add water infrequently but that has always been the case at normal charge rates and the reason the car manufactures specify you check the battery electrolyte levels at service.

Yep, I have a booster diode and have never needed to add water !

Serioulsy I don't know where you are getting this information of older alternators having anything other than a 13.8 volt nominal charging voltage.
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For as long as I can remember the nominal charge voltage on automotive systems has been 13.8 volts ...... yeh and there is paperwork and other information for days to confirm this.
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I've been arround cars and their electrical systems since the late seventies ...... I am a technician & I can read a multimeter ...... have always read around 13.8 Volts at the battery terminals and at the alternator, until I started seeing reasonably recent vehicels and recent replacement alternators. ..... weirdo euro cars don't count.
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Testiment to this fact is my 03 hilux ...... quite soon after I baught it I fitted a digital voltmeter ...... and that meter read 13.8 Volts all day once the battery was up to charge. ...... Because of the age of the vehicle I changed both the starter and the alternator in the interests of reliability ...... now the up to charge voltage reads 14.2 ish volts ..... which agrees with the documention that comes with the alternator. ...... not only do the instruments confirm this ..... there has been a slight bit more willing ness of the vehicle to crank.
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Having lived with screw top batteries in cars for a few decades ..... I can tell you they DO lose fluid and faster than many people want to be bothered about. ...... serioulsy .... tell me how many people check the fluid level in their own batteries.
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It is also a well known and documented fact in the battery business, that 13.8 volts was chosen as the nominal charge voltage because it was the best compromise between rapidity of charge and fluid loss ..... increase the charge voltage above that and fluid loss increases ...... there are graphs and stuff if you can be bothered looking.
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Now back to screw top batteries and modern technology.
A few decades back we saw little other than screw top batteries in cars ....... and those batteries represented the basic, pretty much undeveloped technology.
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Bottom of the market screw top batteries still are much the same as those basic batteries ........ lots of people when they replace a cranking battery are looking for the cheapest option ..... and this is what they get. ....... if you baught a used car ...... this is probably what you got.
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Moving to modern technology ........ quite some time ago it was discovererd that by adding certain other metals to the lead in the plates and changing the composition of the electrolite by adding other chemicals to the simple acid ..... gassing and fluid loss could be considerably reduced ....... to such a point the battery could be sealed. ... this gave us all the sealed battery technologies, " sealed maintenence free", "unspillable batteries", "starved electrolite", "gell" and when the marketing people got hold of it AGM.
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These same metalic and chemical changes, made to reduce gassing, also increased battery life, strorage capacity, and pretty much every other property of the battery.
As you move up the market from the basic battery, more of these metalic and chemical changes will come into play ..... Ya cheapest screw top batteries will be ya basic technology, move up the market and screw top batteries will have some of these improvements....... continue on up and more of this newer technolgy comes into play till we arrive at the top end "AGM" product.
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In any given situation a modern top of the range screw top battery will require considerably less maintenence than a basic battery ...... due entirely to reduced gassing and fluid loss ..due to these changes.
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It is very likley that in the upper part of the screw top market, those batteries will tolerate the slightly higher charge voltages ........ but regardless the fluid loss in any screw top battery will be higher with higher charge voltages ..... its just an unavoidable fact.
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As far as temperature ...... well a lot of us don't live in the south, so even in winter the battery will be warm because mostly they are mounted under bonnet ...... in summer under bonnet battery temperatures will reasonably be in the 40 to 50C + range.
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As far as temperature compensation in alternators ....... in the warmer pats of the country, that will be pretty much irrelivent, because under bonnet, both the alternator and the battery will be hot enough that any temperature compensation will have the voltage wound back to the minimum nominal charging voltage
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The reason why I caution about higher charge voltages and screw top batteries is .... because most people who buy a replacement screw top battery buy on price ....... so are very likley to buy a basic unimproved battery.
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As for me and my recommendation ..... I will never buy another screw top battery, because they are just bad value ....... then there is the maintenence and the unavoidable acid leakage.
Since changing over to exclusivly sealed batteries, I have no problems with corrosion on battery terminals and have not needed to top up a car battery.
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All the sealed batteries will tolerate a higher charge voltage ..... some will require it.
Hence the existance of booser diodes and the like.
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cheers

Quote "!4.2 volts is all good for most of the sealed type batteries ( a few not) ...... but if you run a screw top wet cell battery with a 14.2 volt or higher charge voltage you will have a problem with fluid loss."

No you will not have a problem with water loss. Batteries with screw caps are not minimum maintenance batteries. They are supposed to be gassed a little and loose some water if they are being fully charged. If they are not loosing a bit of water you are not charging them properly. They are fitted with screw caps so you can fully charge them and then replace the water.

On the other hand if you are loosing too much water you are flogging them too much and should do something about the charge rates. However in saying that, if you keep the water up to them you will not be doing much harm. Those batteries are much more resilient to overcharging than VRLA batteries.

Batman I don't know where you get your information from either, if you had taken your car into an auto electrican 19 years back and said it was charging at 13.8V@25C he would have told you you need a new alternator!

13.8V is considered the norm for batteries being float charged 24/7 and not for car charging applications, any car I have had since my teens charged at around the 14.4V@25C mark.

As for :

"The reason why I caution about higher charge voltages and screw top batteries is .... because most people who buy a replacement screw top battery buy on price ....... so are very likley to buy a basic unimproved battery.
As for me and my recommendation ..... I will never buy another screw top battery, because they are just bad value ....... then there is the maintenence and the unavoidable acid leakage.
Since changing over to exclusivly sealed batteries, I have no problems with corrosion on battery terminals and have not needed to top up a car battery."

I believe the battery manufacturers would disagree with you there, I don't believe there is anything such as unimproved battery, as far as I'm aware all batteries now made are calcium hybrid types and use ultra pure lead etc.

As for all sealed batteries will tolerate a higher charge voltage than a flooded type don't know where you got that one from but you had better talk to the charger manufactures as they disagree with you, Redarc for example:

Charge rate AGM/GEL 14.5V, Standard lead acid 14.9V

As for cars and from the web as if its on the web it must be right,

From wekipedia:

"The charging system maintains a fixed voltage of between 13.8 to 14.4 V, this value is adjusted to ambient temperature"

Another source on the web:
"At idle, most charging systems will produce 13.8 to 14.3 volts"

And another:
" What is the correct charging rate for my vehicle?"

Charging rate output from an alternator should be between 13.6 volts with load on
( headlamps ) and 14.4 volts with load off."

And another:

You can expect a 14.2 volt 85 amp Alternator fully loaded or unloaded to supply 14.2 volts up to and including 85 amps

From Bosch who also disagree with you:


To be more technical, from a few manufacturers servcie manuals:

Mitsubishi L200 nominal charge volt 14.4V
Hyundai Santa fe nominal charge volt 14.4V
Rodeo RA7 nominal charge volt 14.0V-14.2V
Navara D22 nominal charge volt 14.1V14.7V
Navara D22 nominal charge volt 14.1V14.7V
Nissan Path finder 14.1V-14.7V
Isuzu Dmax 2013 on nominal charge volt 14.4V
Mazda BT50 upto early 2013 14.2V

Some old models

Toyota Celica 1974 nominal charge volt 14.4V
Toyota Corona 1974 nominal charge volt 14.4V

The list is endless.

I come to a point where I can not be botheered any more..... but a couple of issues.

Valve Regulated Sealed Lead Acid VRSLA batteries represents a very very wide range of product ........ it actually encompasses every sealed lead acid battery there is ......... some sealed batteries, particularly the smaller ones have incredibly poor tolerance for overcharging. ........ on the other had there are sealed batteries that have incredibly good overcharge tolerance.

I doubt that I have ever measured a battery or an alternator voltage when either where at 25C ..... and mostly that will be pretty much irrelivent .... because once the car has started and run ....unless you are in the frozen south in winter the underbonnet temperature will be way above that.

As for the voltages selected by manufacturers such as redarc ...... again irrelivent because they are multistage chargers and they will fall back to a lower voltage.

as for ...... oh why bother

Nope ..... can't be bothered any more.

I don't know why Bantam keeps coming up with low voltage business. He keeps getting contradicted each time. Charging way back in the generator days was up over 14 V. I remember doing regulator overhauls on my Austin 8 (6 V generator) where a setting of 7.2 V was required at lower ambient temperatures.


HKB, it is interesting to see the Bosch temperature compensated graphs you included. Many members of these forums (including Drivesafe) deny they exist. Most of the vehicles I have owned I have kept an eye on the alternator performances. They all have shown that temperature compensation feature as the motors warmed up.

Yes I can't be bothered either simple fact is manufactures have lowered charge rates, older alternators have a higher charge rates than the current high compensation types, anyone playing around with dual battery systems will verify that.

If you buy a replacement alternator from a reputable source that is specified as a direct replacement for a specific model it should have the same charge voltage and characteristics as the OEM alternator. If you fit an after market higher output model etc then it may be different.

Modern screw top (flooded batteries) use very little water.

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I couldn't "be bothered" in the first place......... for obvious reasons. LOL

PeterD,

I have always found the technical support staff at Bosch to be helpful, full technical specs for their alternators is readily available from Bosch, you just need to ask.

Cheers
Leigh

Thanks Allan I like layman terms.I have read some much stuff about batteries made me want sell the Hilux and not go round Oz..it seemed like I need to be NASA scientist to figure it all out ... cheers Steve

Dumb question Allan wheres SunCoast.Just a little fact worked in Mildura sign saidMildura has more sunshine per year than any other populated place in Aus. Cheers

Stephen, "Suncoast" is short for Sunshine Coast, 100k north of Brisbane. Embraces Mooloolaba, Maroochydore and Noosa. Nice climate but no more sunshine here than there is gold at the Goldcoast. lol In fact it is overcast and showering today.

Silly me I thought new Nirvana I not heard of .I lived in Buderim in friends old hotel run as permanent residence.Loved the beaches .I been to many beaches in the world but SunCoast beaches In my opinion the best 8n the world Must be bit crowded now as when I was there many new housing estates and new road at the back being built through sugar cane...awhile ago hey .cheers

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Stephen,
A friend has pointed out to me that it is not the best arrangement to connect an AGM auxiliary battery via a solenoid isolator to the charging battery, even though this is often done. It is better to use a flooded deep cycle battery. Cheaper too!

So are flooded batteries same as marine battery. Cheers Steve

Steve, I have no experience with marine batteries. I'll let someone else answer that.

Allan
I have a flooded century deep cycle battery that is 9 moths old , I use it as my starter battery .
I am going to by an identical battery and run it in Parallel , in your opinion will the old battery affect the newer battery .

Cheers

Mark,
Interesting that you have been successfully using a deep cycle battery for cranking. There are some who would frown deeply at that, although I take the attitude that "what works-- works".

There are also views that to run two batteries in parallel they should be identical make & model and even of the same age. I have even seen it expressed that they should be from the same manufacturing batch!! However I have yet to read an authoritative article that explains just why this is so. Most negative expressions raise charging issues but there are thousands of vehicles using solenoid isolators where the cranking and auxiliary batteries are successfully charged in parallel.

I would believe that it is OK to run two batteries in parallel. Some 4WD vehicles are built with that arrangement to augment the Cold Cranking Amps. The only issue is that if one battery begins to fail with internal discharge it will cause discharge from the second battery and may affect the charging of the second battery although without permanent damage.

The two batteries need not be identical. They can even have differing Ah capacities. Each will only draw as much charging current as it requires and each will supply discharge current as it is able.
However, the two parallel batteries should be of the same chemistry type, i.e. both flooded lead acid or both AGM type. Also, the alternator output voltage has been designed by the vehicle manufacturer to be appropriate for a flooded cranking battery and may not be appropriate if this is substituted for a differing type such as AGM or Gel.

It is interesting though why you wish to do this. If it is to supply auxiliary devices (fridge, lights) while camping you would be wise to separate the two batteries by an automatic isolator to ensure that you did not discharge the cranking battery to a point where you could not crank the vehicle.

Thanks for the info Allan

I use manual isolator ( for simplicity ) , so its not always run in parallel .

I normally run 2 batteries but they both died about 9 months ago , and seeing that I had no big trips planned I only brought 1 battery. So in April I am doing my next trip and will need a second battery ( for the fridge , laptops and some lighting ), hence the query to you.

I use 2 deep cycles flooded batteries because at times I don't isolate the batteries plus they are more robust ( discharging )

Hope that makes sense.



Cheers

Thanks Mark,
Manual isolator is fine..... so long as you have good memory. lol
Before they died, what life did you get from them?

Allan

Don't seem to get more than 2.5 years 3 years max .

Probably don't treat them very well either !!.

Might be time to switch to Gel or AGM.

Cheers

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Hmmm, 2.5 years is not good. Maybe because the deep cycle doesn't like cranking demands.
You may do better to move it to the auxiliary duty and buy a new flooded starter battery for cranking.
Gel is not a good idea for a vehicle battery.... in camper or caravan maybe.
In any case, if you used an AGM or Gel you should also use a dc-dc charger to manage the charging. But that is $350.

Hi Guys

I don't want to butt into your conversation, but you may find the following interesting...

I use a Lifeline AGM deep cycle battery as my secondary battery. It gets a fair bit of use as "all" my non factory accessories run off it. Generally, I have no issues with it, but in saying that, they were only lasting 2 - 2 1/2 years and would often go flat. Others are getting 7+ years with no issues at all. I spent a lot of time (and money at auto electricians) chasing phantom currents, earth leakages etc, etc.

The guys at Battery World finally identified the problem - "do you put it on a battery charger to top it up after a big trip?"

Apparently, the alternator is not sufficient to get it back to 100%.

Solution - Keep Baintech VSR and put on 15+ Amp charger after a big trip or remove Baintech VSR and install a BC-DC charger. Went with the second and no more problems.

Cheers

Anthony

First off ACD 1, did all the others getting 7+ years out of their batteries have DCDC chargers, I bet they didn't.

How long have you been running the DCDC charger to determine your problems are solved?

How many deep cycle batteries did you go through before you fitted the DCDC charger?

What is your model of car?

Allan,
You wrote:

"The simple practical answer is that it is perfectly OK to use a 'flooded' lead acid cranking battery together with either a 'deep-cycle' flooded battery or even an AGM (Absorbed Glass Mat) deep cycle battery. Pundits may claim very minor differences in the ideal charging voltages but in the real practical world it is of no real significance.There must be thousands of this combination running around the backroads of Australia with satisfactory performance."

Then you wrote:

"In any case, if you used an AGM or Gel you should also use a dc-dc charger to manage the charging. But that is $350."

A bit of memory loose creeping in:)

Leigh HKB,

In between those two posts I also wrote an amendment..... "A friend has pointed out to me that it is not the best arrangement to connect an AGM auxiliary battery via a solenoid isolator to the charging battery, even though this is often done. It is better to use a flooded deep cycle battery.".....

Happy?

HKB

All are Landcruiser 105 2006 - purchased as a fleet buy (except mine - it was private)
All are fitted with Lifeline AGM.
All were retrofitted with dcdc chargers after Matson and Baintech VSR's failed (except mine - until the problem was identified)
All are on original lifeline batteries - except one which was damaged in an accident - (now just over 7 years old - except mine)

I replaced 3 batteries prior to this one, the longest lasting no more than 2 years 3 months.
Current battery has been in with dcdc charger for 18 months - no flat batteries, no charging issues and currently showing 13.8 volts (on dcdc monitor).

All of the other vehicles (5 in total) are owned by a mate who runs an Earth Moving business and the vehicles are used by his site supervisors (yes they are 2006 but he won't update them - he loathes Nissans and hates 200 series). He had the Lifelines added after he saw it fitted to mine. He fitted Matson VSR's because he couldn't get Baintech ones at the time.

I can verify the age of his batteries as his supplier stamps them with installation dates (something to do with warranty). The same supplier has sorted my issues (through the addition of the dcdc charger) and has stamped my new battery.

The same supplier has exactly the same battery fitted to his own 60 series and it is over 7 1/2 years old.

I'm happy to say that a dcdc charger on my AGM battery has now solved my problem.

Cheers

Anthony

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Anthony,
Those Lifeline AGM's looked good.......... until I looked up the price.
Hell, $640 for 100Ah. They would want to last 7 years!

Yes Allan!

I believe they are!

So much so, I am running three of them in my trailer. Yes they are expensive, but they have a good reputation - also milspec.

The last one that died (having worked out the issue) was replaced pro rata by the makers - even though it can be attributed to being solely my fault due to poor maintenance. I was required to contribute just under 1/3 the price of a new one because that is what they believed was what I recieved out of the useful life of the battery - makes the useful life of the battery about 6 years nine months.

Gotta be happy with that!

Cheers

Anthony

ACD 1, from what you have written, it appears the isolator was the issue, not the alternators ability to charge the battery, there are many more using simple VSR setups to charge their batteries than DCDC chargers and they have no issues.

Unless your car has an ECU controlled alternator the alternator should be be able to fully charge the battery, it is just not correct that an alternator can't fully charge a battery, this is a myth perpertrated by the DCDC charger manufactures to push their products. If you go to Redacr's website you will see they have carefully worded the literature to state " some car charging systems may not be able to fully charge a battery".

I myself have no problems with my VSR setup and it is charging a Marine Pro in the car and two Haze Gel type AGM's in the trailer.

Alan, what is the technical reason your friend gives as to why it is a good idea to have an AGM in parallel with the cranker?

Leigh, maybe you confused that. I referred to him saying that it was "...NOT the best arrangement to connect an AGM auxiliary battery via a solenoid isolator to the charging battery".

His view was based on the manufacturer's specifications of disparate charging voltages of the battery types and he does have a case although I am not prepared to argue it here. Perhaps he may be considered one of the "pundits" I referred to but I hasten to add that the term is used respectfully.

I must admit that my AGM auxiliaries have lasted longer since I arranged to charge them via Redarc BCDC1220 chargers. Time will tell.

Sorry meant to write "not".

Standard alternators charge at around 14.4V to 14.4@24C, a charger 14.4V@24C, so it is a bit hard to argue that one is better than the other.

A charger might be an advantage if the battery doesn't like high charge rates and you won't to restrict the current. I prefer high charge rate batteries as I have two fridge freezers to keep powered and wish to leep recharge times to a minimum.

Likewise Allan - since putting in the dcdc - I haven't had a flat battery. Before I would average a flat battery every 6 to 8 weeks. Even more frequently if I wasn't doing the long drives. Not ONE in 18 and a bit months - mmmm something sounds like it must be fixed.

HKB - I'm not trying to sell anything, I'm not representing dcdc manufacturers. I'm not trying to convince anybody that their setup is useless, won't work or will damage their charging system. All I can say is what I have observed with my own vehicle and 5 other vehicles with the same setup. Faulty isolators were removed from the equation as these were the first thing the auto electricians said were faulty and were changed out.

After spending a lot of money chasing faults, earth leaks "phantom" currents, changing out destroyed batteries, "faulty" isolators and spending a fortune on other diagnostic tests and fault finding (including the alternator) - the only physical change to my setup is the removal of a VSR and the inclusion of a dcdc charger. The factory wiring harness has not been compromised, the factory charging system has not been compromised. But it WORKS.

I am glad you don't have problems with your VSR setup - I hope it continues to serve you well.

Cheers

Anthony

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Leigh,

The issue revolved about the float voltages.
It is established that AGM's are sensitive to overcharging and their float voltage is commonly specified at 13.3 to 13.8 volts. With an alternator putting out typically 14.4 volts (your expression) clearly there will be overcharge.
The Redarc BCDC1220 when set for AGM mode applies 14.5v in absorption stage but reduces to 13.3v in float stage which is within battery manufacturer's specs so no overcharge.

Now I am not arguing a case, merely stating my friend's point of view, so I have no intention of continuing this discussion.

Leigh, it's a simple choice for everyone to make regarding the care and feeding of additional batteries - look at the manufacturer's specs for aspects such as max-charge-rate, float voltage etc and see how they sit with you vehicle's charging system.

I use virtually the same figures you gave for the "non-smart" charging system - 14v3 to 14v4. All the AGM's I have worked with would be decidedly outside manufacturers' recommendations if floating in that range (charge yes, float NO). That is why I use, and would recommend use of, a DC-DC charging system to ensure the AGM battery is treated properly.

Others may feel differently, or not care about the difference, but with the cost of them being non-trivial that is THEIR call and if they choose to directly (i.e. through nothing more than an isolator) parallel-connect an AGM to the vehicle charging system it *may* work out but I don't have sympathy if if turns out badly.