Full River AGMs

Submitted: Thursday, May 15, 2008 at 21:53
ThreadID: 57647 Views:6502 Replies:7 FollowUps:27
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Evening All,

Is it me or are others having trouble with the archives? anyway i am also looking at these as a replacement for my gel cell.part numbers are HGHL 12430W or DC 110-12A the later looks to be the go.would like to hear from owners of such units.cheers Paul
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Reply By: chisel - Thursday, May 15, 2008 at 23:16

Thursday, May 15, 2008 at 23:16
I have a 120AH Fullriver but haven't used it enough to give much feedback.
I also, coincidentally, have a 100 series TD (which I assume you do from your name). I'm toying with the idea of replacing one of the two cranking batteries with the AGM ... with an isolator between them.
For the moment the AGM will live in the cargo area.
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Follow Up By: jdwynn (Adelaide) - Friday, May 16, 2008 at 04:38

Friday, May 16, 2008 at 04:38
Should not put an AGM under the bonnet - check out advice / experiences on this site.
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Follow Up By: Sand Man (SA) - Friday, May 16, 2008 at 10:55

Friday, May 16, 2008 at 10:55
JD,

In my experience, that perception is a furphy mate.

Providing the battery (any) has a sufficient gap from high heat sources, eg a turbo, there is no reason whatsoever that an AGM battery cannot "live" successfully in an engine bay.

Bill.
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Follow Up By: Mike Harding - Friday, May 16, 2008 at 18:23

Friday, May 16, 2008 at 18:23
>there is no reason whatsoever that an AGM battery cannot "live"
>successfully in an engine bay.

Except for the temperature specifications provided by every AGM battery manufacturer I have ever seen. If you know of an AGM battery specified for underbonnet use I would be most interested to see its specs.

Mike Harding
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Follow Up By: Member - Fifo - Friday, May 16, 2008 at 22:25

Friday, May 16, 2008 at 22:25
Yes, well what does this really mean. Seriously, Mike, a number of people on this forum have posted that they have their AGMs under the bonnet, with no ill effect.

I thought long and hard before I bought 2 90aH Fullriver AGMs and mounted them under the bonnet of my 79 series.

Now, how long do my batteries need to last, and how many other examples of people doing the same thing, will it take before this issue can be put to rest?

I understand what you're saying Mike but the reality seems to imply that there is no problem with mounting AGMs under the bonnet.

And, I suspect a 79 series would get as hot, if not hotter, than most other fourbies.

Peter
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Follow Up By: Harrow - Friday, May 16, 2008 at 23:30

Friday, May 16, 2008 at 23:30
Hi Chisel and fifo

After destroying within 12 months each a sucssion of 3 AGM Aux batteries under bonnet (HZJ105R), I can unequovically state it happens, ($1000-00 of proof)
!x Odessy
2X Lifeline 100AH
Lifeline rep finally suggested not underbonnet, for long drives

It all has to do with the specifics of usage patterns and installation.

To resolve the issue I tried
1) Charging system checked several times
2) Shielding the battery with foil backed A/c insulating panel
3) Ducting to increase cool air flow arround battery
4) Xantrex 3 stage AGM alternator charger, with temp comp and high temp cutout (56oC) , lasted longer but still died

Realy interesting how often the 56oC charge cutout kicked in even with the insulation and cooling, hate to think thetemp is without these measures.

The issue, as temp increases charge voltage needs to decrease to stop overcharging, if charge volt not decreased and you high charge for an extended period then it gets over charged.

Cool climates and short trips ( 1 hour of charging) your problay fine.

Hot climates/ summer and long trips (extended charging at high /(normal) volts for given temps) and they die within 12 months.

My usage patterns, non stop trips Brisbane to Cairns 18 hours+, = hot temps for extended periods

I love AGM's, fantastic battery, but on the camper trailer, having no probs tere

Harrow

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Follow Up By: Mike Harding - Saturday, May 17, 2008 at 07:52

Saturday, May 17, 2008 at 07:52
>Yes, well what does this really mean.

It means AGM batteries are not specified for underbonnet use.

>Seriously, Mike, a number of people on this forum have posted that they
>have their AGMs under the bonnet, with no ill effect.

A number of people on this forum smoke cigarettes with no ill effect. However one should not attempt to project that, statistically irrelevant, information to conclude cigarettes cause no harm.

>Now, how long do my batteries need to last, and how many other
>examples of people doing the same thing, will it take before this
>issue can be put to rest?

Tell me about this sample? How many people? What length of time? what type of journeys do they make? Where in Oz do they live, climate wise? What sort of charging system do they have? What was the storage and transport history of their batteries before they bought them?

We do not design and engineer products by anecdotal experience, we apply engineering and mathematical processes supported by extensive testing of many samples over the full range of environmental conditions the product will be subject to. This is what the manufacturers of AGM batteries have done and they have concluded a maximum working temperature of (typically) 55C is the highest they’ll spec and the charge rate needs to be significantly reduced for that environment. They know, full well, if they speced their batteries for underbonnet use they would have so many warranty returns it would put the company out of business.

Have you looked at the lifetime curves of AGM batteries against temperature? I have because I’ve spent the past year involved with the testing of AGM batteries (and the design of specialised electronic test equipment to perform such testing) to ensure they comply with a particular Australian Standard for a safety critical application.

You can put an AGM in your engine compartment if you wish (it’s your money) BUT there is a _VERY_ high statistical probability you will seriously degrade its lifespan, as the post from Harrow above indicates.

Take a look here:

http://www.ritarpower.com/upload/pdf/2007080916175645273602.pdf

and observe the huge difference in lifespan when the battery is operated at 45C, underbonnet temperatures routinely reach 100C+

NB. Optima batteries use a different construction technique and may be used underbonnet.

Posting technical electrical information to this forum is just like banging one’s head against a brick wall – I’ve, pretty much, given up on it.

Mike Harding
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Follow Up By: Sand Man (SA) - Saturday, May 17, 2008 at 10:18

Saturday, May 17, 2008 at 10:18
Mike,

Does that mean you cannot install an AGM battery almost anywhere in a vehicle???

Apart from under bonnet, the next most common place is in the back of your vehicle. Now in an enclosed vehicle at rest, I would suggest the temperature would be at least equal and more than likely well above the temperature of an engine bay.
In an open vehicle tray, the sun's rays would surely heat up the insides of any battery and/or box it is sitting in, to well above the recommended maximum temperature of the battery.
That means you should remove the battery each time you stop and park, otherwise you risk "cooking" it.
And the same probably goes for the ones stored in the metal, or fiberglass box on the A-frame of camper or caravan.

Now I am of the opinion that the engine bay would provide the most "user friendly" location, provided you keep it away from the turbo or exhaust manifold. If necessary, a piece of aluminium sheet will provide a heat barrier from these potential sources.

I'm no scientist and have no real desire to run a series of tests to "prove" my theory, but I would suggest that the flow of air through the engine bay while driving, would keep the internal heat to a manageable level.

Bill.
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Follow Up By: Andrew Main - Saturday, May 17, 2008 at 10:53

Saturday, May 17, 2008 at 10:53
"I'm no scientist and have no real desire to run a series of tests to "prove" my theory, but I would suggest that the flow of air through the engine bay while driving, would keep the internal heat to a manageable level."

So you don't know what you're talking about and you have no interest in trying to prove it but you're willing to make general statements?

Brilliant!

_IF_ you did know what you're talking about when it comes to electronic design involving automobiles you'd know that the engine bay is one of the most hostile environments in the vehicle, and yes I am an engineer and yes I have run testing to prove this. You obviously have not.

Now I'm going to say this really slowly so you can all grasp it: Manufacturers specify products to a certain temperature because that is the maximum temperature they believe you can run the product at without causing damage resulting in warranty returns and the company going bust. They do not do it because they were bored, guessing or using a dart board, those companies that do end up going bust.

Harding is right: Far too many people on this forum are willing to make statements about technical issues based on no evidence other than "what they think" or anecdotal incidents. I don't comment on heart surgery as I'm not a surgeon and I doubt anyone else here would do so either so why are people willing to comment so readily on technical issues?

The plural of anecdote is anecdotes not evidence.


A somewhat frustrated

Andrew
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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 11:17

Saturday, May 17, 2008 at 11:17
Harrow,

Thanks for replying with your experience. I think it is very helpful that you have stated precisely the scenario you experienced, which led to the failure of your AGMs.

Clearly, driving Brisbane to Cairns non-stop is a very serious test, pushing things to the limit.

However, very surprised to hear that "Xantrex 3 stage AGM alternator charger, with temp comp and high temp cutout (56oC) , lasted longer but still died" did not solve the problem. I suppose the explanation for this is that although the charging stopped when the temp hit 56oC, the battery was still too hot. And, the temperature may have hit 65oC or higher, who knows.

Once again, thanks for providing the feedback and giving the facts as per your experience.

Peter
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Follow Up By: Harrow - Saturday, May 17, 2008 at 11:37

Saturday, May 17, 2008 at 11:37
Hi Sandman

You need to view things a little more dynamically rather a simple literal message.

Remember these points

The loss of capacity is the combined effects of temp and time and charging voltage.

The longer and higher the temps with-out a reduction in charging voltage the worse the problem.

This is determined by each individual case and takes into consideration the following parameters.

Veh charging voltage
Climatic conditions, both latitude and Seasonal (Darwin 33oc year round, Vs Tassie 12oC winter to 22oC summer Ave)
Batery location in engine compartment and under bonet temps
Vehicle usage patterns (Long haul truck Vs Grey Army migration)

In a later post you make the very interesting comment, which strikes to the heart of the problem with AGM's, their low internal resistance, and Therefore reaching full charge quicker, where the charge voltage should be reduced to float and temperature compensated (Somthing that dosnt happen in a veh charging system)

Quote "This is not specific to AGM batteries. In fact an AGM battery charges quicker and more fully than an equivalent sized standard wet cell deep cycle battery"

As to your comments re the external use of AGM's yes temps can get high in external positions but this is climate dependant and time of day dependant.
And the Average conditions needs to be considered

This has an impact on the length of the batterys exposure to high temps while under charge (Remember the conditions while under charge comment as it is important later point)

i.e.

Darwin 33oC day, 24oC night year round
Tassie Summer 12oC night to 24oC day
Winter 4oC night to 12oC day
In tassie your battery would love the external enviroment as it is optimal operating temperatures, but jam the same battery under the bonnet and its temp will go to >50oc within the hour.
Re the cooling comment, I tried oh how I tried Insulated and ducted air, but that battery 56oC charge cutout, just kept kicking in.

Now here's the kicker, when a battery is under the bonnet, the only time it will charge is interestingly enough, is when the motor is running, which generates heat >50oC bat temp after 1 hour, when the charge volt needs to be reduced as
1) Due to AGM's quick charge aceptance is charged and should be now in float mode (DOD depandant)
2) As its temp is now high, requires a reduced float voltage

Keep driving for annother 2l, 4, 8 hours (depending on your driving habbits), you reduce its life "Proportional" to the duration of these conditions.

Now if the battery was outside Hmm

Specifics gentlemen Specifics not dogma.

Harrow
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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 12:00

Saturday, May 17, 2008 at 12:00
Mike,

Thanks for your reply. Some comments in response.

By the fact that you ask "Tell me about this sample? How many people? What length of time? what type of journeys do they make? Where in Oz do they live, climate wise? What sort of charging system do they have?" proves to me that the blanket statement "One cannot mount AGMs under the bonnet" is not a helpful statement to make.

It is correct if all the conditions are met, thereby causing significantly reduced battery life. But, as a blanket statement, I think this is what gets people offside.

You also state that under the bonnet temperatures routinely reach 100C+; I'd be interested to see the evidence that supports this statement. Otherwise, it is anecdotal, the very thing that you refute. But, I am genuinely interested to see this, as follows:

On a hot day for Sydney, 38C, I drove from Dural to Wisemans Ferry (WF) and back. It is about a 45 minute drive each way, with speed limits ranging from 60, 70, 80 & 90 kph. Probably about half the distance is at 90kph.

I have a temperature sensor mounted on the side of my batteries closest to the engine bay, in order to give me the worst case scenario for my under bonnet temperature.

When I got to WF, I immediately turned around to drive back to Dural. I deliberately did this drive to get an idea of what my underbonnet temperature would be on a hot day, 38C.

On the return journey, driving up the hill out of WF, the temperature sensor hit a maximum of 66.1C, much higher than I would've liked but nowehere near 100C+.

Now, admittedly this was not a test where I'd been driving all day. But, I'm not sure whether that would've made much difference to the maximum temperature I measured, since the maximum was reached on the slow, twisting drive up the hill from WF, where the underbonnet airflow was severely reduced. Once I reached 90kph, the temperature dropped back.

Comments appreciated.

Peter
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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 12:04

Saturday, May 17, 2008 at 12:04
Harrow,

Another helpful post. I think your statement "Specifics gentlemen Specifics not dogma", is what we all need to be reminded of.

Thanks,
Peter
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Follow Up By: Mike Harding - Saturday, May 17, 2008 at 12:30

Saturday, May 17, 2008 at 12:30
Fifo: I have had it with this forum. Just like Collyn Rivers a couple of years ago I am fed up with people spouting technical assertions they have neither the qualifications or the experience to make and then expecting others to spend large amounts of time researching references in order to dispute these inaccurate and foolish claims. I must have put the case against AGMs underbonnet at least five times before on this forum.

I have been in the electronics design business for over 30 years, across the world, designing electronic products ranging from telephones to weapons systems to automotive (including underbonnet) to pacemakers. I am currently doing work on AGM batteries (as mentioned) upon which _your_ safety will rely so you had better hope I know what I’m doing. One of the major things I have learned from my experience, and one which I stress to young engineers, is “Do not assume - check”. You have a specification sheet for AGMs I suggest you read it.

Frankly; if you think the manufacturer’s specification for a product can be ignore then I don’t think there is any purpose in my responding to you further – I have posted argument and references above to warn future readers of this thread, my job is done.

Mike Harding
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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 13:23

Saturday, May 17, 2008 at 13:23
Mike: You don't have to post on this forum at all; no-one is asking you to. But, you did post... I didn't ask you to post, remember.

You made the statement that "underbonnet temperatures routinely reach 100C+"; I posted a test result that showed my underbonnet temperature reached 66.1C, worst case from the batteries perspective, on a 38C day.

Nothing anecdotal about that; you may choose not to believe me, and that is your perogative.

I now wish I had a temperature sensor on the other side of the battery, to see what that temperature was; I would expect it to be less than 66C but have no proof.

And, I stated that I was concerned that it got to 66C. However, 66C is no where near 100C+, as stated by yourself.

Now, the most reasonable conclusion I can make, and possibly other readers, is that your statement "underbonnet temperatures routinely reach 100C+", may, in fact, not be correct.

And, let's not forget, that this is what the argument is all about, underbonnet temperatures. I have made an attempt to measure my underbonnet temperature and asked genuinely for a reference supporting your assertion.

You criticize others for "spouting technical assertions they have neither the qualifications or the experience to make" and yet, when asked to back up your assertion, you are either unwilling or unable to.

To me, that's a little strange.

Peter R Fife






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Follow Up By: Sand Man (SA) - Saturday, May 17, 2008 at 13:52

Saturday, May 17, 2008 at 13:52
Andrew,

A little obnoxious aren't we?

I don't need to prove anything via testing because I run an AGM auxiliary battery in the engine bay and have experienced no problems whatsoever from failure due to heat.

Simple as that!!

Bill.
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Follow Up By: Mike Harding - Saturday, May 17, 2008 at 14:07

Saturday, May 17, 2008 at 14:07
>argument is all about, underbonnet temperatures

http://www.osti.gov/bridge/servlets/purl/5046950-dGMWxe/5046950.PDF

http://www.st.com/stonline/products/literature/ta/10674.pdf

There are many more references and many papers have been written on this subject but you, generally, won't find them with Google.

Mike Harding

PS. When was your temperature measuring device last calibrated by a source traceable to national standards?
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Follow Up By: Sand Man (SA) - Saturday, May 17, 2008 at 14:16

Saturday, May 17, 2008 at 14:16
Mike,

Don't delude yourself. You have to earn someone's respect. you cannot just claim it by being "an Engineer".

When I give my opinion on a topic in this forum, I base my input on personal experience in the real world.

I am not an electrical engineer and have never claimed to be.
I do however, have a background as an electrical tradesman, although I have not practised this trade for many years.

I keep up to date on electrical issues and strengthen my knowledge of real world solutions based on initial research, then practical implementation.

If I try something and it doesn't work, I will share this knowledge with anyone who is interested. I never attempt to ram anything down anyone else's throat. I also try to impart knowledge, or experience gained, in a straightforward matter, without any bulls..t.

That's the kind of person I am.

I have made the odd mistake and will be the first to state "that didn't work" if it assists someone else.

So you just spit the dummy if you want to. Who really cares!

Bill.
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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 15:07

Saturday, May 17, 2008 at 15:07
I just had a read of the 2 articles quoted above. Now, one article talks about the fact that electronic components quite often have to be designed to withstand temperatures up to 125C. The other article states that "a large number of hybrid circuit failures occur in certain car models with under-the-hood temperatures at 410 K".

410K is 137C.

Now, underbonnet temperature is the nub of the argument as to whether or not one can mount AGMs under the bonnet. But, to be precise, the underbonnet temperature where the battery/ies are mounted.

I'd be surprised if any manufacturer actually states that an AGM cannot be mounted under the bonnet. No, what they do, is state a maximum temperature, which if exceeded, will shorten the battery's life.

Now, I think most would agree that in the engine bay, there is clearly a wide range of temperatures, in all operating conditions. The difficult thing to determine is what this worst case temperature will be in a given vehicle as used by it's owner.

Therefore, the blanket statement, "that an AGM cannot be mounted under the bonnet" does not stand up to rigorous inspection. It does not matter how many degrees a person may have, if the requirements are not correctly analysed, then incorrect conclusions will typically be made.

However, in Harrow's case, mounting AGMs under the bonnet proved to be an expensive exercise. Likewise, if my AGMs fail in too short a period of time, I may well mount future AGMs elsewhere.

Peter



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Follow Up By: Andrew Main - Saturday, May 17, 2008 at 19:16

Saturday, May 17, 2008 at 19:16
"I do however, have a background as an electrical tradesman, although I have not practised this trade for many years."


So you can wire three wires together, or maybe 5 if you're particuarly experienced. Spare me please!

Electricians are not expert electronics engineers as much as some of them would love to think they are nor are they chemical engineers who are the people who know things about battery chemistry.

"I keep up to date on electrical issues and strengthen my knowledge of real world solutions based on initial research, then practical implementation."

Really? So you read the internet, then read a magazine and give it a go and if it works then you're satisfied that you've covered all the bases? That might be fine for a one off application and you may get lucky but it is _not_ the way industry works, well industry that remains profitable for any length of time that is.

I would actually at this point like to say that I am advertising my services as a brain surgeon. I have no qualifications other than my 1st aid certificate I did 20 years ago but I still read up on medical issues and I'd like to give it some practice. Any takers?

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Follow Up By: Nomadic Navara - Sunday, May 18, 2008 at 00:14

Sunday, May 18, 2008 at 00:14
Mike

There is a very good article on what you said in FollowUp 13 in Site Link

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Reply By: jdwynn (Adelaide) - Friday, May 16, 2008 at 04:46

Friday, May 16, 2008 at 04:46
TD
My understanding is that the HGL series is basically a hybrid (deep cycle/cranker) and that you get twice the amount of deep discharges from the DC version of the fullriver. The renewable store site gives some good detail.Site Link
So its important to get the unit that suits your needs. Cheers JD
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Reply By: Grungle - Friday, May 16, 2008 at 08:19

Friday, May 16, 2008 at 08:19
Hi Paul,

When looking at batteries, work out how far you would discharge the battery then look at the various manufacturers discharge / charge cycles to determine when it is classed as being at the end of its life.

For example, a Fullriver battery will only take 500 discharge/charge cycles if discharged to 50% at a 1.5 hr rate before it is classed as being "end of life". If used daily then this would represent only 1.5 to 2 years lifespan.



However Concord batteries, in particular the sun extender range is designed to be disharged to a lower capacity with out reducing its life therefore it can take 1050 discharge/charge cycles if discharged to 50% at a 1 hr rate (which is a faster rate of discharge that the Fullriver above) before it is classed as being "end of life". If used daily then this would represent 2.5 to 3 years lifespan.

The discharge rates mentioned above is a standard specification for testing and would not be be representative of what we would actually use. We would be more aligned to a 24 to 48hr rate which would mean we would get a lot more years out of the batteries.

(Sorry no pics but there is a link showing expected life cycle data below).

http://www.nooutage.com/pvx.htm

When I started looking for replacement batteries for the camper I ended up buying 4 Concord Sun Extender PVX-1040T batteries due to the fact that they could be discharged and charged more times than any other battery which meant they were more resillant. They also had the highest capacity for their size.

Below is some info on AGM vs GEL as well:

http://www.sunxtender.com/agmvsgel.php

My 2c.

Regards
David
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Follow Up By: Grungle - Friday, May 16, 2008 at 08:21

Friday, May 16, 2008 at 08:21
Oops - I forgot to mention I have a Fullriver 260AHr AGM in the back of the Patrol but it gets little use so depth of discharge is 10-15% at most.

Regards
David
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Reply By: Mainey (wa) - Friday, May 16, 2008 at 08:36

Friday, May 16, 2008 at 08:36
The difference between the Fullriver "HGL" and "DC" range is:
~595 cycles at 75% Depth of Discharge "DC" (DEEP CYCLE battery)
~345 cycles at 75% Depth of Discharge "HGL" (CRANKING battery)

DEEP CYCLE batteries (DC) feature Extra Heavy Duty plates with higher density active material.

CRANKING batteries (HGL) have plates that are designed to deliver maximum power for only a *SHORT* duration.

When a (HGL) battery is used in a DEEP CYCLE application or in a vehicle with heavy accessory loads, the battery life *WILL* be shortened proportionally to how deeply and frequently the battery is discharged.

The Fullriver (DC) DEEP CYCLE battery uses a DIFFERENT chemistry for the plates' active paste material and is filled with a slightly STRONGER acid.
This chemistry difference allows for a much *longer life* in DEEP CYCLE applications with only a slight reduction in maximum power output.

Mainey . . .
AnswerID: 304077

Reply By: Sand Man (SA) - Friday, May 16, 2008 at 09:13

Friday, May 16, 2008 at 09:13
Paul,

I have already replied to your other Post on this subject so I won't repeat myself in this one.

Nothing wrong with the Fullriver battery mate, but do some research on Google, comparing the cost of Fullriver vs Remco.
Only if I required a higher capacity battery than 100 A/h would I choose a Fullriver.

PS.
I am not a retailer, or manufacturer, or distributor of anything associated with Remco.

Bill.
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Reply By: troopyman - Friday, May 16, 2008 at 10:47

Friday, May 16, 2008 at 10:47
My understanding of AGM batts is that you need a three stage charger to top it up to full capacity or it will only charge to about 75% with a standard alternator charging it . Correct me if i am wrong . They have a starting current of 1500amps (first load or something) . Ideal for winches etc . Put some sort of heat shield around if you are worried about it being under the bonnet .
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Follow Up By: Sand Man (SA) - Friday, May 16, 2008 at 11:12

Friday, May 16, 2008 at 11:12
Well mate, I think you are wrong.

This is not specific to AGM batteries. In fact an AGM battery charges quicker and more fully than an equivalent sized standard wet cell deep cycle battery. I have found no need to charge the current auxiliary battery from an external source. It's about 14 months old and generally gives a reading of around 12.8 volts (100% charge) some 12 hours or more after the vehicle was last run. This means any residual charge which may give a false reading on the volt meter has dissipated and the alternator has in fact fully charged the battery.

A multi-stage charger is "kinder" to batteries than a "dumb" one, as it will drop into float mode as the battery reaches full charge capacity, thus removing the chance of overcharging. A battery can be kept in float mode indefinitely.

Bill.
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Follow Up By: Mainey (wa) - Friday, May 16, 2008 at 18:12

Friday, May 16, 2008 at 18:12
Ditto . . . to the Sand Mans post.

Note his 12.8v reading, and not the lower 12.6v of a wetcell battery.

A decent "multi-stage" charger can be left attached for months at a time without any undue battery damage.

Should only power a winch from a CRANKING 'type' battery !!

Mainey . . .
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Reply By: Member -Dodger - Saturday, May 17, 2008 at 12:04

Saturday, May 17, 2008 at 12:04
This is from experience.
Dual batteries under bonnet of 4.2Td GU Patrol.
When towing van for more than 1hr in ambient temp of around 35% C the engine bay on stopping went from 45% C to 6o% c in approx 10 minutes. then proceeded to cool slowly. When bonnet is opened on stopping the engine started to cool immediately.
I did this exercise to see what the difference would be as I was heading into the Outback towing where the temps in actual fact reached an incredible 52% C for several day ambient temps with the nights cooling down to 35% C .
I had under the bonnet 1 x NZ70 cranking battery the aux was a BN70 Deep cycle, both were flooded wet cell bats.
The van had a 120amp hr AGM battery.
All batteries took a real caning over the few months that we were in the heat and survived. I do NOT think that the AGM because of the construction would have survived under the bonnet with the extreme heat that was generated in this area.
Every time I pulled up the bonnet was lifted to help cool bats and the engine and most times the engine was left to idle for at least 5 minutes.
I believe that what others have said about heat and AGM batteries to be correct. So please draw your own conclusions.
I used to have a handle on life, but it broke.

Cheers Dodg.

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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 13:35

Saturday, May 17, 2008 at 13:35
Dodger,

Thanks for your post; these are the sort of posts I like, where actual tests are done and the results posted.

So, on the 35C day towing, engine bay was 45C upon stopping, a 10C differential. Therefore, on the 52C days, engine bay was at least 62C, simply by adding the 10C difference.

However, worked out as a percentage, that is, 10/35 = 28.5% difference, then on the 52C day, engine bay may have been ambient + 28.5% = 66.85C, starting to get a little too hot for comfort, for AGMs, at least.

Peter

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Follow Up By: Member -Dodger - Saturday, May 17, 2008 at 13:56

Saturday, May 17, 2008 at 13:56
Peter
On the 52C days I was unable to test the engine bay however when the bonnet was lifted on one occasion the heat was so high that I was unable to touch any metal or for that matter anything under the bonnet. The daily engine and running checks were all done early before set off as the vehicles took hours to cool down plus the liquid of life was a calling each afternoon.I also had to regularly top up the batts with water. Which ceased when the temps came below 35 C again.
I used to have a handle on life, but it broke.

Cheers Dodg.

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Follow Up By: Member - Fifo - Saturday, May 17, 2008 at 15:18

Saturday, May 17, 2008 at 15:18
Dodger,

I suspect in those conditions, an AGM may well have failed; or, at the very least, had it's lifespan severely shortened.

Peter
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Follow Up By: Nomadic Navara - Saturday, May 17, 2008 at 23:57

Saturday, May 17, 2008 at 23:57
Fifo- Peter

Your calculations regarding percentage differences is in error. If you are going to quote percentage changes you must use the Kelvin scale not Celsius, Leiden, Fahrenheit, Delisle or any other of the scales that do not use absolute zero as their starting point.

PeterD
PeterD
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