Charge rate differences ??

Submitted: Thursday, Jul 13, 2017 at 15:58
ThreadID: 135248 Views:2054 Replies:10 FollowUps:27
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I understand typically AGM deep cycle batteries accept charge faster than the same size standard wet cell deep cycle batteries.

Question is this correct and if so does any one know how much the difference actually is ?

The reason i ask is that i need to replace the 2 x 105 amp deep cycle AGM batteries in my van.
As non AGM batteries are roughly 30 to 40 % cheaper it may be worth using wet cell deep cycle batteries.

Also would it be better to use say 1 x 200 amp battery rather than 2 x 100 amp batteries ?

Thankyou for your replies.
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Reply By: Frank P (NSW) - Thursday, Jul 13, 2017 at 16:23

Thursday, Jul 13, 2017 at 16:23
Tim,
Typically, it's to the contrary. Most AGM deep cycle batteries prefer a bulk charge current of 10 to 15 percent of their rated C20 capacity. So a 100 Ah battery would typically prefer a charge rate of 10 to 15 amps, 200Ah 20 to 30 amps, etc.

Of course, there are exceptions, so you need to ascertain from the battery data sheet or the manufacturer what the preferred rate is. Sometimes it's on a label on the battery case.

Wet batteries generally can accept higher charge rates but they may vent and depending on what's nearby and the environment, there may be corrosion issues as a result. Again, not always the case. I had a wet deep cycle 105Ah battery that required a max charge current of 11 amps - ie same as an equivalent AGM.

If you're not using a dc-dc charger then I'd try to find a deep cycle battery of any type that can accept the charging current of your vehicle alternator.

If you use 1 x 200Ah battery, if it drops a cell (which kills the battery) you've lost everything. If you use 2 x 100 batteries, then if you lose a cell in one battery, you still have half your capacity remaining.

Cheers
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Follow Up By: The Bantam - Thursday, Jul 13, 2017 at 23:25

Thursday, Jul 13, 2017 at 23:25
As Frank has opened the can of worms

There are many strongly held misconceptions about AGM ....... YOU MUST look at the specific spec for the battery in question.

There is also a big difference between "charge acceptance" and " maximum initial charge current".

Charge acceptance is all about the efficiency of the battery accepting charge.

Maximum charge rate is about how much current the battery will tolerate.

It is possible to have a battery with relativly low "maximum Initial Charge Current" but have High charge acceptance.

cheers
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Reply By: Sand Man (SA) - Thursday, Jul 13, 2017 at 17:44

Thursday, Jul 13, 2017 at 17:44
I would not consider using standard wet cell deep cycle batteries.
AGM type batteries are the safe way to go, especially in non-ventilated spaces.

Don't go for a cheaper solution or you may well regret your decision.

Better still, if you invest in a dc-dc smart charger for charging whilst driving, you will extend the useful life out of your batteries as they will receive a multi-stage charging process, without the risk of overcharging and shortening battery life.
This is also the case for on-board AC charging.

Moving to a single battery (if you can lift a 200Ah battery) will not give you much improvement either. Down the track, should one cell in one battery malfunction, the whole battery is useless. With two batteries, you can disconnect the faulty one and survive on one 100Ah battery for a period of time.
Bill


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Follow Up By: Gronk - Thursday, Jul 13, 2017 at 18:54

Thursday, Jul 13, 2017 at 18:54
Better still, if you invest in a dc-dc smart charger for charging whilst driving, you will extend the useful life out of your batteries as they will receive a multi-stage charging process, without the risk of overcharging and shortening battery life.


That sentence is not factually correct. A dc/dc charger can be beneficial if you have a "smart" alternator, but for all other cases an alternator is fine to charge batteries...wet or AGM.
You will not overcharge a battery from the alternator. Millions of cars will attest to that .
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Follow Up By: The Bantam - Thursday, Jul 13, 2017 at 23:31

Thursday, Jul 13, 2017 at 23:31
OH BTW .... ALL and I do mean ALL batteries should be installed in well ventilated locations.

ALL batteries and I mean ALL, can and will fail, can and will vent explosive gasses and acid mist when over heated or over charged.

Curreent best technology, Sealed maintenance free wet cell batteries, can have most or all of the benifits of AGM ( infact use the same technologies), but because they are not starved of electrolite may withstand overcharging and heat considerably better than AGM and cost 1/2 the price.

cheers
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Reply By: Dean K3 - Thursday, Jul 13, 2017 at 18:41

Thursday, Jul 13, 2017 at 18:41
wet cells shouldn't be used where leaks could cause massive amount of damage to either chassis components or human body acid burns etc -IMHO

2nd ever tried to pickup and carry a 200ah battery before ?

a quick google search tells me they probably close to 40kg heading towards 60kg in some instances.

Know all the comms trailers built at my former employer were always smaller 100ah for lifting purposes, one retrofit came in with a single 200ah took 2 guys to lift and remove it only take one to remove and install a 100ah battery

Most 100ah typically give more ah than 100 referenced to around 115 to 120 ah so 2 x is higher than the nominal 200ah capacity gives
AnswerID: 612484

Follow Up By: Tim F3 - Thursday, Jul 13, 2017 at 18:54

Thursday, Jul 13, 2017 at 18:54
Thankyou for the replies , i dont have a dc dc charging set up but have 300w of solar on the roof of the van plus 180 watts of portable solar.

The van has a cteck charger wired in by the manufacturer for when 240v is available.
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Follow Up By: The Bantam - Thursday, Jul 13, 2017 at 23:34

Thursday, Jul 13, 2017 at 23:34
ALL batteries and I do mean ALL batteries hsould be housed in such a way that acid leakage can not cause damage or injury.

ALL batteries will leak or vent acid in overcharge, over heat or failure situations .... ALL batteries will eventually fail.

cheers
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Reply By: Sand Man (SA) - Thursday, Jul 13, 2017 at 19:25

Thursday, Jul 13, 2017 at 19:25
My statement is in fact correct for situations where charging of an auxiliary battery is involved.
When a dc-dc charger is not employed, the common solution is to use a vsr to provide some sort of protection to the starting battery.
The vsr will not enable full charging of an auxiliary battery bank and a shortened battery life is the result.
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Follow Up By: Frank P (NSW) - Thursday, Jul 13, 2017 at 19:40

Thursday, Jul 13, 2017 at 19:40
What statement?
Who are you replying to?
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Follow Up By: Gronk - Thursday, Jul 13, 2017 at 20:06

Thursday, Jul 13, 2017 at 20:06
Me I think ??

The vsr will not enable full charging of an auxiliary battery bank and a shortened battery life is the result.

Again mate, not true. Every 2nd 4wd out there has a vsr and all are charging their aux battery just fine.....and fully.

The only reason an alternator ( via a vsr or not ) won't fully charge a battery is not enough run time. But this will also apply to a dc/dc setup as well.
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Follow Up By: RMD - Thursday, Jul 13, 2017 at 22:48

Thursday, Jul 13, 2017 at 22:48
I don't own a VSR or a DCDC unit but have used a simple continuous duty solenoid to charge the aux and van battery from the alternator. The alt will charge them to a high percentage of charge faster than a 20 amp DCDC will.
The amp input cuts back because of battery resistance to alt charge voltage (14.4v) rises as it is charged.
The AGM is 7 years old and still going and is always charged via the solenoid. 160 watts of solar also assists.
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Reply By: Member - Trouper (NSW) - Thursday, Jul 13, 2017 at 20:34

Thursday, Jul 13, 2017 at 20:34
Tim F3
I have a 35amp hr AGM battery which I use (CPAP) whilst travelling. I just charge it thru a Cig lighter socket. I can normally use the AGM 3 times before I need to recharge it at SOC 60% when I start charging it I put the multi meter on it and it rarely accepts a charge over 13.3 v . But happily the AGM is 'full' at the end of the days run. However the Wet Cells regularly accept 14.2v when they are at SOC 60%.
No smart Alternator its a 2000 model Diesel Troopy no computers.

Jeff
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Follow Up By: Tim F3 - Thursday, Jul 13, 2017 at 20:58

Thursday, Jul 13, 2017 at 20:58
Jeff i have a 2002 turbo 100 series , it has 4 wet cell batteries charged from the alternater plus 180 w solar on the roof when it is parked ..

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Reply By: gbc - Friday, Jul 14, 2017 at 07:05

Friday, Jul 14, 2017 at 07:05
Speed of recharge and charge acceptance in a battery is driven by heat. Heat is caused by the battery's internal resistance. Internal resistance is governed by the purity of the lead used in the construction of the battery.
Check the spec sheets for internal resistance figures and lead purity percentages and you'll get a fair idea of how it is going to recharge.
There is another level of chemistry to talk about as well, but that is the meat and potatos.
Generally speaking, the less you pay for the battery, the more expensive it will end up due to a compromised life span and poor performance. The more "expensive" batteries last longer and perform better and worked back, are always cheaper on a $ per year basis.
Lesson = don't skimp.
Saying vsr is as good is a dc charger is saying a 14.4v power supply is as good as a multi stage 240v charger - not true. Yes, a vsr often wins the bulk charge race, but a dc will often have 5 steps as opposed to being a one trick pony. Long term optima users such as myself will remember having to hook them up to a home charger once a month to prevent them getting a charge memory from alternator charging. We don't have to worry about that any more with dc charging. Each have their merits, but dc will maintain a battery better and keep it alive longer every time.
AnswerID: 612498

Reply By: Battery Value - Friday, Jul 14, 2017 at 08:19

Friday, Jul 14, 2017 at 08:19
G'day Tim,
for better understanding of the matter, there's some charging 101 for you.

The speed of charging is governed by the voltage difference between source and battery.
Example:
Valternator - Vbattery = 1V
So we've got 1 Volt driving the charging current which now depends on circuit resistance which includes the battery's internal resistance (Ohm's Law applies).
For instance, a circuit resistance of 20 milli Ohms will result in 50 amps of current.

If a high charging rate is desired, the voltage difference has to be large which can be achieved by high alternator voltage, a low battery resting voltage or both.
That's why high rate batteries come with lower acid concentration which produces lower resting voltage.
For the battery to actually 'accept' a high rate, most of the charge needs to be stored near the surface of its electrodes, so we want to maximise the surface area, aka number of plates.

Problem with this, thinner plates come with thinner grids which don't retain the lead paste very well. Each cycle will see some shedding of active material which piles up at the bottom of the container, resulting in poor cycle life.

To work around this issue, the enhanced flooded battery (EFB) has been created in which a fleece separator between the plates retains the active mass better.

Then we've got VRLA AGM technology which offers good retention through compressed micro fibrous glass mats between the electrodes.
The other advantage is it enables gas transport between the electrodes so that hydrogen can recombine with oxygen which preserves the electrolyte.

Which battery type combines all of the above?
AGM technology for start/stop cars, predominantly coming out of Europe.

A couple of days ago I replaced an AGM start/stop battery, date stamped 2011, in a Touareg.
So these things are made to last.
AnswerID: 612499

Reply By: swampy - Friday, Jul 14, 2017 at 10:49

Friday, Jul 14, 2017 at 10:49
hi
Tim F3
Charging all batteries is as per the maker suggest . You will be surprised at how different the battery makers are .

charge amps as a percent of there ah capacity
lead flooded 10% slow --20% fast
agm 15% slow -- 30% fast
The above is rule of thumb

Never have wet batteries venting to inside van
AnswerID: 612503

Reply By: The Bantam - Friday, Jul 14, 2017 at 12:24

Friday, Jul 14, 2017 at 12:24
lets sumarise and address some of the points raised.

#1 and above all .. DO NOT believe or take at face value any of, the only partly founded, commonly held "truths" about batteries in particular AGM.

No matter what the "rule" is there is an AGM or other type of battery that proves the rule is false.

We must look at the detail and the manufacturers spec's

There is one reasonably well respected Chineese manufacturer of batteries that manufactures and sells the very same battery in three different forms.

AGM (with little or no free electrolite, all the electrolite is contained in the glass mats), Sealed lead acid ( not claimed to be AGM, which is partly filled with electrolite) and as a Flooded wet cell sealed battery.

All three batteries use the same case, plate structure and materials .... all that varies is the amount of electrolite and some variation in electrolite formular.

The Australian distributor was zipped a few years ago by the ACCC, because there was a batch of partly filled batteries that came into the country and where sold as AGM when they technically where not ..... nothing wrong with the batteries as such , they just where not as discribed.

That manufacturer also builds a range of batteries with differing performance, they make a low current AGM battery that has a maximum initial charge rate of around 20 amps for a 100AH battery ( this battery also has poor high temperature tolerance) they also make a nearly identical range of batteries that has a much higher Maximum initial charge rate around the 50 amps for a 100AH battery and a full blown Cranking battery that makes a lie of every rule about AGM you have ever been told.
This cranking AGM can be charged very hard, its Cold Cranking Amps will make pretty much any conventional battery look sad and they have high temperature tolerance for under bonnet applications.

Generalisations about batteries can be very misleading .... you must consider each battery on it's merits and look at the specifcations.

2/ Do not confuse "Maximum Initial Charge Current" and "Charge Acceptance".

Maximum charge rate is determined by several factors, but it is the limit of how much charge current the battery will tolerate without damage.

Charge acceptance is how much charge the battery will accept and continue to accept.
Two hypothetical batteries ...... both at the same state of charge and condition, both at the same charge voltage and both starting at the same initial charge rate ... all equal to save confusion.

The battery with better "Charge Acceptance" will continue to accept charge at a higher rate as the batteries state of charge rises. ....... it will reach a higher state of charge faster from a given charging source.

The fact that the battery with better charge acceptace MAY ( but not always) achieve higher charge current from a given charge voltage is another issue .... not a seperate issue but another issue.

Charge acceptance is not exclusivly tied to internal resistance ... but it is related.

Saying that Charge acceptance is governed by heat and lead purity is a bit of a stretch.

Saying that charge acceptance and a number of other things are directly related to plate thickness is also a bit of a stretch.
Manufacturers are doing some clever things with plate structures and battery metallurgy and chemistry that make the old plate thickness arguments less and less valid ... not invalid , but less and less of a factor.

One thing that most definitely does influence Charge acceptance in all batteries is, ..... age and condition.

As batteries suffer age and abuse, their charge acceptance suffers ... and badly.
Sometimes this can be recovered a little with good treatment, but all batteries will eventually die from the same things that cause this.

I have had a not fully discharged, mildly neglected N70 marine battery take 3 days to reach full charge on a good 5 amp multistage charger, where a healthy example would recharge in 24 hours from neatly stone flat.

That battery did recover reasonably to live another year in light use.

3/... as for the 200Ah battery .... yeh hell ya don't want to be lifting that ..... most applications that 12V 200AH capacity will be made up of two batteries.
Look at trucks, busses, golf buggies and most small to medium earth moving ...... pretty much all broken down into 12v 100 AH or 6 volt 200AH packages or there abouts.

either two 12 v batteries in paralell or two 6 volt batteries in series

The other thing to consider is the N70 size battery is the most common and bang for bucks battery on the planet, because everything uses them, ya more likley to chisel a deal on an N70 than any other battery .... you will have more choice and a better chance of it being in stock.



4/ DC to DC chargers V direct charging from an alternator.

The notion that you can not or will not fully charge any given battery from an alternator is just rubbish, this is proven untrue in both theory and practice.

To compare the two methods of charging and the erroneous insistences we need to look at detail.

A/ ..... One of the contentions here is what is being considered "Fully Charged" and how is this being measured.

IF you take a battery that has been charged as far as it will on pretty much any given car alternator, then put it on a multi-stage "smart" charger, it probably wont read as fully charged .... WHY .... because the so called "smart" charger is making various assumptions and it's end of charge detection may well be at a higher voltage that the alternators charge voltage.

It must be understood that one of the ways multi-stage chargers ( including DC to DC chargers) stick charge to batteries as fast as they do is using voltages that simply would not be safe on a constant rate charger ..... some will push 16Volts in boost charge mode.

Any argument about state of charge has to discuss how that state of charge is being assessed ...... there are only two valid and accurate ways ..... steady state resting terminal voltage ( after the battery has been rested at least 1 hour preferably 4 hours) and electrolite specific gravity.

B/ ... Some batteries require higher charging voltages or require higher charging voltages when they are in certain conditions.

Many older car alternators where regulated at 13.8 volts, this is not sufficient for some ( but not all) batteries.

but those are not the major concern in many situations.

THE major concern

IF I have a 200AH battery and all my cabling is adequate ....... I have a DC to DC charger that is capable of delivering 20 amps .... that battery is at 50% SOC ... it will, take about 6 to 8 hours driving to " fully charge" that battery given charging losses and charge tapering.
In 2 or 3 hours it will not come close to fully charging that battery.

IF however I have the same battery on adequate cabling, being charged from an alternator capable or 120 amps ...... we will start by kicking in 50 or 60 amps and then drop back to 20 or 30 amps as the SOC increases.

In 2 or 3 hours driving the battery will be in a better state of charge being charged direct from an alternator than via a 20 amp DC to DC charger ..... assuming the battery will tolerate the Charge current and has sufficient charge acceptance.

C/ much of the blame for batteries not getting charge, can be due to inadequate cabling ...... cable size is more often than not underestimated.

D/ THE most common reason for batteries failing to charge and failing prematurely ..... is inaddequate charging time ....... no matter what battery or charging system, you cant hammer a battery all night and expect it to come back to full charge in 2 or 3 hours driving.

5/ OH and remember ALL batteries should be house in a situation where they are well ventilated, and acid leakage is considered an inevitable fact.

cheers
AnswerID: 612507

Follow Up By: Allan B (Sunshine Coast) - Saturday, Jul 15, 2017 at 09:22

Saturday, Jul 15, 2017 at 09:22
.
Ahhh, The Lead acid Battery........"PLANTE'S BOX of MISCONCEPTIONS"

It contains enough mystique to confound the audience for a millennium.

But The Bantam has delved deeply into its viscera and is witness to its secrets.

He is to be believed ----------- seriously.
Cheers
Allan

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Follow Up By: Tim F3 - Saturday, Jul 15, 2017 at 09:44

Saturday, Jul 15, 2017 at 09:44
Bantam thankyou for your exceptionally detailed response.

Slightly off the track might you consider this question.

If we are charging from a 2002 model landcruiser (not present day smart alternater ) 100 amp deep cycle batteries from 50 % soc....

Say a charging time of 2 hours ...if only one x 100 battery or if say 2 x 100 amp auxillary batteries , would the example of 2 batteries adsorb more energy (amps ) than the single battery being charged ?

ie..which example would receive the greater charge and power a load the longest ??
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Jul 15, 2017 at 09:52

Saturday, Jul 15, 2017 at 09:52
Tim, I have a proven answer to that, but I'll let Bantam go first.
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Follow Up By: Tim F3 - Saturday, Jul 15, 2017 at 09:58

Saturday, Jul 15, 2017 at 09:58
Will wait for the replies and learn.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Jul 15, 2017 at 11:50

Saturday, Jul 15, 2017 at 11:50
.
Tim, the Bantam seems to have gone fishing, so I'll go ahead.........

In your given time of 2 hours, if the alternator supplies say 20 Amps you will have contributed 40Ah to a single battery.
If you charge two batteries simultaneously from the alternator, and it is capable of supplying 20 Amps to each, then the contribution will be 40 plus 40 = 80 Ah in total.
So you now have doubled the amount of stored energy to power your load.

In the case of my own vehicle and charging system, the 120A alternator feeds two auxiliary batteries, each with its own 20A dc-dc charger. So they are “looked after” by good individual charging programs contributing a safely controlled optimum charge rate.

While the engine is running, a relay transfers the auxiliary load directly to the alternator so that the chargers do not support that load.

When the engine is ‘at rest’ the two batteries are joined by a relay to equally contribute to the auxiliary load.

This system has served me well. In my camping style, I am never at rest for more than a several days and the 220Ah storage easily maintains the fridge and a few small loads for that time. Full recharge is usually achieved within 4 hours driving time.
The batteries are now 6 years old and seem to be performing adequately.

Cheers
Allan

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Follow Up By: The Bantam - Sunday, Jul 16, 2017 at 10:58

Sunday, Jul 16, 2017 at 10:58
Yeh I went working then dancing ...... must go fishing some time soon.

IN theory of you charge two batteries in parallel directly from an adequate charging source, you will store more charge than a single battery of the same size.

BUT that assumes that your cabling delivers charge and discharge equally.

Very small differences in cable resistance can result in charging favoring one battery over the other ...... in the short term you will still pack more charge but if the cable path is not equal one battery will get lazy and fail before the other.

This is why Allan is charging each battery independently



The question is ...... is that 2 hours adequate to replace what has been drawn overnight pluss charging losses.

THIS is the predominating problem in caravan and touring battery use.

Thousands of batteries die each year because people simply do not put back more than they take out of their batteries day after day after day.

No matter how expensive or how big your batteries are they will die in a very short time.

cheers
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jul 16, 2017 at 11:33

Sunday, Jul 16, 2017 at 11:33
.
Bantam, I'm not much good at either dancing or fishing. You have my admiration.

Yes, in my example I necessarily assumed equal distribution of the charging current and ideally identical batteries etc.

I think Tim's expression of "2 hours" was a notional period but you are of course correct about adequate recharging. I have a pair of Volt/Amp meters on the dash and am reassured when I see the charge current diminishing in its final stage as an indication of approaching battery 'fulfilment'. I consider it a more useful guide than pondering over terminal voltage at various states of the battery.
Because my system is arranged to bypass the load currents past the chargers, the charger algorithm is not disturbed by accessory loads and the ammeter indication truly represents only the charge to the battery.
Cheers
Allan

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Reply By: Batt's - Saturday, Jul 15, 2017 at 08:58

Saturday, Jul 15, 2017 at 08:58
AGM batteries are not that expensive when you look at the extra life span you can get out of them. Also they are not suppose to leak acid if the casing cracks or vent gas like a wet cell which would make them safer all round. Also wait till people have a sale I bought an Amptech from Auto Barn when they had a 25% off sale, I also got one from Giant batteries on sale. I bought a Redarc BC DC charger from a 4WD ebay site and saved a couple of hundred on that. So instead of using wet cells in my canopy I could safely fit 2 AGM's maintenance free and hopefully hassle free for possibly 8 to 12 yrs.
AnswerID: 612528

Follow Up By: The Bantam - Sunday, Jul 16, 2017 at 11:34

Sunday, Jul 16, 2017 at 11:34
REGARDLESS we must assume that ALL batteries will vent explosive gasses and acid mist and will leak acid ..... any other assumption is simply irresponsible.

I've been working with batteries of all shapes and sizes since I was an apprentice & I have had to repair and clean up the mess many times when sealed batteries have leaked or failed.

Yes they are safer, but this is all to often overstated.

As far as the extra life.
Good quality rugged construction wet cell batteries have all the same technology used in AGM ...... in fact some manufacturers build exactly the same battery as AGM and wet cell.

A lot of the comparison is between AGM and low end wet cell batteries ....... compare apples for apples AGM is not as fantastic as it is made out to be.

Further
There is a lot of AGM being sold into situations that are inappropriate, and thus the far more expensive, AGM is not lasting as long as a battery 1/2 or 2/3 the price would.

Two particular issues are so very common

AGM being sold into under bonnet and other high temperature applications where the particular AGM battery does not have good high temperature tollerance.
One particular AGM battery that is very popular has a specified "Maximum operating temperature" of 45C ..... it gets a lot hotter than that under bonnet.
Some of the AGM manufacturers publish "temperature V lifespan" graphs they are very instructive.

AGM with "Low maximum initial charge current" being sold into situations where the charge current is not limited.
The same particular popular battery mentioned above has a maximum initial charge rate of around 20 amps ...... hooked straight to an alternator it will get hammered with over twice that.

People wonder what they get less than 12 months out of these when these two factors are combined.

One respected AGM manufacturer published a reserach paper on these two issues ...... they found that on a battery that could be expected to have an an effective service life of 6 to 8 years under ideal conditions, ( as indicated by their applications data) would fail in under 3 months with what many would consider reasonably modest over temperature and over charge treatment

Nothing wrong with the batteries ... just sold into the wrong applications.

AH YEH .... that same manufacturer builds other batteries with higher temperature tollerance and higher initial charge rates ...... but they are considerably more expensive.

As for getting 8 to 12 years out of a battery ...... you are dreaming.

A good quality AGM ( or for that matter a top spec wet cell battery) treated properly should get 5 or 6 years, no sweat ... the manufacturer testing, spec sheets and general experience will indicate that ....... but start capacity testing around that 5 or 6 year mark the capacity of the battery will be well below what it started with

sorry mate 12 years .. ya dreamin'

cheers
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jul 16, 2017 at 13:21

Sunday, Jul 16, 2017 at 13:21
.
Yeh, my pair of AGM's are just 6 years old and still serving my modest loads. But I really have no certainty of their storage capacity...... i haven't tested them.

But "12 years"????? I really don't think so.

Rather than wait much longer, I may replace them soon as a preventive maintenance operation rather than get caught-out. The question though is.... replace with what? What would be your choice Bantam?


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Allan

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Follow Up By: Frank P (NSW) - Sunday, Jul 16, 2017 at 14:49

Sunday, Jul 16, 2017 at 14:49
My name's not Bantam, but I'll light blue touchpaper and stand well clear (LOL) with this:

LITHIUM!!!! Yep, LiFePO4.

I'm a convert.

Cheers

PS this thread would have been so much shorter and less entertaining had the discussion been about lithium batteries. Maybe a few comments about top balancing vs bottom balancing, but that's about all there is to talk about. You charge them until they are full, and then stop.

Full is full. No temperature compensation, no SG, no Peukerts, no Charge Acceptance, no sulphation, no worries about sitting around partially charged. Just give them amps until they're full and switch off.

Flame Suit on and ducking for cover.
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Follow Up By: Tim F3 - Sunday, Jul 16, 2017 at 16:47

Sunday, Jul 16, 2017 at 16:47
Frank how do you dispose of lithium batteries and at what cost when they die ???
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jul 16, 2017 at 16:54

Sunday, Jul 16, 2017 at 16:54
.
Yes Frank, Lithium is tempting but changing everything to convert does not seem worthwhile.
Their cost would be worth more than the 15yo Troopy. lol
I'll pass this time.
Cheers
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Follow Up By: Frank P (NSW) - Sunday, Jul 16, 2017 at 21:25

Sunday, Jul 16, 2017 at 21:25
Tim F3

There are a few companies accepting lithium batteries for recycling at present. I expect my batteries to last 10+ years with my useage. In that time I expect the penetration of lithium batteries into the recreational market to increase significantly, and consequently the convenience of recycling will also increase and the cost, if any, to reduce.

I have not specifically looked into the cost, but owing to the performance and convenience of my batteries (360Ah) if it costs me a few $$ to recycle them in 10 years, I will happily pay.

Allan,

Depending on what you have already, you may not have to change anything. My dc-dc lead-acid charger is fully programmable. I can select suitable voltages for my LiFePO4 batteries. Likewise, my mains charger and MPPT solar regulator have voltage settings suitable for my LiFePO4. As far as current is concerned, for the application we're talking about in this thread they will happily take whatever you can supply.

There are lithium iron phosphate batteries on the market now that are specifically designed as drop-in replacements for N70 and other automotive and deep cycle lead-acid batteries. Charge straight off the alternator or with other lead-acid charging technology

As for cost, yes the initial outlay is significant. But the cost/useability/longevity equation easily surpasses that for lead-acid, IMO. Would you do it for a 15yo Troopy? - maybe not. But in a younger long-term touring vehicle it might be a good choice.

Horses for courses, I guess.

Cheers
FrankP

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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jul 16, 2017 at 21:48

Sunday, Jul 16, 2017 at 21:48
.

Ah, yes Frank, a younger man may do it for a younger Troopy..... LOL


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Allan

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Follow Up By: The Bantam - Monday, Jul 17, 2017 at 12:57

Monday, Jul 17, 2017 at 12:57
Lithium Iron Phosphate looks realy good apart from the price ... and that IS the sticking point.

In time I expect the price of lithium to come down, but at the moment being an early adopter has a hefty price tag.

There is a lot of AGM about and the lower end the price is reasonable , but when you get up into the high temperature and high current capability batteries the price starts to get steeper.

AND with AGM batteries ... "batteries ain't batteries , Sol" ... there is a wide range of quality and some very different technologies ...... the manufacturing processes can be very different.

As for what I am using ....... I've been using sealed maintenence free wet cell marine batteries a/ because they are reasonably cheap and B/ because I expect to crank or winch off them.

Till recently, my prefered brand is Supercharge, and they have been good to me and are well respected in the boating fishing scene.

The Catapillar earthmoving batteries are popular particularly if you have an account with a Catapillar dealer ...... they are a rugged construction battery just like a marine but with Earthmoving stamped on them.

I've just baught some AC delco Maine batteries, because with my security industry connections I can get them for about half what I expect to pay for Supercharge or an other marine battery thru normal channels. ...yeh not sure about em yet.

There realy is a lot of choice out there, buy it won't be presented to you unless you know to ask.

With the proliferation of small communications sites and solar ( for many purposes), there are some interesting packages, and a lot of battery dealers will have access to them ...... but if that dealer is from an automotive background, they won't even have looked at those pages of the catalogue.

In the RV 4WD market all we seem to hear about is AGM, as if there is no other reasonable choice .......

Get into serious remote power, heavy traction ( golf buggies, fork lifts, industrial machines) wet cell is still king and Trojan screw tops still dominate.

In smaller batteries under 20 AH, I hardly seem to hear the term AGM, most of those batteries could ligitimately be claimed as AGM, but that particular marketing term does not seem to have any traction in that area.

There most definitely ARE sealed lead acids out there that would be AGM but contian some free acid ...... this give the battery better temperature and over charge tolerance ...... but you hardly hear about them and you have to dig in the cataloges and web sites to find them.

Just like we are hearing very little about gell these days.

OH and what ever happened to Nickle Iron. ... that was heavily favoured in remote coms and aviation sites some time back

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Follow Up By: Batt's - Monday, Jul 17, 2017 at 15:01

Monday, Jul 17, 2017 at 15:01
I did say they don't vent gas "like a wet cell" meanig just that but off course they still will vent gas when they have to anyone can read that when looking up specs. I'm not sure about your idea thinking I'm dreaming of getting 8 -12yrs out of an agm as there are people getting that sort of time out of there's also I did say hopefully so if it happens that will be a good thing if it doesn't then that's how the cookie crumbles you can't just assume it cannot possibly happen as you are. As you know the unexpected can happen with any type of battery In April this yr I changed the battery out in my daughters 2010 Kia rio for the first time it was still starting the car without a problem but I didn't want her having any problems while she is away at uni. I've never had a starter batt last that long before in my 30 plus yrs of driving my neighbour has it now running a car radio in his shed.

It's just like any item you buy regardless of what it is you can hope to reach it's min or max life span, some things do some don't and some go beyond that you cannot definitely say it will never happen.
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Follow Up By: Allan B (Sunshine Coast) - Monday, Jul 17, 2017 at 15:28

Monday, Jul 17, 2017 at 15:28
.
Hi Batts,

Both Bantam and I have been working industrially and recreationally with batteries for a long time. Published information and our experiences have revealed that ANY lead-acid battery progressively diminishes in stored capacity both with age and charge/discharge cycles. Manufacturers state life cycles for their batteries.

Certainly, a battery may continue to hold and deliver SOME energy as it ages but it will progressively diminish. The battery does not "last" for 'x' years, it survives to a degree for some time. The decreasing capacity of the battery will cause it to reach a point where it can no longer support the applied loads.

If you select a battery whose size can still support the load after losing considerable capacity then clearly you must have started with a battery of greater size than was required. This may not make economic sense. You invest more capital, take up more space and drag around excess weight.

So OK, you may get a battery to "LAST" for a longer time, in some form, but is that a sensible, economic performance of a battery?
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Allan

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Follow Up By: The Bantam - Monday, Jul 17, 2017 at 15:38

Monday, Jul 17, 2017 at 15:38
actually there should be no difference between how much a wet cell and starved cell battery vents if they are both sealed valve regulated types of equavalent quality..

AND people don't read the specs ....... more particularly people don't read the engineering notes

many sales people and even the some brochures for various sealed batteries over play the sealed and non leaking thing ....... when the engineering notes and the cautionary statements tell a whole other story.

people don't look at the detail ...... Yeh and these sealed batteries vent more than people want to believe ........ they may not be pissing out acid and gobs of explosive gas mix like screw tops do ...... but in the operating temperatures we encounter in Australia they can and will vent in normal operation.

yeh lots of people think they are getting long lives out of batteries, but for the last 2 or 3 years they are probably at 30% to 50% of their specified capacity ......... Yeh I've had 7 years out of an ordinary battery in my old L300 ...... but as long as one plug fired it would run ..... let me tell you when that new battery went in it spun the motor over lickety split.

Yeh ya might get 10 years functional life out of a quality AGM .... IF it is in a 25C temperature controlled room, free of vibration and regulated at exactly the prescribed voltage, never gets deep cycled and hardly ever gets loaded. ... AND that function does not require it to deliver large currents or perform anywhere near capacity.

The manufacturer graphs and research papers tell a pretty accurate story.

Yeh they might have got silly battery life but for the last 3 years it would not hold the fridge up for more than a day.

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