Gel batteries and lead acid batteries on line?

[cormorant]

A previous thread with discussion on batteries and connections.

http://www.ausfish.com.au/vforum/sho...=116996&page=4

[Fed]

A FULLY CHARGED battery has LOW internal resistance, and as the battery discharges, it's internal resistance INCREASES.

Therefore, if you try to charge two batteries in PARALLEL, the battery with the higher charge offers a lower resistance to the flow of current from the charger, and therefore will take most of the current (charge).

In fact the reverse of this is true and the opposite naturally occurs.

Also the real upside to using a battery 1/2/Both/Off switch is to avoid one good battery masking a failing battery.

[TOPAZ]

Oops!

I had always believed this to be true, but on further investigation, I was wrong!

Apologies to all for a misleading post!


Richard (with tail between legs!)

[oldboot]

Oh dear here we go again.

Let me start by saying I do know the difference between series and paralell......As do several of the other much more learned respondents to this thread.

One thing I have come to understand is that there are a great many people installing battery systems and blaitantly ignoring long standing manufacturers recommendations and proven good practice and getting away with it......for a number of reasons......
1/ lead acid batteries are crude tough old things and they will put up with all sorts of stupidity and still work ( to a point),
2/ the vast majority of end users have no ability to assess the performance of their battery system accurately, so they have no Idea if their system is giving the best life out of their batteries,
3/ there are so many other factors that cloud the issue and influence the life of batteries.,
4/ A little BS goes a long way..... especilay with a customer that knows next to nothing.....How many times have you beed BSed this week.

Now onto why you should not IDEALY charge any battery in paralell especilay dis-similar ones.

1/ failure of one battery can degrade the charging and possibly cause the second battery to fail, by discharging it at rest till it dies........this is the most obvious.

2/batteries with different voltage and current charastics WILL NOT charge evenly, the more dissimilar the batteries the worse the imbalance, so one battery may run hotter that the other......this can be a particular problem when the smaller battery also comes to charge at a lower terminal voltage......as we should know a major cause of reduced battery life is heat.

3/ there are problems with batteries that are discharged seperately then charged UNMANAGED in paralell, a fully charged battery ( say the start battery) will discharge into the discharged battery ( say the house battery) as soon as they are paralelled, if strong charging is not commenced the result will be two discharged batteries.

now here is a practical example of a problem
we have a traditional lead acid battery of say 55AH ( car battery size) rigged in paralell to a valve regulated sealed lead acid battery of say 15AH... instaled on its side.......these are being charged by a magnito charging system of a 60Hp outboard motor that regulates at about 15 volts.
This boat has a long range tank and goes for an all day run... both batteries were fully charged prior to the trip........the boat is started and the batteries rapidly return to full charge say within 5 minutes ( typical for my boat anyway). the boat runs ar 4000 RPM contunuoulsy for 4 hours to the reef.... apart from the VHF radio and the suonder no electrics are used....the boat runs 4 hours back to the ramp.

Now.....the big battery is quite happy to gass its little head off for a few hours, worst effect is the loss of a little water.
The SLA however comes does not like being charged for 8 hours at 15 volts.... gets a little warm and vents as designed........because it is on its side it vents a smal amount of acid onto the deck.........If this arrangement is run daily in say a crabbing boat ( even iff the SLA is installed upright I would expect a shortened life from the smaller battery.

Now another thing that has to be understood is that the bigger the battery and mor proportionate the charging system the less some of these factors will appear to be problems.
Additionaly If the charging system regulates to less than 13.8 V, less problems will be had.

If we are charging a 120AH battery in paralell with a 90AH battery with a 50+ amp alternator at 13,8 volts, that is one thing......If however we are charging a 120 AH battery in paralell with a 7AH battery is a different thing all together.

Now I can tell you the concept of batteries self regulating their charge rate is a myth.........This has been proven to me and confirmed my my own tests ......AND I have had to eat my words on this matter on this very forum.
If a battery is in healthy condition and the charging source is capable of delivering enough current...... many batteries will accept enough current to cause damage even at 13.8 volts.
There are certain batteries that will self regulate but this is not normal.

Many manufacturers strongly recomend against unmanaged paralell charging, the training I recieved and much of what I have read ( texts not internet) recommends against paralell charging, particularly of dis-similar batteries.

Now that said....I do not believe that unmanaged paralell charging of batteries is a great sin.....its just something best avoided where possible.

In telephone exchanges where we maintained multiple 1000AH 50V banks, and where we kept records of individual cell voltages and specific gravities, ( and submit them like tax returns) we were drilled to charge and use the banks individulay..... BUT.... the battery management panel had the facility to paralell charge.
The battery polocy of such institutions is bassed on thousands of banks over decades of use, with stringent record keeping.


now a couple of other unaddressed issues.
True gell batteries are a pretty rare and expensive thing these days...... but the term "gel battery" is slashed arround to discribe any sealed lead acid battery... which is a long way from the truth.
We need to be sure of what we are talking about.
The majority of the sealed lead acid batteries we see are "valve regulated sealed lead acid" batteries where the space between the plates is occupied by some sort of porus material that holds the acid......the acid remains very much liquid.

there has been at least one court casein this country recently about an importer not correctly discribing their battery construction. We need to be accurate and sure of the type of battery we are talknig about,

If you realy want to know some stuff about batteries have a look at some of the manufacturers sites.....the sonnenschein site is a real good one.......when it comes to modern gell battery technology ......sonnenschein own the game......most of the worthwhile gell batteries use technology licenced from sonnenschein.......sonnenschein was baught by one of the big battery players a few years ago.

the panasonic VLRA web page is also very good.

Now another matter of concern is that the charging systems on small to medium outboard motors is generaly weak and crude in comparison to an automotive alternator.
If you think you are going to charge a 120 AH battery from flat with any 60Hp, in what would be considered a normal run time outboard you are dreaming .....most cars will push out at least 40 amps from their alternator some heavy vehicles and some moder cars will push out 100A plus.
A small to medium outboard may push out as little as 8 amps and probaly no more than 20 amps, and the available current will vary considerably with motor RPM.
In addition the output voltage will be far less ideal than that of a car.
The bigger outboard motors will have what looks and works more like a car alternator.


cheers

[driveon]

Hi old boot, and sorry mate but I got about halfway through your post and gave up.

Most of that is nothing more than hype and has little to do with reality.

Does the average user actually know how well their batteries are being charged, probably not, but if users are regularly getting 5, 6 and 7+ years of use from their batteries, then they can’t be doing to much mythical harm to their batteries by paralleling them.

Denj’s question relates to paralleling batteries where an alternator is the primary charging device. Providing he has used adequate sized cable to connect everything up with, most of your theoretical post has nothing to do with what he will get from his batteries.

For example, why will paralleling a 120 A/H battery with a 7 A/H battery pose any problems. For many years I manufactured car alarms where the backup battery was a 1.2 A/H 12v gel cell battery wired in parallel with the vehicle’s cranking battery and I produced well over 10 thousand of these devices and the only time there was a problem is when the cranking battery either failed or was disconnected and the alarm triggered, powered via the gel cell, which is exactly what it was supposed to do.

I started manufacturing these devices nearly thirty years ago and by now I imagine, if the vehicles are still around, the backup battery would be stuffed but the alarm would have notified the owner when it was.

As I gave a 5 year warranty with all our alarms, if your theory was correct, I would not have been in business very long, yet I not only manufactured these devices for nearly 15 years, they were also on a number of insurance companies recommended car alarm lists, and again if my gear had failed as you theories it should have, I would not have been on their lists for long.

Next as you just touched on, if the charging voltage is high enough, there is no way that one battery, of any type will effect the charging of any other battery type or size.

Once the motor is started, even with some of the modern alternators running as low as 13.2v, because the alternator’s voltage is always going to be higher than the highest fully charged voltage of ANY vehicle battery, there is just no way that one battery will effect any other battery.

As posted earlier in this thread, I base my finding on 20 years of hands on experience and not just a couple of tests.

[TheRealAndy]

Dont waste your time oldboot

[driveon]

So what your saying Andy, is because you are convinced a myth is correct, all those using dual battery set ups and not having problems are getting it wrong.

All I can say is that I’m glad I don’t have an EXPERT like you working with my gear.

As I have posted repeatedly and not just in this forum, if anybody knows of any on going problem caused by paralleling batteries, please, for the benefit of all, post up the info, and not mythical unsubstantiated theories, because Andy, that’s all you have done, especially when there are many thousands of people, who are not only doing it and have been doing it for many years and contrary to the statements that this won’t work or will damage batteries and shorten their lives, the test of time has clealy shown that there is no problem.

[oldboot]

Here is the bottom line.

regardless of what anybody has been "getting away with" for any period of time.

Charging any batteries unmanaged in paralell, especilay mismatched units... is not, never was, and never will be, best practice.

If any body can produce an authorative text, from a volume high reliability battery user, such as the millitary , aviation or communications, a manufacturer of quality batteries or a reputable text book ..... that recommends charging batteries unmanaged in paralell in preference to charging batteries individulay.....I am only too keen to see it........ but somehow I don't see that happening anytime soon.

If it was not preferable to independently manage the charging of batteries, there would not be a market for charge management devices both for low end, low reliability uses such as camping and motorhomes but also for seriously engineered high reliability applications.

If you wish to justify a view that does not conform to conventional practice as taught and practiced for decades.......( as you seem to be intent on)......the ownus is upon you to provide the proof, not those of us that subscribe ( with reasonable experience proof) to the accepted view........the fact that you get away with something is proof only that it is reasonable to expect to get away with it.

As for your manners, "Driveon", a number of people have tried to have a sensible discussion and have measuered their responses....you however are intent on pushing your point to the exclusion of the views of others and have professionaly insulted several whom I know to be wise and learned in such matters.

As for the original post.
Yes.... it is possible to "get away with" paralell charging the batteries in question, However charging independently or using some form of charge management device would be a better option.

cheers

[driveon]

Oldboot, I fail to see how you can justify your comments as being related to best practice and all the other terms you continually use to validate your argument when tens of thousands of people are doing exactly what I have been saying will work and it is working for them.

Further, you and your mate have continually stated that this form of set up won’t work and batteries will have a short life span and so, yet in reality, quite the opposite is the case.

Oldboot you have put up what I consider valid arguments but can you prove that these arguments will be what is found in real life, because so far that is all you have put up, arguments with out proof.

You and your mate have put up all forms of scenarios that supposedly support your claims, but neither of you have has posted one single fault that is reoccurring and could be construed as showing there is a problem with paralleling batteries in the way denj is intending to use his batteries.

As continually posted, if there is a problem, post up the info to back your claims.

To back my claims, if any one of your theoretical problems was actually happening in the real world, then being as there are literally tens of thousands of people using this type of set up on a day to day basis, if your theories were correct, there would be lines of disgruntled customers at the different caravan and motor home manufacturer’s and a similar scenes at every battery service centre. This is just not the case.

And making statement like “ they get away with it “ is nothing more than scare mongering and as to my manor, I have posted heaps of validating info that can easily be check yet you and your mate have not once post anything justify your theories.

Please, if there are so many problems with paralleling batteries, as you and your mate make out, why can't you simply show us the evidence?

[oldboot]

Drive on I have tried my best both now and in the past (as have others) to have a civilised and rational discussion but you consistently fail to consider that any one else may be in possession of facts or views that could possibly bring into question any view or opinion you may hold.

In the past you have been presented with facts, clear and plain worded evidence from major manufacturers published data and application information but still claim your view is superiour.

I am convinced that you are incapable of admitting any of your technical views may be questionable.

As others have pointed out to me it is completly pointless arguing with you. you are rude, arogant and poorly informed

Above all my concern is that innocent people may take you views as being fact... and thus be misguided.

look to the left of this screen to the thanks records of the various respondents, and you will see how the opinions of the various people are regarded.

Be well aware that in future I will be far less restrained when I come across you one eyed and poorly infromed posts.

Should see you plainly insult someones professional or personal reputation, as you have both in this post and in the past, I will have no hesitation what so ever reporting you to the moderators.

I thank others for there forebearance.

cheers

[driveon]

Above all my concern is that innocent people may take you views as being fact... and thus be misguided.

That's rich mate, because during this debate, I have repeatedly posted up examples to back what I have been saying.

While on the other hand, you have repeated made statements like best practice and so on but you have not once posted one single instance of a real life situation where paralleled batteries have caused a problem.

Your last post is nothing but a smoke screen.

If you are so right with all your theories, why can’t you post a single instance to back just one of your theories.

You can call me all the names you want, it’ doesn’t hide the fact that you have been using unsubstantiated theories as the basis of your arguments.

While your at it, how about posting a link to some of these best practice documents. Your quick to use these sorts of terms but so far, we only have your word for them, and to clarify, we are talking about paralleling batteries in automotive situations.

So I and I imagine others, would appreciate links to some of the “Major manufacturer’s published data” you keep referring to.

The ball is in your court oldboot.

[oldboot]

Ahh somehow I think shouting into the wind wound be a more productive use of my time.

cheers

[foxx510]

Yes it's an argument that can't be resolved here, there are knowledgeable people with different opinions. None of which is helping dnej with his question.

We have to respect the fact that driveon has years of commercial experience under his belt and hasn't encountered problems, but I think driveon should acknowledge that gel batteries generally have a terminal charge voltage that is lower than that of flooded wet batteries to avoid gassing and generally have a different charge algorithm to that of flooded wet cells. There's plenty of data to support that fact and I doubt he would argue that. There is evidence to suggest that a vehicle alternator can go above 14.4v, the upper limit of most gel batteries.

[driveon]

Hi Fox, and while I do agree with you, it is highly unlikely that there are to many alternators that run at voltages over 14.2 volts and most modern alternators, after their initial boost cycle, actually run at much lower voltages.

In any case this will have little to do with paralleling batteries.

I’m still waiting for oldboot to post one single example of where any of these mythical problems he keeps claiming will happen, has happened.

Oldboot, statements like “shouting into the wind” is again, nothing more than a smoke screen. You have made numerous statements condemning the operation of paralleled batteries but you flatly refuse to backup these statements.

With respect to you Fox, it’s unsubstantiated and I might add, mythical claims like oldboots that cause unsuspecting people to go out and spend bucket loads of money on things they just don’t need and in many cases, will actually increase the chances of stuffing their batteries, not lessen the chances.

[cormorant]

For a problem that doesn't exist here is a company that has gone to some effort to create a specific marine product that can do it with battery banks. It all depends on what safety level , how long you want your batteries and alternator to last.

http://www.dg2k.co.uk/xalt.htm