Gel batteries and lead acid batteries on line?

[driveon]

OKAY, now lets say I’m totally wrong in the use of parallel batteries and you all say, in one way or another that there are potential problems, which I do not deny, but can you please explain why so many people are NOT having these potential problems and cormorant, I know of people who are lucky to get 6 months out of a battery and I also know of many MANY people who have been running dissimilar batteries in parallel set ups for 5, 6 and even 7 years.

So as posted quite a few times now, while there may be some theoretical problems with running batteries in parallel, in reality, these theoretical problems don’t show up.

[cormorant]

My guess is that 99% of people have no idea they are not getting full value from their batteries and just accept a short lifespan and replace them.

In reality in high spec systems where you pay for ever watt of power and you calculate dthe cost of one system over another you need to get full value and then the exact charging and discharging becomes very important and does the full useable life of a battery.

I think many of the systems that survive a longer time could survive even longer with correct set up .

Back to the start and I guess 99% of people overspec their batteries , expect only average performance and get exactly what they expect never realising what they are missing. Due to a business my brother was involved in we regularly charged and disgcharge tested batteries and even from new with 5 or 10 cycles exactly to manufacturers specs ( serious computer controlled charger in temp controlled room) only a couple of brands ever met and exceeded specs on a regular basis. The tail off in performance of somem brands was serious and although they didn't die if called for in an emergency on the medical equipment or such you would be stuffed.

Doesn't mean it is right and a lot of it comes from simplified advice that is not specific to the situation.

[driveon]

Cormorant, you said it in one, “YOU GUESS”

Can you tell me where you got the figure of 99% from, because, as I posted, this is my specific field and I don’t just play with some test batteries, I work in the RV industry, designing and manufacturing dual battery controllers and full systems, and I have never heard of figures like that.

A bit of scotch mist I think.

And in keeping with this threads mythical theme, you still haven’t posted either why you shouldn’t parallel batteries, or what mythical problems will occur if you do.

Put simply, the real life facts just don't match the myths being posted here.

I’m serious, if you or anyone else knows of a genuine on going problem that occurs when batteries are paralleled, please post the info up so we can all see, but can you also state when it’s nothing more than a suspicion or a theory, because it would greatly help the credibility of this thread for dnej’s benefit.

[foxx510]

I’m serious, if you or anyone else knows of a genuine on going problem that occurs when batteries are paralleled, please post the info up so we can all see, but can you also state when it’s nothing more than a suspicion or a theory, because it would greatly help the credibility of this thread for dnej’s benefit.

Actually driveon, and don't take this as a personal attack, you are in fact arguing against hard facts like ohms law, internal resistance and gassing voltages here!

They aren't just "theories or myths" they are as-good-as-it-gets facts. Using the old "I'm yet to have a problem" argument isn't that strong in this case in my opinion.

I'm not having a go, I'd like to keep this friendly so we can all learn something. I'm not here to prove anyone wrong to make myself feel good, I hope noone else is.

[cormorant]

Well shit my scientific testing of batteries is nothing compared to your "EXPERIENCE" OF BANGING THEM IN rv for clueless owners to drop back in every now and again and piss in your pocket. I'll give you a hint the batteries we dealt with were used daily and we priced supply contracts and leases based on their performance. When we had to used unmatched batteries we had massive underperformance issues but on occasions had little choice in order to keep coustomers businesses running till we could install new battery packs.

When was the last time you grabbed a mixed battery pack and charged and discharged it repetably and compared it's performance to a matched pack?

I'll spell it out as my other post wasn't clear.

How do you charge different styles of batteries 100% in the same bank????? That is the problem I see with doing it. The manufacturers set out a charging schedule for the best possible life and performance of the battery and I can't see how this can be achieved unless the 2 different batteries have the same specific charging schedules.

You are pretty good at not answering questions

My use of the word "i guess" and the % is probably understating the lack of knowledge about electrical components and how they really work and was more in reference to how a client could possibly guage the true charge and discharge of their battery systems. RV are slightly different in some aspects as they are often connected to mains or gererator power and via a decent charger they have the ability to fully charge a battery - that option is not avaliable on a smaller boat using a outboard alternator.

[driveon]

Hi fox, I don’t take you as having a go or attacking me or anything else like that, I take it as debating and with any debate, there is obviously two ( or more ) points of view and while I have no intentions of arguing against the laws of physics, they are not rally related, as being put forward here, to what is happening in the real world.

I’ll not continue with my rant about how you can parallel batteries, but please, anyone who knows of problem that occurs when doing so, please post up the info.

Fox, I’m cheating here, by playing with a marked deck, because I know there are no problems.

Cheers

[foxx510]

....while I have no intentions of arguing against the laws of physics, they are not rally related, as being put forward here, to what is happening in the real world.

Cheers

I'm not sure how they aren't related though, if they are the laws of physics!

What happens for example when you have two batteries in parallel, one with half the internal resistance of the other. Doesn't ohms law say that the one with the higher internal resistance will be delivering half the current? Won't the same occur during charging?

[driveon]

Cormorant, for a starter, the majority of people, when on a trip, want as much used capacity replaced as is possible while driving and this means their alternator is doing all the work.

In these situations, which from first hand experience is how MOST RV users do it, the alternator is supplying current at at least 13.2 volts. As all 12 volt lead acid batteries are in a fully charged state at 12.8 or less volts depending on the type of battery, being as the applied voltage is at least 13.2 volts or higher, from an alternator, all batteries, no matter how many or what type, will be able to be fully charged and no one battery will have any effect on any other battery because the alternator’s voltage is the controlling voltage.

Using a battery charge is a little different but you can not fully charge one battery while any other battery in the set up is low. The lowest charged battery will draw the greatest portion of the battery chargers current ( if not all of it ) until all the batteries are about the same SoC and then the voltage will rise evenly over all the batteries.

In both situations, whether the batteries are being charged by an alternator or a battery charger, it’s time that controls when the batteries are fully charged, not what type but because an alternator is virtually a constant voltage type charger, one type of battery can reach a fully charged state before another type but the same thing will happen if you have two identical batteries but where one battery is lower than the other when you start charging, the higher charged battery will reach a fully charged state first.

With a battery charge, no matter how different the SoC of each battery when you start, because battery charges are constant current chargers, all the batteries will reach a fully charged state at around the same time.

[driveon]

Hi Fox, just following on from my last post. Just because one type of battery can be charged quicker than another type, that battery still needs the current to be available in the first place and again, if one battery in a set up is lower than the other battery, a battery chargers current is going to be draw by the lowest battery is the set up until all the batteries are about the same SoC.

In a constant current charging system,like how battery chargers work, the voltage of each battery is the controlling factor and the lower the state of charge of a given battery, the greater the current absorption that battery will take.

[foxx510]

With a battery charge, no matter how different the SoC of each battery when you start, because battery charges are constant current chargers, all the batteries will reach a fully charged state at around the same time.

So you are saying internal resistance has no effect on this at all?

[cormorant]

"Using a battery charge is a little different but you can not fully charge one battery while any other battery in the set up is low. The lowest charged battery will draw the greatest portion of the battery chargers current ( if not all of it ) until all the batteries are about the same SoC and then the voltage will rise evenly over all the batteries."


So when battery a comes up from 10.5v to the same level as battery B they happily charge up until one battery ( the lead acid ) is 100% charged. Then what happens? . The current doesn't stop going in and battery b ( a gel) requires more charging but at a slower rate ( by the manufacturers book) to reach 100% capacity. Fact is it never will as it will get too hot and the other battery will boil. It won't as the alternator will cut out assuming it is only charging a lead acid battery. So the gel will never get to 100% charge??

The only way around this is to have a charger finish the charging to get a battery to 100% or a step up.

Is this not a issue?

Do you think a battery will last it's expcted spec life if not fully charged and charged at the incorrect rate and not by the manufacturers table.?

What battery and battery company is that good and will accept my warranty return in 3 years when it fails?

[driveon]

So you are saying internal resistance has no effect on this at all?

No, my reply was just over simplified but the argument is that there are going to be problems, and I’m saying there is not, even with the differences in internal resistance between the different types of batteries.

[driveon]

It won't as the alternator will cut out assuming it is only charging a lead acid battery. So the gel will never get to 100% charge??

Cormorant, I don’t know what you are on about.

For a starter, can you point me in the direction of an alternator that knows when a battery is fully charged, they just don’t work that way.

Most modern alternators, when the motor is first started, will produce current at a give voltage, any thing from 14.2 to 14.8 volts for a given period of time, and then they settle back to their constant operating voltage which can be anything from 14.0 volts down to 13.8 volts and thats where they stay, whether the batteries, cranking of others, are fully charged or not.

The time they run at a higher voltage varies from one vehicle manufacturer to another and can be anything from a few minutes to 30 minutes.

Furthermore, you can fully charge most batteries ( the only real exception being some calcium/lead/calcium batteries) with just 13.2 volts and no one has to take my word on this as they can easily test this one for themselves.

So I don’t know what you base you reply on.

One more point cormorant, there is no way to determine if a battery if 100% charged short of taking the battery to a laboratory and having it analysed.

Even when using something like an Xantrex battery monitoring system, the very best accuracy they state they can give is 98% so your doing real well if you can better that.

[dnej]

from an uneducated battery person, if indeed charging is a problem ,as some think, would one of those units that knows which battery is the lowest, be appropriate, so as only one battery gets charged at a time, or doesnt that work in this instance. Cant remember the name of the product
David

[foxx510]

Where are these batteries being used?