marine battery chargers are they worth the difference in price

[halcyon]

Sorry that seems basically incoherent as well as wrong.
When any current is flowing, either charge or discharge, voltage will be a function of capacity as well as state of charge, since the characteristic curves of a lead -acid battery are pretty much a function of current/capacity. That's why you see graphs labelled c/10, c/20 etc etc.

I have been designing VSR's and multi-stage mains battery chargers since late 1970's early 80's, have those graphs I generated back then still on file. A VSR works on those curves to distribute the charge, not perfect, I have alternate ways, but simple and reliable.

But you cannot discharge or charge one battery more than another, outside working tolerance if they are linked in parallel, unless one is faulty.

Brian

 

[PaulRainbow]

It's a technical subject. People who aren't prepared to take it seriously should leave well alone lest their boats catch fire.

The problem is sort out the lazy people from the completely clueless who need to be told to leave well alone lest they do real damage.
If you expect people to give quality advice that they are going to put some effort into and take care that it's safe and helpful, people need to put a bit of effort into asking the question to show as much understanding as they have.

Yes, they're the people who appreciate the difference between an amp and and amp-hour and make the effort to communicate that.

Sorry that seems basically incoherent as well as wrong.
When any current is flowing, either charge or discharge, voltage will be a function of capacity as well as state of charge, since the characteristic curves of a lead -acid battery are pretty much a function of current/capacity. That's why you see graphs labelled c/10, c/20 etc etc.

You might want to take some of your own advice.

 

[lw395]

You still can't show anything from a reputable battery maker advising that it's OK to parallel assorted batteries in a bank?

 

[PaulRainbow]

I'd be most grateful if you would, if there's anything I need to change I'd appreciate the advice. :encouragement:

At a glance, i can't see anything wrong with your charging arrangements, but they don't work as you think.

The starter battery is charged primarily by the alternator until it is fully charged. When fully charged, the Cyrix battery combiner will close and allow the alternator to charge the house batteries - as they are all the same chemistry this is fine as the charge voltages are all the same - technically they are in parallel, but only under certain conditions, and only when charging. The starter battery will be fully charged when the combiner closes, and it will draw little current - this method is recommended by Victron who supplied most of the components, it also works in reverse and charges the starter battery from the solar when the house batteries are full.

The Cyrix will close after 10 mins of >13v and will stay closed whilst one bank is >12.8v. It has no real way of knowing when the batteries are fully charged, it can only sense terminal voltage and when a charging source is active that voltage is more likely to be that of the charging source.

So in the morning, when the Sun wakes up, and the panel voltage exceeds the battery voltage by 5v, the solar controller will start. After 10 minutes the VSR will close and the batteries will be in parallel. They will stay in parallel until the terminal voltages of both banks are <12.8v. All day, everyday, your little engine battery will be in parallel with the domestic bank. Contrary to what some people will argue on here, that doesn't seem to be doing your batteries any harm. It doesn't seem to be doing any harm to the millions of other boats out there that have the same, or similar, charging systems.

The battery combiner replaces the old diode based isolator (and removes the voltage drop). The other advantage of the combiner is that there is a start-assist function which will combine starter and house batteries for 30secs on a button press should the starter battery be dead for some reason - then the engine can be started by the house batteries.

I'm familiar with the Cyrix, it's a microprocessor controlled relay. I've fitted many of them, i have one on my own boat.

The alternator isn't the best charging method and I would have preferred to put a smart-charge system between the alternator and the batteries but cost was an issue so it looks like it does.

In a perfect World, on a boat with multiple battery banks, alternator charging isn't perfect. On paper, we should have a system that charges each bank completely individually. But then we'd have to fit different systems for the other charging sources and it would be very expensive. In the real World, we compromise a little and the theoretical shortening of our batteries lives is perfectly acceptable. Our batteries last several years and don't cost a fortune.

The Victron 30A charger has 3 independent charging circuits, I use 2 ... one for the starter and one for the house bank so they are charged seperately. I was worried about the combiner kicking in and confusing the charger but according to Victron this isn't an issue and so far, one year in, I have no problems at all.

This is incorrect. The Victron charger has three outputs, but they are all taken from the same charger circuitry, they are simply separated by diodes. The charger can only act on the sensing from one battery bank, all batteries will be charged at the same voltages. The diodes keep the batteries "separate", with having them in parallel.

However, as you have the VSR, the charger will cause the relay to behave exactly the same as the solar controller does, your batteries will again be in parallel. As you have the VSR you could have fitted a single output mains charger, ti would work exactly the same as what you now have.

As i said earlier though, there is nothing wrong with what you have. My original point was, the doom and gloom comments from lw395 are not really reflective of real World applications on boats. Having a 80ah and a 100ah battery in parallel isn't going to be much different to how your batteries are connected.

 

[PaulRainbow]

You still can't show anything from a reputable battery maker advising that it's OK to parallel assorted batteries in a bank?

I can show evidence of millions of boats that have different batteries in parallel without any noticeable ill effects. We're not talking "assorted" batteries anyway, you introduced that nonsense. The OP plans to add an additional battery of slightly different capacity. If those batteries are the same chemistry, there isn't a problem.

 

[Baggywrinkle]

At a glance, i can't see anything wrong with your charging arrangements, but they don't work as you think. ......

Many thanks for that :encouragement:, you live and learn. I can see that during charging, wherever it comes from, the starter battery and house bank are in parallel unless I've shut off the breaker to the Cyrix. From the Cyrix data sheet it looks like they are not connected when no longer charging as the "at rest" or "under load" battery voltages will never be above the Cyrix connection voltage.

Can you answer one more question, why are there recommendations not to mix old/new or different Ah batteries in a parallel house bank?

I assumed it was because the older battery may no longer be as efficient and that there could be currents circulating from one battery through the other, potentially causing early failure of the newer battery. The effects of a failing older battery would be masked to some extent by the new battery until both were shot. Is this correct?

 

[PaulRainbow]

Many thanks for that :encouragement:, you live and learn. I can see that during charging, wherever it comes from, the starter battery and house bank are in parallel unless I've shut off the breaker to the Cyrix. From the Cyrix data sheet it looks like they are not connected when no longer charging as the "at rest" or "under load" battery voltages will never be above the Cyrix connection voltage.

The Cyrix wouldn't ve closed for long after charging stopped, as soon as the voltage falls below the disconnect voltage of 12.8v for 4 minutes.

But when your solar starts charging in the morning, it will be a maximum of 10 minutes before it closes. If the solar controller voltage starts at >13.8 V it will close in 4 seconds.

Can you answer one more question, why are there recommendations not to mix old/new or different Ah batteries in a parallel house bank?

It's a basic principle that old/new batteries shouldn't be mixed, but that might depend on how old the "old" batteries are. If they are on their last legs it would clearly be silly to add a new one. But, if the existing ones were fairly new one might think it a reasonable risk to add a new battery.

Let's say you have a bank of 6 x Trojan T105s and one fails while it's in warranty, i wonder if Trojan would replace all 6 free of charge ?

Providing the batteries are the same chemistry, i don't see a problem with having an 80ah and a 100ah in the same bank, in parallel. Wiring in series is a different ballgame.

 

[Baggywrinkle]

The Cyrix wouldn't ve closed for long after charging stopped, as soon as the voltage falls below the disconnect voltage of 12.8v for 4 minutes.

But when your solar starts charging in the morning, it will be a maximum of 10 minutes before it closes. If the solar controller voltage starts at >13.8 V it will close in 4 seconds.

When I get up in the morning, the house batteries are usually at about 90% according to the monitor - the fridge saw off the last house battery and was the reason I went for solar and increased the capacity. By lunch time everything is up to 100% and stays that way until late afternoon. It works well even if I misunderstood how the Cyrix worked when I built it.

It's a basic principle that old/new batteries shouldn't be mixed, but that might depend on how old the "old" batteries are. If they are on their last legs it would clearly be silly to add a new one. But, if the existing ones were fairly new one might think it a reasonable risk to add a new battery.

Let's say you have a bank of 6 x Trojan T105s and one fails while it's in warranty, i wonder if Trojan would replace all 6 free of charge ?

Providing the batteries are the same chemistry, i don't see a problem with having an 80ah and a 100ah in the same bank, in parallel. Wiring in series is a different ballgame.

Thinking about it, I would have happily replaced the starter battery without replacing the house batteries, and they are charged in parallel. Was more concerned about the long term effects of cycling 2 different house batteries connected in parallel.

 

[PaulRainbow]

When I get up in the morning, the house batteries are usually at about 90% according to the monitor - the fridge saw off the last house battery and was the reason I went for solar and increased the capacity. By lunch time everything is up to 100% and stays that way until late afternoon. It works well even if I misunderstood how the Cyrix worked when I built it.

It's a good system and should work well, as you say. The fact the batteries are paralleled more than you though isn't an issue, there are millions of such installations. Mine is very, very similar to yours. I have 3x domestic batteries, 1 x starter battery, 260w of solar, Victron MPPT controller and a Cyrix. My charger is Sterling, but very similar in operation to the Victron.

 

[lw395]

...... Was more concerned about the long term effects of cycling 2 different house batteries connected in parallel.

That is the issue which Paul cannot deal with.

 

[PaulRainbow]

That is the issue which Paul cannot deal with.

No, that's the issue that you don't understand. Go away and learn the subject before peaching to others how they should do it.

 

[lw395]

No, that's the issue that you don't understand. Go away and learn the subject before peaching to others how they should do it.

Still waiting for you to find a single battery manufacturer who advises mixing ages and capacities doesn't matter.

 

[PaulRainbow]

Still waiting for you to find a single battery manufacturer who advises mixing ages and capacities doesn't matter.

Now you're just trolling.

 

[dunkelly]

I am suitably chastised for my lazy and ignorant notation in my earlier post but for someone to chastise others for such things and then to post a series of grammatically incorrect postings is equally ignorant . All i wanted was some advice . Something as a relative newcomer to the site i rather stupidly thought was what this forum was for . I am only trying to learn, something i thought me betters would applaud not criticise .

 

[lw395]

Now you're just trolling.

No, I'm asking you to admit that paralleling unmatched batteries in a bank is accepted to be poor practice resulting in impaired service life, as advised by various battery manufacturers.

Yes or no?

 

[lw395]

I am suitably chastised for my lazy and ignorant notation in my earlier post but for someone to chastise others for such things and then to post a series of grammatically incorrect postings is equally ignorant . All i wanted was some advice . Something as a relative newcomer to the site i rather stupidly thought was what this forum was for . I am only trying to learn, something i thought me betters would applaud not criticise .

Some advice:
Don't parallel mixed ages batteries in a bank.
Don't parallel mixed capacities in a bank.

Beyond that, you've not really given enough information as to what you are trying to achieve. Your Ctek charger might be fine, if you always have enough charging time to charge the batteries. Our boat for instance does not need a lot of mains charging due to the way we use the boat. Other people use their boats differently and get value from having more powerful chargers and different systems.
What exactly is the problem you are trying to solve?

 

[RIBW]

...... All i wanted was some advice . ..... . I am only trying to learn.......

Well said dunkelly. Don't give up - there is some really excellent advice to be gained from the site. Just learn whose contributions should be skipped over and whose can be trusted.
Unfortunately your subject is one where nearly everyone thinks they have something relevant to say. I used to design satellites. As you can imagine the subsystem design reviews were very rigorous in the expectation of a 7 year life in orbit with no human repair/maintenance. We all dreaded the power supply review agenda item - everyone in the room felt they had a comment of value - in contrast to review of the attitude orientation subsystem, for example.
Cheers
Bob

 

[dunkelly]

Ok ,so i am now aware of some of the pitfalls , i started out saying that i have put the new battery completely separate from the existing two because of the advice from the forum . i was asking for advice as to how to best maintain a charge in this separate battery . is there any way of linking it to the alternator and should i put in a second battery charger . back in the day all chargers were trickle chargers and i am not really sure i understood how technology had moved on and how efficient these new chargers are and how best to integrate a new charger to best maintain the batteries i have .

 

[pyrojames]

Excellent advice is frequently found here it is only the bullies that feel they have to brag and bully newcomers. Ignore their attitudes, and take their advice with care. As far as amp, amp-hours or volts go, none of them individually actually describ a battery's capacity. Watt-hours would be the appropriate technical answer, only no one uses that here, all assuming that everyone works at 12 volts. Anyone with a full understanding knew exactly what you meant and were siimply being picky, rude and technically incorrect all at once. Quite a feat of the virtual world. Please stay and contribute, your question is one that people often want answers to.

 

[PaulRainbow]

Ok ,so i am now aware of some of the pitfalls , i started out saying that i have put the new battery completely separate from the existing two because of the advice from the forum . i was asking for advice as to how to best maintain a charge in this separate battery . is there any way of linking it to the alternator and should i put in a second battery charger . back in the day all chargers were trickle chargers and i am not really sure i understood how technology had moved on and how efficient these new chargers are and how best to integrate a new charger to best maintain the batteries i have .

If you are keeping it completely separate to the other two, what is it powering ?

If you want to continue keeping it separate and keep it charged (obviously you want to charge it) you can charge it from the alternator by fitting something like a Victron Argofet with 3 outputs. You can charge all three batteries with the three output version of the Victron charger i mentioned earlier.

But, why are you fitting a smaller battery, why not another 100ah one ?

By the way, i knew what you meant by 100a/80a in post #1, i didn't think it was worth a comment.