Ideal sized Inverter-?

Thankyou very much for all your replies fellas'. I already have a 130-150w sine wave inverter fitted in my Land Rover Defender, just for the laptop & a small battery-charger for torch batteries, & I'll probably fit that into the boat anyway for the same purpose.
I must admit that after reading an awful lot of sailing blogs I was under the impression that 2-3Kw Inverters were almost 'de rigeur' for long-term cruising, but I can't for the life of me think what I'd need all that capacity for, really. It's just that back in the boatyard, the guys are busy with new cabling & a smart battery-charger so I thought this might be the time to install an Inverter if it's a necessary item.
I'm sure I could install one later if I find I need it, & I'll definitely "save" this thread right now, for future reference.!
Thanks again chaps, very informative, as usual.!
 
[ QUOTE ]
..... I was under the impression that 2-3Kw Inverters were almost 'de rigeur' for long-term cruising, but I can't for the life of me think what I'd need all that capacity for, really.....

[/ QUOTE ]As Englander said, they can be useful for very short periods provided you are sensitive to the needs of the batteries. Otherwise, they are used along with generators having a dc output rather than an ac output. I think that a large-ish dc generator (up to 6kW or so) with a large invertor, is a better solution than a 230V generator with battery charger PROVIDED you can use the invertor with a mains input to charge batteries and provide ship's power when with shore power. I'd like to trade up my 600W invertor to a 1500W but I have better things to spend my money on and I can always start the genny.

I would not want to liveaboard outside marinas without a generator. Even a 2kW Honda-type would be good, but the absence of a generator would make life uncomfortable.
 
We have an aged Mastervolt 750watt inverter but with overload capabilities of twice that amount. We use a 240-volt macerating ‘loo’ which means we need the inverter on for even the very basic functions of life.

However consider the ‘perks’ A small 600-watt mains kettle, saves a load of calor-gas and consequent heating of the cabin in the summer also; as we have no oven, we can utilise one of those cheap work-top cooker units to bake the odd chicken and use as a grill/toaster when required. We always run the fridge on 240-volt when the engine is running.

The TV, satellite dish and lap-top of course, plus many other devices, soldering iron, hairdryer, curling tongs and so on, even the electric blanket is a major bonus on cold nights.

The latest Inverters are very efficient off-load and I would definitely specify a big beefy one if I was buying a new boat.
 
[ QUOTE ]
[ QUOTE ]
If it was my system I would not want the inverter to draw the higher levels for more than a minute or so, indeed, I would probably make the genny start automatically if that was the case, after, say, two minutes, unless locked-off when it is inappropriate.

[/ QUOTE ]

I posed your questions in this and previous posts to James Hortop at Merlin who has been PBO's technical bod. He sold and recommended our setup. His reply was:

"You can safely discharge your lifelines to 50% regularly. Putting them under high draw for the periods of time you mention is not detrimental to their health. I have a full electric galley on board and regularly make dinner or start the aircon without using the generator."

My final comments:
Obviously running the genny IS more efficient - but the point is convenience.
 
[ QUOTE ]
I posed your questions in this and previous posts to James Hortop at Merlin who has been PBO's technical bod. He sold and recommended our setup. His reply was:

"You can safely discharge your lifelines to 50% regularly. Putting them under high draw for the periods of time you mention is not detrimental to their health. I have a full electric galley on board and regularly make dinner or start the aircon without using the generator."

My final comments:
Obviously running the genny IS more efficient - but the point is convenience.

[/ QUOTE ]

Well, it will be interesting to hear how you get on. If it all works fine then there are many people here who presently won't touch AGMs (can't add water, so can't fast charge) reason to change their minds. Please note that historically manufacturers' claims are way over-optimistic. I am not sure why - maybe variable quality in the manufacturing, maybe abuse by users, but people do lose their batteries prematurely.

I don't know anyone apart from you who has ever planned to heat his domestic hot water or run air conditioning from the ship's batteries. It is horribly inefficient apart from anything else. I am prepared to accept that I am out of date and being reactionary, but the proof of the pudding.... Do please keep us informed.

Batteries do have a life, usually over-stated, and this graph comes from the Lifeline AGM website. There is no supporting evidence (pretty much par for the course with batteries. Nothing published.)

graph3.gif


This curve suggests that if you discharge the battery to 50% it will last for 1000 cycles. But what the dickens does that mean? What capacity does the battery have after those 1000 cycles? If it can barely light a 10W bulb for an hour, has it survived? We need to know a lot more before blindly accepting these figures and my experience in the past is that when you start asking those questions the battery suppliers ignore you.
 
[ QUOTE ]

I am prepared to accept that I am out of date and being reactionary...

[/ QUOTE ]

I think you should speak to James at Merlin yourself and get the full picture about Lifeline batteries as oposed to other sem-traction so-called AGMs.

The whole point about Lifelines is their minute internal resistance which means they CAN be fast charged. If they are such rubbish as you suggest why is every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer now fitting them.

At least this thread has aired a few thoughts - maybe you should be prepared to accept that you are now totally out of date and reactionary...at least where Lifeline AGMs are concerned.
 
[ QUOTE ]
I think you should speak to James at Merlin yourself and get the full picture about Lifeline batteries as oposed to other sem-traction so-called AGMs.

The whole point about Lifelines is their minute internal resistance which means they CAN be fast charged. If they are such rubbish as you suggest why is every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer now fitting them.

At least this thread has aired a few thoughts - maybe you should be prepared to accept that you are now totally out of date and reactionary...at least where Lifeline AGMs are concerned.

[/ QUOTE ]

This is becoming weird. Every time you post on this you send me a Private Message as well, this is the third or fourth time. I never, as a rule, publish PMs in public but I am going to make an exception . You posted the following PM to me this morning.....

[ QUOTE ]
More comments from James at Merlin that he didn't want me to post in full........

Hi Matt,

I’m sorry but there are many people who make totally incorrect remarks. If they want to comment on batteries and become a source of knowledge, perhaps they should go back to university or work in the industry for 20 years…. The guy has no idea. Lifeline has a minute internal resistance facilitating fast recharging (it’s a complete load of rubbish that you can’t fast charge because you can’t add water). Lifeline is also the only deep cycle AGM battery available (others are only semi traction). If all these claims are rubbish, why is every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer now fitting lifeline..............

He added a few more choice comments that I won't embarrass you with - so please do call him if you are really interested in this subject.



[/ QUOTE ]

<span style="color:blue"> To understand what's going on, we need the technical details relating to the ageing graph of these batteries. It is meaningless to say that a battery will last for, say, 500 cycles at 50% discharge unless you define what counts as a failed battery. For example, if you are going to include all batteries that retain 5% of their original capacity then almost all batteries are going to pass. If you set the limit at 95% then almost none will pass. You have to have this defined for the data to be meaningful.

As for low internal resistance - that isn't the issue and for him to raise it shows serious lack of understanding of the physics. At high charge currents lead acid batteries (of all kinds, including AGM) start to disassociate water into Hydrogen and Oxygen. This is reduced by adding certain compounds to the plate material and by adding catalytic pellets into the cells, above the liquid level, to help the disassociated gasses to re-combine back into water. That is how sealed batteries can be made - without this you could not seal any lead acid batteries. Now, if the rate of gassing is greater than the catalyst can handle then the pressure builds up and the gasses vent off. Venting is fairly harmless, but the vital Hydrogen and Oxygen are, in fact, your battery water in gaseous form which, in a sealed battery, are irreplaceable. Low internal resistance has nothing to do with it whatsoever. You have to ask the manufacturer to state the maximum charge rate and under what conditions (e.g. temperature). If the man can't point you to the technical data then how can he know what he is talking about - after all, he only sells batteries, he didn't design them or make them.

If he wants to impress us with his superior knowledge, tell him to get back to us with a technical argument supported by facts, and forget about the snide remarks.

The bad news (for you) is that this chap has become rude and abusive while giving no real hard data. I had this problem with Elecsol back in 2005 and look where people have ended up with that shower. Doesn't look good. </span>
 
Where´s this all going?? Batteries are not an exact science, mainly due to the use they get, hard to say "under ideal conditions" no such bloody animal on a liveaboard boat, I agree with Lemain here, to run loads such as AC and cooking firom a battery bank is very in-effiecient, that´s a no brainer.
A lot of folk swear by lead acid which can be topped up, not sure if they are better, but I do know that most batteries for deep cycle long time usage are wet lead acid, top upable! I have AGM´s this time, I´ll see how they perform. Only way to see if a battery technology is for you, is to try it and hope you get a good set of batteries.
Maybe next time go with Rolls batteries, with an excellent reputation for long term usage and a good gaurantee. Wet lead acid.
 
Lemain,
I didn't want this discussion to become personal so this is my final posting on this issue as I’m not prepared to waste any more of my time in trying to be helpful. With over 4350 postings you have obviously got time to waste.

I PM'd you to make sure that you saw my replies to what was an old posting that appeared to have ended. PMs should be used more so that people can have their own discussions and private disagreements without ruining a good thread.

I agree with Englander - “Where’s all this going”?

I’ve suggested before that we need a forum totally dedicated to batteries and electrics – but in the meantime if people are interested in the original Concorde AGMs - “Lifelines” - not to be confused with inferior copies, then visit this site to find out why low resistance IS important to fast charging.
 
I don't want any of this to be personal or on PMs - the whole point of a forum is for people with differing views to chip in, and for everyone to become equally informed (or perplexed /forums/images/graemlins/wink.gif) Anyway, we can't leave it quite at that as your link does not (as far as I can see) answer the question as to why low resistance is important to fast charging. Maybe you can find the exact part rather than just direct us to the whole website?[ QUOTE ]
.....if people are interested in the original Concorde AGMs - “Lifelines” - not to be confused with inferior copies, then visit this site to find out why low resistance IS important to fast charging.

[/ QUOTE ]

There could be some issues in your system (or for anyone else thinking of following your design) particularly as your chap at Merlin seem not to be very clued up on the technicals. I can't find all the data I'd need to be sure one way or another - they don't back their claims by tecnical reports, data or curves. BUT they do say.....

[ QUOTE ]
Fastest recharge. (no current limitations with voltage regulated recharging)

[/ QUOTE ] What does this really mean? It has to mean that there ARE current limitations but that if you charge it at at some (unspecified) voltage you will not exceed the maximum charge. If I had spent all that money on a system like that I would ask them to clarify what the maximum current actually is and if that is not a simple current but a relationship between Voltage, Temperature and maybe State of Charge then you need to know that. I reiterate; if you pass too many Amps through those batteries they will gas and vent. If they do that they will dry out. You need to be sure that the charger you are using is SPECIFICALLY designed for your Lifeline batteries and if they were mine, I would want some means of monitoring performance.

As a matter of interest, how fast do they re-charge? Do they take almost the full output of your generator? Is the charger set to the appropriate voltage for bulk, absorption and float? Is your main engine alternator set to the appropriate charge regime as well?
 
With AGMs or any sealed battery it is vital to ensure that you are not charging at a level beyond that which the internal catalyst can recombine the gasses. Only the manufacturer can tell you that, there is no 'intuitive' way or 'rule of thumb' to work it out. This current depends on the temperature, state of charge and terminal voltage - e.g. at 25C with a battery at 50% state of charge then you can pass tens of amps through with no gassing but as the voltage rises (current falls, capacity is fuller) gassing starts. All is fine as long as the rate of production of gas is within the capacity of the catalyst but if you haven't been told what that is, all you can do is to re-charge as a rate well below any significant gassing. That will require very different charger settings to flooded or, maybe, AGMs from different manufacturers. I seem to remember that you have huge batteries - 1000Ah at 24V? Could be that you are not charging anywhere near the gassing level anyway?
 
Now we can re-vitalize this thread.

I don’t intend to answer all your questions because I’m not qualified to do so, but I’ll just highlight the points about battery resistance:

I quote from the Marine Battery Comparisons pull-down menu:

“Internal resistance of a battery denotes its overall charge/discharge efficiency, its ability to deliver high cranking currents without significant drops in voltage, and is a measure of how well it has been designed and manufactured. Internal resistance in NiCad batteries is approximately 40%, i.e., you need to charge a NiCad 140% of its rated capacity to have it fully charged. For flooded wet batteries, internal resistance can be as high as 26%, which is the charging current lost to gassing, or breaking up of water. Gel acid batteries are better at only approximately 16% internal resistance and require only roughly 116% of rated capacity to be fully charged. Lifeline Advanced AGM has the lowest internal resistance of any battery manufactured only 2 percent. This allows Lifelines to be charged much faster if needed and also to deliver higher power when required. Owners using high output alternators, operating inverter banks, or relying on solar panels can benefit significantly when using Lifeline Advanced AGM batteries with their equipment. "Lifelines" are more efficient!!”


Here are MY comments about other points on the site which I have revisited:

“Faster recharge; no current limitations with voltage regulated recharging.”

Due to the low internal resistance a much higher current is applied for the same voltage (Ohms law). Max Bulk and Absorption voltages are both the same at a max of 14.4volts. As long as the gassing voltage is not achieved they WILL NOT GAS.

You say:
“…if you pass too many Amps through those batteries they will gas and vent. If they do that they will dry out.”

Surely the whole point is that they only gas when the gassing voltage is reached – not the gassing current. Due to their construction Lifeline claim their batteries have no current limitations – don’t ask me why.

Cycles:
Twice as many discharge/charge cycles as the leading gel marine battery – see their chart.




MY SET-UP
My Victron Multiplus Inverter also controls the 4 stage charging and is set to the max of 120 amps into the 5 batteries. This has a complex charging regime that has been optimized for the Lifelines. I’ve honestly no idea how long they take to recharge. The Alternator is also set to the same regime and I monitor the system with a BEP battery monitor.

The DC genny gives the full 280 amps at startup and falls away when the batteries gain charge. That’s when I turn on the water heater to always get 80% of the max current out of the genny. This seems to have caused the most confusion.

Why turn on the genny just to run the microwave for three minutes? Surely it’s more convenient and less wear and tear on the genny to wait until we are down to 75% of the full capacity and then recharge. James at Merlin uses the system in the same way. Just because we are the only people doing this doesn’t mean its wrong!
 
[ QUOTE ]
I quote from the Marine Battery Comparisons pull-down menu:

“Internal resistance of a battery denotes its overall charge/discharge efficiency, its ability to deliver high cranking currents without significant drops in voltage, and is a measure of how well it has been designed and manufactured. Internal resistance in NiCad batteries is approximately 40%, i.e., you need to charge a NiCad 140% of its rated capacity to have it fully charged. For flooded wet batteries, internal resistance can be as high as 26%, which is the charging current lost to gassing, or breaking up of water. Gel acid batteries are better at only approximately 16% internal resistance and require only roughly 116% of rated capacity to be fully charged. Lifeline Advanced AGM has the lowest internal resistance of any battery manufactured only 2 percent. This allows Lifelines to be charged much faster if needed and also to deliver higher power when required. Owners using high output alternators, operating inverter banks, or relying on solar panels can benefit significantly when using Lifeline Advanced AGM batteries with their equipment. "Lifelines" are more efficient!!”

[/ QUOTE ]

It's the first time I have come across resistance quoted in %. Traditionally we have used Ohms although you might consider me to be reactionary. /forums/images/graemlins/wink.gif I wouldn't accept resistance in % even with reluctance /forums/images/graemlins/grin.gif even if there was no impedence /forums/images/graemlins/grin.gif because there would be no gain /forums/images/graemlins/grin.gif

Actually, it's drivel, techno-babble. They are saying that you can fully charge their batteries by putting in only 102% of the total capacity? Nonsense. Makes me wonder whether these people are bona fide. I would be digging very deep into the company before digging into my pockets.

The charging regimes quoted are not that easy to follow. You need to be very careful and make sure that it is set up correctly. Very odd, very fishy.
 
Oh dear you really are a very sad person who seems to know it all.

They describe exactly what they mean by "resistance".... "Internal resistance in NiCad batteries is approximately 40%, i.e., you need to charge a NiCad 140% of its rated capacity to have it fully charged."

They don't try and impress people with impedance and reluctance.

Just to repeat my previous posting ....... why is every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer now fitting Lifeline batteries if they are as rubbish as you say they are?
 
That was about the seventh personal dig you have made - WHY? - Any chance you can keep this discussion to battery systems and leave me out of it? I have not made a single personal remark about you even after all your gybes. Thank you for stopping that deluge of PMs, they were not appreciated.

[ QUOTE ]
Just to repeat my previous posting ....... why is every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer now fitting Lifeline batteries if they are as rubbish as you say they are?

[/ QUOTE ] Every ambulance, lifeboat, tv news van, racing yacht and virtually every quality yacht manufacturer? EVERY?

Incidentally, I have never said that the products are rubbish - I am saying that what they say about these things on their website is suspicious. Be careful how you use them; they are not tolerant to abuse according the limited technical information they have published. The voltage ranges are quite tight and if you do let these things gas for long that's the end of the story.

Did they tell you what voltage and current to expect on your BEP meter, during charging and use?
 
Resistance is expressed in Ohms and not in percentage. Saying that they describe exactly what they mean by resistance is a bunch of bulls..t. The way it is described doesn't mean a thing.
I can appreciate that a lower internal resistance means the battery can be charged with a higher current. Current x resistance = the energy developed by charging. This energy will raise the temperature of the battery, which is bad. I think it logical that the voltage, where gassing starts, is temperature dependent. Most physical phenomena are temperature dependent and gas forming while charging a battery is a physical phenomena.
 
[ QUOTE ]
Resistance is expressed in Ohms and not in percentage. Saying that they describe exactly what they mean by resistance is a bunch of bulls..t. The way it is described doesn't mean a thing.

[/ QUOTE ]That's what's worrying me. How could a reputable company, supplying the aviation and professional marine markets, publish that sort of rubbish on their website? Ohms are understood by the average 12 year old - how could it get through? Usually when I come across this sort of thing I find that the whole thing is a con. However, if this is a con, it is very well done, it certainly looks credible if you close your eyes to the technical nonsense. Puzzling.
 
Good to have a new poster.

When you have expensive kit like this it MUST be installed correctly, and understood.

[ QUOTE ]
Current x resistance = the energy developed by charging.

[/ QUOTE ]
The correct formula is (current)x(current)xResistance = Energy in Watts or (I)x(I)xR = Watts

When the temperature increases the resistance falls and the current would increase if the voltage were not reduced. But to stop gassing you need a top of the range charger - with a battery temperature sensor - to regulate the charging voltage when the resistance falls.

On the question of gassing ALL so called "sealed batteries" must surely be designed to minimise gassing under all but severe overcharging. Their constructions I would imagine means much less water and much less air space for gassing to occur. I would be interested to hear from anyone who really knows the answer to this one.

Since this was a thread about inverters a temperature sensor should be fitted onto the alternator as well. Without this AND whilst running the inverter under engine, the alternator could be asked to deliver its maximum output for longer than designed. Normal its load falls off as the battery charges. This year we had the inverter on under high load and the alternator stopped charging because the temperature sensor cut in. Another good reason to have a battery monitor mounted in a position to be sure that the system is being checked regularly.
 
I will be interested to hear about how this system works in reality, not in theory, for a liveaboard and how long the system works. (and batteries last)
I agree that using the inverter to operate the microwave etc, for a short period is fine and is what I do in practice as a liveaboard.
But to use batteries for AC or cooking is total hogwash and very in-efficient. Thats from somebody who USES his system day in day out, in the meddy, at anchor for long periods.
I have a 3kw victron inverter, two banks of domestics at 550ah each, (1100ah total) engine start at 220ah, 320watts of solar and a 4.5kw genny (plus a backup 3.6kw) and two chargers, 50a and 75a. I find I need to run my genny every three to four days to charge batteries, but wouldnt dream of using my batteries to run my AC (I cook by gas).
Now, thats how I do it in the real world, not in some bullshit data sheets or listening to somebody else who doesnt have a scooby how we actually use our systems, thats 14 years of liveaboard experience and quite a few more years of electrical experience. Plus a brother who has been living aboard for over 20 years.(and a lot of batteries)
"I rest my case your honour!"
 
No, that's not quite right...

Watts is power = Joules per second
Energy is Joules

So "Energy in Watts" is not correct. "Power in Watts" is correct and there is a huge difference, I am not being pedantic.

But I**2R is a second order effect in a battery. It is more significant when drawing very high discharge currents such as cranking, or running huge inverters. The I**R losses in a battery are of little or no concern to the ordinary yachtsman running lights, pumps, PCs, TVs, etc. I'm not sure why you raised it?

[ QUOTE ]
When the temperature increases the resistance falls and the current would increase if the voltage were not reduced. But to stop gassing you need a top of the range charger - with a battery temperature sensor - to regulate the charging voltage when the resistance falls.

[/ QUOTE ] Where did you get that from? That isn't how your batteries are supposed to be charged. The Lifeline spec specifically calls for a constant voltage charger, the voltage is CONSTANT and does not vary until the charge is deemed to be complete. That's one of the problems with AGMs, it seems to me. With FLA batteries we equalise the cells at around 14.5V for half an hour and provided the current has fallen to a few amps at 14.5V you can be sure that the battery is 100% full (if you read your BEP manual it explains all this).

However, with AGMs (see the Lifeline data) they state categorically that if you equalise the cells you will out-gas, losing irreplaceable water. i.e. you shorten the life of the batteries. It is something you should never do unless your cells have sulphated, according to the literature although they don't tell you under what circumstances the cells become sulphated in the first place, or how to avoid it /forums/images/graemlins/frown.gif

Minimising gassing in sealed batteries is accomplished by a strict charging regime to reduce gassing, special plate materials to reduce gassing and catalytic convertors to help re-combine gas back into water.

As for alternators, some designs are inherently self-limiting and will not overheat, other designs require a thermostatic switch. As you say, you need an alarm to tell you when you are not charging - even the most basic yacht engine alternator has an alarm to tell you when the battery is not charging, are you sure that yours hasn't? It would be a serious oversight and should be corrected free of charge. You shouldn't need to rely on your BEP monitor to alert you to this, it should be instant and direct from the alternator system.

You should be careful with your batteries to ensure that your alternator charging system is designed for your batteries - if you were to replace it by an ordinary alternator in an emergency it would ruin the batteries very quickly so you need to carry an appropriate spare when cruising. Most conventional yacht alternators can be fixed by the humblest garage far away from bright lights - indeed, the small rural or coastal garage is more likely to be used to repairing alternators than the average UK garage used to throwing them away.

You say that a good battery monitor is useful and I agree. But, as I asked you earlier today, have they told you what you should expect to see on your monitor? It is not the same as you'd expect for a charging system for Flooded Lead Acids or normal gels. If you don't know what it should be reading, what's the point in having the meter?
 
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