Sealed Domestic Batteries for Liveaboard

[Gibbo]

??

 

Ok I'll answer it another way.

 

Yes, one battery bank is better. Like it was when I, and many others, first said so on here about 5 years ago. Like it was when I said on the website nearly three years ago ( http://www.smartgauge.co.uk/splitting.html ), like I, and many others, said so at the beginning of the three recent threads that have all got turned to this one same subject and like I, and many others, said in the other (almost identical) thread on the exact same subject a couple of months ago (I think there was also another identical one about 18 months ago).

 

The same tired idea keeps coming up. It won't work.

 

No amount of wishful thinking is going to change it because the laws of physics are pretty immovable

[n.b.Goldie]

Not read the whole thread but............has anybody mentioned Pukert's Law yet?

 

Edited to add; I meant PEUKERT'S LAW

Edited December 19, 2010 by ditchdabbler

[nb Innisfree]

Ok I'll answer it another way.

 

Yes, one battery bank is better. Like it was when I, and many others, first said so on here about 5 years ago. Like it was when I said on the website nearly three years ago ( http://www.smartgauge.co.uk/splitting.html ), like I, and many others, said so at the beginning of the three recent threads that have all got turned to this one same subject and like I, and many others, said in the other (almost identical) thread on the exact same subject a couple of months ago (I think there was also another identical one about 18 months ago).

 

The same tired idea keeps coming up. It won't work.

 

No amount of wishful thinking is going to change it because the laws of physics are pretty immovable

 

Yeah I know all that but what does LMAO mean?

 

Can I ask you a question? apologies if this is old ground. Reinout Vader in his book 'Electricity on Board' that partial state of charging is ok provided a monthly absorption/equalisation charge is carried out but in my comparatively limited experience more like a weekly one is needed, the only thing I can put it down to is his statement that electrolyte stratification is prevented by the normal movement of a boat or vehicle but of course that doesn't apply to canal boats. Could this be having a significant effect?

 

Cheers

 

Not read the whole thread but............has anybody mentioned Pukert's Law yet?

 

Edited to add; I meant PEUKERT'S LAW

 

Yes

Edited December 19, 2010 by nb Innisfree

[Robin2]

ARGGGGGGGGGHHHHHHHHHHHHHHHH!!!!!!!!!!!

 

 

 

 

 

Why you no rissen??????????

 

 

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

you clearly have alternator capacity to spare and you would be better strapping both batteries together

 

 

W H Y ? ? ?

[Gibbo]

Yeah I know all that but what does LMAO mean?

 

I'll let someone else answer that.

 

Reinout Vader in his book 'Electricity on Board' that partial state of charging is ok provided a monthly absorption/equalisation charge is carried out but in my comparatively limited experience more like a weekly one is needed, the only thing I can put it down to is his statement that electrolyte stratification is prevented by the normal movement of a boat or vehicle but of course that doesn't apply to canal boats. Could this be having a significant effect?

 

I suspect it's more to do with a combination of what is deemed acceptable capacity loss due to not regularly achieving full charge as compared to the fuel costs of doing it more regularly, and also that he'll be talking about real high quality, expensive, batteries whereas we're usually meddling with cheapo "throwaways" because we're too lazy to look after them properly and/or too tight to buy expensive ones.

 

I don't think there's a right or wrong answer, it's really a compromise strike.

 

W H Y ? ? ?

 

I've told you three times.

 

Not read the whole thread but............has anybody mentioned Pukert's Law yet?

 

Edited to add; I meant PEUKERT'S LAW

 

What's that?

[RLWP]

W H Y ? ? ?

 

Because if the voltage is at 14.8 volts, the battery is in the acceptance stage (right hand side of the graph). If it was in bulk, it would be in the left hand side of the graph with a rising voltage).

 

Richard

[Robin2]

Because if the voltage is at 14.8 volts, the battery is in the acceptance stage (right hand side of the graph). If it was in bulk, it would be in the left hand side of the graph with a rising voltage).

 

Richard

 

That's not the question I was asking.

 

People on the forum (and I have no doubt all comments are well meant) have repeatedly said that joining three batteries into a single bank is better than using then separately in the way that I envisage and as far as I can recall that is due to the Peukert effect - the big battery will be discharged less and will last longer (and I am not challenging Peukert). Of course the smaller batteries will be more deeply discharged and will have less life cycles, but that is offset by the fact that they are discharged less often.

 

While there have been some queries about whether three batteries in different states of charge might cross-feed each other I think that concern has been laid to rest and there is no technical obstacle to managing the batteries in my way.

 

Even though there have been 80 contributions to this thread nobody has said that with a particular alternator and battery it will take X hours charging per day to meet a given daily load, with a bigger battery it will take Y hours and WHY there is a difference.

[nb Innisfree]

That's not the question I was asking.

 

People on the forum (and I have no doubt all comments are well meant) have repeatedly said that joining three batteries into a single bank is better than using then separately in the way that I envisage and as far as I can recall that is due to the Peukert effect - the big battery will be discharged less and will last longer (and I am not challenging Peukert). Of course the smaller batteries will be more deeply discharged and will have less life cycles, but that is offset by the fact that they are discharged less often.

 

While there have been some queries about whether three batteries in different states of charge might cross-feed each other I think that concern has been laid to rest and there is no technical obstacle to managing the batteries in my way.

 

Even though there have been 80 contributions to this thread nobody has said that with a particular alternator and battery it will take X hours charging per day to meet a given daily load, with a bigger battery it will take Y hours and WHY there is a difference.

 

The way I see it a small bank will be receiving a comparatively larger load so will reach acceptance sooner and charge rate will reduce lengthening the period to replace daily needs. Conversely a larger bank will stay in bulk longer and shorten the time needed to replace daily needs.

[bottle]

First: LMAO = Laughed My Arse Off.

 

Second: Robin go ahead and do it your way.

 

Third: Gibbo you have the patience of a saint.

[weeble]

W H Y ? ? ?

 

Ah! you had me fooled for a minute.......

 

You're really Chris_w...... and I claim my 20 quid

[RLWP]

<snip>

 

Even though there have been 80 contributions to this thread nobody has said that with a particular alternator and battery it will take X hours charging per day to meet a given daily load, with a bigger battery it will take Y hours and WHY there is a difference.

 

So, your question is, you have two batteries both of capacity X, an alternator of capacity Y and a load of Z. What is the difference in discharging and charging one then the other as opposed to discharging and charging both as a pair? And you'd like an arithmetic answer if possible.

 

Is that it?

 

I'm not trying to be unhelpful, although I'm not sure I can see why there is a difference as I'm taking out and putting in the same amount of energy either way.

 

Richard

 

edit: I can't answer this. The only one I know of with the necessary expertise and experience is Gibbo, and I'm not sure you'll believe his answer

Edited December 19, 2010 by RLWP

[ymu]

So, your question is, you have two batteries both of capacity X, an alternator of capacity Y and a load of Z. What is the difference in discharging and charging one then the other as opposed to discharging and charging both as a pair? And you'd like an arithmetic answer if possible.

 

Is that it?

 

I'm not trying to be unhelpful, although I'm not sure I can see why there is a difference as I'm taking out and putting in the same amount of energy either way.

 

Richard

 

edit: I can't answer this. The only one I know of with the necessary expertise and experience is Gibbo, and I'm not sure you'll believe his answer

This is the point of robin's idea, as far as I can tell - he's trying to put the same energy in using less diesel. Charging both simultaneously means you get the acceptance charge for free by doing it at the same time as another bank is on bulk charge - which, if possible, would be a massive saving in diesel given how few amps you get during acceptance, per litre of fuel burnt.

 

However, it isn't possible - at least with standard equipment - because, as Gibbo has pointed out, if one battery is bulk charging then, by definition, the voltage will be too low to provide a meaningful current for the battery which is in acceptance.

 

It may or may not be possible to do this with some fancy electronics and/or two alternators, but I haven't got my head round those arguments yet.

 

But yeah, anyway, the main point would be that the energy expended does not equal energy in, because the alternator is being used very inefficiently during acceptance charging. However, you are using more energy from two banks than you would from one big one (due to Peukert), and you could probably make similar fuel savings using a generator for acceptance charging, so even if you could rig something up the only real saving would be in halving the charging time.

 

I think ...

[Pretty Funked Up]

Even though there have been 80 contributions to this thread nobody has said that with a particular alternator and battery it will take X hours charging per day to meet a given daily load, with a bigger battery it will take Y hours and WHY there is a difference.

for me personally i dont put as much in as i take out (not invcluding solar)

so the thought of cutting my bank in half is nut

 

also all the dicking about with wiring would drive me nuts

 

edit: cant be arsed to correct typos

Edited December 20, 2010 by Pretty Funked Up

[blodger]

This is the point of robin's idea, as far as I can tell - he's trying to put the same energy in using less diesel. Charging both simultaneously means you get the acceptance charge for free by doing it at the same time as another bank is on bulk charge - which, if possible, would be a massive saving in diesel given how few amps you get during acceptance, per litre of fuel burnt.

 

However, it isn't possible - at least with standard equipment - because, as Gibbo has pointed out, if one battery is bulk charging then, by definition, the voltage will be too low to provide a meaningful current for the battery which is in acceptance.

 

It may or may not be possible to do this with some fancy electronics and/or two alternators, but I haven't got my head round those arguments yet.

 

But yeah, anyway, the main point would be that the energy expended does not equal energy in, because the alternator is being used very inefficiently during acceptance charging. However, you are using more energy from two banks than you would from one big one (due to Peukert), and you could probably make similar fuel savings using a generator for acceptance charging, so even if you could rig something up the only real saving would be in halving the charging time.

 

I think ...

 

Well summed up for those that miss the context of this & previous threads.

 

Gibbo said no but there is still the possibility that using an inverter and charger as a second charge source could work but no=one has come back and said it does (save fuel that is)

[RLWP]

Well summed up for those that miss the context of this & previous threads.

 

Gibbo said no but there is still the possibility that using an inverter and charger as a second charge source could work but no=one has come back and said it does (save fuel that is)

 

When the battery is in bulk, it takes all of the alternator output. So, introducing further electronic devices that need their own power to run them must surely be less efficient - the power to work the chargers is not available for charging

 

Richard

[Robin2]

This is the point of robin's idea, as far as I can tell - he's trying to put the same energy in using less diesel. Charging both simultaneously means you get the acceptance charge for free by doing it at the same time as another bank is on bulk charge - which, if possible, would be a massive saving in diesel given how few amps you get during acceptance, per litre of fuel burnt.

 

However, it isn't possible - at least with standard equipment - because, as Gibbo has pointed out, if one battery is bulk charging then, by definition, the voltage will be too low to provide a meaningful current for the battery which is in acceptance.

 

It may or may not be possible to do this with some fancy electronics and/or two alternators, but I haven't got my head round those arguments yet.

 

But yeah, anyway, the main point would be that the energy expended does not equal energy in, because the alternator is being used very inefficiently during acceptance charging. However, you are using more energy from two banks than you would from one big one (due to Peukert), and you could probably make similar fuel savings using a generator for acceptance charging, so even if you could rig something up the only real saving would be in halving the charging time.

 

I think ...

 

Thanks for your clarity.

 

I have an open mind about how little acceptance current there can be alongside the bulk current. I don't think it is a black and white issue - electricity, like water, will flow from high pressure to low pressure wherever it gets the opportunity. There is so much wasted electricity now that a slightly longer, but more productive, charge period would be not be a problem. In any case there is probably a technical solution to the problem, if it is a problem.

 

The real issue is that the charger spends a relatively short period in the bulk phase - and that time will be shorter with a big battery bank because it is discharged less.

 

Another thing that I have not mentioned so far is that I am very cautious about investing in 300Ah of battery capacity as a single bank (which I can't really afford) only to find after a year that it is knackered (like the ones I have now) or to find that I have to use a huge amount of diesel to preserve the batteries. The idea of buying a single battery and being able to monitor it carefully is altogether more attractive.

 

I have a Smartgauge, though I haven't been using it for some time. My experience with it was that it was always telling me to run my engine longer (while only a tiny percentage of the alternator output was being used) with no end in sight for my diesel bill. There must be a better way to use my alternator capacity - I'm surprised that others are not as concerned to find a solution as I am.

[DeanS]

Why does this thread have to be SO complicated.

In my mind it is quite simple.

 

Charge batteries full.

SWMBO puts hairdrier on.

Batteries are now completely dead.

No lights.

No TV.

No water pump. No shower.

 

Run solar panel, generator, and engine all together for 6hrs.

 

Batteries now full.

SWMBO puts hairdrier on.....

 

 

 

;-)

Edited December 20, 2010 by DeanS

[nb Innisfree]

Battery life depends on a certain amount of discharges, the deeper the discharge the shorter the life so therefore a larger bank will lengthen the life due to shallower or less frequent discharges, the nearer it is to 100% SoC the better (with the exception of discharge to more than 95% SoC) So it's therefore better to try to stay in absorption territory to prolong batt life, split bank will result in deeper discharge which due to Peukert will equal more than twice the batt capacity used. So to me it's better to have one larger bank and minimise use of large engine with an occasional equalisation using a small genny. the only other alternatives are unreliable wind power or, better, solar power. You're always going to have spare alt capacity it's unavoidable.

[blodger]

When the battery is in bulk, it takes all of the alternator output. So, introducing further electronic devices that need their own power to run them must surely be less efficient - the power to work the chargers is not available for charging

 

Richard

Yes but one of the problems is circumvented, that of segregating the batteries and giving a higher voltage to the bank in acceptance plus the bulk stage does not last that long anyway so such merely prolongs it.

 

I have done this in times past to get more out of the alternators usually when under way not to save fuel which it could?

[Evo]

Battery life depends on a certain amount of discharges, the deeper the discharge the shorter the life so therefore a larger bank will lengthen the life due to shallower or less frequent discharges, the nearer it is to 100% SoC the better (with the exception of discharge to more than 95% SoC) So it's therefore better to try to stay in absorption territory to prolong batt life, split bank will result in deeper discharge which due to Peukert will equal more than twice the batt capacity used. So to me it's better to have one larger bank and minimise use of large engine with an occasional equalisation using a small genny. the only other alternatives are unreliable wind power or, better, solar power. You're always going to have spare alt capacity it's unavoidable.

 

 

Best all round explanation I've seen on here to date...!! especially the last statetment. I've never seen that before. That has always been my problem with this stuff, I want to use all my alternator power, and haven't understood why I cant, there must be a way..?? However it appears not...!!!

 

 

 

It seems to properly charge your batteries and make them last a long time you need to charge them for a very long time...2 hrs a day dont cut it. You cant fully charge a battery in 2 hours...!!

 

Paralleling the alts seems a total waste of time because you never want your bats to discharge low enough to require that kind of charging. Bulk charge never lasts long anyway and if it does your most likely in the sh*t regardless - well your batteries are.

 

Splitting your battery bank up for quicker more efficient charging is a total waste of time because your normal level of useage will not over stress your alternator anyway, hence no gain, just a lot of effort and wiring for 2 alternators doing what one could do, and you will still need to accept charge for 6 hrs or more whatever.

 

 

Are my above interpretations correct..??

 

 

 

Edit to add...:- SO WHAT IS THE IDEAL SETUP EXACTLY..??? in terms of no./rating of Batteries to size of Alternator for an average domestic setup ..(fridge, telly, lights pumps, phone charger, computer).

Edited December 20, 2010 by Evo

[nb Innisfree]

I just need to qualify my statement that you will always have spare alt capacity, if it's possible to have an engine using the optimum amount of fuel for the charge being accepted by the batts then you won't have spare capacity, you will always be generating optimally. But even with a digital genny where the engine speed is variable it's not possible to achieve this, when our batts are in the latter half of absorption our digi genny is already at tickover.

[RLWP]

<snip>

 

 

Edit to add...:- SO WHAT IS THE IDEAL SETUP EXACTLY..??? in terms of no./rating of Batteries to size of Alternator for an average domestic setup ..(fridge, telly, lights pumps, phone charger, computer).

 

Coal fire, paraffin lamps, diesel engine, books?

 

Richard

 

[nb Innisfree]

 

Edit to add...:- SO WHAT IS THE IDEAL SETUP EXACTLY..??? in terms of no./rating of Batteries to size of Alternator for an average domestic setup ..(fridge, telly, lights pumps, phone charger, computer).

 

There isn't one, we opted for an alt with output of 20-25% of battery capacity (when new) One advantage I have realised with our large bank (8x125ah) is the ability to still store enough juice to last us 24hrs even though they are knackered, if we had 4 batts for instance we would have had to replace a long time ago.

 

Problem is a lot of people want a simple answer not just electrically but also about life in general, an all encompassing rule of thumb. There isn't one, period. You have to read, read, and read again and be prepared after all that to keep accepting you have got some things wrong, you have to constantly redraw your 'map' or 'picture'. It's a long road.

Edited December 20, 2010 by nb Innisfree

[blodger]

Best all round explanation I've seen on here to date...!! especially the last statetment. I've never seen that before. That has always been my problem with this stuff, I want to use all my alternator power, and haven't understood why I cant, there must be a way..?? However it appears not...!!!

 

 

 

It seems to properly charge your batteries and make them last a long time you need to charge them for a very long time...2 hrs a day dont cut it. You cant fully charge a battery in 2 hours...!!

 

Paralleling the alts seems a total waste of time because you never want your bats to discharge low enough to require that kind of charging. Bulk charge never lasts long anyway and if it does your most likely in the sh*t regardless - well your batteries are.

 

Splitting your battery bank up for quicker more efficient charging is a total waste of time because your normal level of useage will not over stress your alternator anyway, hence no gain, just a lot of effort and wiring for 2 alternators doing what one could do, and you will still need to accept charge for 6 hrs or more whatever.

 

 

Are my above interpretations correct..??Edit to add...:- SO WHAT IS THE IDEAL SETUP EXACTLY..??? in terms of no./rating of Batteries to size of Alternator for an average domestic setup ..(fridge, telly, lights pumps, phone charger, computer).

Your interpretation may be right for you but it may not be so clearcut for someone with loads of batteries (past their use by date or not). I have two engine start batts and 13 110 amp domestics aboard. What Robin2 proposes may not work for two banks of a battery apiece. I am not so sure if you have much larger banks.

[Evo]

What can a 55a/hr alternator do..!!! can it service 4 110amp deep cycle batteries in the first place, and if it can how long will it take to get the batteries to 100% SOC on a dailly basis - given average domestic consumption.....THis must be approximately known surely..!!!

 

Innisfree, you have 8 batteries, not only that they are knackered. There must come a point where you are not being cost effective. Your gobbling diesel/petrol/mains only half charging the things twice as often aren't you.

 

 

At the moment I have 4 100ah batteries on a 100amp alternator, is that overkill..?? It cant be, but you have 8 batteries - actually double - on I assume the same sort of alternator. One of us is nearer to the optimum..aren't we..?? I realise our relative electrical consumption comes into this.

 

Our batteries are new and our alternator is new....from fully charged I wouldn't like to go more than 2 nights. I've not actually tried it but I'm guessing we'd start to see dimmer lights and the telly switching off on the third night. Does it follow that if I had eight batteries you could make that easily 4 nights and the 8 batteries would still charge back up in the same time as 4 batteries would..???

Edited December 20, 2010 by Evo