Power audit question.

[Slow and Steady]

I'm plugged in on a marina with an accurate meter on the supply bollard.

This provides for 240V and battery charging. Most of our use is 240v. Just lights and pumps on 12v.

If I were to note a week or a month use on the bollard meter, is there a formula to translate that into the expected use powering everything via batteries / inverter / inverter losses?

I think if there is, that would be good start point to assess whether it's even possible to live with solar / engine / Lithium.

Possibly more realistic than guessing our use and power requirements for each separate item on board. I'm sure the standby and loss figures for the inverter I have are in the blurb and we are creatures of habit regarding power use so every day would be more or less the same usage.

 

Thanks for reading.

[Paul C]

Yes, but you'd need to know:

 

start and end state of charge/discharge of the leisure battery bank*

efficiency of inverter

any standby losses running the inverter

efficiency of battery charger and the charging process*

 

Those could be guessed, but there would be an inaccuracy/error introduced there.

 

You could do a calculation and also take into account the error band of your guesses/assumptions, which would save having to do a power audit of a list of all items etc.

 

*If you started and ended with fully charged batteries (and could be sure of this), it would simplify it to what you've suggested in the OP.

Edited June 25, 2022 by Paul C

[Slow and Steady]

12 minutes ago, Paul C said:

Yes, but you'd need to know:

 

start and end state of charge/discharge of the leisure battery bank*

efficiency of inverter

any standby losses running the inverter

efficiency of battery charger and the charging process*

 

Those could be guessed, but there would be an inaccuracy/error introduced there.

 

You could do a calculation and also take into account the error band of your guesses/assumptions, which would save having to do a power audit of a list of all items etc.

 

*If you started and ended with fully charged batteries (and could be sure of this), it would simplify it to what you've suggested in the OP.

Last bit - my batteries are always fully charged and by "going Lithium" I would avoid most of the state of charge / charging while discharging complexity? But yes, I would be attempting to keep up with battery use through the lossy inverter and whatever losses in the charging system.

I would be looking to over-cook the whole system a bit, I wouldn't be happy having to fully charge/fully discharge the batteries every day, but as a start point I do need to know approximately what my current unfettered use is which is a sort of bad as it gets state. From what I've read, it's far easier to predict all this stuff with Lithium batteries.

 

So, I'm just looking for an equation to get a rough but reasonably realistic figure to start thinking from, not one to design from at this stage as all I need to know right now is whether my lifestyle is remotely sustainable or simply a non-starter. All I know at present is that £100 in the meter lasts "quite a while". 

[Tony1]

One thing that's worth bearing in mind when you go lithium is what kind of engine charging power you want to have, for when the solar dies out.

In my case, with about 1400 watts of solar, I need engine charging for about 3-4 months of the year, so I couldn't justify spending well over £1500 on a big alternator, plus a poly V crank/pulley upgrade that was needed for my Canaline 38 to run a big alternator.  Plus an alternator regulator/controller thing. 

 

But the lithiums will be capable of faster charging than lead acids, so in winter when you have almost no solar, you can stuff a day's charge of say150 Ah into the batteries in just over an hour, but only if your alternator will run at that level without getting too hot.

Mine couldn't do it, so I ended up with a mish mash solution involving B2Bs and using my two existing alternators, and that will charge at about 100amps. 

If you already have a good alternator you're halfway there, and you might only need an alternator regulator such as the mastervolt unit. 

But however it pans out, its certainly worth factoring the engine charging into the overall picture. You dont want to be running the engine for 3 or 4 hours a day as some do in winter.  

 

Edited June 25, 2022 by Tony1

[Tony Brooks]

1 hour ago, Slow and Steady said:

If I were to note a week or a month use on the bollard meter, is there a formula to translate that into the expected use powering everything via batteries / inverter / inverter losses?

I think if there is, that would be good start point to assess whether it's even possible to live with solar / engine / Lithium.

 

Assuming that you don't use any supplementary charging in that month so it is only the mains battery charger then the power you take from the shoreline already includes the inverter and charger losses. However, I assume that you are looking to go off grid so you won't be using the charger so whatever that has drawn during the month needs to be subtracted from your total. Likewise during that month you will be drawing all the mains power from the shoreline, not the inverter, so the portion of the  mains power provided by the shoreline plus the inverter losses needs to be added to the total. Once you have done those calculations the result in Watt hours (multiply KWh x 1000) can be divided by 12 or 24 to give Ah the battery would have to provide for the month so divide by the days in the month to get the use demand per day. However, if you fed the charger through a power meter that would give the figure you need to subtract directly. That is still not a lot f use if you have solar because its output is so variable.

 

I feel it will be far easier just to do the power audit and divide all 240V AC loads by 10 to allow for inverter losses. You do not guess, you use the consumption figures provided by the manufacturer, but you may have to guess the hours used.

 

I would also suggest that if you can survive using lead acids there is no  doubt you will more than survive with lithiums because they will take the maximum charge the source can supply until your system terminates charging.

 

 

[Slow and Steady]

56 minutes ago, Tony Brooks said:

 

Assuming that you don't use any supplementary charging in that month so it is only the mains battery charger then the power you take from the shoreline already includes the inverter and charger losses. However, I assume that you are looking to go off grid so you won't be using the charger so whatever that has drawn during the month needs to be subtracted from your total. Likewise during that month you will be drawing all the mains power from the shoreline, not the inverter, so the portion of the  mains power provided by the shoreline plus the inverter losses needs to be added to the total. Once you have done those calculations the result in Watt hours (multiply KWh x 1000) can be divided by 12 or 24 to give Ah the battery would have to provide for the month so divide by the days in the month to get the use demand per day. However, if you fed the charger through a power meter that would give the figure you need to subtract directly. That is still not a lot f use if you have solar because its output is so variable.

 

I feel it will be far easier just to do the power audit and divide all 240V AC loads by 10 to allow for inverter losses. You do not guess, you use the consumption figures provided by the manufacturer, but you may have to guess the hours used.

 

I would also suggest that if you can survive using lead acids there is no  doubt you will more than survive with lithiums because they will take the maximum charge the source can supply until your system terminates charging.

 

 

Thanks for taking the trouble to provide that detailed answer Tony. Obviously at present I don't use the inverter at all, I feed mains equipment with mains from the bollard and lights/pumps from the battery bank for which the charger is permanently on. No solar complicating the calculations at present which is partly why I want to do this now.

 

I think I'd be near enough and more accurate by assuming all my current use is via the 240V supply because the vast majority including the fridge is. As we know it takes more energy to charge the batteries than I get out of them, the lights pump part would calculate out on the safe side as the 240 supplying the charger is more than  the consumption?

 

So, meter reading converted to KWh x 1,000/12 x running inverter losses + a chunk of standby inverter losses would be not too far out? Maybe divide by 13 (12.7) rather than 12 to be safer? Then assume the worst and multiply the final answer by for example 120%... or even 150% to be sure I'm over-estimating. The aim here is not to penny pinch on the system if it means I then have to limit my normal day to day consumption to fit the system I install. At the same time I'm very aware that my present consumption may well be unfeasible and I might have to have a good hard think about how I live. Hence this wish to do the rough calculation.

 

I have no idea if I can survive on LA as TBH their only function at present is to provide a way for the shore power to convert to 12v via the charger. Doing this I've probably already ruined the batteries but in this situation that literally doesn't matter.

 

Plan is yes to survive out in the wild on solar in the summer and charge Lithium via Travel power/mains charger in the winter. I won't be fitting all this complex lithium malarky myself, the plan is to ask Four Counties Marine to install the Lithium and organise/wire the charging but before I talk to him (to save wasting his time) I do need a good idea of the size of system I want and whether the panels required will fit on the roof etc I'm pretty sure his first question would be "How much power do you use?"

Edited June 25, 2022 by Slow and Steady

[Alan de Enfield]

8 minutes ago, Slow and Steady said:

So, meter reading converted to KWh x 1,000/12 x running inverter losses

 

A 12v battery is not 12v - it is probably being charged at ~14 volts for the majority of the time.

 

Then you need to allow for losses in inverting / transforming / altering voltages up and down

 

You plug you Laptop charger in to charge

 

The engine alternator has losses making 12v DC from its AC generation to charge the battery, the inverter then takes the 12v DC out of the battery and works on it, making 230v AC, you then poke 230v AC this down the wires until it gets to you lap top charger, which then takes the 'expensively made' 230v AC and converts it to 19v DC.

 

Losses at every stage of the charging process

[Slow and Steady]

17 minutes ago, Alan de Enfield said:

 

A 12v battery is not 12v - it is probably being charged at ~14 volts for the majority of the time.

 

Then you need to allow for losses in inverting / transforming / altering voltages up and down

 

You plug you Laptop charger in to charge

 

The engine alternator has losses making 12v DC from its AC generation to charge the battery, the inverter then takes the 12v DC out of the battery and works on it, making 230v AC, you then poke 230v AC this down the wires until it gets to you lap top charger, which then takes the 'expensively made' 230v AC and converts it to 19v DC.

 

Losses at every stage of the charging process

Sure, but if you read my boring posts...

I suggested using 13 instead of 12v

I don't have a laptop.

I won't be directly charging batteries using an alternator.

Charging losses are somewhat irrelevant to consumption.

I'm trying to get a figure for consumption.

 

[Alan de Enfield]

13 minutes ago, Slow and Steady said:

I suggested using 13 instead of 12v

 

But you suggested dividing the Watts by 12.

 

13 minutes ago, Slow and Steady said:

I don't have a laptop.

 

You 'mains PC' will be unlikely to operate at 230v it will have a transformer inside (all chips, fans etc will be operating on ~12v

 

16 minutes ago, Slow and Steady said:

I won't be directly charging batteries using an alternator.

You will never be charging the battery / running the engine ? - Solar will not supply sufficient for 4 or 5 months of the year.

 

17 minutes ago, Slow and Steady said:

Charging losses are somewhat irrelevant to consumption.

 

It is all part of the 'system' you have to put more energy in than you get out. You will get 'consumption losses' when cruising simply by using your invertor to make mains electric, and further losses when the AC is converted back to DC inside whatever appliance it is (TV, charger, Computer etc)

 

 

A very 'down and dirty' idea will be (as you suggested) take a reading on your bollard meter and weekly readings thereafter for a month or two.

take the average daily / weekly reading and that will be an approximation - but it will be 'what has gone into the boat' from the bollard and will not include anything produced from running the engine or from solar panels.

 

I'd reckon it would be a fair-bet that your actual consumption would be higher than your bollard reading.

[Tony Brooks]

48 minutes ago, Slow and Steady said:

As we know it takes more energy to charge the batteries than I get out of them, the lights pump part would calculate out on the safe side as the 240 supplying the charger is more than  the consumption?

 

Not too sure I understand what you mean. If you assumed all the power supplied by the shore line would need t be supplied by the batteries then you need to allow for the inverter losses. For  easier maths and because recharging lead acids is so long-winded we usually assume the inverter losses are about 10%, hence the divide watts by 10 for inverter loads rather than 12. However, modern quality inverters are probably far more efficient than that, but as you say increasing the whole shoreline load by 10% or 20% would put you very much on the safe side.

 

In the best monitored and charged LA systems we would reckon to regularly use just 50% of the battery capacity but with the difficulty of charging to 100% it is more likely to be about 30% to 40% of battery capacity.  As LI are happy to accept all the currant your charging source can throw at them and don't suffer the same degree of life loss by deep discharges you can probably rely on using about 80% of their capacity (For optimum life the control system is unlikely to ever fully charge them, and you should never totally discharge them). So if you keep the same capacity that your LAs have then the bank would probably be well over specked. You should also be safe with just 50% of your LA capacity.

 

Unless you are messing with 40 to 50 amp alternators and no solar I don't think recharging LIs will be a problem as  Tony1 explained. 

 

I don't see why supplying all your 12V needs via a charger would ruin the batteries, if anything it should keep them in better condition than trying to use solar and engine charging. Basically they will be kept all but 100% charged, so much  reduced sulphation, and as the charger will be supplying the load for most of the time very much reduced cycling, so a much lower loss of cyclic life.

[nicknorman]

5 hours ago, Slow and Steady said:

I'm plugged in on a marina with an accurate meter on the supply bollard.

This provides for 240V and battery charging. Most of our use is 240v. Just lights and pumps on 12v.

If I were to note a week or a month use on the bollard meter, is there a formula to translate that into the expected use powering everything via batteries / inverter / inverter losses?

I think if there is, that would be good start point to assess whether it's even possible to live with solar / engine / Lithium.

Possibly more realistic than guessing our use and power requirements for each separate item on board. I'm sure the standby and loss figures for the inverter I have are in the blurb and we are creatures of habit regarding power use so every day would be more or less the same usage.

 

Thanks for reading.

Yes I’d say it will give you a fairly good approximation. Errors will arise because the fixed power drain of the charger (ie the mains power consumed even when the output to the batteries is zero) will not be the same as the fixed drain from the inverter, and any ac loads powered by the inverter will suffer conversion losses which doesn’t apply when the ac loads are powered direct from the mains. You say “most of our use is 240v” but it’s not clear what you mean by “most”. You could have 100 phone chargers plugged in not doing much, or one tumble drier on for a couple of hours. And the latter would use a lot more energy!

 

But anyway, if you work out the daily kWh from the meter, and add 10%, you are going to be fairly close and it’s never going to be an exact science. It can be helpful to work in kWh rather than Ah, saves having to change units! so for example we have 600Ah of Li, voltage around 13v, say 90% of that is “available” so we have about 7.8kWH available,

 

Of course it is not so much about how much battery capacity you have available, it is more about how to replenish what you’ve used. If we used 7kWh in day, that would take a lot of solar and/or engine running to replace!

 

I suppose another thing to bear in mind is whether your daily practices will be the same off grid as on grid. For example, you might keep the immersion heater on 24/7 when on shore power, but off grid water heating will at least in part be catered for by engine running (assuming you have a calorifier) or diesel (if you have a Mikuni/Webasto/Eber thingy). You might use an electric kettle on shore power, but switch to gas when off grid. Etc etc.

[Tony1]

18 minutes ago, nicknorman said:

For example, you might keep the immersion heater on 24/7 when on shore power, but off grid water heating will at least in part be catered for by engine running (assuming you have a calorifier) or diesel (if you have a Mikuni/Webasto/Eber thingy). You might use an electric kettle on shore power, but switch to gas when off grid. Etc etc.

 

I think with a 400-600Ah battery bank and say 1000 watts or more of solar, there would be no problem using a 1000 watt electric kettle or a 1000 watt electric immersion heater. 

I always avoid having both things on at once as I only have a 2000 watt inverter, but within those constraints its pretty feasible to heat water via solar on most days after early to mid April, especially if you have a mooring with most of the sky clear. And in the current conditions I could probably heat 3 or even 4 tanks of water each day, there is so much spare charge. 

One of the positives about using an electric kettle is that my gas bottles now last twice as long. My current bottle has now lasted 5 months and has at least another month in it before needing to be swapped.

A side benefit is that on hot summer days a gas ring would add to the heat inside the boat, whereas the electric kettle doesn't. 

I would say that in June, July and August there might even be enough spare charge to run a small aircon unit for a few hours a day, but on my 50ft boat there is the perennial problem of where to store big gadgets that only get used for maybe 6 weeks in each year.

 

 

[Slow and Steady]

Tony/Allen, I'm struggling to think How I could be more clear.

 

At present I have 12v lights and pumps. Everything else is 240V, everything, all of it. Even the 12V does in that the battery charger is permanently on maintaining a couple of old leisure batteries that are probably useless in their own right.

None of it presently runs via the inverter, ever, I'm permanently plugged into 240 AC residing in a marina. I do have a 3000w inverter though.

That is now. That is where I am to calculate my power use. Batteries, alternators are irrelevant at this point. Yes if I ever started the engine I could charge the leisure batteries with the domestic alternator but as I never start the engine...

Pointing out that lots of things have internal transformers is splitting hairs. Ultimately they are fed with 240V AC.

 

Future

Lithium battery bank providing 12v for lights and power via inverter for all the 240v ac stuff. Any advice regarding LA batteries is pointless as I won't have any.

Perhaps I should list the 240V stuff, it's a small list:

Fridge without ice box.

1 x phone charger for 1x phone that provides internet. Constantly on the charger.

2 x computer monitors - 12+ hours a day

2 x PC's - not laptops, proper ones. - 12+ hours a day

2 x powered speakers - could cut to average 2-3 hours a day

1 x drill battery charger - a few times a year.

occasional power tool use which I can time to use via the travel power when the engine is running.

Not really much, we don't have a TV. It's the constant computer/screen consumption that worry me TBH, The CPU in mine is 125w alone and when I'm making music it gets THRASHED. Mostly though it sits at about 30W so it's variable.

 

Solar for the summer proving unknown amount of charging.

Winter / supplementary charging using the travel-power supplying a 120A charger. OK yes it's got a "special" alternator powering the travel power but I'm likely to just take the belt off the domestic alternator OR maybe get an alternator controller and up my charging possibilities. I'm lead to believe charging the lithiums via the travel power and mains charger is a neat simple way to get started.

 

Hot water - very very rarely use the 240V calorifier. Shower at marina, nick the marina's hot water to wash up - heck I'm paying.  In the future yes - engine will heat water and maybe, just maybe, I'll have spare solar to heat the water a bit in the summer sometimes. No electrical high power gadgets, never use the webasto central heating. To be fair, apart from trying to run a computerised recording/mixing studio in the boat we're already on top frugal mode. My son and I live on under £10K/year including absolutely everything, we're no strangers to "not using stuff". £5k/year each. Our best year was nearer £7k and when you consider £3k goes in mooring fees and licence you get the idea - we're good at this already. TBH I expect our costs to rise quite a bit when we set off to live outside the marina.

 

Nick - thanks for reading, understanding and your answer. I do surely hope I'm not burning through 7Kw a day, I very much doubt that.

 

I'll take some meter readings and get back to this thread with some real numbers to see what I'm in for.

 

Thanks to all for taking the trouble to post your helpful advice.

 

Edited June 25, 2022 by Slow and Steady

[Alan de Enfield]

15 minutes ago, Slow and Steady said:

Tony/Allen, I'm struggling to think How I could be more clear.

 

 

You did read where I wrote :

 

 

3 hours ago, Alan de Enfield said:

A very 'down and dirty' idea will be (as you suggested) take a reading on your bollard meter and weekly readings thereafter for a month or two.

take the average daily / weekly reading and that will be an approximation - but it will be 'what has gone into the boat' from the bollard and will not include anything produced from running the engine or from solar panels.

 

I'd reckon it would be a fair-bet that your actual consumption would be higher than your bollard reading.

 

[Slow and Steady]

46 minutes ago, Alan de Enfield said:

but it will be 'what has gone into the boat' from the bollard and will not include anything produced from running the engine or from solar panels.

Sure I read it. Did you read the bit where I never run the engine, don't have any solar and get ALL my power via the bollard? Remember I'm doing an audit here, not planning my charging.

4 hours ago, Alan de Enfield said:

You will never be charging the battery / running the engine ? - Solar will not supply sufficient for 4 or 5 months of the year.

Again, I'm doing a power audit here, not charge planning, but just for you...

There's a difference between charging the batteries directly with the domestic alternator and using the travel power. Both run the engine. Only the travel power is designed for the constant high output lithium batteries need so no, I don't intend to charge the batteries with the alternator,  but yes as I clearly said, I will be charging them by running the engine. For future ref, I'm not a complete idiot, I posted this thread to get views on calculating my USE via the bollard meter reading, clearly stating that ALL my power derives from the bollard. I must have repeated that ... several times by now.

Edited June 25, 2022 by Slow and Steady

[nicknorman]

1 hour ago, Slow and Steady said:

 

Winter / supplementary charging using the travel-power supplying a 120A charger. OK yes it's got a "special" alternator powering the travel power but I'm likely to just take the belt off the domestic alternator OR maybe get an alternator controller and up my charging possibilities. I'm lead to believe charging the lithiums via the travel power and mains charger is a neat simple way to get started.

 

Yes travelpower plus charger is a good way to charge lithium. I just sound a small note of caution - we have a travel power and a Mastervolt Combi including 100A charger. However, whilst I get 100A for a while, the Combi heats up and the current gradually decreases. About 65A continuous is as much as I can get, and that is with the device in the engine room (well ventilated). I’m not entirely sure there isn’t a problem with one of the fans, but anyway best to check that you can actually get a continuous 120A from your charger.

 

One bodge you can try is to insert a long length of wire between domestic alternator and batteries (appropriately fused) so that the additional resistance reduces the current to avoid overheating the alternator. Or of course use a proper alternator controller! You should be able to charge at at least 1/2 C without shortening the life of the batteries, so if you have say 600Ah you could happily charge at 300A if the charging system can supply that. The aim of course being to minimise the static engine running time. Depending on the domestic alternator you might get another 100A or so out of it.

[Slow and Steady]

8 minutes ago, nicknorman said:

However, whilst I get 100A for a while, the Combi heats up and the current gradually decreases. About 65A continuous is as much as I can get, and that is with the device in the engine room (well ventilated). I’m not entirely sure there isn’t a problem with one of the fans, but anyway best to check that you can actually get a continuous 120A from your charger.

Interesting. Mine's a Victron Combi and 15 years old, I wonder if these things were designed assuming LA batteries where the high draw would be limited. I think the domestic alt is 140A so yes, looks like I might be better combining the two rather than thrashing one of them, I can limit the max charge with dip switches ostensibly to suit the battery bank size so it's an option. Thanks for that info.

Edited June 25, 2022 by Slow and Steady

[Tony Brooks]

The Travelpower IS an alternator.

 

I don't think you were explicit but as I read your question you wanted to know your total power requirement when you are OFF grid. Otherwise, there is no point in even doing the calculations. The mains and battery charger will supply all your loads, just as they do now. It is only an issue when off grid.

 

Travelpowers are engine driven alternators having a 230V AC output so normally charge whatever batteries you have via a mains battery charger or lithium mains charge controller.

 

I don't see why you seem to be ignoring the charging side of the calculations unless you intend  to stay on shore power, but your talk of a Travelpower seems to contradict that. Ignore charging and destroy batteries, but probably not as fast with lithiums as with lead acids.

 

I answered the best as I understood things so I don't think I can try to help any further.

[Slow and Steady]

2 minutes ago, Tony Brooks said:

The Travelpower IS an alternator.

 

I don't think you were explicit but as I read your question you wanted to know your total power requirement when you are OFF grid. Otherwise, there is no point in even doing the calculations. The mains and battery charger will supply all your loads, just as they do now. It is only an issue when off grid.

 

Travelpowers are engine driven alternators having a 230V AC output so normally charge whatever batteries you have via a mains battery charger or lithium mains charge controller.

 

I don't see why you seem to be ignoring the charging side of the calculations unless you intend  to stay on shore power, but your talk of a Travelpower seems to contradict that. Ignore charging and destroy batteries, but probably not as fast with lithiums as with lead acids.

 

I answered the best as I understood things so I don't think I can try to help any further.

Tony, I simply want to know what my power requirements are right now as they will not change when I'm off grid. I don't understand why my equipment would be using a different amount of power off grid. Please explain. I understand that power would be derived from batteries and there will be losses in conversion which was part of the original question.

Yes Travel power's are engine driven alternators but they are not like 12V alternators are they? They are designed for continuous high load unlike a regular 12V alternator that from all I've read will cook when you try and suck it's max amps out continuously. I was trying to make that distinction.

 

I'm not ignoring the charging side of the equation, - how can I possibly plan that if I don't know the requirements One thing at a time eh? Start at the beginning. I know for a fact that if I started posting about charging your first reply would be "How much power do you use, do a power audit". That's all I'm trying to do, but I'm answering all the charging questions as best I can simply because it's impolite to ignore people who seem to be trying to help.

 

I'm merely trying to find out roughly how much power I would need to suck out of 12V batteries to maintain my hooked up lifestyle. Once I know that I can think about bank size and how I'd charge them, or I can think about how I could reduce my requirements. Any charging plans would be peeing in the wind at this point don't you think?

 

Sorry if I've appeared to be rude, but I do know what my question was and I really didn't want to get into charging at this point. Instead of that we have a page of people querying my charging plans, pointing out the errors in a plan I haven't even more than vaguely thought about and me trying my best to steer it back to converting bollard power to battery power. Sorry again, I thought it was a simple enough question!

[Tony Brooks]

I understand that Travelpowers are modified Bosch alternators, the magic happens in the metal box and that mafic may include current limiting.

 

We are back to my original answer. At present your charger is using power to work itself converting the mains 230V AC to 12+V DC so that needs subtracting from the total used. If it is a decent charger it probably will not be much unless it gets hot. Whatever you end up with it will be the total electricity used on the boat.

 

Once you go off grid all the 240V AC loads on the boat will have to be provided by an inverter unless you intend to run the Travelpower for periods, but that only complicates things because you can subtract the Travelpower output from the total boat power required. That new figure or the original one if you do not use the Travelpower, minus the 12V DC loads (another complication) will have to be supplied by the inverter and that uses power to work itself so that needs adding to  the boat's demand.  In my view it is a very complicated way of going about what is usually the simple procedure of doing a power audit.

 

I suspect that just taking the figure from the shoreline will be fairly close but I can't say that with any certainty. If you want a quick and dirty figure just increase the bollard figure by 10%.

 

 

 

 

 

[Tony1]

A while back Alan de Enfield posted a listing for an energy monitoring plug-  it plugs into your 240v socket, and then you plug your household electrical devices into the back of it, and it provides an accurate measurement of power usage over say a 24 hour period.

You could get one of those, and use it for 24 hours on each of your computers and devices, and within 10 days you'll know all the significant usage. 

You'll see plenty of them on ebay, and probably Amazon. 

7Kw does sound a lot, but you do seem to have a lot of hardware, but either way it does look like you'll want as much solar as you can fit on the roof, allowing some space in the important places, e.g. around the centre line ring, the back edge of the roof, and along the roof sides.

But it depends on the cruising months. If you're only out cruising from say June to end of Aug, the solar is generally very good on most days, so a smaller array might work. But if you want to be self sufficient with all that hardware in say April, May, Sept and Oct, that's a somewhat different solar requirement. 

If its any help, as an example my 750 watt panel set have been giving between 1.5 and 2.3 kWh most days, for the last couple of weeks. 

 

Edited June 25, 2022 by Tony1

[Slow and Steady]

1 hour ago, Tony Brooks said:

I suspect that just taking the figure from the shoreline will be fairly close but I can't say that with any certainty. If you want a quick and dirty figure just increase the bollard figure by 10%.

Thanks, I suspect the same, it'll be ball park and for now that's fine. I'll know if it's 50, 100, 200 or 500Ah. That will be a great overview. THEN I can worry about either cutting that down by changing my behaviour, building a system to store and systems to charge that storage or a bit of both but it all depends on usage. I'll always err on the safe side so I have no need to push anything to it's limits. Who knows, I might find it's impossible to live as I like to while generating my own power in which case I might abandon the whole idea and stay in the marina, though it would be nice if that were choice rather than necessity, I might pee the marina off and get chucked out! (not really)

1 hour ago, Tony1 said:

A while back Alan de Enfield posted a listing for an energy monitoring plug-  it plugs into your 240v socket

I looked at that, realised they all extend upwards from the plug and as my sockets are all just under the gunnels I couldn't plug the beggars in! If not for that I'd be doing this to break down the total usage a bit and when I find it's alarmingly high I'll probably have to buy a short extension to enable that. But first things first.

 

1 hour ago, Tony1 said:

you do seem to have a lot of hardware,

Yes and it gets a lot of use. I don't think any of it is alarming in it's wattage, it's more the long hours constant use adding up. I know from experience that a 12V fridge might only draw 4A but when it's on full time 24/7 even switching on and off it adds up. Then there's the inverter, I think mine is 2A on standby and probably burns more in use so there's another battery a day. Yep, could be an unliveable total but I'm not in the best of health and get a lot of pleasure from making and mixing music on ze computer. Cost peanuts and is better quality than a multi-million pound studio was in the 80's 90's. Computers - got to embrace them. I make tracks with people around the world, I've just been working with a singer in Argentina. I've got a b-side out with a singer in America. I've made a few tracks with a lady drummer from Germany, a UK singer and an Italian Bass player. I've made a few tracks with a singer/guitarist from a tiny French Island off the East African coat. It's just for fun, it's impossible to make money like this these days - 20,000 tracks are uploaded to Spotify every day... but musicians are nice, well behaved, polite, encouraging people and it beats watching telly.

Edited June 25, 2022 by Slow and Steady

[Bod]

As I see it, with no supplementary charging, the bollard readings will give the total power used, for a given period.

How to maintain the current lifestyle, when the boat is removed from that bollard, is the question.

Convert this bollard 240v reading to 12vdc will give the capacity of the storage and charging required to maintain that lifestyle.

How that power is replaced is a question for another day.

 

Bod

[Tony Brooks]

37 minutes ago, Bod said:

Convert this bollard 240v reading to 12vdc will give the capacity of the storage and charging required to maintain that lifestyle

 

Except it will be an underestimation because of inverter losses in converting 12V DC or 230V AC plus the current used while it is not inverting. If the OP added 10 to 20% then that is likely to be a more accurate figure.