How many batteries

[blodger]

Well high noon should get somewhere near max say 90% so 400 watts / 12 = 33,3 amps - 10% so say 30 amps for 3 hours = 90 amps That leaves 9 more hours to get the other 90 amps. I looked at some charts based on the weather last year in Bristol and that's what came out on av for the hottest 8 weeks,(height of summer} of course the months leading up and following will gradually reduce respectively. I will double check this though as I want to be sure I'm not running the engine in the summer, so if more panels needed then so be it.

I was going by the output of my 220w of panels, 100 & 2 60s, secured flat on the roof.

 

When I see 8 amps surging through around lunch time I think I am doing well so talking 400w 15 amps seemed about right.

 

Keep intending to put a wattmeter in line and see what I actually get

 

A 40 watt panel I have on a shed roof rarely shows an output much above an amp. I have concluded that solar wattages are what might be attained nearer the equator, half it for 54N.

Apparently, you loose 30% of what is available just by not pointing them directly at the sun, etc etc

Edited August 20, 2011 by blodger

[Ex- Member]

I'm gonna be corrected here...but here goes :

 

If something draws 1 amp on 240 volts....amps x volts = watts....so that is a 240 watt appliance...

If its on an invertor from 12 volts...the batteries will be still supplying 240 watts ( ignore invertor loss)

But...as its 12 volts....the current draw will be 20 amps...(simplified)...20 amps x 12 volts = 240 watts.

 

I always work roughly on 1 amp at 240 volts..is 20 amps from 12 volt...and it seems about right.

 

I'm not sure what you mean by 27 amps a day ?

It will draw a current..?...power..?

If its 5 amps when its on...and its 240 volts..it will be 1200 watts ?

By my calculations..it will be drawing 1200...divided by 12 volts...100 amps ?

No ?

 

When an electrical appliance operates...it draws a current...like pressure..in a way..

The battery rating will be...amps per hour...a 110 amp battery can supply (simplified) 110 amps...for an hour...or 55 amps for 2 hours etc....

If you had a 5 amp...240v fridge...and it stayed ON for an hour...you would run out of 110 amp hour battery..in an hour...just about...

This is more simplified...as the frideg would cut in and out..BUT when it cuts in..it takes a hefty chunk of power for a few seconds...way more than the running power.

 

bob

 

Hi Bob

 

The fridge is rated 117kwh per year It's a Bosch a+ rated so pretty economical. So I made that 117000 watts per year divided by 365 days is 320.54 watts per day divided by 24 hours = 13.35 watts per hour.

 

Is that the correct way?

 

 

 

[14skipper]

l guess it does not matter how many times a question is asked there is always more to discuss !

So l have to take all our electrical items and add up the amp hour and then ?

Sorry but whats travel power ?

 

14skipper

Edited August 21, 2011 by 14skipper

[blodger]

l guess it does not matter how many times a question is asked there is always more to discuss !

So l have to take all our electrical items and add up the amp hour and then ?

Sorry but whats travel power ?

 

14skipper

Teavel power is a rather expensive mains AC alternator driven by the engine just as the starter/domestic batt alternator

[Robin2]

Hi Bob

 

The fridge is rated 117kwh per year It's a Bosch a+ rated so pretty economical. So I made that 117000 watts per year divided by 365 days is 320.54 watts per day divided by 24 hours = 13.35 watts per hour.

 

Is that the correct way?

 

I presume when you mentioned 27amps in your first post you meant 27 amps at 12v, not 27 amps at 230v.

 

You are using your terminology incorrectly - which may be adding to the confusion. Something that consumes 1 amp will consume 24 amp-hours in a day. One does not say "amps per hour" as that is meaningless. The correct expression would be "amp-hours per hour" but of course that is just "amps".

 

I believe it won't work to average the power consumption of your washing machine over several days. You need to do separate calculations for the days when you use the machine and the days you don't because the washing machine will seriously deplete your battery on the day it operates and if that is followed by several dull days you may found your battery SOC much lower than you bargained for.

 

You should be careful in interpreting the watts from your solar panels. What is the nominal voltage of the panels - lets assume its 20v to make the maths simple. That equates to 20 amps for 400 watts. If you have an mppt controller that should, in theory (but I have no practical experience yet) equate to 31 amps at 13v into your batteries. And I would assume at least a 10% efficiency loss from those figures. If you don't have an mppt controller you will only get 20amps into your batteries (at 13v) or 260 watts.

[Ex- Member]

Thanks guys, I clearly need to get a better understanding of all this. So will start again. Some time ago I had a brilliant chart that made this quite easy, I lost it when er in doors cleaned out a computer, so this time I was doing it from memory but knew I had something wrong.

 

Things like the twin tub washing machine are tricky too,on wash it uses 365W Wash Motor, on spin 165W Spin Motor

230 volt supply. Lynn reckons wash cycle 10 minutes and spin 5 minutes on average once per day. Probably a bit over the top, but better over than under.

[blodger]

You should be careful in interpreting the watts from your solar panels. What is the nominal voltage of the panels - lets assume its 20v to make the maths simple. That equates to 20 amps for 400 watts. If you have an mppt controller that should, in theory (but I have no practical experience yet) equate to 31 amps at 13v into your batteries. And I would assume at least a 10% efficiency loss from those figures. If you don't have an mppt controller you will only get 20amps into your batteries (at 13v) or 260 watts.

If you don't have an mppt controller you will only get 20amps into your batteries (at 13v) or 260 watts.

We are talking peak/high noon amps here and I would say less up to 30% if you are not using a tracking/elevating system

[nb Innisfree]

Yeah see what you mean, we have a powermaster 3 kva pure sine, I'm sure I recall it being 98% efficient, might be wrong though, won't know till back on the boat next week.

 

No way, Victron quote 95% for 48v inverter and that is the best figure there is though I would think Mastervolt will be similar.

[Ex- Member]

I have now recalculated the 220v/240vappliances. I had made some basic errors, this should now be correct.

 

Amps daily. 240 volt use.

 

 

 

240v fridge 1.4 amps x 24 hours 33.6amps per day

 

Wilo CH pump 0.2amps x 24 hours 12 amps per day winter only

 

Twin tub washer 11amps based on 15minutes per day 4 amps

 

Mini freezer 2.1 amps x 24 hours 50.4 amps per day

 

Oven fan 1 hour 0.5 amps x 1 hour per day 0.5 amps

 

 

 

Total amps 100.5

 

+ 10% 1nverter 111

 

Also double checked 12 volt and some slight corrections have been made.

 

Amps daily 12 volt.

 

 

 

Meos TV 4 hours per day 2.5amps x 4 hours per day 10 amps

 

LED lights 6 0n 6 hours per day 1 amp x6 hours per day 6 amps

 

Lap top 4 hours daily 2.5amps 4 hours per day 6 amps

 

Dab radio 8 hours daily 0.5 amps x 8 hours per day 4 amps

 

1 comp fans 24 hour 0.1 amps x 24 hoursper day 2.4 amps

 

4 comp fans 6 hours 0.1 amps x 6 hoursper day 2.4 amps

 

Shower pump Combined

 

Water pump Combined Est daily 4.0 amps

 

 

 

Total amps 34.8 per day

 

 

 

Total amps 145.8 per day.

 

 

 

 

 

I also did some checking on solar panelperformance and found this here along with a solar irradiance chart.

 

 

 

 

Output in summer

Thefigure you will be quoted by manufacturers is the 'peak power' of the panel.Essentially, it's the maximum you can expect to get from the solar panel in UKconditions - your 100 Wattsolar panel will be givingabout 100 Watts on a cloudless summer day at noon, ifthe panel is pointing directly at the sun. Of course, it isn't always sunny,and very few people have tracking devices to allow the panels to follow thesun. However, in the summer in the UK, you can expect to get on average about 5hours of full power output each day. That means, your 100 Watt solar panel will give you about 500 Watt-hours of energy on a summer day. For a 12 volt system,that corresponds to 41.7Amp-hours put back into your battery bank each day. On sunny days, you willget more; on overcast days you will get less.

 

 

 

I calculated 180 amps daily for 400 watts, on the above that would be 166.8 amps so not a great difference.

 

 

 

http://midsummerenergy.co.uk/solar_panel_information/solar-panel-power.html?power=100

 

 

 

I also found the original chart for solarirradiance, really handy chart.

 

 

 

http://www.solarelectricityhandbook.com/solar-irradiance.html

Edited August 21, 2011 by Julynian

[Robin2]

If you don't have an mppt controller you will only get 20amps into your batteries (at 13v) or 260 watts.

We are talking peak/high noon amps here and I would say less up to 30% if you are not using a tracking/elevating system

 

I know, but that was not the point I was making. I had hoped to explain that the panels would not produce 400w in full sunshine unless the controller properly matches them to the batteries. I think Julynian understands the need to derate the maximum output (from 400w or from 260w) to allow for the UK weather.

Edited August 21, 2011 by Robin2

[Robin2]

I also found the original chart for solarirradiance, really handy chart.

 

http://www.solarelectricityhandbook.com/solar-irradiance.html

 

Based on similar data these are the average daily amp-hr figures (at 12v) for each month for a 400 panel (assuming my spreadsheet is ok).

 

J 21.4

F 42.0

M 72.3

A 118.7

M 157.3

J 160.0

J 162.0

A 131.0

S 93.0

O 52.7

N 26.1

D 15.3

 

For planning purposes I believe these should be significantly reduced to allow for such things as being in a sub-average year, being moored in shade some of the time, birdsh*t on the panels etc etc.

Edited August 21, 2011 by Robin2

[Ex- Member]

I know, but that was not the point I was making. I had hoped to explain that the panels would not produce 400w in full sunshine unless the controller properly matches them to the batteries. I think Julynian understands the need to derate the maximum output (from 400w or from 260w) to allow for the UK weather.

 

Hi Robin, I do understand that, I'll make sure I buy the best equipment too and even allow for additional panels in the future. I'm assuming of course that you don't have to purchase a separate MPPT for each panel. I would prefer to buy one unit say a MPPT at 500 watts but having only 400 watts of solar, so if I add an additional 100 watt panel I can do without purchasing another MPPT controller.

 

We have a solar shop locally I'm due to visit, so I'll get up to speed with all these options hopefully.

 

 

 

[Robin2]

Hi Robin, I do understand that, I'll make sure I buy the best equipment too and even allow for additional panels in the future. I'm assuming of course that you don't have to purchase a separate MPPT for each panel. I would prefer to buy one unit say a MPPT at 500 watts but having only 400 watts of solar, so if I add an additional 100 watt panel I can do without purchasing another MPPT controller.

 

We have a solar shop locally I'm due to visit, so I'll get up to speed with all these options hopefully.

If you have space for more solar panels you might get more watt-hours for your £ by buying an extra panel rather than an mppt controller. And that would not prevent you from buying the mppt controller later. The economics require careful calculation unless investment funds are unlimited.

 

I have 3x80w panels that I got recently and I have no space for more - or I'm not willing to give up space for coal and bicycle. I am thinking carefully about mppt in my own perverse way.

[Ex- Member]

Based on similar data these are the average daily amp-hr figures (at 12v) for each month for a 400 panel (assuming my spreadsheet is ok).

 

J 21.4

F 42.0

M 72.3

A 118.7

M 157.3

J 160.0

J 162.0

A 131.0

S 93.0

O 52.7

N 26.1

D 15.3

 

For planning purposes I believe these should be significantly reduced to allow for such things as being in a sub-average year, being moored in shade some of the time, birdsh*t on the panels etc etc.

 

Good point, We realise that part of a daily routine will be cleaning the panels, a lot more difficult though to ensure mooring in a good open space. I do plan a certain amount of tilt by fixing the panels on aluminium poles, these will tilt but only be about 30 degrees but will ensure that the panels can be at the very least always be flat on the roof so not angled away from the sun, This of course would need some attention a couple of times a day.

 

I'm also moving my battery bank to be easily accessible so we can maintain the batteries easily and regularly. From reading stuff on batteries keeping them in tip top condition can make a massive difference in their capacity to store energy efficiently. And of course correct wiring for charging which is also ready to be implemented from the diagrams posted by gibbo.

 

Diesel will only get more expensive, we intend not to have to rely on it as a source of energy, it's ridiculously expensive now let alone a year down the road.

 

Any more comments appreciated.

 

 

 

[soldthehouse]

What an interesting thread. I hesitated before entering but was soon encouraged by Richardhulas down to earth reply giving a typical example,Great. Also Bobbybass gave actual appliances and equipment needed. Then it was downhill from there....

 

Percentage this and watts and amps everywhere with the ubiquitous " it all depends" statement.

 

The op is obviously looking for what works on a day to day basis with some help as to how many batteries are needed in a typical scenario. The first rply gives a good datum to work from and a guide as to what size battery banks can cope with what, He will obviously do some calculations and I would have thought the question was to ascertain what worked for real paople than to be lectured on how to calculate consumption and conversion...

[Ex- Member]

If you have space for more solar panels you might get more watt-hours for your £ by buying an extra panel rather than an mppt controller. And that would not prevent you from buying the mppt controller later. The economics require careful calculation unless investment funds are unlimited.

 

I have 3x80w panels that I got recently and I have no space for more - or I'm not willing to give up space for coal and bicycle. I am thinking carefully about mppt in my own perverse way.

 

We have a wide beam, I could easily get a KW on the roof but don't want to be cleaning the Bird sh1te of all those

 

I don't have an unlimited budget that's for sure, but I reckon solar panels now only take 18 months to repay them selves if you can get them as cheap a £2.00 per watt.

So I'm hoping I can get the 400 watts and controller for around a grand which I've set aside. It certainly wouldn't take long to spend a grand in diesel at today's prices let alone the saving on engine wear and maintenance. I don't have to buy yet and panels seem to be getting cheaper and cheaper. currently in China they can't make them quick enough, so I hope it doesn't go the other way and demand out strips production then they'll start going up in price.

 

A grand over the next 18 months equates to £1.83p per day.

 

Blimy, think I'll buy them on credit

 

 

 

[Robin2]

He will obviously do some calculations and I would have thought the question was to ascertain what worked for real paople than to be lectured on how to calculate consumption and conversion...

 

There seems to be circular logic here...

 

If you have an unlimited budget (for diesel, solar panels or batteries) you can blissfully ignore the watts and amps. If you want to get value for money they are unavoidable.

[soldthehouse]

There seems to be circular logic here...

 

If you have an unlimited budget (for diesel, solar panels or batteries) you can blissfully ignore the watts and amps. If you want to get value for money they are unavoidable.

Unlike some I prefer not to make assumptions I have no knowledge of the op,s budget or whether the motivation is value for money all I see are certain types who wish to divulge every theory or law relating to the subject of power and consumption in an "I know more on the subject than you debate" Rather than giving an informed concise opinion and then the op can judge for themselves.

[Bobbybass]

I have now recalculated the 220v/240vappliances. I had made some basic errors, this should now be correct.

 

Amps daily. 240 volt use.

 

 

 

240v fridge 1.4 amps x 24 hours 33.6amps per day

 

Wilo CH pump 0.2amps x 24 hours 12 amps per day winter only

 

Twin tub washer 11amps based on 15minutes per day 4 amps

 

Mini freezer 2.1 amps x 24 hours 50.4 amps per day

 

Oven fan 1 hour 0.5 amps x 1 hour per day 0.5 amps

 

 

 

Total amps 100.5

 

+ 10% 1nverter 111

 

Also double checked 12 volt and some slight corrections have been made.

 

Amps daily 12 volt.

 

 

 

Meos TV 4 hours per day 2.5amps x 4 hours per day 10 amps

 

LED lights 6 0n 6 hours per day 1 amp x6 hours per day 6 amps

 

Lap top 4 hours daily 2.5amps 4 hours per day 6 amps

 

Dab radio 8 hours daily 0.5 amps x 8 hours per day 4 amps

 

1 comp fans 24 hour 0.1 amps x 24 hoursper day 2.4 amps

 

4 comp fans 6 hours 0.1 amps x 6 hoursper day 2.4 amps

 

Shower pump Combined

 

Water pump Combined Est daily 4.0 amps

 

 

 

Total amps 34.8 per day

 

 

 

Total amps 145.8 per day.

 

 

 

 

 

I also did some checking on solar panelperformance and found this here along with a solar irradiance chart.

 

 

 

 

Output in summer

Thefigure you will be quoted by manufacturers is the 'peak power' of the panel.Essentially, it's the maximum you can expect to get from the solar panel in UKconditions - your 100 Wattsolar panel will be givingabout 100 Watts on a cloudless summer day at noon, ifthe panel is pointing directly at the sun. Of course, it isn't always sunny,and very few people have tracking devices to allow the panels to follow thesun. However, in the summer in the UK, you can expect to get on average about 5hours of full power output each day. That means, your 100 Watt solar panel will give you about 500 Watt-hours of energy on a summer day. For a 12 volt system,that corresponds to 41.7Amp-hours put back into your battery bank each day. On sunny days, you willget more; on overcast days you will get less.

 

 

 

I calculated 180 amps daily for 400 watts, on the above that would be 166.8 amps so not a great difference.

 

 

 

http://midsummerenergy.co.uk/solar_panel_information/solar-panel-power.html?power=100

 

 

 

I also found the original chart for solarirradiance, really handy chart.

 

 

 

http://www.solarelectricityhandbook.com/solar-irradiance.html

 

I'm still not sure about this...?

I was hoping for some more knowledgable people to come along ..but here goes :

 

Still can't see your correlation between 240 volt and 12 volt ?

Sorry if I'm being thick...

If you draw 1 amp on 240volts...via an invertor...your invertor will take 20 amps from a 12 volt battery..to produce this 240 volt at 1 amp.

In other words..your 1.4 amp an hour fridge on 240 volt...over 24 hours...will take 1.4 x 24 x 20 = 672 amps from 12 volts.

It appears to me..(actual appearing may vary from description)....that you still need the 'hours' figure worked into this.

 

I 'think'..but am sorry if I'm wrong....that you think...(they think ?..nah)..that an amp on the 240 volt draws an amp from the 12 volt...but this is not so...

You come back to the wattage again...

Look on the back of your appliance...and see its wattage rating while running..

If its a microwave.....and it says '240 volt...1000 watts'...then it is drawing 4.16 amps while running on 240 volts...divide wattage by voltage = current (amps)

To supply this from an invertor..(ignore loss)...you must take 1000 watts from your 12 volt batteries...

BUT...instead of dividing the wattage by 240 volts..to get 4.16 amps..you have to divide the wattage by 12 volts...

That is a wopping 83 amps......and that is what you are taking (losses ignored)...from the 12 volt batteries..

 

If your mini freezer draws 2 amps while running...( and was continuous) and is 240 volts...that is 240 x 2 = 880 watts...in an ideal hour...

Running that on the invertor...from 12 volts...you divide 880 watts by 12v = 73 amps in an hour...!!

 

PLEASE...is there somebody more inteligent here...can help...a drownng Bob !!

 

 

bob

Edited August 21, 2011 by Bobbybass

[Gibbo]

If its a microwave.....and it says '240 volt...1000 watts'...then it is drawing 4.16 amps while running on 240 volts...divide wattage by voltage = current (amps)

To supply this from an invertor..(ignore loss)...you must take 1000 watts from your 12 volt batteries...

BUT...instead of dividing the wattage by 240 volts..to get 4.16 amps..you have to divide the wattage by 12 volts...

That is a wopping 83 amps......and that is what you are taking (losses ignored)...from the 12 volt batteries..

 

Correct.

[Bobbybass]

Correct.

Is that it...?

The answer to the universe...is 49 !!

 

I've been floundering around here...hoping for some support from higher powers...and all I get is...correct...

 

PS. You haven't told him to get a Smart Guage yet...you're slipping...!

 

 

bob

[Gibbo]

Is that it...?

The answer to the universe...is 49 !!

 

I've been floundering around here...hoping for some support from higher powers...and all I get is...correct...

 

PS. You haven't told him to get a Smart Guage yet...you're slipping...!

 

 

bob

 

You made a statement and questioned whether it was correct. I confirmed it was correct. What more do you want?

 

Sarcastic arse.

[Bobbybass]

You made a statement and questioned whether it was correct. I confirmed it was correct. What more do you want?

 

Sarcastic arse.

 

Smartguage fancier !!

 

I 'thought'..you would jump in...and say that 'your basic theories are correct...but they are completely wrong...becuase......etc etc ...'...as...I have come to expect...

Edited August 21, 2011 by Bobbybass

[bottle]

Bobby

 

Quit while you are ahead.

 

Just one thing if you divided by 10 instead of 12, that would roughly take care of the losses you ignored.

 

Of course that will give even more frightening figures.

[Gibbo]

Smartguage fancier !!

 

I 'thought'..you would jump in...and say...

 

So again you were wrong? You must be used to it by now.