Noobie Solar questions/battery

[shavermcspud]

Hi everyone.

I decided to make my home bar/pub off grid with Solar, inverter and batteries.
I didnt want to spend fortunes as my power requirements are minimal, around 370watts with the LED lights on, fridge running and sonos running when its active, during no activity, only the fridge is running.

I purchased the following
6x Dokio 100watt mono panels for their lightweight and easy mounting option for my wooden roof and they had good reviews.
1x photonic 40amp MPPT controller plus remote
1x 1000watt pure sine inverter / 2000 watt surge
6x 100AH 12v AGM batteries, brand new (get these for free)
all the relevant cabling, fuses, bus bars etc

I have been experimenting over the last few days with wiring them two lots of 3 in series and parallel and all in parallel.

Im not sure what the best method for my setup would be, unfortunately im not directly south facing here in the UK or even if my battery capacity is suitable for the load im putting on it/recharge capacity during the day.

Any insights would be greatly appreciated

 

[tictag]

My gut instinct is that your system is under-specified, but let's do the maths.

ENERGY OUT
How much energy do we expect to consume over the course of one day?

Item	Rating	Time	Energy
Fridge	120W	12 hours	1,440Wh
Lights	15W	6 hours	90Wh
Sonos	30W	6 hours	180Wh
Inverter losses	10W	24 hours	240Wh
		TOTAL	1,950Wh

ENERGY STORAGE
Batteries are used to buffer inverter and other loads i.e. for stability, and/or to provide an emergency off-grid capability. You are basically just planning to run off-grid permanently so your focus is more on ensuring ENERGY OUT = ENERGY IN rather than having a large storage solution. But, with that said, 600AH at 12V = 3,600Wh maintaining a maximum of 50% DoD (for lead-acid) or around two days at the consumption calculated above (3,600Wh per day / 1,950Wh per day = 1.8 days).

ENERGY IN
You generally want to replenish your daily consumption every day, this means that your storage can be used to provide autonomy when weather isn't favourable. Whilst there are solar irradiance websites out there, my rule of thumb based on my own experience living in the UK (Lancashire) is to use 5 'good sun' hours per day and apply an efficiency index of 80% during Summer, 20% in Winter.

Therefore, your 600W array will produce 2,400Wh per day in Summer and 600Wh per day in Winter (600W x 5 'sun hours' x 80% = 2,400Wh in Summer, 600W x 5 'sun hours' x 20% = 600Wh in Winter).

So during the summer you will have a glut of energy but, unfortunately, you will not be able to supply your anticipated consumption during Winter, your batteries will slowly discharge over a number days. Is this a problem? I don't know ... will you consume the same energy in Winter? The fridge will likely consume less in colder conditions but is it inside and, therefore, does it operate within a heated room?

I would suggest measuring the energy use of your devices to sure-up your daily consumption calculation then consider either expanding your array or reducing consumption e.g. more efficient fridge etc.

 

[shavermcspud]

Hi Tictag

That is a very explanatory response and i really appreciate the time and effort you have put in to that.
That has given me a whole new understanding of my needs.

The only difference being time use per day, the bar/summer house is used probably once or twice a month in the winter at weekends and its not an every day usage scenario, the only item under constant draw will be the fridge. in the summer this will probably go up.

I presume I would benefit with adding more panels to the overall setup to give me the extra power in during the darker days.

For me this isn't about costs or trying to be super green, it was more of a lets see if i can do this.
im happy to double the solar capacity to 1200watts

 

[tictag]

Before you go buying more stuff I would encourage you to do an energy audit by measuring the energy use of your devices, particularly the fridge. Whilst they may be rated a certain power consumption, they do not generally operate 24/7 because they are thermostatically controlled. Just get one of those cheap energy meters and plug in the fridge - measure consumption over say a week. Something like this would do.



I've assumed 1,440Wh per day but it could be half that, or twice that and, as this is by far your biggest load, it makes sense to get an accurate measurement as possible.

Some fridges have a 'storage mode' as well. Something to consider if you're only using it once or twice per month.

Edit: Added energy meter.

 

[shavermcspud]

You read my mind, i brought one home from work yesterday and got it plugged in, hovers between 80-130w fridge only, unfortunately it doesn't store data through the day so I can only see the here and now. the fridge is one of the small beer type fridges you see, not a domestic home fridge/freezer.

I have some more time today being the weekend and the sun is shining this morning (kind of) so gives me a better idea, just had a quick peak with the panels wired 3x series by 2x parallel and getting a charge current of 26 amps@12v not sure if that's good or bad

 

[tictag]

Are you sure it doesn't store the ongoing energy consumption? I mean, it's just that most of them do. Look out for a 'kWh' setting/display - that's the cumulative energy consumption. Take the value after 24 hours (or better after a week, then divide by seven days) and that's the value you plug into the table above.

In a perfect world, the rated power of your array would be converted into charge current for your battery i.e. 600W / 12V = 50A. Now you're never going to get this! Time of year, panel angle to the sun, weather etc. I live in Lancashire at around 55o latitude and my rule of thumb is to expect 20% of rated output during Winter, in other words, I'd be happy getting 10A from your array!!

 

[svetz]

...I decided to make my home bar/pub off grid with Solar, inverter and batteries. ...
6x 100AH 12v AGM batteries, brand new (get these for free)

Free? Nice!

...So during the summer you will have a glut of energy but, unfortunately, you will not be able to supply your anticipated consumption during Winter...

What a great post! Kudos!

Stray thoughts.... First, if he get's batteries for free DoD isn't important. If it's a one time deal you might want to triple/quadruple up so you don't go below 50% DoD and you've got some reserve (I know, the UK hardly ever has a cloudy day ? ). But I was wondering.... is this an outdoor bar? I know you said UK, but why go solar unless it's outside not near power...that's my logic anyway. As I read the OP the picture to the right came to mind... If it is outside, will it really see much use in winter? In which case the power requirments would be lower. Finally... if it is outside in the winter, will the refrigerator still run 50% of the time? Doubtful in the UK, so again the winter power requirements would be less.

Update: Should have read farther...

... the bar/summer house is used probably once or twice a month...[usage] in the winter ... [is] not an every day usage scenario...

 

[svetz]

... [the fridge] hovers between 80-130w ...

If it has a freezer beware the energy cost of the defrost cycle. The 80-130w is probably the normal draw (although weird it isn't steady, don't get that).

 

[shavermcspud]

Are you sure it doesn't store the ongoing energy consumption? I mean, it's just that most of them do. Look out for a 'kWh' setting/display - that's the cumulative energy consumption. Take the value after 24 hours (or better after a week, then divide by seven days) and that's the value you plug into the table above.

It doesn't unfortunately, but I have just bought an inline one with remote monitoring back to my PC so will see how that goes.

Svetz, this is just a small beer style fridge, no freezer or anything, this is the charge rate im seeing at the moment, batteries seem to be at 80% in the morning after darkness and appear to fully charge during the day so far.

I could run mains to the bar at the end of the garden but I just fancied getting involved in Solar and giving it a try, always enjoyed electronics in general and messing about. pics of my little bar.

 

[svetz]

...this is just a small beer style fridge, no freezer or anything,...

The varying power might be from the computer/display activity.

Although your blowing my preconceptions of a brit as I don't see a dart board and I thought they liked warm beer.

 

[tictag]

Just one word, @shavermcspud, epic! But where are the pickled eggs?! ;-)

 

[tictag]

Don't forget the TV and mini-arcade game in your energy calculations!

 

[shavermcspud]

The varying power might be from the computer/display activity.

Although your blowing my preconceptions of a brit as I don't see a dart board and I though they liked warm beer.

HAHAH I did have a dart board but the wife thought stuff might get damaged so was replaced with a TV instead which doesn't get used at all Warm beer is not on my list or many Brits I don't think, unless its an Real ale or such.

 

[shavermcspud]

Just one word, @shavermcspud, epic! But where are the pickled eggs?! ;-)

Cheers pickeld eggs are behind the bar, running low on crisps at the moment though. the arcade machine is a direct 12v feed for the screen and a buck converter to run the raspberry pi to 5v for the games, hardly a noticeable draw on the system and again only gets used when people are in the bar.

 

[tictag]

and I though they liked warm beer.

Interestingly, I drink Coors Light a lot these days. Looking forward to the US-UK trade deal, frankly.

 

[ghostwriter66]

It doesn't unfortunately, but I have just bought an inline one with remote monitoring back to my PC so will see how that goes.

Svetz, this is just a small beer style fridge, no freezer or anything, this is the charge rate im seeing at the moment, batteries seem to be at 80% in the morning after darkness and appear to fully charge during the day so far.

I could run mains to the bar at the end of the garden but I just fancied getting involved in Solar and giving it a try, always enjoyed electronics in general and messing about. pics of my little bar.
View attachment 9099View attachment 9102View attachment 9101View attachment 9103View attachment 9104

Whats the link to the INLINE one you purchased ??

Second -- totally wicked floor -- wow ... and awesome shed ... wow x 2

One of my linemen messed up and had a couple picked eggs and then got called out on a job - over bumpy roads -- in 110 degree heat -- hmmm -- apparently having "child proof" doors turned on for the back seat guys was NOT a good idea ...

 

[shavermcspud]

Whats the link to the INLINE one you purchased ??

Second -- totally wicked floor -- wow ... and awesome shed ... wow x 2

One of my linemen messed up and had a couple picked eggs and then got called out on a job - over bumpy roads -- in 110 degree heat -- hmmm -- apparently having "child proof" doors turned on for the back seat guys was NOT a good idea ...

I will dig out the link for it, hopefuly it will arrive shortly so I can hook it up.