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Author Topic: Please help a newbie out.  (Read 43004 times)
biffanio
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« Reply #15 on: November 24, 2013, 12:46:28 AM »

If I bought 4 of these batteries Martin would it be OK to run them on the Inverter I wanted as a 12 or 24 volt system?

I did ideally want to draw up to 1.5kw of power.

This would only be used when available and only for 10% of the battery's capacity.

Sorry to be a pain!
« Last Edit: November 24, 2013, 12:49:07 AM by biffanio » Logged
martin
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« Reply #16 on: November 24, 2013, 08:52:32 AM »

I wouldn't! It's up to you, but I'd work "at the other end" to reduce consumption first - if you want that large an inverter you really need to go to to 24 or 48 volts, and have a socking great bank (a 1.5kw inverter will draw 125 amps @ 12v), so it would be within the capacity of the batteries at 1840 ampere hours to supply that, but you also have to replenish what you've used with more pv panels, and have a bigger regulator......... If it's not a rude question, what on earth do you think you need such an enormous inverter?(What do you have in  mind running off it?).
I've tried to design a simple system within the budget - by the sound of it you're chomping at the bit for a 5k (or more) system!
« Last Edit: November 24, 2013, 10:17:44 AM by martin » Logged

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clockmanFR
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« Reply #17 on: November 24, 2013, 08:54:21 AM »

Hi biffanio,
1.5kw draw is excessive on your batts.

I am running a 24v 400ah system for 24v lighting in my machine shed and  the Mrs greenhouse that also has underfloor heating.

http://www.navitron.org.uk/forum/index.php/topic,21161.0.html

The underfloor heating is 200w, which I have added a LVD, low voltage disconnect, which switches of the heating when the batteries get down to 24.50v. and will not switch back on until the batteries reach 25.50.

http://www.reuk.co.uk/wordpress/project-of-the-day-24v-low-voltage-disconnect/

Its what is charging your batteries that is important. New Mono PV panels give about 10% of their rated output in ambient light, ie when it is dull using a MPPT controller. So INCREASE the NUMBER OF YOUR PANELS as much as possible, especially as they are good prices at present.
 I am now rating my 24v system for worse caser scenario. What i will have is 2kW of panels.

With my big 48v system, 1300ah, I still require another 5kW of panels, I already have 5kW and 3off 3.7m dia Wind turbines, and I get 500w from my present PV on dull days. Yes, I am saving up for an Electric Forklift truck and more 1200ah batteries.

SO PV, PV, PV and more PV.  Grin

  
« Last Edit: November 24, 2013, 09:01:53 AM by clockmanFR » Logged

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biffanio
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« Reply #18 on: November 24, 2013, 09:26:00 AM »

Thank you for your comments guys.

I can see how building and tweaking these systems could get very addictive, lol.

Hi Martin

The reason I set my heart on a large 1500w Inverter was to open up the amount of appliances I could use as I upgraded my system.

Being set to a tight initial budget I did not take into account the severe battery limits and strains on them.

I think ill stick to 2 batteries of 920 amps and go for a low Inverter then.

Thanks also for your help Clock Manfr!
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martin
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« Reply #19 on: November 24, 2013, 09:31:31 AM »

Brilliant! -as many people find out to their cost, it pays not to stint on getting good batteries in the first place (the Rolls batteries really are some of the best), and then doing the sums carefully to make sure they last well.....
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offthegridandy
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« Reply #20 on: November 24, 2013, 09:41:01 AM »

Biffanio,

Accepting that you are working to a limited budget and aim to be off grid; as others have said you ideally need to start by considering what both your static/base load will be and also what your expected normal load will be.  Base load = items drawing power 24/7 ie fridge/freezer/inverter/ etc. Normal load = all the things you will switch on and off in the normal course of living ie lights, computer, heating pumps etc.

Find out or calculate the watts that all the items are using, from this you can find out what the minimum size batteries are required.

In my opinion, unless you are living the most frugal life style it is unlikely that you can manage in winter with PV alone. It's likely that you would need a genny to recharge batteries or you will kill them very quickly.  Although Paul and I would say get a Lister, even a small Honda petrol genny can be set up for auto start.  Plus a genny can give you more power if needed for power tools cement mixer etc.

As Martin says you shouldn't charge batteries at a rate higher than 10%, so if you put in 1800A/hr of batteries you would need to charge for perhaps 10 hrs at 180A/hrs to recharge them' and that's over and above any load you have on at the time. This will never be achieved on a small PV array.  So its for sure you'll stuff the batteries.

Earlier this year our hosts had a sale which included some unwarranted PV panels with a nominal 30 V out put around 210W each.  Don't know if they still have any but might be worth an ask.

 It is possible to feed a 24V battery set from 30V panels without regulation, given that the battery size is large enough. You could add a charge controller later when you grow the system and funds allow.  To put this in context I have 2500W of PV capable of producing 80 Amp/hr feeding 24V cells.(1000A/hr).  We are always drawing min 100w per hr and need 7.5Kwhrs per day to run the house. Theoretically I could therefore feed 80 amp an hr to the batteries from the PV with out any regulation and not over charge that batteries.

I don't think you'll achieve what you want for less than 1500 pounds minimum.

Assume SH genny                                        300
Assume cheap Navitron panels 4 X 200W +/-  500
Inverter ??                                                  200
Batteries for 1st year 4 X 450amp 12v
car type to last 1 year only @ 85 each           350
link batteries series and parralel to make
 24V bank at 900amps
Cable, connectors etc                                      50
PV charge controller
Home >> Off-Grid >>  Chargers + Load Controllers >> 30A Provista Charge Controller
PVCCISC3020
30A Provista Charge Controller                       70

Min total  +/-                                              1500

This way most of the kit will stay useable and you know your batteries won't last, but we all kill the first set of battereis due to ignorance and poor maintanance.  As your system grows you can upgrade both inverter and charge controller by putting second unit in in parallel rather than throwing away items. But do consider having a genny!!!!

Hope this helps.

Andy
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biffanio
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« Reply #21 on: November 24, 2013, 09:52:53 AM »

Thank you Andy.

That does make a lot of sense.

My aim was not to permanently run set appliances off this set up but to rather monitor battery power and run when the power allowed.

My outlook was to create a small amount of power whilst reducing my carbon footprint slightly.

This is where I got confused with the Inverter.

My newbie logic told me that is I got a 1500w Inverter i would only use power as the battery allowed ie fully topped up.

The rest of the time I would use grid power soley.

I hope in not being to much of a pest to you all as I am so enjoying learning and sharing your knowledge and expertise!
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offthegridandy
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« Reply #22 on: November 24, 2013, 09:56:29 AM »

Be very careful then.  You will need to isolate your off grid circuits from mains power supply.  If you are on the grid and connected to you off grid system in the event of mains power cut you will be sending 240V up the line and could kill the men trying to restore power!!!!!!!!!!!!!!

YOU must think this through very carefully.  More info required from you please or all our advise will be wrong

Andy
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24 Volt 1000amp battery bank
Outback VFX3024
4.6 Kw PV array ground mounted
Outback Flexmax 80
2 X Flexmax 30 PV CC
2.5 Kw WT H Piggot design 4.5 Mtr Dia AC coupled
12 Mtr free standing Tower.
u/floor heating from oil boiler cross linked to 12 K wood stove
biffanio
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« Reply #23 on: November 24, 2013, 10:01:46 AM »

Sorry it's me not explaining myself properly.

I will not be generating any electric on grid.

My generating of electric will be Purley off grid.

I will be relying on my normal electric supply when not using off grid power.
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martin
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« Reply #24 on: November 24, 2013, 10:04:58 AM »

I'd go for something simple and "self contained" in this case  - the original system I suggested (or similar) feeeding (for instance) your computer, wifi modem, tv and a light - if you have them all running off a 5 way socket, you can simply unplug it from the inverter, and plug it into the mains when the batteries start to flag........
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jonesy
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« Reply #25 on: November 24, 2013, 01:20:29 PM »

Is your aim to reduce your carbon footprint (as originally stated) save money, go off grid, or have a new hobby.  I only ask, as you won't save any money with any sort of battery derived system.  If you're doing it as a hobby, then the money is immaterial, but then your carbon footprint will enlarge, as you are buying environmentally unsound batteries. Think of all the energy required to both make and recycle a battery.  Plus, you can never use all of the energy coming from the panels ie the point at which the batteries are fully charged; so the panels are further enlarging the carbon footprint as their energy is being wasted.
The current standby power in UK is larger than the generating capacity of the new nuclear power station being built.  The best way to reduce your carbon footprint is to switch stuff off.  Do you need a clock on the oven and microwave, spare room.  Turn them off, save 30/year with 3 appliances.  If your fridge is over 5 years old change it.  Half my consumption comes from the 90W fridge motor on a A+++ rated fridge.  Look critically at things plugged in.  A PC & monitor 'off' are taking around 5W, same as any appliance you can turn on with a remote control.  Unplug them.  Do you use your router when you are asleep?  Unplug it.
I agree with Martin to stay simple; it'll cost less and it's a good introduction to all the things you don't know; a battery is 80% efficient at start of life; an inverter at best is 90% efficient; panels produce almost nothing when it's cloudy (I've generated 21kWh (~2 if bought) this month (1 day of sun) compared to 121kWh only 3 months ago on a 1.1kW system)
Please be careful; running extension leads around a house is not safe from both a falling over them point and electrical point.  Earth the inverter down and install protection, just as you would for a house.  Just because it's fed off 12V does not make it safe- the 230V out will still kill you, your family or friends in less than a second.
I was off grid for 2 years with a 1000AH/24V battery system whilst waiting for grid connection, and I've now put my panels onto a grid tie.  Wouldn't go back, and I still use the batteries on gloomy days to power the laptop and other 24V gear to save a few , but I should just sell them for scrap.  My annual bill is ~50+ standing charge.
Enjoy your new hobby and we're all here to help and advise; there's a lot of experience to tap into here.
 
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martin
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« Reply #26 on: November 24, 2013, 01:48:41 PM »

You make a very valid point - it really does pay to do the "repaying the embodied energy" sums too - often we've had people who for instance want to light a remote lambing shed for a couple of weeks a year, and have with the best intentions been looking at pv/battery systems, - if you take everything into account (especailly needing most electricity in winter's gloom, when pvs are producing bog all), it can often be far more eco friendly to buy and run a small genny, or good old-fashioned "Tilley" lamps..... whistlie
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biffanio
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« Reply #27 on: November 24, 2013, 02:17:35 PM »

Thank you for your advice everyone.

I was honestly under the impression that the off the grid system would pay for its self after maybe 10 years or so.

Also I was on the understanding that the rolls batteries I would be purchasing would last a very long time if properly maintained.

Now I'm starting to question  everything, lol.
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biff
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« Reply #28 on: November 24, 2013, 03:39:49 PM »

Then maybe you would like to be independant,
                             Design and build your own off-grid system.Perhaps you live way out in the country with no near neighbours or like minded neighbours but there is a certain satisfaction in generating your own electrictiy,especially if the mains is down and your own little plant is dishing out the max possible.  Then you have to sit and study the triangle of volts-amps-watts,learn that higher voltage means lower amps and lighter cables.Study the specs on the panels and work out if they suit your purpose.
          Even building a small off-grid system with a parallel run of 8 sockets can be extremly rewarding as long as you dont abuse your batteries and crock them by draining then down past 12.4volts.You just need to look at what is already up and working among the members and see if it suits your needs.
  Starting off on a small scale will show you what is possible.But the key to success is not wasting any electricity whatso ever and keeping it for when you really need it.That in itself is an education.
                               Biff
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jonesy
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« Reply #29 on: November 24, 2013, 03:44:45 PM »

I possibly painted it over black, so for that I apologise.  It depends what you hope to get back out of your 'investment' - independence is a compelling argument as biff says.

My grid tie is most likely not going to pay back, and I can use every drop of production, and I get 10% more sun than you.  The only reason I grid tied was because the panel prices had dropped so much I would get buttons selling used panels.  I wasn't eligible for FITs.  FIT's make solar power pay back.  IIRC cost/kWh for off grid is around 20-25p vs 15p on grid.  I would have been far better off running a small genny for 2 years rather than solar power - as Martin said.  
Mu off grid days were rewarding and I learned a lot, but I prefer grid tie; I never ran out of juice but I came within an estimated 2 days of running out and I had about 10 days storage.

If you plan to live for say 15 years in your current house,  grid tie might work - I've seen on this forum quotes for around 4k for a installed 4kw system.  It's more than your budget, but it may still work with a loan factored in.  
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