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Author Topic: System question - thoughts please...  (Read 5807 times)
teledemon
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« Reply #15 on: May 07, 2009, 03:42:16 PM »

Thanks everyone!

 - I'm now thinking along the lines of a separate charger/battery/inverter/relay system and I'm looking around for a 24v system to power the C/H pump and a separate lighting circuit.

Uh oh, another question...will my 70w pump start and run ok with a modified square wave inverter? What about compact flourescent bulbs - low watts maybe, but will I need a pure sine wave for those too?

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knighty
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« Reply #16 on: May 08, 2009, 11:35:57 AM »

what about powering the things you really need, c/h pump, tv etc... with some smaller invertors...

something like one of these but make sure you get a good make so it will last a long time...

one of those (or smiler) for each item that needs power, then hook the whole lot up to the same battery bank... and add a decent charger for the battery bank... one which can power all the inverters and charge the batteries at the same time....


that way when you have power, the battery charger will be charging your batteries and powering the inverters

then when you don't have power... the batteries will provide it via the inverters :-)


----------------------------------------------------------------------

but... you might be better off if you tried to sort out some kind of community scheme... so you could all chip in and set up a system to provide power for all of you ? - if your power is already subsidised... maybe you could get some kind of grant for this ?
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teledemon
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« Reply #17 on: May 08, 2009, 11:24:40 PM »

I've been doing a bit of power monitoring and I estimate that I'll need less than 500w continuous output to run the circulation pumps and fire the boiler; this will take care of the heating requirements - at least we won't freeze to death  Smiley We don't need to power anything else if we just go to bed earlier (but I'll miss the breadmaker!). I did some shopping and bagged a PSW (to be on the safe side with the pumps) inverter/charger - I think it's a Smart-UPS unit - so all that remains are the batteries.

I don't want to spend silly money  Grin I'm looking at some Powersafe 92AH on fleabay but the delivery charges will be horrible. But should I even be thinking about used batteries? I just missed blagging the old backup set from our phone exchange which could've saved a couple of hundred quid and I wouldn't have minded in the slightest  Wink

Anyone do decent priced batteries with reasonable delivery?

If i was to wire this type of inverter/charger into my C/H circuit am I right in thinking I don't need a relay?

Getting there slowly...not long to go till lights out!





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martin
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« Reply #18 on: May 08, 2009, 11:59:09 PM »

I'm afraid this is where cold, hard reality kicks in - there ain't no such thing as a free lunch, and where loads of sums need to be done........... Roll Eyes
As people who actually "live off batteries" will tell you, if you go the "cheap" route, it ends up expensive and you have a large stack of knackered batteries in a very short time..........
Here are some figures to play with - they are not "exact" by any manner of means, but give a good general view of battery use/longevity- you've probably been looking at battery adverts (and prices), some of the more honest suppliers will quote figures like "300 cycles to 70% DOD" - which means you can, on average take 70% of the charge contained in the  battery quoted 300 times before it knackers out - so that means if you cycle it every day, you'll need a new set in under a year.........or very roughly, "pro rata" - take only 10% out per day, you should be looking at over 2,000 cycles (days) - 6 years or so...........
For your sort of use, the very least I'd look at it something like Elecsols (new!) - they are relatively inexpensive, and carry a 5 year guarantee. Personally, I'd design to never take more than 20% of it's capacity per cycle, preferably nearer 10% Wink
If in doubt "10%" is good to remember (only ever charge a battery at a maximum of 10% of it's capacity, or drain it at the same maximum rate) -
I'm very aware this is only "skimming the surface" of a very complex subject - but hopefully it'll give you an idea of the sort of sums you need to do.........One thing I would be tempted to look at is to replace the fridge with a bottled gas (caravan) job - it'd save gobbets of electricity
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knighty
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« Reply #19 on: May 09, 2009, 02:26:32 AM »

do you know what times they want to cut the power off / turn it on again ?


for the frdige... as said earlier you could just leave it off overnight.... even better if you turn it down colder so when it does run while you have power it gets a big colder and works up more of a "cold store" Smiley
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EccentricAnomaly
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« Reply #20 on: May 09, 2009, 12:55:24 PM »

for the frdige... as said earlier you could just leave it off overnight.... even better if you turn it down colder so when it does run while you have power it gets a big colder and works up more of a "cold store" Smiley

I imagine that with a decent modern fridge overnight shouldn't be a problem at all.  It'd help to have lots of stuff in there though to increase the thermal mass so maximising the amount of "cold" stored.  If it's shortly before shopping day then maybe put some plastic bottles of water in to increase the mass.

I've mumbled here and on other fora before about putting phase change materials in fridges or freezers to extend the storage.  Vegetable oil or salt water for a freezer, maybe specialist phase change waxes for a fridge.

Always bear in mind that it's much cheaper to store energy thermally than in a battery if it's practical on the timescales involved.  You don't have to get a battery very hot to make it store more energy thermally than it can electrically/chemically, for example.
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billi
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« Reply #21 on: May 09, 2009, 04:59:39 PM »

Quote
Anyone do decent priced batteries with reasonable delivery

You can try  local forklift companies for second hand forklift batteries (New they are rated i think  with 1200 cycles ) , perhaps you find a good used one

So you need less then 500 watt over 7 hours .... So 2-3 kwh   

a 500 AH hours battery (24 volt) can store theoretical  about 12 kwh      and if you take 25 % out  thats then 3 kwh

Billi



   
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
MR GUS
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« Reply #22 on: May 09, 2009, 05:08:41 PM »

FOLKS! ..are we forgetting the ECO fridge? which is on the forum here as I recall
The energy for that especially overnight was minimal although it was a chest freezer originally, for height (ie not reaching into the bottom you could again add to the mass by means of clean water filled containers)? ..in order that little folk could use it without too much trouble.
clever person to supply a link soon I imagine...

http://mtbest.net/chest_fridge.html

and in particular the two links to PDF files at the bottom

http://mtbest.net/chest_fridge.pdf
http://mtbest.net/part-list.pdf

« Last Edit: May 09, 2009, 05:23:29 PM by MR GUS » Logged

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daftlad
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« Reply #23 on: May 09, 2009, 05:27:10 PM »

MR GUS
Is this the eco fridge you are on about?
http://www.ecofreak.co.uk/products/0/117/Eco-Mini-Portable-Fridge.html
if so, how many cans of wife beater (stella larger) will it take?
laters
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MR GUS
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« Reply #24 on: May 09, 2009, 05:32:03 PM »

Nay (daft) lad.
 Theres a long thread somewhere of a diy low energy chest freezer to fridge transformation which was then tinkered with further with insulation on some aspects.. from about a year back.
it's a familiar uk model (under a different name) that is a hotpoint / whirlpool/...?
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EccentricAnomaly
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« Reply #25 on: May 09, 2009, 06:57:58 PM »

Was it on this forum or somewhere else that I read about problems using freezers as fridges?  A I recall, the problem reported was that with some freezers running at warmer temperatures causes condensation somewhere and thereby corrosion.

Obviously the Mt Best chap didn't have this problem so presumably he was lucky enough to get the right sort of freezer.
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teledemon
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« Reply #26 on: May 09, 2009, 11:00:12 PM »

Love the ecofridge daftlad...only 30w! Perfect...If our family of six requires, say, 300 litres thats about...hmm, 6 litres each...that's erm...50 ecofridges  wackoold

BTW the Ececsol batteries look a very good option indeed  Smiley
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EccentricAnomaly
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« Reply #27 on: May 09, 2009, 11:27:43 PM »

MR GUS
Is this the eco fridge you are on about?
http://www.ecofreak.co.uk/products/0/117/Eco-Mini-Portable-Fridge.html
if so, how many cans of wife beater (stella larger) will it take?
laters

Any idea if that ad is a parody?  33 watts average.  That's 289 kWh/year: i.e., about the same as a modern full-sized fridge.  No wonder it's discontinued.
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Mike McMillan
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« Reply #28 on: May 10, 2009, 08:05:48 AM »

We are off grid and have been for a number of years. My 8 x 180 watt 24v pv panels charge 4 x 200 ah 12 v lead acid batteries (2 banks of 24v in parallel). These easily give us all the power we need for fridge (which lives outside, which means it's hardly ever on in the winter and is running very efficiently in summer), tele's, pumps ( 6 panels of 15 E.T. hot water) lap tops, lights etc for 9 months of the year, the other 3, I have to assist with an average of 3 hours charge a day with a 2 kw diesel gen, charging through a 40 amp battery charger. Having worked on yachts for most of my life, I have had no difficulty with 24v. The last yacht was a 135 ft schooner, 52 gel batteries, 6 KW inverters, 800 amps charging. Much easier and cheaper to use 24 volt in my opinion. The old classics I used to sail on in the late 60's early seventies had 110v DC. Fridges, Freezers, toilets, anchor winch etc were all 110v. Huge single cell batteries that needed tons of distilled water, but the batteries were 20 years old and still holding a good charge!

Mike McMillan

Isle of Wight
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teledemon
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« Reply #29 on: May 11, 2009, 10:39:12 PM »

Ok, ok, enough already!  Wink

The inverter's on its way, and I'm on the mainland, city-bound...having cash sucked out of my wallet (no shops where I live  Huh)

I've got 24hours to get myself some deep cycle batteries (and save the world)...then somehow smuggle them onto the ferry  Roll Eyes

These batteries will be discharged to 50% max overnight...
Soooooo....thoughts please on Elecsol; anyone using them? Mixed reviews on some fora  Undecided but 1000 cycles @ 80% should last me three years at least, am I right? Thinking cost efficiency here...Aye, ye can tak the laddie oot o' Aiberdeen...etc etc etc  laugh

Thanks folks, for all your help!

Dennis





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