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Author Topic: What Inverter  (Read 6435 times)
doubletap
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« on: February 17, 2008, 07:50:23 PM »

Hi,

I'm running a 24v 300w wind turbine set up, off grid. What size inverter is reccomended, 300w or 1000w plus. If I can run a higher inverter will it use more power? Generally I only want to run a laptop and put on the odd light.

Spud
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martin
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« Reply #1 on: February 17, 2008, 08:30:44 PM »

I wouldn't bother with an inverter at all.................use a cheapo switch mode voltage converter for the laptop (under a tenner off Fleabay), and 24v energy saving lightbulbs or fluorescents! Grin
That way you save the cost of the inverter, all the losses involved, and the difficulty of even running energy saving bulbs off a modfied sinewave inverter (you really need true sinewave.......) Roll Eyes
In my humble opinion large inverters are grossly oversold, and most vendors never forewarn of how swiftly large ones will drain even large batteries stone dead flat...........
(if you use a 1kw inverter off a 24v system, it draws 40 amps full tilt - 2x110 amp/hr batteries will last at best 2 hours before cutout - and unless they're high priced deep cycle gel jobs will expire permanently in a very short time!)
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billi
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« Reply #2 on: February 17, 2008, 10:51:19 PM »

martin good thought , but wouldnt it require a battery as well nevertheless  24volt dc or inverted ac system?


regards 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
martin
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« Reply #3 on: February 17, 2008, 10:57:55 PM »

I'm presuming he's got at least a rudimentary 24v battery system! Wink
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Bob
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« Reply #4 on: February 18, 2008, 06:34:14 AM »

Hi Doubletap

I assume you have some batteries?  What sort of storage capacity?

You don't have to have the inverter on all the time.  If you buy a small one (300w) then it won't run that power tool you really have to use to do the job you really need to do..

How much they draw on standby varies a lot from inverter to inverter.  I have known cheapo 300w units from the local autofactors to use more standby current than a decent 1.5kw one.

Quote
most vendors never forewarn of how swiftly large ones will drain even large batteries stone dead flat

I have a 3.5kw running of a battery  with a capacity of 750Ah (at present).  It takes days to exhaust the battery unless I decide to run an electric kettle from it.  It's what you use that matters

One point definitely in favor of inverters as opposed to DC systems is that you do normally get some protection from totally destroying your batteries.  A friend of mine went to the UK for a month.  He left a couple of LED's on and came back to a system at 9.6v - we are nursing it back up but it's not easy!  An inverter would have shut down at about 10.5v.

In short.  Buy a good quality (I love my KiPoint from ebay) inverter, true sine wave if possible, and remember that when you are running something big you are draining your system very quickly.

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doubletap
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« Reply #5 on: February 20, 2008, 01:39:03 PM »

.......... many thanks for all your advice. Martin, your'e right mate, I was running 2 x 100 amp batts and 2 hours was all I was getting off the laptop before the inverter alarm kicked in - nightmare and the inverter people do not tell you the truth re how much power the thing draws.

Like I say, I only use a laptop and the odd light so, for a couple of hours a day. I may try what you suggest. Then try a 300w inverter if all else fails.

(Now I've connected another batt bank giving me 4 x 110amps but no wind for a few days, thinking of a solar panel too). Will let you all know how I get on.

Once again mant thanks to you all.

Rgds, Spud
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billi
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« Reply #6 on: February 20, 2008, 08:54:41 PM »

hi

i donot know many inverters , but i do know bad batteries....


martins idea makes sense .... with dc-dc


but , how do you know about what power is drawn from the inverter ? or from the few lights , or the laptop ? or how much  capacity is in your battery ?


my two 3 kw inverters  use about 3 A  ,when i look at the control panel every morning

 in the first was a lot to me .... donot know how much more they consume when the power needs are increased,  but it would not drain your battery in two hours if the battery is ok !


and i think that was a point bob meantionted


regards 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
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« Reply #7 on: February 20, 2008, 09:23:28 PM »

Hi DT,

I managed just fine for years on a 12v DC system charged by a small wind turbine for lights, CD, even a little TV but I did destroy MANY batteries and at only 2 hours running your laptop I suspect your batteries are shot too, unless you have proper deep cycle batteries or a low voltage cut out of some sort you'd be amazed how quickly they die. It took me several years to learn this  Roll Eyes  I still have my 12v system running alongside a bigger turbine/inverter system and it's great to know it's there in an emergency but I'd never go back to it. Like Bob says it's great to be able to use power tools without starting a genny. If you do get an inverter do your homework and get a good pure sinewave one.

Good luck, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SMA SI6.OH, 800ah Rolls, 9kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Bob
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« Reply #8 on: February 21, 2008, 07:41:23 AM »

Spud

What type of batteries are you using?  I had all manner of grief until I bought the correct deep cycle standby power ones.  Starting type are no good for anything, traction (ex forklift) are better but not by much.  Try to get ones that have been used in a backup power system.  They will not be available in your local autofactor!  And be warned, new they are very expensive.
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doubletap
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« Reply #9 on: February 22, 2008, 07:47:25 AM »

Hi all

Thanks for the posts.

Bob, my batteries are newish non abused leisure type 110 amps each. My cottage is a small 2 up 2 down and I have 6 lights (low energy bulbs) and 6 sockets both individual circuits. I never have more than 1 light on at any time and only use 1 socket at anytime too. Maybe I am losing power through the circuits although they are both short runs!!

Spud
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Bob
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« Reply #10 on: February 23, 2008, 05:57:57 AM »

Hi doubletap

I am always very dubious about "leisure" batteries.  Most of the people I know who have had them end up wishing that had spent their hard earned cash on something different.  They are after all aimed at the caravan market.

You have a 300w turbine.  That's 300w in a 20mph wind (approximately).  Most of the time you will be lucky to get 50w.  I have a 2kw and am quite happy with 250w. 

A couple of years ago I supplied some batteries and an inverter to man who had bought himself three "1Kw" wind turbines of ebay.  Over the space of the next two months I had all manner of problems convincing him that the batteries weren't cr*p and that they were going flat simply due to a lack of charge.  He just could not accept that the bloody thing might  be spinning but it ain't charging at 1kw.  It needs a 20mph wind for that (and judging from his blade diameter I wasn't too sure of that).

Get your self am ammeter.  A cheap multimeter with a 10A range will just about do but a moving iron with a full scale deflection of 15A would be great.  Connect this in series with your turbine and battery.  Sit back and watch.  See what it actually produces.
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doubletap
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« Reply #11 on: February 23, 2008, 07:26:08 AM »

Bob

I'll do that cheers. My batteries do show a charge of 24.7 v and when my inverters' alarm kicks in volts show 19.9 or even 22.3 after only 20 mins on the laptop.

I may look at a Navitron 1kw. What batteries do you suggest?

Spud
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Bob
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« Reply #12 on: February 24, 2008, 07:05:59 AM »

You are going to need a mortgage or some serious luck (get to know BT's exchange engineers)

Something like these, sorry its an Irish site but you will be able to find them in the UK

http://www.abpowersystems.ie/prod01.htm

and they end up looking like this



* battery1.jpg (61.91 KB, 563x381 - viewed 494 times.)
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The Slow Old Man
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I couldn't be more chuffed with our wind turbine


« Reply #13 on: February 24, 2008, 01:25:29 PM »

Hi Bob
One thing i have noticed none of these sites have a price list for the batteries.

Brian
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billi
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« Reply #14 on: February 24, 2008, 01:40:26 PM »

brian

these batteries are called OPZS

I got quotes for  800 ah at 24 volts C10

hoppecke  battery 3200 euro
bae battery         3200 euro

and from the mentioned irish company above a quote

for hawker batteries   7000 euros

regards 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
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