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Author Topic: Upgrading from 48vDc to 120vDc, Pro's and Con's?  (Read 7950 times)
biff
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« Reply #15 on: August 10, 2013, 06:56:16 PM »

Hi Paul,
      You need that fancy inverter with the ac out and they dont come cheap.EricW had a little board that clockman got going.I honestly would not mind something like that If it was not too complicated.What I have at the moment is pretty good but I think a relay on the AC side would help things as well,I actually have another ac immersion on the water heater in the hall and maybe I could bring that into action when I fit my third and final 120v array. another 1140watt. I have been reluctant to install it because the results from the present setup more than meet our demands on sunny days and you can only heat so much water but a dump on the ac side means we could trigger an electric fire or a storage heater or underfloor heating like clockman.
                                                                                      Biff
                                                                                                           
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camillitech
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« Reply #16 on: August 10, 2013, 07:04:38 PM »

You could always just turn the array off Biff, that's what I do with my hydro turbines if there's too much power. No point cooking the dump loads or running hot water into the septic tank once all your needs are satisfied.

Cheers, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW 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,
biff
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« Reply #17 on: August 10, 2013, 07:51:07 PM »

Good point Paul,
                Thats what I had in mind for the mobile array,I would have to have a heavy switch between the incoming live from the array and the live connector on the controller.I wonder is there some kind of soft landing switch that would be suitable for reconnecting when the sun is bright.Something like the soft start up you get now on some grinders.
         I suspect that if I was foolish enough to try and connect in bright sunlight i might blow the blocking diodes on the panels.I can connect 56 volts and lower by pushing a fuse home but 120 volt (180v before going into the controller)is just too wicked.I will just have to find a way round it but switching off the array is the simplest and best idea like you say.
                                                              Biff
                   
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camillitech
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« Reply #18 on: August 10, 2013, 08:07:04 PM »

You should have a DC breaker capable of breaking at full load anyway Biff and it's the sudden amperage that wrecks the contacts not the voltage.

Cheers, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW 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,
biff
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« Reply #19 on: August 10, 2013, 08:31:12 PM »

The only emergency disconnect I have are anderson connectors,
                               Fine to disconnect in sunlight but not to connect.I also use a large blue tarp to cover the arrays if I need to disconnect or connect .I have a healthy respect for these things.Everything at 48v and below is fused but the 120 volt depends on the controllers,which come already fused internally and easy worked at.
  Have you any idea of the type of breaker that would suit,?
                                                                     Biff
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« Reply #20 on: August 10, 2013, 08:56:15 PM »

I use these http://compare.ebay.co.uk/like/130873544226?var=lv&var=sbar&_lwgsi=y&cbt=y&lpid=66&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=66 Biff up to 25amps, which at 120v is 3kw

Cheers, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW 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,
biff
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« Reply #21 on: August 10, 2013, 09:08:53 PM »

Thank you for that link Paul,
                      Those will do just nicely. fingers crossed!.
                                      Biff
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clockmanFR
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« Reply #22 on: August 10, 2013, 09:35:07 PM »

Paul, I am happy with my system at 48vDc.

However, I am always being asked what battery system voltage is best,? and if I started from scratch now knowing what I now know, what would I use?

At present I reply that there is sufficient charging/controllers/inverters at 48vDc. But to be real efficient then 120vDc system would be advantageous.

But honestly, Charging/controllers & Inverters seem pretty thin on the ground at 120vDc.

Biffs Symentry Inverter sounds okay, any others you know off Biff? 
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biff
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« Reply #23 on: August 10, 2013, 09:43:47 PM »

Yes C/M,
           There are two other types but I have only one other which is 2,700watt x 120v.I will post the name and model tomorrow.These are not that expensive,work out around £150.00 a time.I keep one or two in case something goes wrong(you never know).The symmetra is more or less bullit proof and gives lovely clean power.
       Paul,
            I bought 5 of those fused breakers and paid just under 11 euros each,now you might think I got stung there but I could not find anything like that before and it is money well spent.So thanks again,
                                                              Biff
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« Reply #24 on: August 10, 2013, 09:51:18 PM »

My priority  , would be simplicity  nowadays

The base  is the Inverter and a tough battery  ,  and i am very happy with those two components  i have (ok my charge controllers are great as well , but i would reduce charge controller costs today )
PV i can pick up somewhere  today for £300-500 per kw  and our 4 kw PV runs our house easy for 9 month a year , so another  4 kw  would do the 12 month trick and lots of hot water and some heating and perhaps electic driving later ..........

Keep on rocking.... oh i mean  focusing on the production side.... in a free world (ok, not so free  Roll Eyes)
« Last Edit: August 10, 2013, 09:53:30 PM by billi » Logged

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 #25 on: August 10, 2013, 10:26:36 PM »

I would agree 100% Billi,
                    Simple controllers,simple inverters and a layout that can be easily understood and remembered ( Grin)
                                                                  Biff
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camillitech
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« Reply #26 on: August 11, 2013, 07:40:16 AM »

Paul, I am happy with my system at 48vDc.

However, I am always being asked what battery system voltage is best,?

The answer should then be, 'it depends what you want from it'. If you want a reliable 'off grid' system that can be left in the hands of numpties then it has to be a 'proper off grid inverter' that will make all the decisions for you. One that will start a generator to 'load share' or when your batteries are low, and most importantly charge them quickly and correctly. If on the other hand you're enthusiastic, capable, on grid or don't mind watching meters or being careful about what you switch on then go 120v. It's certainly cheaper and more efficient when it comes to cabling and second hand UPS systems but you won't have the flexibility of the many dedicated controllers the use of 'AC coupling' or be able to charge your bank quickly.

Cheers, Paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW 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,
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« Reply #27 on: August 11, 2013, 11:53:55 AM »

Hi Tinbum,
           If you go into the solar pv threads and look for "Solar pv direct to the battery,,temp"  by Rithym you will find Rogerico,s contribution on the subject,I have found the same thing happen in 48volt and 120volt. Its intresting.
                                                                                   Biff

Yes I'd seen that previously, but good reminder. Personally I think the probable reason for the failure of the Morningstar will be due to overvoltage. 4 panels in series at a VOC of 33v is too close to the max of 150v that the controller can handle. (I did it with similar panels, Suntech 250S-20/Wd, but the controller survived so now I have 4 strings of 3 panels).
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« Reply #28 on: August 11, 2013, 11:55:40 AM »

DC in higher voltages is a dangerous beast.  It seems to develop a "momentum" in cables and can jump/arc switch gear.  I remember my dad telling all kinds of weird accidents which happened on the 120v DC Lister gen set.   whistlie
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« Reply #29 on: August 11, 2013, 12:05:34 PM »

It made me laugh when my first lot of PV was installed by a so called PV installation company- Never again but that's another story.
They said they would have to turn the power off (remove DNO Fuse and break all the seals!!!) to connect it up. I asked why. They said for safety.
I then saw them working on the live DC cables, approx 600v that's so much more dangerous!! I guess ignorance is bliss.
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
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