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solar and battery config with 12/2 wire bottleneck?
#11
There's also the question of gear location:
Does all gear incl batteries, inverter, etc live in the garage so you're sending AC mains down the cable
OR
Just the panels in the garage & DC (safety considerations) down the cables > house where you've got the inverter, etc.

+1 Getting the correctly rated cable happening sounds a better way.
DCkiwi likes this post
Running off solar, DIY & electronics fan :-)
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#12
(06-08-2019, 04:18 AM)Redpacket Wrote: There's also the question of gear location:
Does all gear incl batteries, inverter, etc live in the garage so you're sending AC mains down the cable
OR
Just the panels in the garage & DC (safety considerations) down the cables > house where you've got the inverter, etc.

+1 Getting the correctly rated cable happening sounds a better way.

I was under the impression that DC doesn't travel well long distances, so the 12/2 will carry AC. So essentially it's solar panels, controller, battery, inverter all in the garage. Then 12/2 wire with AC power from garage to house... oh, do I need a new breaker panel where this feed comes in or do I keep running it all the way to tie it into the main breaker panel?
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#13
(06-08-2019, 06:46 AM)crashintoty Wrote: I was under the impression that DC doesn't travel well long distances, so the 12/2 will carry AC. So essentially it's solar panels, controller, battery, inverter all in the garage. Then 12/2 wire with AC power from garage to house... oh, do I need a new breaker panel where this feed comes in or do I keep running it all the way to tie it into the main breaker panel?

Redpacket brings up an excellent point, I think.

'long distances' is ... i guess ... a relative term, but ... 20 metres aint that far for DC, as long as the current doesn't peak/spike too much.

by putting 'all in the garage' you are by definition would be putting the existing cable under peak/spike load/stresses, VS if you have just solar there, then your current is relatively smooooooth. in my experience not many houses need 2KW all the time, mine averages out at a tad under 500W (24/7/365, that is). so IFF I could get 10A @ 48V around the clock, and had big battery/inverter closer to loads, then .... that would power my whole house forever. but solar doesnt run at night, so ... i'd need a good 30-50A feed for the solar to do this ... see where Im going?

YES, breakers are REQUIRED (AFAIK) at entry point to house ... rules and regs speaking ... but beyond that ... no such thing as too many fuses/breakers. ever hear of a plumber complain there were too many taps and choices as to how to turn water off while maintenance being done? nah ... me either. heard more than a few though complain there weren't enough taps. spoil yourself, if nothing else ... buy a spanking new breaker and sleep easy. Hope that helps.
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#14
DC is more efficient at longer distances (hundreds of miles) than AC for power transmisison newtorks, hence the few 1MV and higher long distance links around the world.

There are also DC interconnects in several countries that are also 'monopole' and use an earth return loop (e.g. Victoria to Tasmania).... they 'effectively' only use 1 wire and the ground provides the other, like the principle of the early telegraph lines. I have never seen anyone try for a monopole DC power pack transmittion line though. The earth electrodes do corrode quickly an need replacing though.

The cable you have to the garage may be SWA rated for 600V, so another option is to put the solar feed down this cable and setup the solar to the Voc (max no load V) is say 550V and Vmp around 400V. If the cable is only rated 100% duty for 15A then you have 6kW to play with... Beware with HV DC and cables though because the failure mode can end up with the cable arcing and slowly burning like a fuse down the whole length if the arc is not extinguished. 500V can sustain a DC arc around an inch and the core separation in a typical multi core cabe is well under that.. This is the sort of experiment for youtube to show, take a typical 2.5mm 2 core SWA (600V rated) and then with an open end, short it to create an arc and then see how much of the end of the cable burns off before the arc goes out.

That said, I am using 2 core flex (yes, arctic flex) to run the supply back from my panels (4 in series for 100V, 1kWp) to the MPPT controllers and would never try flex with 200V DC as I think it would just burn through the whole length under a fault.

The garage in the end is the 'safe' option as to where to put hunderds/thousands of 18650 cells of various states of health and this is what i would base my decision on.

Inverter to back feed to the house, GTIL-2000.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#15
(06-08-2019, 08:58 AM)completelycharged Wrote: DC is more efficient at longer distances (hundreds of miles) than AC for power transmisison newtorks, hence the few 1MV and higher long distance links around the world.

There are also DC interconnects in several countries that are also 'monopole' and use an earth return loop (e.g. Victoria to Tasmania).... they 'effectively' only use 1 wire and the ground provides the other, like the principle of the early telegraph lines.  I have never seen anyone try for a monopole DC power pack transmittion line though. The earth electrodes do corrode quickly an need replacing though.

ahem.  backfeeding through the ground is ILLEGAL in most civilised countries.  for very REAL health reasons. (ever wondered why cows stand on two feet?  or why the pigs are ALL sick right now, or why people die of heart attacks when they go swimming, or ... yeah.

do NOT use our EARTH as any part of your circuit ... anyways ... *whew* glad to have gotten that off my chest (PM's invited/welcome!).

Quote:Beware with HV DC and cables though because the failure mode can end up with the cable arcing and slowly burning like a fuse down the whole length if the arc is not extinguished.

very good advice.  HV DC is ... nice, but ... 'hot' electricity (there's more than one type, afterall *tweaky*) is serious stuff ...

Quote:The garage in the end is the 'safe' option as to where to put hunderds/thousands of 18650 cells of various states of health and this is what i would base my decision on.

meh.   I disagree (sorry CC!).  EG my garage gets too cold (out of spec for my cells).  I do have a shed option (planned, for future, soon, once I have a system:load/fans/waste-heat from 18650's+inverters to keep shed above 10degC) ... but for now, I'm sleeping solid with a few thousand cells online in my house ok.  of course though ... I do have ----> MANY <---- fuses.  did I mention that I had lots of fuses?  point made.

anyways ... this (all/posts) is probably a lot of help to the OP ... and I'd like to hear more from him in terms of spec and plans and leanings ... we could all wax lyrical for much longer, but ... help us all out here ... lol.


Quote:Inverter to back feed to the house, GTIL-2000.

above my pay grade, so no comment.  completelycharged is on the ball though, so ... give us some feedback crashintoty!

PS if you ARE in the USA, then you can bet your utility is backfeeding through the ground.  naughty them ...
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#16
So to summarize the OP has a roof area of approx 20 feet x 12 feet for panels & a 20 A circuit back to the house.
For the safety reasons mentions already, the 20A circuit should carry AC mains not DC.
It seems with the available area, the OP won't be generating massive solar input & therefore having an inverter >20A output would drain down any stored power very quickly.
Assuming you're located in the USA, 120VAC @ 20A is 2.4kW continuous.
This should be adequate for running at least part of the house for now & you can always upgrade later.

PS suggest going lithium for the batteries, you'll get so much more storage & battery life.
Running off solar, DIY & electronics fan :-)
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#17
(06-08-2019, 09:57 AM)Redpacket Wrote: So to summarize the OP has a [...] 20 A circuit back to the house.
For the safety reasons mentions already, the 20A circuit should carry AC mains not DC.
It seems with the available area, the OP won't be generating massive solar input & therefore having an inverter >20A output would drain down any stored power very quickly.

Then why not pipe the solar as DC to the house???!?!???  (notice my DC bias?)

Quote:PS suggest going lithium for the batteries, you'll get so much more storage & battery life.

agreed,  except for the PS part.  

performance.  lifespan.  power density ... all plus's in my books.  and then there's the aspect of giving old cells a Second Life as Storage (get it?!).  save the planet.  use what others can't/discard.
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all systems nominal... rock on.
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#18
Basslink (Victoria to Tasmania) : https://en.wikipedia.org/wiki/Basslink
"Basslink is a monopolar with metallic return"
http://www.basslink.com.au/basslink-inte...perations/

https://www.abc.net.au/news/2019-06-02/h...e/11172028

It does create some interesting issues though as you can hook up to the power flow with a couple of earth spikes.... bit different from getting power via a large coil under a HV overhead line though :-) Ahem, both illegal, as your stealing the power or absorbing the EMF pollution depending on how you view it...

The smaller GTIL-1000 could work ok, I like these units as they are relatively self contained, cut-in / cut-out and with a CT to allow your home power demand to be netted off, at a lot cheaper price than some other inverters....

Agree, temperature can cause issues for 18650's, although I just don't like the failure mode of 18650 cells because if they are all packed together they tend to cascade once cell to the next in a firework show. Fuses can prevent one cause for failure.

One option I have not seen people do is to dig a hole and put the pack in, 2m down. Temperature would be stable year round and excess heat from the pack through the year will raise the temperature up high enough to avoid low temperatures above ground, even well below zero...

Agree with Redpacket, go lithium, lead-acid is a slow decline legacy technology that worked well for over 100 years. Same reason we dont have an abacus in our pocket..
DCkiwi likes this post
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#19
(06-08-2019, 10:11 AM)completelycharged Wrote: The smaller GTIL-1000 could work ok, I like these units as they are relatively self contained, cut-in / cut-out and with a CT to allow your home power demand to be netted off, at a lot cheaper price than some other inverters....

question: what is 'CT'?

genuine question, I dont know that acronym, so maybe others dont too?? i'm very ignorant about most things to do with inverters, so ... spiel away! : )
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#20
Boy its been busy here overnight.

DCKIWI


Quote:do NOT use our EARTH as any part of your circuit ... anyways ... *whew* glad to have gotten that off my chest (PM's invited/welcome!).

Ya better tell mother nature to stop with those lightning strikes  I understand its her circuit not ours but don't you think we can use just a wee bit of it.
CT is current transformer that tells the GTIL how much current you are drawing from the grid.


I agree a GTIL 1000 would be Ideal to supply 1 leg of his grid supply.
Throttle it to 900W and the max you will be drawing from a 48V nominal bank is ~19 Amps
Put your constant usage devices such as phone chargers, PC, maybe even the fridge on that leg of your split phase.
With lots of solar and a good battery bank you would essentially not draw any power from the grid on that leg.

Wolf
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