I have been quiet because i have not done SI but I have done several Outbacks. One system is 12 OB GVFX 3648s on one battery bank of 600AH, the system will run with less batteries, in fact I left the battery off for a month and did not notice any loss of exported power to the grid. (this is 3 phase) (I had no grid shutdown and did not need critical power) the system would start and run everyday without a battery.
On the other end of the scale I have a Standalone house, using 2 OBs and the battery bank is 48 volts 3500 AH --- On Tue, 10/20/09, Glenn Burt <glenn.b...@glbcc.com> wrote: > From: Glenn Burt <glenn.b...@glbcc.com> > Subject: Re: [RE-wrenches] AC Coupled Re-visited > To: "'RE-wrenches'" <re-wrenches@lists.re-wrenches.org> > Date: Tuesday, October 20, 2009, 2:13 PM > > > > > > > > > > > > > > > > > SMA recently told me that the > recommended Ah of the battery bank > is related to the amount of PV and connected > inverters. > > They recommended a 500Ah bank > with a 5kW PV SB, and a 600Ah bank > with a 6kW PV SB. > > 100Ah to 10,000Ah are the > supported capacities. > > > > I don’t believe you need > to have a separate battery bank > with two SI’s. I have been told they can share one. > One SI is programmed > as the master & of course they are data commed together > so they can talk. > > > > -Glenn > > > > > > > > From: > re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On > Behalf Of Mark > Frye > > Sent: Tuesday, October 20, 2009 2:42 PM > > To: 'RE-wrenches' > > Subject: Re: [RE-wrenches] AC Coupled > Re-visited > > > > > > > > Thanks Kent. And so I understand > more clearly, in the case of 2 SIs > as you describe, each SI has it's own battery bank, and > the solar would be > split between the two. > > > > Considering the charging capacity > of the SI, what would you say is > the largest battery bank size for each SI to insure an > effective "C" > value? > > > > Mark Frye > > > Berkeley Solar > Electric Systems > > 303 Redbud Way > > > Nevada > City, CA 95959 > > (530) 401-8024 > > > www.berkeleysolar.com > > > > > > > > > > > > > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On > Behalf Of Kent > Osterberg > > Sent: Tuesday, October 20, 2009 11:10 AM > > To: glenn.b...@glbcc.com; RE-wrenches > > Subject: Re: [RE-wrenches] AC Coupled > Re-visited > > In off-grid mode the Sunny Island uses > frequency shift power > control to reduce the output of the Sunny Boy inverters and > thereby regulate > the battery voltage. At some frequency shift (+1, or > 2, or 3 Hz, I'm not > sure) the output of the SB is reduced by 100%. > It's proportional so that > 1/2 as much frequency shift gives a 50% reduction in the SB > output. To > keep clocks accurate, the Sunny Island later shifts the > frequency a negative > amount, but the SB inverters ignore that. For a grid > backup system, a > RS-485 cable is required so the Sunny Island can activate > (or deactivate) the > frequency shift power control capability of the SB. > > > > You need to stack two SI inverters to get 240-vac, but that > will allow you to > have a 10-kW of grid backup power with up to 12-kW of > solar. If you need > more, you can stack four of SI inverters. > > > > Kent Osterberg > > Blue Mountain Solar, Inc. > > > > > > Glenn Burt wrote: > > Our installations of Sunny > Islands (SI) with Sunny Boys (SB) > have always used the recommended RS-485 communications > between all units > involved. This with reprogramming the SB’s to be able > to switch to > off-grid mode per the SI instructions allows a more > integrated system. > > We have had problems with the > OB PSX-240 and stepping up the 120 > to 240 for the crit load panel (where the SB’s > connect) when the site has > slightly high AC voltages. The SB pushes the existing ACV > higher, then it goes > out of UL spec & disconnects. Also the SB is now > sensitive to imbalance on > L1 & L2 because of the neutral sensing – we had a > customer where the > SB was disconnecting due to this as well… > > I thought the freq shifting was > to allow other non-SMA inverters > to be controlled when batteries were full? > > Where is the SMA rep on this > list? > > -Glenn > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] > On Behalf Of Kirpal Khalsa > > Sent: Tuesday, October 20, 2009 12:05 PM > > To: RE-wrenches > > Subject: Re: [RE-wrenches] AC Coupled > Re-visited > > > > Greetings......it is my understanding > that the Sunny Island > coupled with Sunny Boys is able to taper charge in an AC > coupled system as the > 2 inverters are able to communicate with each other and the > Sunny Island alters > the frequency input of the Sunny Boys and lowers the total > output of the Sunny > Boys to match the needs of the battery bank....this is > SMA's method of not > using their "charger"....they simply alter the > amount of available AC > input into the AC to DC converter present in the Sunny > Island.....This logic is > what encouraged me to select SMA's for an AC coupled > design rather than mixing > brands of battery-less and battery based inverters.....in a > mixed brand > scenario there is no communication other than an on/off > command so no > regulation is available.....My understanding may be > flawed--please correct me > if so.... > > Another way for mixed brands to AC couple and provide some > charge > "control" would be to have an AC dumpload on the > AC input side of the > battery based inverter to suck up some of the excess power > from the GT > inverters so not as much power is available for battery > charging.....This > dumpload would be voltage based and in a mixed brand system > would add more > relays to the mix...in many cases there may not be that > many auxillary outputs > available to connect relays to..... > > I would like to see more GT inverter companies make > compatible battery based > inverters......One idea is for micro inverters to be paired > with the battery > based inverters and when less power was needed to > facilitate a taper charge one > solar panel at a time could be switched > off......effectively providing a > smaller available charge current to help with the taper > charging..... > > > > -- > > Sunny Regards, > > Kirpal Khalsa > > NABCEP Certified Solar PV Installer > > Renewable Energy Systems > > www.oregonsolarworks.com > > 541-218-0201 m > > 541-592-3958 o > > > > > > On Tue, Oct 20, 2009 at 8:34 AM, Mick Abraham <m...@abrahamsolar.com> > wrote: > > Hi, > All~ > > > > On an AC coupled system as Jeff describes, the > "battery charge > circuitry" on the battery based inverter is not even > participating. > > > > A straight pure sine inverter...with no charger function > built in...would also > "charge" the battery if AC coupled to a SunnyBoy > with no grid > available. The "charge" is just the > inverter's way of dealing with > back EMF. > > > > I agree that better control over that "recharge" > is an important > area; I hope somebody is working on that. It's true > that the "wild card > recharge" only occurs if grid goes away but as Jeff > mentions, it only > takes a few times of crummy end of charge management to > ruin a nice set of > sealed batteries. > > > > Mick Abraham, Proprietor > > www.abrahamsolar.com > > > > Voice: 970-731-4675 > > > > > > > > > > > > > > On Tue, Oct 20, 2009 at 9:21 AM, Jeff > Yago <jry...@netscape.com> > wrote: > > > > > > > > > > > > > > > > We have > completed several totally different AC coupled systems > using different inverters, > due to large ground mounted arrays that had to be located a > great distance from > inverter-battery-generator-grid BAS, which are working just > fine even with the > mis-match of inverter brands. The SunnyBoy seems to > not care what its > connected to or how, as it just keeps doing what it does > and if a relay cuts > off its connection to the grid when the battery voltage > goes high then it just > waits and re-connects when the grid is back or the battery > voltage drops. > > > > > > What > I am bothered by is the need to custom design a power > relay circuit on > each project which takes lots of fine-tuning of > setpoints to get > everything to work correctly. If you have not done > one the problem is > simple - when you backfeed the AC output from a remote > grid-tie inverter "through" > the AC side of a battery based inverter, everything works > great and the solar > AC just passes straight through the sub-panel, back > throught the battery > inverter, back into the grid. However, when > the grid is down and the > battery-inverter is no longer receiving (or sending) power > from the grid, for > some reason I cannot begin to understand, any AC being fed > from the solar > inverter goes straight into battery charging with > absolutely no limit on charge > rate or charge limit, and if you do not add a relay to > dis-connect or shut-down > the solar inverter you can quickly destroy a bank of AGM > batteries if there are > no major system loads as it just keeps charging and > charging. > > > > > > I > am not an electronics engineer, but if the battery is being > charged by the > battery charger built into the inverter, I just do not see > why the same battery > charger suddenly has no clue that the battery is being > overcharged when its now > receiving AC power from a different source. I think > with larger and > larger arrays being installed as module costs fall, higher > DC array string > voltges to reduce wire costs, and more people worried about > grid reliability, > there would be a good market niche for an inverter that can > properly charge a > battery bank regardless of which way the AC power comes > into the charger section. > Whats the problem? > > > > > > Jeff > Yago > > > > > > DTI > Solar > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -----Inline Attachment Follows----- > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
