So in essence, you had the PV's connected directly to the inverter's DC battery connection point. What did the MPPT charge controller do without the battery as a buffer? Did the efficiency go up on the system without batteries to keep charged?
Todd On Wednesday, October 21, 2009 10:12am, "Darryl Thayer" <daryl_so...@yahoo.com> said: > 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 > >
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