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 > > > ------------------------------ > Netscape. Just the Net You Need. > > _______________________________________________ > 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
