It's already built - 6 years old - I didn't do it. The new property owner just purchased a very expensive battery bank and wants to protect it, understandably, because she had problems with her generator not starting as expected when not at the property. It was suggested by the original installer to install a load shedding contactor as the manual suggests (albeit in an opaque manner). I just can't seem to wrap my head around why this is a good idea. The integrated battery protection mode should handle this function. A contactor (or series of relays and a contactor) carries too much risk of failure that could result in another problem for the owner altogether. I understand protecting the battery, but the cure can't be worse than the disease. I'm looking for a balanced approach, which I believe is to just implement the BPM unless I'm missing some deficiency in that strategy.
The system worked great in an AC coupled configuration until the generator started becoming unreliable. In Florida I like AC coupling in a scenario like this where the most challenging load is in the summer, essentially concurrent with peak sunlight (air conditioning). However, I have been looking at trying out a Sol-Ark as soon as the opportunity arises with a combination of DC and AC coupling. With no separate charge controller involved, it becomes much less complicated and you get the best of both worlds in theory. Jason On Thu, Jan 21, 2021 at 3:36 PM Tump <[email protected]> wrote: > IF this system has yet to be built I would STRONGLY suggest that AC > coupling is NOT considered. IF it is them i would consider HV CC DC > coupling. > T > > On Jan 21, 2021, at 3:15 PM, Jason Szumlanski < > [email protected]> wrote: > > Hi Mac, > > Yes, I considered using a pilot relay - it makes sense to run it on 120V > because relays are readily available. I had the exact same concern - more > to fail. > > In this scenario, the inverter/battery room is remote from the house so > there is only one load I can switch easily with a contactor, and that's the > whole house load. Otherwise, I would definitely consider switching > non-critical loads in a low battery situation. > > It just seems prudent enough to use the integrated Battery > Preservation Mode (BPM), even in this AC coupled system. I considered a > small DC array to charge the batteries in a heavily depleted situation, but > it's a 60kWh battery so I would need a pretty substantial "backup" array I > think. It does not seem like a reasonable solution. I would expect BPM to > do it's job and keep the batteries from reaching a state that they are not > recovered quite easily. > > Jason > > > > On Thu, Jan 21, 2021 at 2:37 PM Mac Lewis <[email protected]> wrote: > >> Hi Jason, >> >> The only reason to load shed, without using the internal preservation >> mode is if you have certain loads you'd like to keep on longer than other >> loads that you shed. The various preservation modes can be complex, >> especially if you are AC coupled, so you really have to think through your >> strategy. >> >> You can always use a pilot relay, with a coil rating that suits your >> needs, and then feed the 100A contactor with that. Unfortunately, its just >> one more piece to fail... >> >> On Thu, Jan 21, 2021 at 12:13 PM Jason Szumlanski < >> [email protected]> wrote: >> >>> I just learned from the manufacturer that the mercury displacement >>> relay's coil is rated for 43.2 to 52.80V. Obviously, the battery voltage >>> can exceed 52.8 pretty significantly. Does the Sunny Island regulate the >>> output voltage on this relay to 48V or is the actual battery voltage passed >>> through on this terminal? >>> >>> The more I read about this load shedding strategy, the more it seems >>> overly complicated. It's also another thing to fail. If the N.O. contactor >>> coil fails, the loads to the house are going to lose power. That's not good >>> for a remote installation. I guess you have to weigh battery protection >>> with how critical the loads are. >>> >>> I'm wondering why the internal Battery Preservation Mode isn't >>> sufficient enough. What's the purpose of load shedding if the BPM does >>> effectively the same thing. I can see perhaps shedding some parts of the >>> load and that is a nice feature, but to protect the batteries, why isn't >>> BPM enough? >>> >>> Jason >>> >>> >>> >>> >>> On Tue, Jan 19, 2021 at 8:48 PM Mac Lewis <[email protected]> wrote: >>> >>>> Hi Jason, >>>> >>>> I have done this with mercury displacement relays: >>>> >>>> https://www.mdius.com/mercury-relays/two-pole-relays-contactors/two-pole-100-amp >>>> <https://mailtrack.io/trace/link/d70ece28567af41275941f7d3b22f54c0587b1e3?url=https%3A%2F%2Fwww.mdius.com%2Fmercury-relays%2Ftwo-pole-relays-contactors%2Ftwo-pole-100-amp&userId=1613865&signature=3b642ecb564a461a> >>>> >>>> They do have a 100A 2P 48V coil relay. They seem to work perfectly. >>>> >>>> Good luck >>>> >>>> On Tue, Jan 19, 2021 at 2:51 PM Jason Szumlanski < >>>> [email protected]> wrote: >>>> >>>>> Does anyone know where I can get a load shedding contactor described >>>>> in SMA documentation for use with a multi-function relay in a Sunny >>>>> Island? >>>>> >>>>> Thanks, >>>>> >>>>> Jason Szumlanski >>>>> _______________________________________________ >>>>> List sponsored by Redwood Alliance >>>>> >>>>> List Address: [email protected] >>>>> >>>>> Change listserver email address & settings: >>>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>>> <https://mailtrack.io/trace/link/caf14456cb57eca504c4e65dd95645c6d312160d?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=e1c235b1977d450d> >>>>> >>>>> There are two list archives for searching. 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