DIY Solar Power Forum

Hedges
Hedges
Yes. I first bought one SI 5048, planned to use a 120/240 transformer and switch half of my four SWR 2500U from unprotected grid side to protected side, due to relay pass-through limit. Then picked up more which were left over some someone's grid-support development, then bought a pallet of SI 6048 that someone got at the DC Solar bankruptcy auction.
Hedges
Hedges
What I've installed is 2S2P SI 6048, with 405 Ah 48V SunXtender batteries. I have SB 10000TLUS connected (turns out they support grid-tie or Island modes, but grid-backup doesn't work due to firmware bugs.) The SWR 2500U, at least with the ROMs in mine, don't support frequency-shift control of power.
Hedges
Hedges
I have a load-shed relay to disconnect the house at 70% DoD so system can still be running when sun comes up and it can recharge.
Hedges
Hedges
I'm still considering more PV capacity, switching it between unprotected and protected side because my system "only" allows 112A 240V pass through in either direction.
Hedges
Hedges
I also want to set up additional load-shed to automatically disconnect heating, cooling, laundry, yard lights so battery hardly gets cycled at night, but lots of direct PV to AC can be used during the day. My PV is considerably in excess of what SMA recommends for the battery size I have.
Hedges
Hedges
(these messages have a 420 word limit. Wonder what they're smoking?)
M
melkier
I just bought 4 6048s ... am about to install them. I have about 50kw of batteries I need to hook up as well (racked/bms/cabled/etc). I also bought 60 305W panels (~18kw). I'm looking at getting 4 Sunny Boy SB5.0.
M
melkier
(cont'd)I definitely need more battery. I'll be running my own private grid (not grid tie). Is that what you're doing? I'm thinking about doing "using grid as generator" so I can draw from the grid when batts are low/no sun.

How did you configure yours? The load shed option sounds very cool - I'm digging through the manual right now.
M
melkier
i didnt see the previous comment on your setup (had to click ... show)

I'm also going to do 2S2P on the 6048s. I bought 2 of those 96S BMW Active-E battery packs from batteryhookup. I need to buy the Sunny Boy SB5.0 yet (which will support freq shift).
Hedges
Hedges
Load shed is a necessity with AC coupling if batteries could get run down. Inverter shuts down at low battery voltage, no AC generated, so Sunny Boy never turns on. I don't think it will even connect to AC input (grid or generator) in that state. There is an emergency charging procedure documented.

If SI can auto-start generator and avoid shutdown, then you're OK. Or if there is a DC charger.
Hedges
Hedges
SMA's 100A load disconnect relay only seems to be available overseas. I purchased a couple and had them shipped. It has a dual coil, draws massive current for a moment then opens an extra contact for much lower hold current. That lets the 0.5A PTC fuse on 48V supply do the job. Other brands do have that dual coil as well.
Hedges
Hedges
Mine is grid-backup. Utility has generally been reliable, but had a couple unscheduled outages the past month. I had a 12.5 kW grid-tie system and finally added Sunny Island, 2S2P with 405 Ah 48V SunXtender AGM. That's 14 kWh @ 70% DoD, would only put out 24 kW for 20 minutes.
Hedges
Hedges
The batteries are only there to create AC for Sunny Boy. All major loads would operate daytime only. The battery should make it through the night (with four refrigerators and freezers) but only if I turn off all yard lights and a tube amp.
Hedges
Hedges
The house load-shed is set at 70% DoD. Plan to use second relay at 10% DoD for certain other loads (garage/lab), also wire to A/C thermostat, one leg of electric dryer (let motor run but turn off heat), electric duct heater (in line with gas furnace, selectable), yard lights on house circuit. Then it should be automatic.
Hedges
Hedges
Right now I manually switch and interlocked breaker to put house & garage on (load shed) output of Sunny Island. So I manually disable some loads at that time. I'll split those to a couple different branches. With it set up automatic we'll have UPS to keep internet etc. running, more convenient while working from home.
Hedges
Hedges
I could get by with 100 Ah instead of 400 Ah if all refrigerators and freezers were load shed. Ideally I'd also add a thermostat to re-enable if temperature rose above a critical setting.
Hedges
Hedges
SMA says 100 Ah per Sunny Island, also 100 Ah per 1 kW of PV. I have about 100 Ah per 4 kW of PV, plan to make that per 8 kW of PV. not sure anything bad happens; it's not like fully charged batteries could take the current anyway (a few seconds while frequency slowly swings.)
Hedges
Hedges
Default charge rate after quick-start configuration of a battery is about 0.1C from grid but 0.55C from all sources (especially PV). Following guideline of 100 Ah per 1 kW of PV brings that down to 0.22C. But my battery is way under that size, so would hit 0.55C; I adjusted that setting for 85 A, 0.21C for 405 Ah.
Hedges
Hedges
"using grid as generator"
If grid is available, it is cheaper than battery. The cheapest batteries may be as low as $0.16/kWh (I posted links to Real Goods with $/kWh for many batteries.)
My batteries were about $0.60/kWh.
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