Cheapest and easiest way to keep panels working during a power outage
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Hedges
I See Electromagnetic Fields!
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These should do it.
Sunny Island is 120V, so you either need two for 120/240V, or one and an auto-transformer.
msrp is around $5750, retail street price $4750, but there are liquidation bargains due to DC Solar bankruptcy, also used ones.
But your cheapest option would be to buy a low-cost AIO ($500 to $1500) and rewire PV panels in series to feed them.
Sunny Island is 120V, so you either need two for 120/240V, or one and an auto-transformer.
msrp is around $5750, retail street price $4750, but there are liquidation bargains due to DC Solar bankruptcy, also used ones.
SMA Sunny Island SI 5048U 5kW Inverter 60 Hz | eBay
Find many great new & used options and get the best deals for SMA Sunny Island SI 5048U 5kW Inverter 60 Hz at the best online prices at eBay! Free shipping for many products!
www.ebay.com
SMA Sunny Island SI 5048U 5kW Inverter 60 Hz | eBay
<p>SMA Sunny Island SI 5048U 5kW Inverter 60 Hz. </p><br /><p>Used but works well.</p><br /><p>Warehouse overstock.</p>
www.ebay.com
But your cheapest option would be to buy a low-cost AIO ($500 to $1500) and rewire PV panels in series to feed them.
I think the sunny island would not be a lot more expensive but would have a lot more flexibilityThese should do it.
Sunny Island is 120V, so you either need two for 120/240V, or one and an auto-transformer.
msrp is around $5750, retail street price $4750, but there are liquidation bargains due to DC Solar bankruptcy, also used ones.
SMA Sunny Island SI 5048U 5kW Inverter 60 Hz | eBay
Find many great new & used options and get the best deals for SMA Sunny Island SI 5048U 5kW Inverter 60 Hz at the best online prices at eBay! Free shipping for many products!www.ebay.com
SMA Sunny Island SI 5048U 5kW Inverter 60 Hz | eBay
<p>SMA Sunny Island SI 5048U 5kW Inverter 60 Hz. </p><br /><p>Used but works well.</p><br /><p>Warehouse overstock.</p>www.ebay.com
But your cheapest option would be to buy a low-cost AIO ($500 to $1500) and rewire PV panels in series to feed them.
wattmatters
Solar Wizard
AC coupling is not cheap.
Neither are batteries.
The cheapest option as far as I can tell to have several days of grid backup is a generator with sufficient fuel on hand to last for whatever duration you need, with propane being easiest to store for long periods without spoiling.
If your concern is outage coverage (rather than running from off-grid PV), then I would look into storing more propane. Don't know what propane costs there but where I am 1 x 45kg tank of propane would cost US$24/year bottle rental and ~ US$150 for the gas.
1 x 45kg tank of propane running a generator should provide roughly 100 kWh of electrical energy.
While I have a home outage backup system (PV & battery) to complement our grid-tied PV, our EV is actually part of the backup solution. It has vehicle to load capability so is itself a source of emergency backup power.
Hedges
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Sunny Island is supposed to get minimum 100 Ah 48V lead-acid or 50 Ah lithium.
Quality AGM would be $1500 for 100 Ah. FLA golf cart batteries could be a cheaper option.
It would work with four automotive starting batteries from the junkyard, but of course those wouldn't give much cycle life. Should be OK if shut off when the sun goes down.
There are 100 Ah server rack batteries from $1200, but you're on your own getting them to work well with inverters.
For clarification, OP has 11kW AC coupled solar. So, SMA supports Sunny Island with 100Ah battery for AC coupling 11kW?
Hedges
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Not according to the manual. But it might work.
I remembered 11kW, but looked back to first post and read "I think my panels will reach 7-8kw mid day"
One Sunny Island could pass 56A 120v back to grid, 6.7kw. If not backfeeding grid it could manage 12kW.
To backfeed grid, get two for 13.4kW backfeed (and 24kW capability off grid.)
Or, split GT PV half directly on grid and half on output of Sunny Island. Or all directly on grid. Manual switching could make all available when grid is down. That way relay isn't a limit.
As for battery, SMA recommends 100 Ah per 1kW of AC coupled PV, so they're recommending 1100 Ah.
I'm running about 100 Ah per 3kW of PV. I think how far you can push it depends on how big an AC load suddenly gets shut off. And how much current your batteries can accept. I've got my SI set to charge at 0.2C, but battery manufacturer says they can accept vastly higher current. I don't know if SI briefly exceeds that setting during load dump.
I remembered 11kW, but looked back to first post and read "I think my panels will reach 7-8kw mid day"
One Sunny Island could pass 56A 120v back to grid, 6.7kw. If not backfeeding grid it could manage 12kW.
To backfeed grid, get two for 13.4kW backfeed (and 24kW capability off grid.)
Or, split GT PV half directly on grid and half on output of Sunny Island. Or all directly on grid. Manual switching could make all available when grid is down. That way relay isn't a limit.
As for battery, SMA recommends 100 Ah per 1kW of AC coupled PV, so they're recommending 1100 Ah.
I'm running about 100 Ah per 3kW of PV. I think how far you can push it depends on how big an AC load suddenly gets shut off. And how much current your batteries can accept. I've got my SI set to charge at 0.2C, but battery manufacturer says they can accept vastly higher current. I don't know if SI briefly exceeds that setting during load dump.
zanydroid
Solar Wizard
No, this is for sure the cheapest way materials wise. Take a look at 6000XP + a server rack battery + wiring.
Generator is cheaper but a fair comparison in terms of user experience is a fully IP65 rated outdoor unit, not one of those that are for temporary use.
Labor wise, maybe it gets closer to an AC coupled solution. Since code compliance is harder with DC
Single 120VAC Multiplus with autotransformer for microinverters is theoretically the cheapest AC coupling solution. But this is not for the faint of heart and you can only manage like 2.4kW of microinverters.
zanydroid
Solar Wizard
Read the fine print. Unless you have one I’m not familiar with, it only has the ability to do that when on grid. Whole different ballgame when it needs to be fully balanced system without the grid for overflow
wattmatters
Solar Wizard
I was going by what the OP asked for - something to get by for a few days without grid power and be able to get some charge into an EV but with a very limited budget.
For that purpose a half decent portable genset, some power cords and a store of propane is perfectly fine, and far cheaper than anything else.
Once you go for dedicated backup generation or PV and battery storage systems (be it an AC coupled / off-grid), well we are well beyond their budget parameters.
You can make a portable hand truck system and some second hand panels but charging an EV would be problematic. EVs typically have a minimum charge rate. I need at least a 1.8 kW AC supply to charge mine and that will only add ~ 6-7 miles of EV range per hour.
That said, when I think about my initial home backup system:
I picked up some pre-loved sealed lead acid batteries which came from data centre and they cost ~US$650. 48 V 190 Ah, so a reasonable size to pair with an AIO inverter for very occasional use. I used a cheap 4 kW AIO Voltronic clone. Later I added a 2.2 kW off-grid PV array to it.
Then if the OP had a way to redirect part of their existing GT array as an input to their AIO then they might have a fighting chance to slow charge an EV and have enough power for overnight essentials. If one of their GT strings had a string voltage compatible with an AIO, then it would be possible to rig that up without too much hassle, assuming either the GT inverter wiring was accessible, or the MC4 connectors on the PV array were accessible..
zanydroid
Solar Wizard
I missed the part about charging an EV. Probably because I got distracted by the unrealistic AC coupling expectations.
EV charging is fine with a generator, no need for IP65 one, since you can configure the EVSE at optimal efficiency curve.
But. The EV can move. Just drive to a charging station. And with high probability the SoC on the EV is probably pretty usable.
Rereading OP I see this is a search for SHTF solution on the cheap so that won’t work.
EV charging is fine with a generator, no need for IP65 one, since you can configure the EVSE at optimal efficiency curve.
But. The EV can move. Just drive to a charging station. And with high probability the SoC on the EV is probably pretty usable.
Rereading OP I see this is a search for SHTF solution on the cheap so that won’t work.
zanydroid
Solar Wizard
The min charge rate on an EV is probably 700W. 6A is the minimum current under J1772. Efficiency will be terrible at 700W in, probably like 60%
zanydroid
Solar Wizard
Battery less AIO and reconfiguring enough panels when SHTF to activate will definitely fit in $3000 budget. It’ll just be a ton of work to setup and undo.
Or stockpile $1500 of panels in the garage to manually deploy in the yard.
Or stockpile $1500 of panels in the garage to manually deploy in the yard.
Samsonite801
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I just remembered, there's this guy who comes out to our off-grid community co-op (which is about 90 miles out of town) and helps this other guy build his house, he showed me his Nissan Leaf one day, and he has one of those portable solar/battery generators that has solar input on it (he puts in the trunk, its pretty big), and he carries several big fold-up solar panels he carries in the back seat.
He says he can charge with that setup anywhere (I can't remember how many watts he said it can do, but it was pretty impressive I remember)... I'll have to ask him next time I see him and find out what all the gear was again. He talked like he did all the research and got the best portable solar/battery generator (like the biggest one), enough foldable panels to max out the solar generator input, and it all fits in the car (and he just brings it all with him out here to charge his car to get back to town again).
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That makes more sense. My back hurts just thinking about lifting and moving that much AGM batteries.
Hedges
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Regulations and recommendations are made to be intelligently disregarded.
Sunny Island will regulate charge current to whatever you set.
Battery bank can be massive or tiny. AC coupled PV could be just about any size, even way above recommended. I suppose at some SB/SI ratio it might go unstable. Load step has to be picked up by SI, with 6kW rating and 11kW 3 second surge. Load dump has to be absorbed by SI. Oversize AC coupled PV should be OK so long as load dump doesn't exceed SI peak battery charging of 140A or maybe user setting ~20A for 0.2C (not sure if it will briefly stuff max in batteries, or if it obeys setting.) 20A at 50V would be 1kW of load dump. 140A x 50V x 2 inverters = 14kW of load dump.
Easy on the flat. Difficulty is elevation changes and offroad.
I just moved 750 Ah, 24 pieces 6V 250 Ah FullRiver.
Seller dead-lifted each 76 lb battery into my pickup. The ramps were so steep on level ground I struggled with dolly.
I previously moved 8 pieces 6V 405 Ah SunXtender, 120 lbs, through back yard.
I have these (now clearance priced $99)
After getting home, I backed up to sloped driveway and unloading was easy. Now recharging starting with lowest (6.05V, 40% SoC, hope it isn't due to one low cell - wishful thinking?) These were used in 12s 72V for motive power.
Kenny_
Solar Addict
I read a bit of this thread earlier and just ran across this battery system from LG....not sure if it would be useful to you or not, but here ya go:
www.cnet.com
LG ESS Home 8 Review: A Large Home Battery That Packs Power
The Home 8 offers a lot of storage capacity and a powerful inverter at a fair price. Here's what you should know.
www.cnet.com
Hedges
I See Electromagnetic Fields!
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previous LG powerwalls (RESU-H) were recalled for fires.
This one appears to also be a lithium-ion that is not LiFePO4.
I would avoid it.
Tesla may also be of an Explody chemistry, but they appear to have managed risks better. They were aware before introducing the roadster and addressed it.
The EG4 PowerPro is attractive.
diysolarforum.com
The LG ESS is AC coupled, EG4 PowerPro is DC, so the following from EG would be equivalent of LG product:
This one appears to also be a lithium-ion that is not LiFePO4.
I would avoid it.
Tesla may also be of an Explody chemistry, but they appear to have managed risks better. They were aware before introducing the roadster and addressed it.
The EG4 PowerPro is attractive.
I really like the new powerpro battery..
I didn't realize it until last night, but I think this battery is pretty sweet. The look, form factor, busbar with quick connectors, communication ability, internal heaters, outdoor rated and the list goes on. Now I want to dump my server rack batteries. Which one would you rather have. This...
diysolarforum.com
The LG ESS is AC coupled, EG4 PowerPro is DC, so the following from EG would be equivalent of LG product:
