Battery Backup Design

[bflavell]

I'm designing a battery backup system and wanted to get your thoughts. I use about 15,000 kWh/year, but am taking additional steps to reduce that (e.g. more LEDs, new variable pool pump). I figure an 8kW to 9kW system will get me to around 12,000 kWh, which I think will end up covering my use once I reduce some more. Here is the proposed system:

27 x LG Neon 320W Panels
1 x Radian 8048a with GSLC Load Panel, Mate 3 and HUB 10.3
3 x Midnite Solar Classic 150
1 x Midnite Solar 12 CB Combiner Box
1 x Midnite Solar 3 CB Combiner Box
5 x Midnite Solar MOV Surge Protectors (3 DC for combiners, 1 DC for GSLC and 1 AC for GSLC)
16 x L16RE-B Batteries (two 48V strings in parallel)
1 x DIY Sealed/Vented Battery Box (w/ two 48V Zephyr fans)
Racking (still figuring this out, but likely Ironside)
Cables/connectors (PV, batteries, inverter, etc)

I'm wiring the panels in 9 strings of 3 each. The reason for the three CCs is that I have three different roof facings: S (9 panels), SW (6 panels) and East (12 panels). So I wanted one CC per roof facing. I'll run two CCs (S and E) from the 12x combiner and the third CC (SW) from the 3x combiner. This also requires me to add another PV breaker in the GSLC and swap out the 2-pole GFDI with a 4-pole GFDI.

I was going to use FM80s at first, but I need AFCI and using the Classic 150s seemed to be the most cost effective way since Outback still does not have a great solution yet. They are coming out with the new Flexware ICS Plus, which has AFCI and rapid shutdown, but I hear it will be around $2K. California has not adopted 2014 NEC yet, so I don't need to have rapid shutdown, but I still need to comply with AFCI under 690.11 of the 2011 NEC.

Thoughts (good and bad are welcome)? Anyone using anything similar?

Thanks.

[solarix]

If I might ask, why do you want a large battery backed system? A pure grid tied system would be a lot less expensive and a lot more reliable...

[ButchDeal]

You probably are going to want the battery monitor. Have you looked at the FlexPower Radian? It comes integrated with much of what you need as well as AC and DC breakers, PV GFDI, monitoring, etc. (FPR-8048A)

http://outbackpower.com/outback-products/integrated-systems/item/flexpower-radian?category_id=523

[bflavell]

Solarix, as for why batteries in general, it's really just a part of my overall emergency preparedness (earthquake, storm, SHTF). Agreed that straight GT is cheaper and perhaps more reliable, although the Outback equip has a pretty good reputation.

As for size, the general rule of thumb is that I need 100Ah of batteries (@48V) for each 1kW of PV. The Radian uses the batteries as a buffer in GT mode and too small of a battery bank can cause DC ripple, which in turn can result in the inverter going in and out of sell mode. The L16's get me 740Ah, so I'm pretty close to the 100Ah guideline. The batteries themselves certainly are not cheap -- about $5,200 -- but not a huge amount relative to overall costs. And since they will not be cycling often, with proper maintenance (water, EQ, etc.), I would hope they would last 8-10 years. Trojan says 3000 cycles if DoD is 20-30%. If I do need to use them for extended period of time, I could probably get my daily kWh use down to 5-8 kWh (no A/C, pool pump, electric oven or 2nd fridge use), which would give me a couple or three of days of power if sun was low. While sun was good, I could keep DoD quite low.

The alternative system I was considering was Solaredge w/ Powerwall. I like the optimizers given my multi-face roof. But it looks like there is a long backlog on the Powerwall (I’ve heard 2017), and I would want at least 2. I'm actually unclear about how much these cost standalone (i.e., w/o a Solarcity system). I don't think the $3500 applies to standalone, some have said double that. I think the Storedge system is only compatible with the high voltage Powerwall, and not a lower voltage lead acid bank. I need to get the system this year. Although the federal tax credit has now been extended through 2019, the net metering tariffs in CA are going to be redone at the end of 2016 and most think that sell credits will be significantly reduced. Once in, you are grandfathered for 20 years.

[bflavell]

ButchDeal, I was planning on using the FlexPower Radian, but it comes with the two FM80s. Then I need to deal with AFCI. I’m not sure why OB doesn’t add AFCI to the FM80s. That’s why I decided to go with the Classic 150s instead. The actual load center I am looking at is the same one that comes with the FPR, just no inverter or CCS, but otherwise fully prewired with breakers and all, including the FlexnetDC battery monitor. I think the part number is GSLC175-PV-120/240.

The only problem is that it comes wires to accept two CCs. So I spoke to Outback, and I can use three CCs, so long as I don’t exceed overall DC current capacity. I just need to add on more 80A PV breaker and I need to swap out the 2-pole GFDI with the 4-pole GFDI. There are three empty breaker slots, so that is just enough to make these changes.

Thanks for the input.

[Sunking]

27 x LG Neon 320W Panels
1 x Radian 8048a with GSLC Load Panel, Mate 3 and HUB 10.3
3 x Midnite Solar Classic 150
1 x Midnite Solar 12 CB Combiner Box
1 x Midnite Solar 3 CB Combiner Box
5 x Midnite Solar MOV Surge Protectors (3 DC for combiners, 1 DC for GSLC and 1 AC for GSLC)
16 x L16RE-B Batteries (two 48V strings in parallel)
1 x DIY Sealed/Vented Battery Box (w/ two 48V Zephyr fans)
Racking (still figuring this out, but likely Ironside)
Cables/connectors (PV, batteries, inverter, etc)

I'm wiring the panels in 9 strings of 3 each. The reason for the three CCs is that I have three different roof facings: S (9 panels), SW (6 panels) and East (12 panels). So I wanted one CC per roof facing. I'll run two CCs (S and E) from the 12x combiner and the third CC (SW) from the 3x combiner. This also requires me to add another PV breaker in the GSLC and swap out the 2-pole GFDI with a 4-pole GFDI.

I was going to use FM80s at first, but I need AFCI and using the Classic 150s seemed to be the most cost effective way since Outback still does not have a great solution yet. They are coming out with the new Flexware ICS Plus, which has AFCI and rapid shutdown, but I hear it will be around $2K. California has not adopted 2014 NEC yet, so I don't need to have rapid shutdown, but I still need to comply with AFCI under 690.11 of the 2011 NEC.

Thoughts (good and bad are welcome)? Anyone using anything similar?

Thanks.

With 8640 Watts of panels operating into a 48 volt battery requires a minimum 1440 AH battery.

You DO NOT WANT to use parallel batteries. You will need 2 Volt cells to be able to have 1440 AH. In the Trojan Line Up that is a IND27-2V. You will need 24 of them. If you try to use the L16RE-B's you have listed hitting them with 180 amps, you will burn your $6000 battery in a week.

Of course we all know this will never happen, No one in their right mind is going to spend $50,000 on something they never use. FWIW you have forgotten the most important piece of equipment you will need. Well actually three more pieces:

10 Kva LPG Generator
200 Amp 48 Volt AC Charger
550 Gallon LPG storage tank.

[ButchDeal]

With 8640 Watts of panels operating into a 48 volt battery requires a minimum 1440 AH battery.

You DO NOT WANT to use parallel batteries. You will need 2 Volt cells to be able to have 1440 AH. In the Trojan Line Up that is ahttp://www.trojanbattery.com/product/ind27-2v/"] IND27-2V[/URL]. You will need 24 of them. If you try to use the L16RE-B's you have listed hitting them with 180 amps, you will burn your $6000 battery in a week.

Since this is grid tie bimodal for occasional backup, it would be cheaper, simpler, and more efficient to go with VRLA AGM 12v 200ah. I prefer the Outback setup which uses batteries rated for long shelf life, limiting charge losses.
Try the IBR 3 shelf http://www.outbackpower.com/outback-...ategory_id=442
And the energy cell GH http://www.outbackpower.com/outback-...ategory_id=442

The system has integrated balanced bus wiring. You can build your own system like it with other batteries at less cost ( and efficiency).

[ButchDeal]

The alternative system I was considering was Solaredge w/ Powerwall. I like the optimizers given my multi-face roof. But it looks like there is a long backlog on the Powerwall (I’ve heard 2017), and I would want at least 2. I'm actually unclear about how much these cost standalone (i.e., w/o a Solarcity system). I don't think the $3500 applies to standalone, some have said double that. I think the Storedge system is only compatible with the high voltage Powerwall, and not a lower voltage lead acid bank. I need to get the system this year. Although the federal tax credit has now been extended through 2019, the net metering tariffs in CA are going to be redone at the end of 2016 and most think that sell credits will be significantly reduced. Once in, you are grandfathered for 20 years.

I have confirmed that the SE7600A-USS StorEdge inverter will function without the powerwall so you can install it, the auto transformer and consumption meter while you wait for the powerwall. Initially the inverter will support only one powerwall though they may have an upgrade to support a max of two per inverter by the end of the year ( they would not confirm this option or timeline). We are offering this powerwall ready system, not to be confused with a regular SE7600 inverter which can be latter upgraded to StorEdge.

[Sunking]

Since this is grid tie bimodal for occasional backup, it would be cheaper, simpler, and more efficient to go with VRLA AGM 12v 200ah. ).

Are you suggesting a 200 AH battery and hitting it with 180 amps of charge current?

Now I can possible see using the Inverters built in 100 Amp charger and throttle it back to charge a 200 AH AGM battery. But with an Interactive, I see no reason for any charge controllers.

[bflavell]

Sunking, correct me if I'm wrong, but I don't think my batteries will ever see 180 amps. First, since this is for backup only, the charger will be in float mode and so the inverter will be in sell mode, so won't PV current just be converted to AC and go to critical load panel and grid? And if grid goes down and I do have to charge, charging voltage will be at 59.2V per Trojan instructions, so current would be 145 amps. But that assumes 8640W is produced, which is nameplate. I have three different roof azimuths: S, SW and E, so instantaneous power will be lower but extended for more hours. Plus there are normal losses. I think I'd be lucky to see 120 amps. That's C/6 for my batteries, assuming no other loads. And this is really only an issue during bulk charge mode. If too high, I can just adjust the bulk current limit in the Classic, right?

And why not two parallel strings? I would keep all wire lengths identical to minimize imbalance. And I will install type T fuses in each string in case of a short. The advantage I see is if I lose one battery, I still have half of my bank.

[bflavell]

Thanks for the info on Storedge.

[ButchDeal]

Are you suggesting a 200 AH battery and hitting it with 180 amps of charge current?

Now I can possible see using the Inverters built in 100 Amp charger and throttle it back to charge a 200 AH AGM battery. But with an Interactive, I see no reason for any charge controllers.

That battery and rack arrangement would be a ~600ah bank
He wants the CC for a bimodal system to net meter power 99% of the time.

[gmanInPA]

I'm designing a battery backup system and wanted to get your thoughts. I use about 15,000 kWh/year, but am taking additional steps to reduce that (e.g. more LEDs, new variable pool pump). I figure an 8kW to 9kW system will get me to around 12,000 kWh, which I think will end up covering my use once I reduce some more. Here is the proposed system:

27 x LG Neon 320W Panels
1 x Radian 8048a with GSLC Load Panel, Mate 3 and HUB 10.3
3 x Midnite Solar Classic 150
1 x Midnite Solar 12 CB Combiner Box
1 x Midnite Solar 3 CB Combiner Box
5 x Midnite Solar MOV Surge Protectors (3 DC for combiners, 1 DC for GSLC and 1 AC for GSLC)
16 x L16RE-B Batteries (two 48V strings in parallel)
1 x DIY Sealed/Vented Battery Box (w/ two 48V Zephyr fans)
Racking (still figuring this out, but likely Ironside)
Cables/connectors (PV, batteries, inverter, etc)

I'm wiring the panels in 9 strings of 3 each. The reason for the three CCs is that I have three different roof facings: S (9 panels), SW (6 panels) and East (12 panels). So I wanted one CC per roof facing. I'll run two CCs (S and E) from the 12x combiner and the third CC (SW) from the 3x combiner. This also requires me to add another PV breaker in the GSLC and swap out the 2-pole GFDI with a 4-pole GFDI.

I was going to use FM80s at first, but I need AFCI and using the Classic 150s seemed to be the most cost effective way since Outback still does not have a great solution yet. They are coming out with the new Flexware ICS Plus, which has AFCI and rapid shutdown, but I hear it will be around $2K. California has not adopted 2014 NEC yet, so I don't need to have rapid shutdown, but I still need to comply with AFCI under 690.11 of the 2011 NEC.

Thoughts (good and bad are welcome)? Anyone using anything similar?

Thanks.

bflavell - I have a similar system (though only 4.2kW of PV) designed around Schneider XW components. So far, I'm pretty happy with it aside from some glitchy software. All that aside, I agree with Sunking that you've neglected the most important part of that system which is a generator and fuel storage (though I am partial to diesel vs propane). Without such, you will need a tremendous amount of PV and CCs and a helluva lot of good fortune to keep batteries charged continuously during a protracted power outage.

[bflavell]

bflavell - I have a similar system (though only 4.2kW of PV) designed around Schneider XW components. So far, I'm pretty happy with it aside from some glitchy software. All that aside, I agree with Sunking that you've neglected the most important part of that system which is a generator and fuel storage (though I am partial to diesel vs propane). Without such, you will need a tremendous amount of PV and CCs and a helluva lot of good fortune to keep batteries charged continuously during a protracted power outage.

Thanks gmaninPA. I agree on having the generator as well, and I already have one, which we use for camping -- the Yamaha 3000w portable (EF3000iSEB). I like it a lot because it is very quiet and has an eco-throttle. It only outputs at 120V, so I would need an AT (like PSX-240) to connect it to the Radian. So another $500. The main issue is fuel storage. The genny runs on gasoline only. In my former house, I stored 50 gals of gas in high-quality 5-gal metal Jerry cans in an outbuilding away from the house. I don't have that luxury in my new house, and don't like keeping that much fuel in the garage (and my insurance company probably has similar feelings). Maybe I'll look into a propane genset, but still need to figure out where to put the storage tank. Time to buy or build a small shed.

I've also decided to change the batteries to Rolls Surrette S-605s. That gives me some additional amp-hours (932) and the manual allows a maximum bulk charge of C/5, which is 186A. That is more than my panels will ever produce. Given the several roof angles, I think 145A is the best I would see. And this only applies after an outage since the batteries will be on float charge most of the time.

[gmanInPA]

Hi bflavell - Do you have space limitations for fuel storage, or limitations for proximity of fuel? Propane tanks can be buried if the specs for doing so are followed. 1000g of propane can go a long way. If you want to keep your existing generator, you could look into a tri-fuel conversion kit for your existing generator. A company called Motor Snorkel (dot com) makes them and they work pretty well. I have two of their kits for portable Generac generators and they're easily installed. That could allow you a long-term, stable, and bulk fuel storage, but to keep your existing generator.

I can't speak to those batteries because the only one(s) I have experience are the large industrial ones I have which are a different animal and not for everyone. Many here (and elsewhere) seem to have good things to say about Rolls. Some would also say you're going to wreck your first set of batteries, so don't get premium batteries. To me, it's similar to learning to play the guitar. If you get a $100 guitar and start to learn, you might not know if you're learning much, because it's hard to play and you will sound terrible. Then again, if you get a $2000 guitar and you aren't a good player - you'll have spent a lot of money to find out Aim for a middle-of-the-road (guitar) battery that will handle your inexperience the first time, but not short you on quality and longevity. You are gonna need to replace it in about 5 years, and by then you'll know more specifically how to treat them.