Hello from Northern California, South Bay Area

[CCAT Racing]

Hi, first solar forum registration. I finally purchased about $20K in solar equipment. Didn't like ANY of the offers from installers, or the type of systems, so I designed, and built my own! I am using 3 GROWATT 5KW Off Grid Inverters, 2 Solar Edge 5KW Midpoint Transformers, 2 WATTS247 PV Combiners, 2 BIGBATTERY.COM 48V 233AH "KONG" batteries, combined into 1 466AH Battery I call the "KING KONG" Battery, a DALY 200A Smart BMS, and a Renogy 500A Battery Monitor Display. With the extra BIGBATTERY.COM case, I made a 2nd 550AH Lifepo4 battery using 160 60280 55AH Lifepo4 cells, with same DALY BMS, and Renogy Display. For panels, I am using 24 ET Solar Mono 375W panels in 4 strings. System is up an running, need to install 2 more strings of panels on roof, finish 2nd battery, and finalize wiring in conduit.

I am hoping there are some GOOD residential electricians in here to help me verify my wiring is correct, and safe. Its ALL custom, so no wiring help available. I will post up a rough wiring diagram of my system once I get it finished on the PC.

I hope to be of some help here too, so any questions don't hesitate to ask!

Chris

 

[FilterGuy]

I finally purchased about $20K in solar equipment.

I am hoping there are some GOOD residential electricians in here to help me verify my wiring is correct, and safe.

Wow! A 20K leap of faith!!! Keep us posted.

 

[NwCali]

By "northern ca" where about do you mean? I'm 30 minutes from Oregon on the coast...

My hat is off to you trusting BigBattery....

 

[Bud Martin]

Do you have to go through city and county permit and inspection?
Is it 100% off-grid?

 

[Hedges]

Welcome!
What we may lack in being actual "electricians" we make up for in various professional and amateur experience.
Pictures of what you've done may let us spot something.
Links to specs, gauge of wires, ratings of any fuses, breakers, switches.
Any schematics and description of what you're trying to accomplish.

Since we've read threads on LiFePO4 batteries burning, no longer think of them as completely safe. Suggest they be located where, if they do burn, nothing else is lost.

 

[CCAT Racing]

By "northern ca" where about do you mean? I'm 30 minutes from Oregon on the coast...

My hat is off to you trusting BigBattery....

Sorry, I am in the city of Santa Clara, about 30 minutes from Santa Cruz (the coast).

NOT a good experience from Bigbattery! $8600 for 2 of their KONG batteries. 1 obviously had a BMS problem, the other has a bad #13 cell. This is right out of the box! Of course I have to pay to ship both 400 pound batteries back! The cost of 1 cell, and 2 BMS's were cheaper than shipping. And from what I read, I will probably get same problem back, or another one. So I decided to forfeit any warranty, and repair/upgrade them myself.

I would NOT rec BIGBATTERY.COM to anyone!

 

[CCAT Racing]

Do you have to go through city and county permit and inspection?
Is it 100% off-grid?

It is a "grid use only" system. Fully self sufficient, but I have grid power if need be.

 

[CCAT Racing]

Welcome!
What we may lack in being actual "electricians" we make up for in various professional and amateur experience.
Pictures of what you've done may let us spot something.
Links to specs, gauge of wires, ratings of any fuses, breakers, switches.
Any schematics and description of what you're trying to accomplish.

Since we've read threads on LiFePO4 batteries burning, no longer think of them as completely safe. Suggest they be located where, if they do burn, nothing else is lost.

I have them in metal battery boxes, in a closet that I lined with cement fire board. I installed a smoke detector in the closet also. All fuses, wires, etc are rated at or above required specs. I will get pics up soon, I'm trying to get my 2nd battery finished, last 2 strings of panels, and my 3rd inverter installed. I'm using the GROWATT 5000ES Off Grid Inverters. VERY configurable, and working GREAT with the partially finished system.

 

[Hedges]

Sorry, I am in the city of Santa Clara, about 30 minutes from Santa Cruz (the coast).

I'm minutes away (so when seconds count, you can call me?)

I have them in metal battery boxes, in a closet that I lined with cement fire board. I installed a smoke detector in the closet also. All fuses, wires, etc are rated at or above required specs.

Especially for non-UL listed lithium batteries, I suggest having them a safe distance from the house. Not sure a LiFePO4 kiln in a closet is sufficiently safe.

Weather here is usually mild, a good freeze once in a decade. LiFePO4 can't be charged at all below 32 degrees F, probably 0.5C at room temperature, but between those temperatures the allowed current varies. Between your available charge current and cold disconnect of BMS you should be able to set protection levels.

My system is AGM because just backup of occasional power failure. Is yours net metering, or zero export? With lithium, you can cycle it many times, get value by using your stored power to avoid either drawing from grid or drawing during peak times.

 

[CCAT Racing]

I'm minutes away (so when seconds count, you can call me?)



Especially for non-UL listed lithium batteries, I suggest having them a safe distance from the house. Not sure a LiFePO4 kiln in a closet is sufficiently safe.

Weather here is usually mild, a good freeze once in a decade. LiFePO4 can't be charged at all below 32 degrees F, probably 0.5C at room temperature, but between those temperatures the allowed current varies. Between your available charge current and cold disconnect of BMS you should be able to set protection levels.

My system is AGM because just backup of occasional power failure. Is yours net metering, or zero export? With lithium, you can cycle it many times, get value by using your stored power to avoid either drawing from grid or drawing during peak times.

Since you posted this, and I went and looked at a couple forum members fires, I have re-thought my battery storage. I am planning on converting a closet into as fire resistant room as I can. I am going to layer the whole room with 3 layers of 5/8" type c gypsum (1 hour and 45 minutes fire rating per sheet), and 1 layer of 1/2" cement board. Behind first layer of type C Gypsum, against standard sheetrock will be 1" of fire resistant fiber insulation. Installing an auto sprinkler head right above batteries, and low pressure super fine misters in lower corners. For exhaust, triple wall all fuel 6" piping out top of closet, to nearest side wall, out, and up. I am going to coat inside of closet with this fire resistant intumescent paint: https://www.amazon.com/gp/product/B07RBYPXXF/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1 When it contacts fire, it grows a char type of fire barrier. I am taking batteries out of metal case so water and mist can do their job.

Water will drain out bottom of closet through cooling fan opening. My calculations put length of fire to about 4 hours... fire barrier without water, paint, or cement board is apx 5 hours.

Any thoughts, ideas, or concerns, please feel free to let me know...

I am still working on an electrical diagram to get help with, and finishing my last battery.

 

[Hedges]

Done right, all that fire-stop work should let you escape.
Whether it would save the house, I don't know.
If code requires something different (e.g. UL listed energy storage system), then something non-compliant could give insurance company an out.
I would rather put lithium batteries where they can't affect the house.

 

[CCAT Racing]

Done right, all that fire-stop work should let you escape.
Whether it would save the house, I don't know.
If code requires something different (e.g. UL listed energy storage system), then something non-compliant could give insurance company an out.
I would rather put lithium batteries where they can't affect the house.

Alright, you convinced me. I found a spot about 6 feet away from house in backyard. The battery cable run will be about 50 feet. I found a decent 7x3 metal galvanized shed to house them in. I will still still make the shed fire resistant, with a standard fire sprinkler, and a fine mist fire sprinkler. I went with 2/0 cable for best cost vs voltage drop. Just batteries outside, everything else stays in the hall closet.

I have my wiring schematic finished also. Im about to look for the proper section to post it in. I still need confirmation it is safe... While I am here, I will go ahead and post it here too. Assume all circuit breakers, cable sizes, fuses, are all at, or above spec. I'm just concerned on the ac wiring, and the ability to safely trip GFCI circuits, not catch fire, etc. I did accidentally spill water on a power strip that was plugged into a GFCI circuit, and the GFCI tripped before the power strip breaker, which I'm assuming is a good thing. My GFCI circuit tester, and circuit anylyzer all come up good. From my best unserstanding from countless hours researching NEC codes, electrical forums, videos, etc, the 2 neutral to ground bonds in 2 seperate buildings, that are grounded together are acceptable as long as they are different utility sources. This counts as 2 seperate utilities as the neutral in solar system is supplied by the mid point transformers. So each utility has it's own path to return to their respectful sources. The inverters are grid power "use only" so no return neutral back to grid power is needed.

 

[Hedges]

6 feet away, but 50' wire run? Calculate IR drop, see if it will be OK for your inverter.
Unfortunate it isn't more like 10' of cable.
Can inverter be at battery, so wire run is higher voltage AC, like 230Vrms rather than 48VDC?

This manual (page 43) says not more than 98', so it can be done.

https://files.sma.de/downloads/SI4548-6048-US-BE-en-21W.pdf

 

[CCAT Racing]

6 feet away, but 50' wire run? Calculate IR drop, see if it will be OK for your inverter.
Unfortunate it isn't more like 10' of cable.
Can inverter be at battery, so wire run is higher voltage AC, like 230Vrms rather than 48VDC?

This manual (page 43) says not more than 98', so it can be done.

https://files.sma.de/downloads/SI4548-6048-US-BE-en-21W.pdf

Everything is setup in hall closet already. Its an 1100 sq foot house, so not much room. With my max loads, I will barely see 1 volt drop in 50 feet. It will prob be closer to 40 feet, but should be fine. I have full control over min, max votages in my Growatt 5000es inverters. I can easily compensate to still get full range of battery voltage to inverters.

 

[Hedges]

200A main panel
225A main breaker (?)
125A branch breaker would be OK, but 125A backfed PV breaker doesn't obey 120% rule.


Is 125A an acceptable breaker for inverter input? If too high, you might add fuse or breaker for each.
I used two, 2-pole 63A DIN rail breakers to feed my four inverters (which are stacked 2s2p)

If you want backup to garage circuits, you can add in interlocked backfed breaker adjacent to main panel, and run a wire from house panel to it. (When you use that, shut off the breakers feeding inverters from main panel in garage.)

 

[CCAT Racing]

200A main panel
225A main breaker (?)
125A branch breaker would be OK, but 125A backfed PV breaker doesn't obey 120% rule.


Is 125A an acceptable breaker for inverter input? If too high, you might add fuse or breaker for each.
I used two, 2-pole 63A DIN rail breakers to feed my four inverters (which are stacked 2s2p)

If you want backup to garage circuits, you can add in interlocked backfed breaker adjacent to main panel, and run a wire from house panel to it. (When you use that, shut off the breakers feeding inverters from main panel in garage.)

Each imverter has its own circuit breaker, as I posted above, just concerned about wiring safety. "Assume all circuit breakers, cable sizes, fuses, are all at, or above spec. I'm just concerned on the ac wiring, and the ability to safely trip GFCI circuits, not catch fire, etc."

 

[FilterGuy]

I would rather put lithium batteries where they can't affect the house.

IMHO, the high amperage DC wiring is more likely to cause a fire than the LiFePO4 cells.....but we all have slightly different views on the safety of LiFePO4. If we were talking about tesla modules or any cobalt based chemistries..... I would have a very different opinion.... In fact, I would not use any of those batteries in a DIY system even if they are not in the house.

 

[CCAT Racing]

IMHO, the high amperage DC wiring is more likely to cause a fire than the LiFePO4 cells.....but we all have slightly different views on the safety of LiFePO4. If we were talking about tesla modules or any cobalt based chemistries..... I would have a very different opinion.... In fact, I would not use any of those batteries in a DIY system even if they are not in the house.

What's your opinion on a 48v, 45 foot battery cable run using one 3/0 and one 2/0 cable together to carry the extra current/heat? I have 100 feet of each, so I could double up...

 

[FilterGuy]

What's your opinion on a 48v, 45 foot battery cable run using one 3/0 and one 2/0 cable together to carry the extra current/heat?

Since I don't know the current, I have no idea if that is sufficient. However, 45ft on a 48V circuit seems bat-shit long.

 

[CCAT Racing]

Since I don't know the current, I have no idea if that is sufficient. However, 45ft on a 48V circuit seems bat-shit long.

125 amps @ 48-54 vdc. Both pos and neg will be double cable. 3/0 & 2/0 cables will be stripped, and joined together in one 250 MCM tinned copper crimp lug, at a length of 45 feet. That should easily carry that current with minimal voltage drop. (I hope)