importance of earthing a rack battery and its cabinet ??

[rmharrington]

1) No, when the grid goes down the inverter will isolate the grid input, and not feed any power back.

2) Yeah the ground from the main to the sub panel is good enough, using the sub panel is a good choice for centralizing your grounds on this system.

Excellent. Last points, and I will leave you be.

1) Would a grid connect to the inverters continue feeding a subpanel even if the inverters went bad.?
2) If not, then feeding the grid into the subpanel for an either/or seems my best choice. Eitherway, can you recommend a panel with 20 breaker slots along with a slider switch that would permit me to switch completely off the solar and back to the grid if necessary?
3) Would twin 70amp breakers, one set for the inverter connection and one set for the grid be reasonable for my system?

I've got eighteen 345 volt 9 amp panels on two strings, one to each inverter. I'm thinking of handling 110 volt electrical outlets and lights in the den, kitchen, and maybe one other room, along with running a 1100 watt microwave when necessary. Later, if all goes well, I'll add another battery and try to include 220 connections for my well and hot water heater.
No other heavy pulls.

You've been lots of help and greatly calmed my nerves. If you don't mind sharing a bit about your credentials, I you've resolved most all my remaining concerns. If you were near Concord, NC, I'd hire you to finish this task for me.

Thanks for going above and beyond.

 

[pvgirl]

Excellent. Last points, and I will leave you be.

1) Would a grid connect to the inverters continue feeding a subpanel even if the inverters went bad.?
2) If not, then feeding the grid into the subpanel for an either/or seems my best choice. Eitherway, can you recommend a panel with 20 breaker slots along with a slider switch that would permit me to switch completely off the solar and back to the grid if necessary?
3) Would twin 70amp breakers, one set for the inverter connection and one set for the grid be reasonable for my system?

1) most likely if the inverter fails, it will not pass power thru.
2) a panel with a slide interlock kit added will let you bypass the inverter and run off the grid, incase of inverter issues, maintenance and upgrades.What you can get locally will be the best bet.
3) 70 amp breakers are fine for both

 

[ksmithaz1]

How many k does your home pull in a day?

In July 95-120KWH. Right now around 50-60 if I don't charge a car. Maybe a little higher today it hit 100, and I charge my EV's on the weekends or one day a week. The nitetime lows have been in the high 60's low 70's the last couple weeks. I only have good data on this from the last 45 days or so. This is direct from the inverters, 9/1 was a cloudy day. I had a problem from 9/20-9/22 with a BMC on one of my batteries. At this point I am 100% output from the inverters. Since 9/14, at night I top up the batteries from the grid with a chargeverter to 20% until 0430. TOU peak starting 10/1 is 0500-0900, 1700-2100, so you will see the output slightly higher than production, as I am charging out of band of the inverter. I'm working on the software to regulate that a bit better. I am not tied to the grid, but I have a transfer switch that kicks over to the grid if the inverter drops out.

 

[ksmithaz1]

One of my very good friends was the CFD for the City of Hickory. My kids were born in Fayetteville. Charlotte is about the most awful place to try and drive east-west in. 74 is a traffic light every mile from marshville to the beltway. Used to work out of Greensboro/Madison all thru the furniture belt. Concord is not far enough west, I'd get up a little higher in the mountains ;-). Were you there when Hugo rolled thru?

 

[rmharrington]

In July 95-120KWH. Right now around 50-60 if I don't charge a car. Maybe a little higher today it hit 100, and I charge my EV's on the weekends or one day a week. The nitetime lows have been in the high 60's low 70's the last couple weeks. I only have good data on this from the last 45 days or so. This is direct from the inverters, 9/1 was a cloudy day. I had a problem from 9/20-9/22 with a BMC on one of my batteries. At this point I am 100% output from the inverters. Since 9/14, at night I top up the batteries from the grid with a chargeverter to 20% until 0430. TOU peak starting 10/1 is 0500-0900, 1700-2100, so you will see the output slightly higher than production, as I am charging out of band of the inverter. I'm working on the software to regulate that a bit better. I am not tied to the grid, but I have a transfer switch that kicks over to the grid if the inverter drops out.

View attachment 171129

Nice. Sounds like you're using an automatic transfer switch. That's rather near to what I have planned. Please elaborate and maybe include a picture or two. It go a long way toward helping me seal my plans.

 

[rmharrington]

One of my very good friends was the CFD for the City of Hickory. My kids were born in Fayetteville. Charlotte is about the most awful place to try and drive east-west in. 74 is a traffic light every mile from marshville to the beltway. Used to work out of Greensboro/Madison all thru the furniture belt. Concord is not far enough west, I'd get up a little higher in the mountains ;-). Were you there when Hugo rolled thru?

Lived through Hugo with minor damage to our roof. How often do you get around Concord? I'm looking for someone to help me finish up correctly. I'm down to installing a subpanel and making sure the wiring goes right.

 

[ksmithaz1]

Too close to Charlotte . Just take your time, build a thread, post some pic's. If you catch the bug you are going to want to go deeper. I just made my 'sub' panel a full size 240v 100A with 24 breaker slots. I put the transfer switch in front of it behind a 100A breaker in the main panel, and starting moving loads over. If you really want to go off grid, I'd do something similar and make it 240 from the start. I do a lot of computer stuff, and I already had 240 back to my office, probably 1/3+ of my static draw, but if you go ahead and plumb for 240 your life will be easier as you move up. In other words run #2 to an oversized sub-panel and beef it up. You can still push it from a 70A breaker, then just bump it up when you get that bonus check.

My goal was always 24KW of output. I balanced my loads, and put sensors on the high load circuits. My peak load has been around 18KW, so I'm spot on where I want to be. Cloudier out your way, YMMV.

 

[rmharrington]

Too close to Charlotte . Just take your time, build a thread, post some pic's. If you catch the bug you are going to want to go deeper. I just made my 'sub' panel a full size 240v 100A with 24 breaker slots. I put the transfer switch in front of it behind a 100A breaker in the main panel, and starting moving loads over. If you really want to go off grid, I'd do something similar and make it 240 from the start. I do a lot of computer stuff, and I already had 240 back to my office, probably 1/3+ of my static draw, but if you go ahead and plumb for 240 your life will be easier as you move up. In other words run #2 to an oversized sub-panel and beef it up. You can still push it from a 70A breaker, then just bump it up when you get that bonus check.

My goal was always 24KW of output. I balanced my loads, and put sensors on the high load circuits. My peak load has been around 18KW, so I'm spot on where I want to be. Cloudier out your way, YMMV.

Sounds like you are really cooking. Are you located out west or something? Is it a permitted system? I'm not looking to replace the grid, just cut some of the expense with the ability to grow as circumstances evolve.

 

[automatikdonn]

Remote telecom systems are positive grounded battery systems.

Trust in Tim

 

[rmharrington]

Sounds like you are really cooking. Are you located out west or something? Is it a permitted system? I'm not looking to replace the grid, just cut some of the expense with the ability to grow as circumstances evolve.

Hi. I fired up today with one inverter just to see if it would charge the batteries (I have two eg4 LL batteries in a rack). I noticed that the top battery charges maybe 10 percent quicker than the second one. I saw where Will Prose reversed the negative busbar to eliminate this problem. Care to offer some insight?

 

[webbbn]

Hi. I fired up today with one inverter just to see if it would charge the batteries (I have two eg4 LL batteries in a rack). I noticed that the top battery charges maybe 10 percent quicker than the second one. I saw where Will Prose reversed the negative busbar to eliminate this problem. Care to offer some insight?

I made a rambling post in this thread with my analysis of the issue.

10% is pretty significant, and I would be interested if you do find that just swapping the cables around completely solves the issue. Can you provide more details on how you charged your batteries and what the cabling is like between the batteries (maybe you discuss the later in this thread?)? The amount of charging current is most important.

Also, what do you mean by "10 percent quicker", and what were you using to determine the voltage / SOC on each battery? I have two batteries, both with JK BMS, and the BMS show over a volt difference between the two, even though they're in parallel, and the true voltage on each of them is about half way in between.

 

[rmharrington]

Ignore this post

 

[rmharrington]

I made a rambling post in this thread with my analysis of the issue.

10% is pretty significant, and I would be interested if you do find that just swapping the cables around completely solves the issue. Can you provide more details on how you charged your batteries and what the cabling is like between the batteries (maybe you discuss the later in this thread?)? The amount of charging current is most important.

Also, what do you mean by "10 percent quicker", and what were you using to determine the voltage / SOC on each battery? I have two batteries, both with JK BMS, and the BMS show over a volt difference between the two, even though they're in parallel, and the true voltage on each of them is about half way in between.

Read the statements concerning your rambling post. I think I agree with the viewpoint of a diagonal connect with hot at the top of the left busbar and negative at the bottom of the right busbar.

For the record:
1) I charged the two batteries using only solar input wherein I had available 392 volts at 8 to 9 amps of consistent flow.

2) The top battery started with a 56% charge. The bottom started at 54%.

3) In the course of thirty minutes, the top battery ran up to 71%. The bottom battery only reached 63%. Not exactly a 10% difference, but relative.

4) The amount of voltage and amps the system applied to the top battery ran 10% to 12% higher average than the bottom unit. This detail taken from the digital readout on the individual batteries. Note that the above figures are from my flaky memory rather than notes taken on site.

5) When I shutdown the solar, the second battery went into a discharge mode; therein adding even more charge to the first battery.

Don't know what would happen if I permitted the top battery to reach full charge. Not there yet. But from what has happened so far, it's obvious the second battery will work harder than the top battery. Once I get everything up and running full from solar panels to electric subpanel, I'll compare all and if necessary, I'll get longer cables so I can flip the negative busbar.

 

[webbbn]

If I'm understanding correctly, the solar power was around 400V at 8-9A, which should equate to 30ish A / battery, which isn't really all that high, so I wouldn't expect there to be much voltage drop between the batteries. The voltage differential has to be 0 when you stop charging, and should start to reverse when you start discharging. If that's not the case, then it's not caused by differing resistances.

Have you top-balanced your batteries and calibrated the SOC? How are you determining all your stats? As I said, I don't the BMS values are very accurate.

 

[rmharrington]

If I'm understanding correctly, the solar power was around 400V at 8-9A, which should equate to 30ish A / battery, which isn't really all that high, so I wouldn't expect there to be much voltage drop between the batteries. The voltage differential has to be 0 when you stop charging, and should start to reverse when you start discharging. If that's not the case, then it's not caused by differing resistances.

Have you top-balanced your batteries and calibrated the SOC? How are you determining all your stats? As I said, I don't the BMS values are very accurate.

Today, the top battery is pulling 54.6 volts and charging at 14amps the bottom is pulling 53.6 volts and charging at 7.8 amps.

 

[webbbn]

I think you need to slow down and work with each of the batteries individually. Some of the stats that you're seeing seem odd, and suggest to me that the batteries are at differing / unknown SOC. The most glaring is your #5 above.

If the lower battery is at a lower voltage and lower SOC, it should not have started charging the upper battery.

I would first measure the actual voltage across each of the batteries and compare that to what the battery is reading. That would allow you to at least apply some correction when comparing voltages. After that, I would connect each battery individually and make sure the SOC is calibrated and that it's properly top balanced.

Until you're sure that each battery is properly calibrated independently, you can't properly understand what's going on when they're connected together.

 

[rmharrington]

I think you need to slow down and work with each of the batteries individually. Some of the stats that you're seeing seem odd, and suggest to me that the batteries are at differing / unknown SOC. The most glaring is your #5 above.

If the lower battery is at a lower voltage and lower SOC, it should not have started charging the upper battery.

I would first measure the actual voltage across each of the batteries and compare that to what the battery is reading. That would allow you to at least apply some correction when comparing voltages. After that, I would connect each battery individually and make sure the SOC is calibrated and that it's properly top balanced.

Until you're sure that each battery is properly calibrated independently, you can't properly understand what's going on when they're connected together.

Thanks for the input. I need to take a few days away from it all, now. I switch on the battery breaker for the second inverter without having the inverters paired. Main inverter immediately died. Now I'm not showing any DC current entering the inverter, even though IMO incoming is same as at the solar panels. Since the cover prevents me from reading the output of the IMO at the source, I'm back to lost and adrift at sea.

 

[webbbn]

Thanks for the input. I need to take a few days away from it all, now. I switch on the battery breaker for the second inverter without having the inverters paired. Main inverter immediately died. Now I'm not showing any DC current entering the inverter, even though IMO incoming is same as at the solar panels. Since the cover prevents me from reading the output of the IMO at the source, I'm back to lost and adrift at sea.

I hope you don't have a hardware issue. There's alot to learn with these systems, especially with the batteries. I'm just learning myself, but starting to get some understanding of the battery issues. I'm curious to see how your battery wiring sorts out.

I just brought a second battery online, but mine are both wired directly to a common busbar that goes into the inverter. The wires are similar length, but not exact. That's another solution if you determine that it is an issue with the wiring. Wire both batteries to a common busbar and then to the inverter. You'll likely have to do that anyway if you add more batteries.

It took me a while to get the batteries both balanced properly, but now they seem to be working very well. I'm currently running a discharge test, and this is what it looks like:



The right meters are on a shunt that is on the common wire to the inverter, so it shows the combined battery voltage, which is about half way between what the BMSs are reading. The current draw is very well balanced, and it's pretty similar when charging. I'm anxious to see how balanced the two batteries are toward the end of the discharge test, but that's hours away!

 

[rmharrington]

I hope you don't have a hardware issue. There's alot to learn with these systems, especially with the batteries. I'm just learning myself, but starting to get some understanding of the battery issues. I'm curious to see how your battery wiring sorts out.

I just brought a second battery online, but mine are both wired directly to a common busbar that goes into the inverter. The wires are similar length, but not exact. That's another solution if you determine that it is an issue with the wiring. Wire both batteries to a common busbar and then to the inverter. You'll likely have to do that anyway if you add more batteries.

It took me a while to get the batteries both balanced properly, but now they seem to be working very well. I'm currently running a discharge test, and this is what it looks like:

View attachment 171372

The right meters are on a shunt that is on the common wire to the inverter, so it shows the combined battery voltage, which is about half way between what the BMSs are reading. The current draw is very well balanced, and it's pretty similar when charging. I'm anxious to see how balanced the two batteries are toward the end of the discharge test, but that's hours away!

Got my two batteries wired in to a signature solar 6 unit battery rack. The cables run one set from each inverter through one breaker for each hot wire, then both positives connect to the top of the positive busbar and both negatives connect to the top of the negative busbar. Signature Solar tech said this would work fine. I'm starting to wonder. lol.

 

[rmharrington]

Excellent. Last points, and I will leave you be.

1) Would a grid connect to the inverters continue feeding a subpanel even if the inverters went bad.?
2) If not, then feeding the grid into the subpanel for an either/or seems my best choice. Eitherway, can you recommend a panel with 20 breaker slots along with a slider switch that would permit me to switch completely off the solar and back to the grid if necessary?
3) Would twin 70amp breakers, one set for the inverter connection and one set for the grid be reasonable for my system?

I've got eighteen 345 volt 9 amp panels on two strings, one to each inverter. I'm thinking of handling 110 volt electrical outlets and lights in the den, kitchen, and maybe one other room, along with running a 1100 watt microwave when necessary. Later, if all goes well, I'll add another battery and try to include 220 connections for my well and hot water heater.
No other heavy pulls.

You've been lots of help and greatly calmed my nerves. If you don't mind sharing a bit about your credentials, I you've resolved most all my remaining concerns. If you were near Concord, NC, I'd hire you to finish this task for me.

Thanks for going above and beyond.

Sorry if I upended you by asking for credentials. Your advise is the best I've read concerning my grounding issues.