Adding a second full rack of batteries to existing full rack

[thanhrodke]

Did you ever do a slow top balance for both battery racks?

I did not, and don't know that I can even tell you what that procedure would be exactly. All 12 batteries have reached the 100%+ mark, and sat there for at least 12 hours.

I ended up terminating the other set of ~3ga wires that comes with the EG4 rack, and using that in parallel with the first one. So the first rack is terminated to the inverters, and the second rack is cabled to the first rack with a pair of ~3ga cables.

They charge/discharge a little more evenly now, but at some point here before too long, I will order all matching cables, and convert the system to bus bars so that both racks and both inverters are in parallel.

 

[Zapper77]

I did not, and don't know that I can even tell you what that procedure would be exactly. All 12 batteries have reached the 100%+ mark, and sat there for at least 12 hours.

I ended up terminating the other set of ~3ga wires that comes with the EG4 rack, and using that in parallel with the first one. So the first rack is terminated to the inverters, and the second rack is cabled to the first rack with a pair of ~3ga cables.

They charge/discharge a little more evenly now, but at some point here before too long, I will order all matching cables, and convert the system to bus bars so that both racks and both inverters are in parallel.

100% at 56.5 volts?

 

[thanhrodke]

100% at 56.5 volts?

56V+, I would not promise 56.5V, but I can easily get that tomorrow. I don't have a screenshot of that info.

well, looking back through my Home Assistant data, the answer is no, they have only touched the 55V+ mark for a very brief period of time.
listed as full, but I am guessing not fully absorbed.

I dug through the forum and can't find a clean procedure on top balancing the EG4 LifePower4 rack batteries that have the built in BMS. Can you point me to one? I can easily just leave the system alone, and let them all sit at 100%+ for a couple days if that's needed.

 

[Zapper77]

56V+, I would not promise 56.5V, but I can easily get that tomorrow. I don't have a screenshot of that info.

well, looking back through my Home Assistant data, the answer is no, they have only touched the 55V+ mark for a very brief period of time.
listed as full, but I am guessing not fully absorbed.

I dug through the forum and can't find a clean procedure on top balancing the EG4 LifePower4 rack batteries that have the built in BMS. Can you point me to one? I can easily just leave the system alone, and let them all sit at 100%+ for a couple days if that's needed.

I had 5 batteries out of 6 that still hadn't top balanced even after 75 days (they were reporting 100% SOC at 54V. They were throwing off my SOC high and low. I manually set both inverters to charge from utility at 10 amps each...set the battery to User. Set bulk and float at 55v and upped the voltage every 2-3 hours until all batteries reported 100% SOC at 56.5 volts. For good measure I held the BMS reset button and cycled the battery breaker. Now I can use the default EG4 battery charge profile setting and the SOC settings work. Batteries also enter passive balance mode as expected using the default inverter settings. It took about 16 hours to top balance.

 

[629658]

I used the Victron Lynx power in for my buss. Rated 1000A. Works great and additional power ins can be added to each other. Very nice buss system

 

[thanhrodke]

As an initial test, I had made up the second pair of 3 gauge cables that came with the second rack, and hooked those up in parallel with the first set between rack 1 and rack 2. So that meant the power and ground from both inverters was going to the bus bars on rack 1, with the parallel 3 gauge conductors between rack 1 and rack 2. It did reduce the delta in charging and discharge current between rack 1 and rack 2, but there was still a noticable current difference, maybe 30% or more under heavy load or heavy charge.

This morning, I made another wiring change, and moved both grounds (one from each inverter) to the second rack. That meant the power cable from each of the two inverters was going to the positive bus bar in rack 1 and the grounds from each of the two inverters were going to the ground bus bar of rack number 2. That left the parallel 3 gauge wires between the two racks carrying both positive and ground, this beginning the hunting factor between both racks. If nothing else, this should ensure that there is the same amount of resistance between all of the batteries in n both racks and both inverters themselves.

I know it's not ideal, but fun to experiment with to see the differences.

 

[MadCow]

Asking for a friend....
Can rack #1 & Rack #2 connect to a common buss ( + and -) that feeds the inverters?

 

[thanhrodke]

yep, that's the way that you would do it if you had multiple inverters and battery racks.

in my case, it's four inverters and two banks of six batteries each. I have the cables from the battery racks stacked on the center posts. One battery bank on top of one post, and the bottom of the other post. Reverse for the other one. Same for the other bus bar. Then the two right hand inverters stacked on the right post, and the left two inverters on the left post. Same thing on the other bus bar, but with the cable stack order reversed. The cable stacking reversal is likely overkill, but required minimal extra effort during the cabling process.

everything is 1/0 AWG with the appropriate terminal hole size for either the battery bus, the bus bars, the breaker or the battery. All cables are from https://www.batterycablesusa.com and were ordered to size for minimum length. All cables that are in parallel are identical in length.

The bus bars are hard to see in the inverter pic, but they are bottom center, behind the right hand battery rack.

 

[MadCow]

Thanks for the info. Your set up looks awesome.
I have another full rack of the eg4s ordered to give me a total of 12 to go along with my 2 LVX6048s.

 

[iSwannie]

Hi Solar Enthusiasts,

I have a similar system setup with 9 batteries with 2 EG4 6500ex inverters. They are working well.