Two banks in one rack?

[Stotts47]

So, I have an 18kvp, a powerpro 280ah battery, and 6 Lifepower4 100ah batteries. I have an EG4 rack for the six LP4 batteries. However according to EG4 hooking a bank of six LP4 to the system will create "sever" balancing issues. So I have to have banks of 3, but I don't want to purchase another 6 slot rack and have two half empty racks taking up twice the floor space. And I don't want to drop another $3500+ on another wall mount battery to balance things out.

So my question is, can I just cut the busbars in the rack in half and have two banks of three in one rack? Will this pass code, and if not, does it cause any safety issues? How large a gap do I need between the two busbars so there is no arcing?

Thanks!

 

[chrisski]

So, I have an 18kvp, a powerpro 280ah battery, and 6 Lifepower4 100ah batteries. I have an EG4 rack for the six LP4 batteries. However according to EG4 hooking a bank of six LP4 to the system will create "sever" balancing issues. So I have to have banks of 3, but I don't want to purchase another 6 slot rack and have two half empty racks taking up twice the floor space. And I don't want to drop another $3500+ on another wall mount battery to balance things out.

So my question is, can I just cut the busbars in the rack in half and have two banks of three in one rack? Will this pass code, and if not, does it cause any safety issues? How large a gap do I need between the two busbars so there is no arcing?

Thanks!

I don't think you can put 6 in one rack, but not for reasons ou mentioned; code may limit you to 20 kWh per battery.
.
I think UL9450A limits a single residential battery pack to 20 kWh. Each of those batteries is just short or just long of 5 kWh. So for different reasons than you ask, if the AHJ sticks to a 20 kWh maximum per battery pack, four would be tops. I have a battery that is 5.1 kWh, so I'd hae 20.4 kWh if I put 4, just above the 20 kWh limit, so I might not be able to put 4 depending on what the inspectors say.

https://www.ul.com/services/ul-9540a-test-method

Up to 80 kWh can be stored in something like a garage. other areas 40 kWh. Each 20 kWh needs to be separated; I think 3' minimum. So if you cut the busbars, the next battery would need to be 3' apart, which means yo need to buy a sperate UL approved case.

Because commercial uses can be 50 kWh, I think that's why a rack of 6 can be sold and meet UL standards, but only for commercial use, not residential use.
====
Edit: Thought I'd throw this in. I thought the EG4 was wired like the Top method from the Victron Wiring Unlimited:

 

[Stotts47]

I don't think you can put 6 in one rack, but not for reasons ou mentioned; code may limit you to 20 kWh per battery.
.
I think UL9450A limits a single residential battery pack to 20 kWh. Each of those batteries is just short or just long of 5 kWh. So for different reasons than you ask, if the AHJ sticks to a 20 kWh maximum per battery pack, four would be tops. I have a battery that is 5.1 kWh, so I'd hae 20.4 kWh if I put 4, just above the 20 kWh limit, so I might not be able to put 4 depending on what the inspectors say.

https://www.ul.com/services/ul-9540a-test-method

Up to 80 kWh can be stored in something like a garage. other areas 40 kWh. Each 20 kWh needs to be separated; I think 3' minimum. So if you cut the busbars, the next battery would need to be 3' apart, which means yo need to buy a sperate UL approved case.

Because commercial uses can be 50 kWh, I think that's why a rack of 6 can be sold and meet UL standards, but only for commercial use, not residential use.
====
Edit: Thought I'd throw this in. I thought the EG4 was wired like the Top method from the Victron Wiring Unlimited:

Thanks, so 20kw or less for code. And if I am ignoring code, anyone see any dangers with cutting the bus bar and putting two banks of three in one rack? How much space between bus bars to eliminate danger of arcing?

 

[chrisski]

And if I am ignoring code, anyone see any dangers with cutting the bus bar and putting two banks of three in one rack? How much space between bus bars to eliminate danger of arcing?

If you're ignoring code, as much space as you can and put some non-conductive materiel between the different busbars to avoid sparking.

 

[42OhmsPA]

So, I have an 18kvp, a powerpro 280ah battery, and 6 Lifepower4 100ah batteries. I have an EG4 rack for the six LP4 batteries. However according to EG4 hooking a bank of six LP4 to the system will create "sever" balancing issues. So I have to have banks of 3, but I don't want to purchase another 6 slot rack and have two half empty racks taking up twice the floor space. And I don't want to drop another $3500+ on another wall mount battery to balance things out.

So my question is, can I just cut the busbars in the rack in half and have two banks of three in one rack? Will this pass code, and if not, does it cause any safety issues? How large a gap do I need between the two busbars so there is no arcing?

Thanks!

I see zero reason this would create a balancing issue if wired correctly, positive to the top of + bus and negative to bottom of - bus or vice versa.
Many members are running 6 packs in parallel and this is the first of heard of only having 3... Why sell a 6 slot cabinet if this is the case?
I'm betting there was a misinterpretation or poor advice.

@EG4_Jared care to shed some light?

 

[Brucey]

I see zero reason this would create a balancing issue if wired correctly, positive to the top of + bus and negative to bottom of - bus or vice versa.
Many members are running 6 packs in parallel and this is the first of heard of only having 3... Why sell a 6 slot cabinet if this is the case?
I'm betting there was a misinterpretation or poor advice.

@EG4_Jared care to shed some light?

I think they are suggesting two "300Ah equivalents" to go with the 280Ah power pro.

 

[42OhmsPA]

I think they are suggesting two "300Ah equivalents" to go with the 280Ah power pro.

That makes more sense but I still don't see how it would cause an issue.

 

[Stotts47]

See this post by Jared and associated white paper here:

Can you share EG4-LifePower4 with EG4 PowerPro ?

I have an 18kpv currently running with 4 EG4-LifePower4 48V . I got a EG4 PowerPro recently and want to use them all together. Is this possible and if so how should I wire it?

diysolarforum.com

I also called EG4 and they told me if I hooked up the rack of 6 Lifepower4 to my 18kvp along with my powerpro it would cause "sever" balancing issues and not to do it.

I contacted signature solar and they suggested creating two banks of three and hooking those to the powerpro, but for some reason EG4 did not say this was an option, they told me I needed to get another Powerpro.

 

[Steve_S]

I must point out that several of us run with 6 Packs up to 10 Packs in ONE BANK ! I'm one of those.
When properly & correctly wired pack balancing within the bank is NOT an issue ! HONESTLY... I have 6 280AH Hot ATM, by 13:00 hours they are existing Absorb and going to Float, by that point there "may" be 1.0 V difference between packs and typically less than 0.050V deviation between cells in the packs, A 1/2 Hour after entering float, they are all below 0.010 deviation and fully balanced at 100%.

Qualifying :
I have run my Bank with Mixxed AH Packs in a bank, 1x100AH, 2x175AH, 3x280AH and even that worked exactly as expected, of course with the math being done and settings tweaked. Belive me that there are few minor gotcha's but easy enough to sort if one is patient enough.

The GOTCHAS:
- Your wiring from Batt to Bank Busbars "must" be equal length !
- Your BMS settings need to match & be identical (preferably same BMS, that really makes a difference {easier})
- You "must" calibrate & compensate for voltage drop & losses so that charge/discharge cutoff points are correct to 0.1V. Every Terminal, Lug, Fuse/Breaker etc adds resistance & contributes to looses, even wire length & improper gauge are contributors at address. This basically means that you have to correct & adjust your settings in devices & BMS'. A high quality Digital Mutimeter that is 2 Decimal Accurate is needed for this.

3/4 of the problems people encounter when setting up a Battery Bank is a direct result of not calibrating or doing it improperly. It is "critical" to get that right. If the Battery Pack at the terminals reads 50V the Solar Controller(s) & Inverter/Charger system must also see that as 50V and not 50.1V or 49.8 V. All Lithium Chemistries are MilliVolt & MilliOhm sensitive unlike Lead Acid (brute force tech of old).

Battery RACKS designed for 6 packs usually provide a bus for 6 packs. As shown in images of Post #2, the top one with Busbars is the Correct way to do that... (+) & (-) are attached at opposite ends.

Hope it helps, Good Luck.

 

[Stotts47]

I must point out that several of us run with 6 Packs up to 10 Packs in ONE BANK ! I'm one of those.
When properly & correctly wired pack balancing within the bank is NOT an issue ! HONESTLY... I have 6 280AH Hot ATM, by 13:00 hours they are existing Absorb and going to Float, by that point there "may" be 1.0 V difference between packs and typically less than 0.050V deviation between cells in the packs, A 1/2 Hour after entering float, they are all below 0.010 deviation and fully balanced at 100%.

Qualifying :
I have run my Bank with Mixxed AH Packs in a bank, 1x100AH, 2x175AH, 3x280AH and even that worked exactly as expected, of course with the math being done and settings tweaked. Belive me that there are few minor gotcha's but easy enough to sort if one is patient enough.

The GOTCHAS:
- Your wiring from Batt to Bank Busbars "must" be equal length !
- Your BMS settings need to match & be identical (preferably same BMS, that really makes a difference {easier})
- You "must" calibrate & compensate for voltage drop & losses so that charge/discharge cutoff points are correct to 0.1V. Every Terminal, Lug, Fuse/Breaker etc adds resistance & contributes to looses, even wire length & improper gauge are contributors at address. This basically means that you have to correct & adjust your settings in devices & BMS'. A high quality Digital Mutimeter that is 2 Decimal Accurate is needed for this.

3/4 of the problems people encounter when setting up a Battery Bank is a direct result of not calibrating or doing it improperly. It is "critical" to get that right. If the Battery Pack at the terminals reads 50V the Solar Controller(s) & Inverter/Charger system must also see that as 50V and not 50.1V or 49.8 V. All Lithium Chemistries are MilliVolt & MilliOhm sensitive unlike Lead Acid (brute force tech of old).

Battery RACKS designed for 6 packs usually provide a bus for 6 packs. As shown in images of Post #2, the top one with Busbars is the Correct way to do that... (+) & (-) are attached at opposite ends.

Hope it helps, Good Luck.

I am afraid this might be above by paygrade, but I really appreciate the advice.

 

[Stotts47]

So I just received a response from Signature Solar telling me to just go ahead and attached 6 Lifepower4 batteries in one bank to the Powerpro, saying that the Powerpro will discharge at the rate of three batteries to compensate. Not sure what this means or why it's suddenly OK.

@EG4_Jared can you please clarify on how best to set this up. I have 6 LIfePower4's, 1 PowerPro, and an 18kvp. Also any setting or firmware updates that need to happen on the 18kvp or Powerpro? Two banks of 3 LIfepower4s connected to the powerpro busbar, or?

 

[SignatureSolarJess]

This is possible, it just won't be 100% perfect.

 

[Stotts47]

This is possible, it just won't be 100% perfect.

Possible how? I can't get anyone to actually give me specific instructions on how to wire everything and what settings. I keep getting general non-specific answers that keep changing and conflicting each other depending on who I talk to. Two banks of 3 LifePower, or one bank of 6? Connected to the inverter or connected to the PowerPro? I am told I need to use the coms for both banks, how do I do this, there is only one com port on the 18kvp. I also think I need some special com cable to connect the 18kvp to the LIfePower4 bank, what's it called and where do I get it? How do I connect two different banks coms to one com port? Do I need to change discharge settings? I received most of this stuff around Jan 27th or earlier, does the firmware, etc. need to be updated on anything, I haven't. How do I update the inverter firmware with a laptop or do I have to have the app? Where do I even get the app, I have no cell signal at my property. Please help

 

[SparkyGage]

(NOTE: I wrote this before SigSol responded, but I think its still pertinent to the discussion.)

So lets talk about what goes one with a rack mount battery:

• In terms of circuit logic, the batteries connected to the buss bars are ONE BATTERY.
• The "rack" is a framework to support the batteries and ancillary equipment. All the items in the rack are grounded together to prevent static discharges and "noise" from affecting the electronics within the rack.
• The battery terminals and buss bars are an isolated system "floating" within the rack. The power to feed them and the power drawn from them does not contact the rack. There is no flow of current from the batteries and buss bar to the rack. And if there is, they will likely have a closed casket at your wake. ("Here lies Sparky who didn't properly isolate his batteries")
• While the grounding of the rack becomes an emergency "dump" for AC power in the event of a short circuit, it is NOT an emergency dump for the DC from the battery as that would likely cause "an event" with the batteries. Fuses are our friends.

If the buss bars are properly isolated from banks (ideally a distance of a few inches and a physical insulating barrier of a non conductive material like glass, PVC, or HDPE) it is not an issue. My racks at work are bolted together, so if some rouge current hits one, its hitting the whole thing - to any current, this is ONE giant rack.

(Something that I've seen a lot of on this site that has bothered me is that I've seen a lot of systems with exposed buss bars. Systems where a conductor could make contact with a buss bar and the rack. Even there it shouldn't matter if it's only a positive or negative, but still "shouldn't" isn't as good as "can't". It's not that the insulation needs to be all that thick Most wires in a 48v DC and under system only have shielding on the wires of 2mm or less. It's only when you get to higher voltage that you really get a spark that wants to jump through the air. My understanding is Amps kill and Volts spark.)

So, in my main office, my racks can each hold 20K easy, but because they are bolted together, that would be 40K total in the physical rack. But that would still be 2 isolated 20k systems.

What my comment hasn't address so far: if you connect one pack to another, whether series or parallel, you are creating ONE BIG BATTERY. If you connect to them to the same inverter, then you have not isolated them. If you connect them in parallel, the balancing of one pack WILL affect the balancing of the other as they will want to balance with each other. How that plays out in the real world will depend on the design of the individual batteries in the pack as well as where they physically meet in the circuit.

So my takeaway: two or more "banks" in one rack that do not interact with each other doesn't scare me. Running more than the manufacturers accepted number of battery packs in one bank does. YMMV.

And a gratuitous photo of my HAL3000. He's not as smart as the HAL9000, but he hasn't locked me out of the office....yet.....

 

[42OhmsPA]

Possible how?

See attached, I'd also add a disconnect between the inverter and bus bar.
I'm no expert, just really bored at work.
Sorry my quick drawing isn't as good as something from @FilterGuy .

 

[SignatureSolarJess]

See attached, I'd also add a disconnect between the inverter and bus bar.
I'm no expert, just really bored at work.
Sorry my quick drawing isn't as good as something from @FilterGuy .

This is a good little drawing of it! If you'd like to send me a DM with your email address, I can get your questions escalated and have someone reach out to talk through it with you a little more. @Stotts47

 

[Stotts47]

This is a good little drawing of it! If you'd like to send me a DM with your email address, I can get your questions escalated and have someone reach out to talk through it with you a little more. @Stotts47

So you just wire everything in parallel as one big battery, OK, how does this address the balancing issue? How do you hook up the coms for two different banks to one com port? And where do I get the special wire for connecting the coms on the the Lifepower4 bank, video on EG4 website said you could not use a standard com cable to hook the Lifepower4s to the 18kvp.

 

[SparkyGage]

See attached, I'd also add a disconnect between the inverter and bus bar.
I'm no expert, just really bored at work.
Sorry my quick drawing isn't as good as something from @FilterGuy .

That looks like a balancing nightmare. The 280 will be flat before the 600 (and if I'm not mistaken, the system will act like a 600 and a 280) and charging will be just as wonky.

 

[42OhmsPA]

That looks like a balancing nightmare.

I don't think so.

The 280 will be flat before the 600

I would hope so.

(and if I'm not mistaken, the system will act like a 600 and a 280) and charging will be just as wonky.

I disagree. Assuming wiring to the bus bar is equal length and resistance is the same (no bad connections) I really don't see any issues.

It shouldn't matter if the PowerPro goes empty first, the 6 server rack shouldn't see more than 0.5C rates if everything is wired correctly.

My current setup is two 230Ah and one 305Ah pack in parallel, I don't have any issues. My next expansion will consist of of two 460Ah, one 230Ah and one 305Ah in parallel, I don't expect any issues.

@Stotts47 I can't help you with communications, I only run open loop. I would absolutely use 4/0 between the server rack stack, Powerpro, bus bar and inverter; I didn't specify that earlier.

 

[DIYrich]

So you just wire everything in parallel as one big battery,

yes.

OK, how does this address the balancing issue?

the batteries will work proportionately. Roughly 2/3 of the power goes to/from the 600 ah rach, and 1/3 comes from the 280ah.

They stay in balance because of the physics of voltage. They all have to see the same voltage. Plus/minus the difference in cable/busbar.

How do you hook up the coms for two different banks to one com port?

You don't. Like trying to attach 2 keyboards to the same usb slot. The inverter has to be designed to support more than one battery type, and they usually are not. Solar Assistant might be, but inverters are not.