Changing my battery bank to Midnite Solar Powerflo5 batteries...input requested.

[AH Trimble]

Here is what I am trying to accomplish with this thread: Properly replace my existing battery bank with a matched set of LifePo4 batteries; with those batteries connected to each other and to my existing system for a closed-loop communications system resulting in increased efficiency and stability.

I am hoping to get feedback from folks as to what I am thinking for the new configuration, cabling, etc. All thoughts, issues, concerns, and/or questions will be appreciated. I am sincerely hoping to get it right the first time.

Existing system:

• 100% off-grid
• 5.5kw of PVs
• 10kw of inverter power
• 32.7kwh of LifePo4 batteries
  

Existing Equipment:

• Canadian Solar PV’s (primarily, 4.7kw out of the 5.5kw)
• 2 x 150/70 Victron MPPTs (master/slave configuration, connected to GX via “ve.direct) port
• 2 x Victron Quattro 5K/120v/70a (split-phase configuration, comms daisy chained connected to GX via “ve.bus” port)
• Color Control GX “brain”
• Victron Lynx Shunt connected to the GX “ve.can” port
• 2x205ah LifePo Elite batteries + 1x 230ah LifePo Trophy battery (none of the batteries are comm connected to each other and not connected to the GX)
  

Notes:

• I am using a 1000a Victron PowerIn as my busbar for the batteries.
• Each battery is currently wired to the busbar with a battery switch to isolate the battery from the busbar. I am using 2/0 for each battery, 4/0 busbar to shunt.
• I have a 400a Class T fuse between the busbar and the Victron Shunt.
  

New Equipment:

• 8 x Midnite Solar Powerflo5 batteries (replacing all existing batteries)
  

Why replace my existing batteries? 1) I want a bit more power reserve, 2) I want matched batteries, 3) local support, 4) potential efficiency improvement through battery-to-battery and battery-to-system comms. And as a bonus...they are brand new

Why Powerflo5 batteries? 1) great reviews and great name recognition, 2) got a killer deal from a local supplier, 3) have used MidNite products for years with zero failures or problems.

Proposed battery configuration:

• 4 ‘banks’ of batteries paralleled to 1000a busbar (Victron PowerIn)
• each ‘bank’ will be 2 batteries wired in parallel
  

First question: Does anyone see an issue with 4 banks wired in parallel, of 2 batteries each wired in parallel?

Second question: #2awg terminals are included in the box with the battery. I thought it might be a mistake...until I started doing some math and research. The batteries are 75a nominal and 100a maximum charge/discharge. Considering my cable runs are <5’, that means #4awg is sufficient, #2awg is a nice safety margin. Each battery has a built-in BMS shut down at 100a, plus a 125a circuit breaker. And if I am reading the charts right, a 125a breaker will protect a <5’ run of #2awg just fine. Even with 2 batteries in a bank it appears that #2awg will be just fine. So each battery in a bank will be connected to each other via #2awg, and the bank will be connected to the busbar via #2awg as well. Any thoughts?

Third question: Since each battery has a circuit breaker, it also acts to isolate the battery from the busbar. And turning off both batteries isolates that bank from the busbar. That means no need for a battery switch for either a battery or the bank. Agree or thoughts?

Fourth question: Since each battery has a circuit breaker there is no need for any fusing between the battery and the busbar or between batteries. Agreed or thoughts?

Fifth question: Even with 4 ‘banks’ I plan on daisy-chaining all 8 batteries via the comm ports. The Pylontech BMS software will ID the master which will be hooked to the CC-GX “ve.can” port. Even though there are technically 4 banks, each battery will still be communicating properly with the master if I am thinking it through correctly. Any thoughts or potential problems with this?

Sixth question: Since I will be connecting the ‘master’ battery to the CC-GX ve.can port (after removing the Victron Shunt cable from the CC-GX) and enabling BMS control (which automatically enables DVCC) there is no longer a need at all for the Victron Shunt. Agreed or thoughts?

Seventh question: Since the CC-GX is an earlier, and more primitive version, of the Cerbo GX, does anyone see problem using the CC-GX vs the Cerbo GX? They both use the “ve.can” ports and both support DVCC.

Open forum: I would sincerely appreciate any additional thoughts, potential issues, possible problems, or any questions from folks regarding this upcoming change. Please feel free to join in!

 

[sunshine_eggo]

Why replace my existing batteries? 1) I want a bit more power reserve, 2) I want matched batteries, 3) local support, 4) potential efficiency improvement through battery-to-battery and battery-to-system comms. And as a bonus...they are brand new

Replacement means you aren't accomplishing 1) to the fullest extent, i.e., if you want more reserve, you should use what you have.

#2 has no technical basis and is simply a preference.

3) you have local support with Trophy.

4) There will be no efficiency gain.

First question: Does anyone see an issue with 4 banks wired in parallel, of 2 batteries each wired in parallel?

Nope.

Second question: #2awg terminals are included in the box with the battery. I thought it might be a mistake...until I started doing some math and research. The batteries are 75a nominal and 100a maximum charge/discharge. Considering my cable runs are <5’, that means #4awg is sufficient, #2awg is a nice safety margin. Each battery has a built-in BMS shut down at 100a, plus a 125a circuit breaker. And if I am reading the charts right, a 125a breaker will protect a <5’ run of #2awg just fine. Even with 2 batteries in a bank it appears that #2awg will be just fine. So each battery in a bank will be connected to each other via #2awg, and the bank will be connected to the busbar via #2awg as well. Any thoughts?

I'd stick with 2awg.

Third question: Since each battery has a circuit breaker, it also acts to isolate the battery from the busbar. And turning off both batteries isolates that bank from the busbar. That means no need for a battery switch for either a battery or the bank. Agree or thoughts?

I would be okay with this, but a single physical isolator between the bank and system is desirable.

Fourth question: Since each battery has a circuit breaker there is no need for any fusing between the battery and the busbar or between batteries. Agreed or thoughts?

The best practices bunch says don't trust just the breaker and use one Class-T per battery. Given Midnite's reputation for awesome breakers, I might consider trusting the breakers.

Fifth question: Even with 4 ‘banks’ I plan on daisy-chaining all 8 batteries via the comm ports. The Pylontech BMS software will ID the master which will be hooked to the CC-GX “ve.can” port. Even though there are technically 4 banks, each battery will still be communicating properly with the master if I am thinking it through correctly. Any thoughts or potential problems with this?

No issues.

Sixth question: Since I will be connecting the ‘master’ battery to the CC-GX ve.can port (after removing the Victron Shunt cable from the CC-GX) and enabling BMS control (which automatically enables DVCC) there is no longer a need at all for the Victron Shunt. Agreed or thoughts?

Not a fan of the Lynx, and without VE.Can, it can't interface with the system, BUT I still like having my BMV-702 sanity checking my Batrium SoC, current and voltage values.

Seventh question: Since the CC-GX is an earlier, and more primitive version, of the Cerbo GX, does anyone see problem using the CC-GX vs the Cerbo GX? They both use the “ve.can” ports and both support DVCC.

I have a CCGX, and I will likely upgrade to a Cerbo GX though run headless when I add VE.Can MPPT. You should be fine though.

Open forum: I would sincerely appreciate any additional thoughts, potential issues, possible problems, or any questions from folks regarding this upcoming change. Please feel free to join in!

Use all the LFP you have. Wait a minute. I'm concerned you may have heard me say, "use a lot of LFP," but what I said is, "use ALL of the LFP you have." (Ron Swanson)

 

[AH Trimble]

First off...a huge thank you for the feedback. I really appreciate it.

Here's what I was thinking...

• You are correct, I am going from 690ah to 800ah. Just a 110ah/5.6kwh upgrade, only 16% boost. What I was thinking was; 1) all new batteries, 2) all communicating with each other, 3) communicating with the system, 4) local vendor to back the battery warranty.
• No local support for the Trophy, great phone support, great warranty, relatively new company. The Elites have no support and no warranty.
• "There will be no efficiency gain." Explain? Everything I have read, there should be. But I am a total novice at the whole comms thing.
• "single physical isolator" What do you recommend?
• I considered each battery with a Class T but like you I trust Midnite breakers. And it would run another $800 to Class T fuse (Blue Sea) each battery with a 200a fuse and block. Budget is kinda tight right now.
• I would love to upgrade to a Cerbo too but just can't do it in this upgrade. The ve.can on the CC-GX should handle the master battery comm connection, yes?
• I still have my old BMV-712 sitting in a drawer. I didn't consider integrating into the the new system. Thoughts?
• As for "use ALL of the LFP you have"...I agree 100% ! ! ! The downside for me right now is cost. I am doing a trade for first/new 2 of the 8, I am selling my current batteries to pay for the other 6 plus cabling, etc. I had considered just adding the "trade for 2" but then thought why not upgrade to all new and incorporate the comms. And as a bonus I get better warranty coverage overall. Your opinion?

And thank you again!! I appreciate your extensive knowledge of Victron...and all things solar.

 

[sunshine_eggo]

• "There will be no efficiency gain." Explain? Everything I have read, there should be. But I am a total novice at the whole comms thing.

I define efficiency as energy in vs. energy out. There will be no difference.

How do you define efficiency?

• "single physical isolator" What do you recommend?

As many of these as you need:

https://www.victronenergy.com/upload/documents/Datasheet-Battery-Switch-275-A-EN.pdf

• I would love to upgrade to a Cerbo too but just can't do it in this upgrade. The ve.can on the CC-GX should handle the master battery comm connection, yes?

Yes. You just change it to 500kbps, and it should work. Works fine with my Batrium.

• I still have my old BMV-712 sitting in a drawer. I didn't consider integrating into the the new system. Thoughts?

I would.

• As for "use ALL of the LFP you have"...I agree 100% ! ! ! The downside for me right now is cost. I am doing a trade for first/new 2 of the 8, I am selling my current batteries to pay for the other 6 plus cabling, etc. I had considered just adding the "trade for 2" but then thought why not upgrade to all new and incorporate the comms. And as a bonus I get better warranty coverage overall. Your opinion?

That's different. If you're funding new with the old, then you're using it, just not for capacity.

 

[AH Trimble]

• I'll go with your "efficiency". Now, share your opinion on this...Just connect the batteries' comms together and not to the system? Here is my concern...Midnite warranty exclusion "Damages incurred from voltage or current spikes due to open-loop lithium battery communications." Your thoughts?
• Victron Battery switch 275A...sounds good. Just one between the batteries and system? I already have a Blue Sea Systems 6006200 m-Series Battery Switch (300a/48v). Do you think that would work instead?
• So I could install the BMV-712 in my CC-GX case sitting in the drawer next to the 712...along with the CC-GX. Connect the 712 to the open ve.direct on the CC-GX. Then I would install the SmartShunt back into the system but I could take the Victron Lynx Shunt out of the system. Yes? Bottom line...the 712/SmartShunt replaces the Lynx shunt? But no connection to the batteries because there is no benefit?

You are a gold mine of knowledge and help! !

 

[sunshine_eggo]

• I'll go with your "efficiency". Now, share your opinion on this...Just connect the batteries' comms together and not to the system? Here is my concern...Midnite warranty exclusion "Damages incurred from voltage or current spikes due to open-loop lithium battery communications." Your thoughts?

Standard CYA. Open or closed loop, the BMS should protect the battery.

• Victron Battery switch 275A...sounds good. Just one between the batteries and system? I already have a Blue Sea Systems 6006200 m-Series Battery Switch (300a/48v). Do you think that would work instead?

275A may not cover it all. I selected it because it gives a 60V max voltage vs. the ambiguity when they say "48V". If Blue Sea says, "48V system voltage" then yes. Unfortunately, it says "max voltage."

• So I could install the BMV-712 in my CC-GX case sitting in the drawer next to the 712...along with the CC-GX. Connect the 712 to the open ve.direct on the CC-GX.

Yes

• Then I would install the SmartShunt back into the system but I could take the Victron Lynx Shunt out of the system. Yes? Bottom line...the 712/SmartShunt replaces the Lynx shunt? But no connection to the batteries because there is no benefit?

Yes. It's just a secondary shunt to sanity check what the BMS is reporting for the bank.

You are a gold mine of knowledge and help! !

Watch out for iron pyrite!

 

[AH Trimble]

Dang, the Victron spec sheet says 60v maximum voltage, but their Amazon listing shows 48v "operating voltage". Missed that one. I did email Blue Sea to see if it was the same issue "operating" vs "maximum".

Bluntly speaking...Would you bother to connect the battery bank to the system? If there is no real advantage, then why go to the trouble...or rather, why ask for trouble?

"Watch out for iron pyrite!" Now that's funny...but you are not capable of that...pure gold

 

[sunshine_eggo]

Dang, the Victron spec sheet says 60v maximum voltage, but their Amazon listing shows 48v "operating voltage". Missed that one. I did email Blue Sea to see if it was the same issue "operating" vs "maximum".

Confession: I have a 600A 48V blue sea on my system, but I rarely exceed 120A, so I'm pretending it's fine.

Bluntly speaking...Would you bother to connect the battery bank to the system? If there is no real advantage, then why go to the trouble...or rather, why ask for trouble?

For comms? Yes. VRM logs available battery data, and the BMS protections are "softer," i.e., rather than the BMS just cutting itself out of the circuit abruptly, CCL is reduced in stages "throttling" the system instead.

The big ?? is if the batteries are imbalanced, and I suspect that at least one will be. In some cases, closed-loop can slow/cripple the balancing process, but this is about BMS programming. If you can alter the balancing parameters, you can easily get there with closed-loop.

"Watch out for iron pyrite!" Now that's funny...but you are not capable of that...pure gold

A polished turd is still a turd.

 

[AH Trimble]

"Confession: I have a 600A 48V blue sea on my system, but I rarely exceed 120A, so I'm pretending it's fine."

Using Ohm's Law the switch is actually rated for 14.4kw. You've not used more than about 6.2kw. So you should be fine!!!!
Now that there is "iron pyrite"

 

[AH Trimble]

Man, can you learn a whole lot talking to company tech experts!!!

I just spoke to Rick at MidNite, he is the MidNite PowerFlo5 tech expert. We talked through the cable issue in detail. Bottom line, a Victron Type A cable is the one to use. Although, technically/theoretically either cable will work. Why? He said that the battery side doesn't use a "GND". So as long as Victron VE.CAN pin 8 matches battery side CAN pin 5 (low) and VE.CAN pin 7 matches battery side CAN pin 4 (high)...it should work.

Or, I imagine, a properly custom made cable with VE.CAN pin 8 matches battery side CAN pin 5 (low) and VE.CAN pin 7 matches battery side CAN pin 4 (high) and no "GND"...it should work.




I hope that helps. I know for me, I will just buy a Victron VE.Can to CAN-bus BMS Type A cable and not worry about making my own.

He did mention that the following:

1. Make sure the master battery "link out" connects to the "link in" on battery #2.
2. He said to test the battery comms by having all the batteries turned off. Then turn on the master battery via the power button. The other BMS's should turn on automatically once the master is cycled on. This with the circuit breakers turned off. NOTE: I guess the battery BMS's will turn on even with the breakers turned off (which makes sense). I will do this test prior to connecting the master battery (BMS) CAN to my CCGX ve.can port. That way I will know the batteries are all connected together correctly. Then shut them down, connect the can cable, and go through the manual's power on sequence.

I also asked if it was acceptable to power connect 4 batteries together in parallel into a set/bank, then power connect two sets/banks in parallel to a busbar...and have all 8 batteries comm connected/linked together and connected to my CCGX. He said yes.

I also looked at the Victron Lynx Class T unit. I like the unit and I like the way it would connect to my Victron PowerIn (used for distribution: inverters and MPPTs). Each battery bank would be protected separately with a Class T, I really like that idea. I am going to eliminate a battery isolating switch altogether. I just don't see a need for it. If I need to do work I can use my transfer switch and put the house on my genset. And for simplicity sake I am going to eliminate the idea of a Victron BMV-712 and shunt. The battery BMS/ve.can connection will provide the SoC through the VRM portal and I can visually verify it within an acceptable range by the master battery SoC lights. My installation doesn't require a more accurate or more verified SoC number...and I don't see the need for the functioality of a BMV-712.

Here is a quick view of my proposed battery upgrade...



Any thoughts?