Question about parallel battery Banks and how to properly link them

[ericfx1984]

Okay.. so I have a question about parallel battery Banks...

I am going to be building a pair of 4s, 230 amp hour Eve cells (so a total of 8 cells)

Each one of these 4S packs will have a 200 amp BMS

The plan is to join the BMS positive outputs together.. so I'm wondering should I have a jumper of appropriate size connected to the BMS and then jumping over to the other BMS? And then running my leads off from there or should I purchase or build a bus bar that can handle in theory 400 amps? I figure I can make one out of either copper or potentially aluminum but I'd like to avoid aluminum...

I guess what I'm asking is what is the best way to link parallel bms's?

Another way that I was thinking I might be able to make this work is to simply run two separate lines, one off of each BMS directly to the inverter.. in the middle of that I will have a 200 amp ANL fuse on the inverter side of the ANL fuse

 

[Samsonite801]

I have the same type of battery I built, 4s2p. Just so you know, the BMS is wired on the negative side of the 4s battery pack. On mine, I put breakers on both of the positives for easy disconnecting of each bank. I try to keep all my wire lengths the same across both packs so they theoretically act like symmetrical system together (charge and discharge at same rates in relation to each other).

I am bridging them together on a single terminal using a Blue Sea Systems selector switch.

(w/ AFD Feature):

Amazon.com : Blue Sea Systems 3003 Heavy Duty Battery Switch with Alternator Field Disconnect, 1-2-Off-Both : Boating Battery Switches : Sports & Outdoors

Amazon.com : Blue Sea Systems 3003 Heavy Duty Battery Switch with Alternator Field Disconnect, 1-2-Off-Both : Boating Battery Switches : Sports & Outdoors

www.amazon.com

(One w/o AFD Feature):

Amazon.com : Blue Sea Systems HD Battery SELECTOR 4POS : Boating Battery Switches : Sports & Outdoors

Amazon.com : Blue Sea Systems HD Battery SELECTOR 4POS : Boating Battery Switches : Sports & Outdoors

www.amazon.com

While one could bridge them at a switch of this type (Blue Sea Systems selector switch), putting Terminal 1 going to one 4s pack, and Terminal 2 going to other 4s pack, I am not.

I am bridging on Terminal 2 with both LFP cables joining there, while Terminal 1 of the selector switch runs to my old SLA battery bank on the motorhome (just the way I decided to do it)... Mainly so I can select which bank (LFP vs SLA bank), I can connect to the house / cabin loads on the motorhome.

Here is a picture showing just one side of my 'dual' bank, the other side you can't see looks identical to this side. I don't have any newer pictures of the install yet so I can't show any more of the cabling I am doing yet.

 

[HRTKD]

My preference is to use a set of common bus bars like the ones linked below (this is not an endorsement of those specific bus bars, they're just an example).

Wire each battery to the bus bar, do not wire each battery to the other.

Large 4 Post Terminal Connector Busbar 250 Amps with Cover

www.batterycablesusa.com

There's usually more to this than a direct connection.

Battery (Positive) -> Fuse -> Switch -> Common Bus Bar (Positive)
Battery/BMS (Negative) -> Shunt -> Common Bus Bar (Negative)

 

[Samsonite801]

My preference is to use a set of common bus bars like the ones linked below (this is not an endorsement of those specific bus bars, they're just an example).

Wire each battery to the bus bar, do not wire each battery to the other.

Large 4 Post Terminal Connector Busbar 250 Amps with Cover

www.batterycablesusa.com

There's usually more to this than a direct connection.

Battery (Positive) -> Fuse -> Switch -> Common Bus Bar (Positive)
Battery/BMS (Negative) -> Shunt -> Common Bus Bar (Negative)

Yeah that is a great way to bridge them, can even add more banks if you want...

 

[Jbbonnette]

I have the same type of battery I built, 4s2p. Just so you know, the BMS is wired on the negative side of the 4s battery pack. On mine, I put breakers on both of the positives for easy disconnecting of each bank. I try to keep all my wire lengths the same across both packs so they theoretically act like symmetrical system together (charge and discharge at same rates in relation to each other).

I am bridging them together on a single terminal using a Blue Sea Systems selector switch.

(w/ AFD Feature):

Amazon.com : Blue Sea Systems 3003 Heavy Duty Battery Switch with Alternator Field Disconnect, 1-2-Off-Both : Boating Battery Switches : Sports & Outdoors

Amazon.com : Blue Sea Systems 3003 Heavy Duty Battery Switch with Alternator Field Disconnect, 1-2-Off-Both : Boating Battery Switches : Sports & Outdoors

www.amazon.com

(One w/o AFD Feature):

Amazon.com : Blue Sea Systems HD Battery SELECTOR 4POS : Boating Battery Switches : Sports & Outdoors

Amazon.com : Blue Sea Systems HD Battery SELECTOR 4POS : Boating Battery Switches : Sports & Outdoors

www.amazon.com

While one could bridge them at a switch of this type (Blue Sea Systems selector switch), putting Terminal 1 going to one 4s pack, and Terminal 2 going to other 4s pack, I am not.

I am bridging on Terminal 2 with both LFP cables joining there, while Terminal 1 of the selector switch runs to my old SLA battery bank on the motorhome (just the way I decided to do it)... Mainly so I can select which bank (LFP vs SLA bank), I can connect to the house / cabin loads on the motorhome.

Here is a picture showing just one side of my 'dual' bank, the other side you can't see looks identical to this side. I don't have any newer pictures of the install yet so I can't show any more of the cabling I am doing yet.

View attachment 75958

Damn! that's a great looking battery. Good job! So clean!

 

[S Davis]

I run my two 12v 280ah to a battery switch and then to a 600amp buss bar, I can combine the two or run one at a time or both off.