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08-12-2022, 05:15 PM #1
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Why You Should Use Buss Bars in your Multi Battery Installation
There are several reasons to connect multiple batteries using Buss Bars instead of "Daisy Chaining" them together.
In the PDF attached (below) is a research paper that explains the electrical draw from each battery using various "Daisy Chaining" methods versus using Buss Bars to connect the batteries to the load and how Buss Bars even out the load on each battery.
Here is a Video explaining the advantages of using Buss Bars by analyzing an installation using "Daisy Chaining" and a new configuration using Buss Bars.
Note: pay special attention to the temperature differentials...
https://www.youtube.com/watch?v=eWqJjlHoW9A
PS: in order to make this post more useful in planning your installation, I have also attached a Wire sizing chart for your reference...David and Peggy
2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
2018 Solitude 310 GK
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08-13-2022, 07:07 AM #2
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David,
As you know from my recent thread, I'm adding two more BBs for a total of four. I asked BB about a bus bar vs. jumpers and their response was, with just four batteries, to tie the load(s) to one of the middle two batteries and it will be fine for that few batteries. Was this poor advice in your opinion? If so, I need to order some more parts before I start the installation...
RobU.S. Army Retired
2012 F350 DRW CC LB Lariat PS 6.7
2020 Solitude 310GK-R, MORryde IS, disc brakes,
Sailun LRG tires, solar, DP windows, W/D
(Previously in a Reflection 337RLS)
Full time since 08/2015
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08-13-2022, 07:39 AM #3
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Installing the Victron 712, I called BB to confirm the connection recommendation for two batteries. The picture BB sent is below and was their recommended parallel install with Victron connection. My positive and negative ends do go to bus bars but the implication was that for the Victron to correctly monitor, it needed to be the only connection on last in line battery. I didn't ask about 4 batteries though I am thinking about adding another 200ah.
Robin & John
2020 Ram 3500 LB SRW 4WD Crew Laramie 6.7HO Aisin, 55gal Titan
2022 Solitude 310GK-R - Dual pane, factory solar & Onan, 8K axles with discs, 18K GVWR, W/D, Heat Pump, Goosebox, Battleborn
2023 stays
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08-13-2022, 08:17 AM #4
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Rob,
I can provide a little theory behind wire gauge size vs. bus bar.
Wire that carries current has increasing resitive properties as the current increase; this is due to several different electrical properties of the wire (which I won't get in to). Resistance manifests itself as heat and as the name implies, resists current flow; resistance of current flow also has a byproduct of reducing the voltage flow. For example, lets say we are putting 12VDC at 100 amps down a copper wire with a standard resistivity of 1.72e-8 megohms. It is travelling 12 inches. The voltage drop for an 18 AWG wire is 1.27394 volts; for a 4 AWG wire, the voltage drop is 0.0495735 volts; and for a 4/0 wire, the voltage drop is 0.00977913 volts, almost non-existent.
A bus bar is similar and calculated as to a solid piece of 4/0 wire, however, you can have multiple connection points along the bus bar and still have the circuit see it as a single point connection.
What Battleborn is saying is with a sufficiently large wire gauge, connecting it to the middle of the battery bank, is electrically similar to a bus bar, with a "small" number of batteries (I would assume 4 or less). This is true that it is similar to a bus bar, but the limiting factors are cost, future expansion, ease of replacement, loss of Ah because one cable or battery failed.
A picture is worth a thousand words.
Last edited by MoonShadow_1911; 08-13-2022 at 08:19 AM.
Mark & Mary. Full-timing across the USA (and Canada)!
Current Coach: 2021 Grand Design Reflection 320MKS
Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel
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08-13-2022, 08:32 AM #5
Last edited by huntindog; 08-13-2022 at 08:35 AM.
2021 398M Full Body Paint 8k axles. LRH tires. Disc brakes.
Two bathrooms, no waiting 155 fresh, 104 black, 104 grey 1860 watts solar.
800AH BattleBorn Batteries No campgrounds 100% boondocking
2020 Silverado High Country 3500 dually crewcab Duramax Allison
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08-13-2022, 08:41 AM #6
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Thanks @SolarPoweredRV, the article you posted is where I learned what I needed to decide on a busbar installation. The video confirmed what I've observed in practice, no observable increase in temperature on the cables and nodes while the inverter is in operation (and thus higher efficiency).
The busbar also helped with another issue. The BMS on my batteries limited them to 100 Amps. So in a daisy chain setup, my understanding (I didn't try it) is that the BMS on the last battery in the chain would limit the entire battery bank to just 100 Amps at a time, not good for me since I have an inverter that can easily pull more than 100 Amps.
Yes, the busbar takes more room and was a little less tidy than a daisy chain, but the results speak for themselves (I'm very happy with the way my setup works).Stephen and Judy
2022 Reflection 150 Series 260RD (Stella)
2017 Chevy Silverado 2500 HD (Blue)
Traded - 2018 Forest River Rockwood Minilite 2104S
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08-13-2022, 08:47 AM #7
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08-13-2022, 09:01 AM #8
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@MoonShadow_1911, could you comment about cable size when using a busbar setup? I (probably incorrectly) assumed that all cables in the system should be capable of carrying the max expected load (300 Amps) and so I used 4/0 cables from the batteries to the busbar and from the busbar to the fuse and shunt on the load size. I've seen elsewhere the suggestion that smaller cables would be sufficient for the connections between the batteries and the busbar. Is that correct in your estimation? I'm personally not sorry to use heavier cables, but they do cost more and probably were not necessary.
Stephen and Judy
2022 Reflection 150 Series 260RD (Stella)
2017 Chevy Silverado 2500 HD (Blue)
Traded - 2018 Forest River Rockwood Minilite 2104S
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08-13-2022, 09:09 AM #9
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Taking the load off of the two middle batteries would be fine, however, by adding two extra cables to your battery bank, you can achieve the same results as you would get by using the Buss Bars. I am referring to method 4 in the research paper linked above.
Bottom line, unless you are running your Air Conditioner, taking the load from the two middle batteries (Method 4 in the research paper above, without the long wires added) is definitely better than the typical "Daisy Chain" installation that is very common in RV battery bank installations.
If you are planning to run your A/C from your Inverter, I would definitely recommend using the Buss Bar installation method.David and Peggy
2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
2018 Solitude 310 GK
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08-13-2022, 09:26 AM #10
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@MoonShadow_1911 Same question as I also ran 4/0 but only because the factory had 4/0 to the inverter. In your diagram it appears that if you lose the load side battery, you lose the capacity of anything behind it without bus bars?
Robin & John
2020 Ram 3500 LB SRW 4WD Crew Laramie 6.7HO Aisin, 55gal Titan
2022 Solitude 310GK-R - Dual pane, factory solar & Onan, 8K axles with discs, 18K GVWR, W/D, Heat Pump, Goosebox, Battleborn
2023 stays
Breakaway Switch Question
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