Parallel connecting four 48v 100AH batteries - cables or busbar

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
I'm planning on paralleling four LifePower 48V 100AH rack mount batteries. My original plan was to make a bunch of cables for them from 4/0. The terminals allow cables to run up/down so my plan was to run from one terminal to the next in the rack. BUT... recent Will video he mentioned, "of course if you were using more than one battery, you might want to use a busbar" - is he suggesting running everything to a busbar with terminals (which I have seen but don't see a huge advantage) OR is the suggestion to get copper stock, drill out where terminals are, and "hard connect" all the batteries.

Searchs for "busbar" mainly turned up the former. For those who have made busbars to connect their batteries, what did you use for insulation for the exposed copper between batteries?
 

robby

Photon Vampire
Joined
May 1, 2021
Messages
1,740
Use a Busbar!
I did not use anything to shield the exposed copper, but it is already inside a case so for my setup it was not needed.
I used these. They come with covers so in your case that may be perfect. I did not need the covers so I dumped them.
Victron
 

JWLV

One Million Dollars!
Joined
May 27, 2020
Messages
136
I use busbars whenever possible. But sometimes it's not so easy to get the batteries in the right position/orientation to connect busbars. Cables are much easier since you can bend them, loop them, do whatever you want to get from point A to point B.

For insulation, I use large heat shrink tubing. I don't know if that's the proper way to insulate busbars, but that's what I use.
 

HRTKD

Boondocker
Joined
Apr 24, 2020
Messages
7,692
Location
Somewhere South of Denver
I have two 6' lengths of copper flat bar on order. If my experience is any gauge, you might want to buy off-the-shelf bus bars. I ordered in early December and nothing has shipped yet. In that same time frame, I bought a couple of Blue Sea bus bars (Power Bar 1000) and had them in my hands within a week.

I do agree with the use of a bus bar to bring all four batteries together, ensuring that the cables from each battery are the same length. Positives all the same length, negatives all the same length.
 

Biasjo

Renewable energy user - North Carolina
Joined
Dec 19, 2021
Messages
477
I'm planning on paralleling four LifePower 48V 100AH rack mount batteries. My original plan was to make a bunch of cables for them from 4/0. The terminals allow cables to run up/down so my plan was to run from one terminal to the next in the rack. BUT... recent Will video he mentioned, "of course if you were using more than one battery, you might want to use a busbar" - is he suggesting running everything to a busbar with terminals (which I have seen but don't see a huge advantage) OR is the suggestion to get copper stock, drill out where terminals are, and "hard connect" all the batteries.

Searchs for "busbar" mainly turned up the former. For those who have made busbars to connect their batteries, what did you use for insulation for the exposed copper between batteries?
I did mine this way.
It’s going to be up to your physical constraints and budget.
I used different gauge cable from Ben but used same panel and breakers.

 

robby

Photon Vampire
Joined
May 1, 2021
Messages
1,740
I did mine this way.
It’s going to be up to your physical constraints and budget.
I used different gauge cable from Ben but used same panel and breakers.

I like Ben but I disagree with that video and would never use an AC breaker for 48VDC which in this case is really 54Vdc.
AC breakers depend on Zero crossing and that does not exist with DC. You get an Arc going in that breaker and it won't matter if it fly's open. It may work and it may not but I would not take the chance.
 
Last edited:

Biasjo

Renewable energy user - North Carolina
Joined
Dec 19, 2021
Messages
477
I like Ben but I disagree with that video and would never use an AC breaker for 48VDC which in this case is really 54Vdc. AC breakers depend on Zero crossing and that does not exist with DC. You get an Arc going in that breaker and it won't matter if it is open. It may work and it may not but I would not take the chance.
It’s worked so far. 3 years and counting.
 

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
OK. Change of Plan - Can't do solid copper busbar because positive terminal is in line with breaker for each battery pack (see pic). It comes with short cables, but they are 16mm (which I think translates to 6AWG). I am putting 4 in parallel and will put a fuse off the positive for 300 Amp. I had planned on using 2/0 or 4/0, but the terminal on the battery is sooo small - looks like 1/4x20 (see the pic of the ring terminal on the wire that came with it). I guess they assume the short cables are to run a bunch in series? Not sure what to do. I had planned to make cables an crimp on ring terminals, but where will I get a ring terminal for 4/0 that fits something like 1/4x20?
 

Attachments

  • 2022-01-06 15.45.50.jpg
    2022-01-06 15.45.50.jpg
    593.4 KB · Views: 26
  • 2022-01-06 15.46.39.jpg
    2022-01-06 15.46.39.jpg
    727.2 KB · Views: 27
  • 2022-01-06 15.51.04.jpg
    2022-01-06 15.51.04.jpg
    670 KB · Views: 27

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
Cables to a bus would be my preference. Depending on conditions I would be looking to go #4 wire.

https://shop.pkys.com/Blue-Sea-2127-Maxibus-BusBar-250-Amps_p_2775.html

And get the cover for the bus.
Thanks for the link. When I originally said "busbar" I was thinking of a solid copper bar going from one terminal to the next. It there a harm in daisy chaining the connecting cables - a cable from 1+ to 2+, then a second cable from 2+ to 3+, then another from 3+ to 4+? Same for negative and then conencting cables go back to inverter from 1+ and 4-
 

RichardfromEG4

The "Do-What's-Needed" Solar Guy
Joined
Dec 23, 2021
Messages
837
Location
Sulphur Springs, TX
Our battery racks for these actually have bus bars on the side that you connect to with a short cable. That would be my recommendation - that is, get a bus bar and connect to it with short cables off-set from the battery. You don't need the battery rack itself - just the idea of the bus bar with the short cables. Here's a picture of the side and you'd just connect to it with short cables typically. I wouldn't recommend daisy chaining if you have the ability to use a busbar.

1641590114946.png
 

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
Our battery racks for these actually have bus bars on the side that you connect to with a short cable. That would be my recommendation - that is, get a bus bar and connect to it with short cables off-set from the battery. You don't need the battery rack itself - just the idea of the bus bar with the short cables. Here's a picture of the side and you'd just connect to it with short cables typically. I wouldn't recommend daisy chaining if you have the ability to use a busbar.

View attachment 78748
I guess that's tinned copper with insulators holding it on to the rack? It's nice, but...more work...
 

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
And a followup question. If I'm running to a real cupper busbar, then the cable that connects each battery to the busbar does not need to be sized for the max current (250-300Amps), but the busbar and the cables connecting them to the inverter do. The short cables that came with the battery are 6AWG. I think they can carry about 65 amps. Too small?

Edit: I did more maths (who knew solar was so math laden). If max output of the inverter is 240voltx50amp=12000 watts, then the max ciming from the battery at 48 volts is 250A, which would run on 4/0, and the max current from each battery is 62.5A which those smaller cables that came with the battery shoudl handle. All of this assumes I ignore momentary inrush/start currents. Is this reasonable?
 
Last edited:

Tony Scott

Solar Enthusiast
Joined
Feb 25, 2020
Messages
184
Our battery racks for these actually have bus bars on the side that you connect to with a short cable. That would be my recommendation - that is, get a bus bar and connect to it with short cables off-set from the battery. You don't need the battery rack itself - just the idea of the bus bar with the short cables. Here's a picture of the side and you'd just connect to it with short cables typically. I wouldn't recommend daisy chaining if you have the ability to use a busbar.

View attachment 78748
Orderef mine last week and if you think you could DIY it it would cosr $150 more.not including shipping costs from all the vendors
 

RichardfromEG4

The "Do-What's-Needed" Solar Guy
Joined
Dec 23, 2021
Messages
837
Location
Sulphur Springs, TX
Orderef mine last week and if you think you could DIY it it would cosr $150 more.not including shipping costs from all the vendors
Agreed - if you DIY the entire rack. But if you just mount your inverters and stack your batteries, you could run a few cables and a bus bar for pretty inexpensive - I can't imagine more than $50.... again this is just for the bus bar etc. Probably add some funds for a safety cover and mounting hardware and you are looking pretty for fairly affordable pricing. If you want a full rack that you can attach wheels to and very professional looking, I 100% agree you won't beat our price on this rack.
 

RichardfromEG4

The "Do-What's-Needed" Solar Guy
Joined
Dec 23, 2021
Messages
837
Location
Sulphur Springs, TX
And a followup question. If I'm running to a real cupper busbar, then the cable that connects each battery to the busbar does not need to be sized for the max current (250-300Amps), but the busbar and the cables connecting them to the inverter do. The short cables that came with the battery are 6AWG. I think they can carry about 65 amps. Too small?

Edit: I did more maths (who knew solar was so math laden). If max output of the inverter is 240voltx50amp=12000 watts, then the max ciming from the battery at 48 volts is 250A, which would run on 4/0, and the max current from each battery is 62.5A which those smaller cables that came with the battery shoudl handle. All of this assumes I ignore momentary inrush/start currents. Is this reasonable?
Sounds good to me! Haha, seriously though, I know that the wire size we include with our products is rated at or above minimum requirements for the distance/amperage no problem. And if you are using a solid conductive busbar you will definitely be in overkill on hitting the requirements!
 

JustPractical

New Member
Joined
Aug 31, 2021
Messages
58
OK. I ordered 1/4"x1"x36" copper bars (110 copper) - they were $48 each on Ebay. 1/8" thick would have worked current capacitywise, but I thought it might bend around. Went looking for copper nuts and bolts, but those seem tough to find, so going with Stainless Steel (whcih seems to get along well enough with copper. Now to seach for insulated standoffs to mount the bars.
 

Cajunwolf

Solar Addict
Joined
Sep 23, 2019
Messages
360
Location
Houston, the free state of Texas
OK. I ordered 1/4"x1"x36" copper bars (110 copper) - they were $48 each on Ebay. 1/8" thick would have worked current capacitywise, but I thought it might bend around. Went looking for copper nuts and bolts, but those seem tough to find, so going with Stainless Steel (whcih seems to get along well enough with copper. Now to seach for insulated standoffs to mount the bars.
LoL, I'm doing the same thing but in 3/16" because I want some bend from the battery to the main bus bars, now the two main bars are 1/4". You say you need standoffs; here you go.
Standoffs.
 
Top