Homemade copper bar battery interconnect?

[xionide]

I have 4X Wattcycle 12v 100ah batteries that I will be running in parallel hooked up to a Victron Energy MultiPlus 12/1200/50 in my travel trailer. I have a couple of 24"x1.5"x1/8" copper bars and I was planning on using them as bus bars. I haven't seen to many people use copper bars like this to connect batteries together so I am just looking for some general input. I could easily go another route but I though this might keep the batteries balanced compared to using battery cables.

 

[400bird]

You can home brew a coating for corrosion protection or use heat shrink between the bolt down connection point. Otherwise, make sure the cross sectional area will support your current needs. It should work great.

What's your plan for the inverter connections?
Id either bolt down cross connected (positive on batt #1 and negative on batt #4) or drill a 5th hole in each bus bar for the battery cables (positive between 1/2 and negative between 3/4)

 

[xionide]

You can home brew a coating for corrosion protection or use heat shrink between the bolt down connection point. Otherwise, make sure the cross sectional area will support your current needs. It should work great.

What's your plan for the inverter connections?
Id either bolt down cross connected (positive on batt #1 and negative on batt #4) or drill a 5th hole in each bus bar for the battery cables (positive between 1/2 and negative between 3/4)

This system will never see a 200A load as that is what the internal fuse on the multiplus contains. I will be running the DC system in the travel trailer and rarely see more than 20A load. I will be attaching this 200A DC circuit breaker directly to the bus bar:

Nader DC Circuit Breaker | 60V 200Amp

The Nader DC Circuit Breaker rated at 60V and 200A provides robust protection for DC circuits, ensuring safety and reliability in electrical installations requiring high current handling capacity.

signaturesolar.com

I have temco pure copper 2ga cable welding cable with Selterm UL listed 3/8" copper lugs to connect to the inverter. This cable meets the cross-section requriement in the inverters manual. That will be connected directly to the circuit breaker. I will have another cable on top of the lug running to the rest of the dc system. Ground side will have my 500A victron smart shunt with an equal length cable to the inverter. I am still weighing options for the rest of the dc system's power distribution. I'll probably end up with some BlueSea bus bars though. Eventually I will be adding a Victron MPPT 150/35 into the mix.

The plan was to use ground on batt #1 and positive on batt #4 but I didn't know that you could connect it between positive on batt 1/2 & negative on batt 3/4 and end up with a balanced charge. That may work better for this layout. Just need to mock everything up when the rest of the stuff shows up next week. Thanks for the info!

 

[400bird]

If this is a mobile installation, you need to be 100% sure there is no relative movement between the batteries if using a solid bus bar. If the batteries move independently, something inside the batteries will likely flex and fail before the bus bar.

I hadn't considered this being a mobile installation, in this case, there's definitely a reason that many don't use bus bars.

It's pretty difficult to ensure the batteries are one solid mass that can't move around and flex the bus bar.

 

[xionide]

If this is a mobile installation, you need to be 100% sure there is no relative movement between the batteries if using a solid bus bar. If the batteries move independently, something inside the batteries will likely flex and fail before the bus bar.

I hadn't considered this being a mobile installation, in this case, there's definitely a reason that many don't use bus bars.

It's pretty difficult to ensure the batteries are one solid mass that can't move around and flex the bus bar.

It's a mobile solution but this travel trailer will almost never be moved. I was also thinking that mounting it rigidly might put additional stress on the terminals due to fluctuations in temperature and thermal expansion/contraction. Any thoughts on that? I am just going to use the bus bars for now because I have them but I'll be checking on the torque periodically.

 

[robbob2112]

It is better to use a short copper bus bar and cables to the bar in mobile connections. Also with 4 batteries in parallel you need a MRBF on the positive post of each battery.

The short bar and the cables allow flex and move from vibration and you don't have the huge long bus bars.

If you do go with the long bars - nickle plate them - there are many articles on how to do it at home - the main thing is a container than can hold them and the vinager and nickle solution without contaminating it - thing glass or glazed pottery.

You can cut the bars with a table saw, miter saw, jig saw, sawsall, etc... just go slow and wear apropriate PPE.

See the second spoiler in my signature on parallel connecting batteries to balance the load. You want the cables to the inverter or other devices about 2/3rds between the end lugs and the next ones....

The terminals on the batteries just bolt through the plastic and have cables on the bottom side - worst that might happen is you pop the terminal out of the plastic if they move a lot - a small amount of movement isn't a problem.

Just remember the expansion and contractions is across the length of the long bar - so if there is a large swing in temp they could move quite a bit.

If people use the long bars like you have they are typically mounted to something and the insulator holes are oval shapped to allow for expansion and contraction with cables or breakers bolted to them