Battery terminal question

[JJJJ]

I have read a number of threads about available terminals that can be used for battery boxes.

My challenge is space. The first photo shows how the wire currently comes in. While this will be a stationary install I am concerned about lateral stresses on the terminal over time.

The second photo is a concept I am considering. Run an extension straight out and then attach to that.

I have both 1/0 and 2/0 available. Initially I will have two 24v 8s batteries feeding a Victron 3000 inverter and will be adding a third battery in the future.

 

[JJJJ]

Just had a third idea. If I ran a short piece of wire from the terminal at an angle, and bent the lug against the wall about 45 degrees or so, I could affix it to a terminal.

 

[timselectric]

In the first picture the hole in the lug is too big. You are losing surface area for the connection.
Not sure what you are showing in the second picture. But I wouldn't stack lugs on a battery terminal.
Each battery should have its own main wires ran to bus bars. This is where they are connected together.
And don't forget OCP for all wires.

 

[JJJJ]

Understand. Each battery has a bms and will be running to a Victron distributor which will have fuses via a dedicated line. The one line still needs heat shrink. I will look at the lug. Thank you

The second photo was a thought which would let me come off the battery terminal at 90 degrees and connect to another lug via a terminal to allow a 90 degree turn avoiding any stress on the battery stud.

 

[timselectric]

I see.
As long as the cable weight isn't straining the terminal, there shouldn't be any problem. If it sits happily on the terminal without the bolt/nut then there's no stress to worry about.

 

[brum]

Neither the nut nor the lugs are appropriate. You need a flange nut and lug for a 6mm bolt.

The same goes for the busbar. The nut should be with a flange. The flange should not be flat, but a locking one.

Fuses should be as close as possible to the cells. They should be rated with high interrupt current (10kA or more). The BMS comes after the fuse.

 

[timselectric]

The BMS comes after the fuse.

The BMS should be on the negative.
The fuse should be on the Positive.

 

[RV8R]

I’m not sure of your application, but for my AGM systems I tend to use these;

 

[timselectric]

I’m not sure of your application, but for my AGM systems I tend to use these;

View attachment 123097

Those are the best option.
You can't get any closer to the source.

 

[brum]

The BMS should be on the negative.
The fuse should be on the Positive.

Depends on the BMS. Mine is on the positive. But in general - I agree. Most of them are on the negative.

 

[timselectric]

Depends on the BMS. Mine is on the positive. But in general - I agree. Most of them are on the negative.

Oh
That's an odd one. What's the brand?

 

[JJJJ]

As long as the cable weight isn't straining the terminal, there shouldn't be any problem. If it sits happily on the terminal without the bolt/nut then there's no stress to worry about.

That is the ten thousand dollar issue. While it shows resting in the photo, it is the threads of the stud that are holding it in place.

I am curious though. The Victron distributor has a dedicated fuse for every battery. The positive cable to the battery goes directly to the fuse before getting to the rest of the system. Why wouldn't this work? This photo shows the relative position. It has not gone through the final install yet so proper positioning, heat shrink, cover are still needed.

Will definitely be looking at updated nuts and lugs though.

 

[brum]

Oh
That's an odd one. What's the brand?

Seplos.

 

[RV8R]

That is the ten thousand dollar issue. While it shows resting in the photo, it is the threads of the stud that are holding it in place.

I am curious though. The Victron distributor has a dedicated fuse for every battery. The positive cable to the battery goes directly to the fuse before getting to the rest of the system. Why wouldn't this work? This photo shows the relative position. It has not gone through the final install yet so proper positioning, heat shrink, cover are still needed.

Will definitely be looking at updated nuts and lugs though.
View attachment 123106

There is a difference between what “will work” & “best install practices“.

We are only seeing bits & pieces of your install. Your original question seemed to be about battery terminal connections & now has drifted towards the Victron “fuse bus” equipment.

Do you intend to protect your battery terminal “close to the positive terminal”? If you do & incorporate a battery terminal fuse holder like the one I referenced in post #8 (available in single & duals) it might “kill 2 birds with 1 stone”.

 

[JJJJ]

No offense intended. Please forgive my omissions. The rest of the system has been presented in previous posts and changes were made accordingly. The actual purchasing was performed with a system tech review from a reputable supplier.

The actual build and purchasing has spanned nearly two years. I was not objecting to an additional fuse, rather like the idea. I was just curious on the difference between a fuse on the battery vs a short distance from the battery. This was in conjunction with a video Will presented on the topic a while back.

Please also keep in mind that there is redundancy up the system for fusing prior to the inverter.

 

[RV8R]

No offense intended. Please forgive my omissions. The rest of the system has been presented in previous posts and changes were made accordingly. The actual purchasing was performed with a system tech review from a reputable supplier.

The actual build and purchasing has spanned nearly two years. I was not objecting to an additional fuse, rather like the idea. I was just curious on the difference between a fuse on the battery vs a short distance from the battery. This was in conjunction with a video Will presented on the topic a while back.

Please also keep in mind that there is redundancy up the system for fusing prior to the inverter.

No Offense taken ?

I’m new here & have not read thru the volumes, & am know nothing of your 2 year build.

To answer your question; The reason why a fuse at the Victron is not “best practice“ is it does not protect the battery terminal “the source“.

So if your wire from the battery “shorts” on something before the Victron, then you have an expensive short term “arc welder” & possible fire.

That is why “Tim” made his comment & the reason why “Blue Sea” manufacturers these thangs;




Further;

If you do incorporate battery terminal protection with these, the lug/hole size issue & stress geometry issue might get resolved “all with the addition of these terminal fuse holders”.

I am sure there are other “close to the source” equipment out there.

I personally would not build a system without them.

Also there is a difference between code & safe as there is with “will it work” & “should I do it this way”.

 

[JJJJ]

So if your wire from the battery “shorts” on something before the Victron, then you have an expensive short term “arc welder” & possible fire.

Agree. An ounce of prevention.... That is one of the reasons I went with wire sizes larger than required. My goal was to make the fusing the weak link in the system, not the wiring. Still like your idea though.

 

[RV8R]

I’m also curious about what I assume is your Victron Lynx;

What is the reason(s) for having that in your system?

 

[RV8R]

Agree. An ounce of prevention.... That is one of the reasons I went with wire sizes larger than required. My goal was to make the fusing the weak link in the system, not the wiring. Still like your idea though.

But without fusing the top of your battery terminals, all you have done protection wise is extend those terminals the length of your wire ,,, whatever that is ,,, unprotected.

bigger wire size just makes a bigger arc welder until the battery fries or worse.

In welding terms larger diameter rod ?



I recently watched a “Will” video. I might have watched a total of 60 mins of his videos now. I like them.

He was talking about tools & getting insulating handles on the ratchets ?. I chuckled to myself as I have worked around live batteries & had 1st hand experience ,,, knowing better but being lazy to get my insulating ratchets when unhooking 12vdc batteries ,,, cause you know (I know what I am doing) ?.

 

[JJJJ]

I wanted a solid brand bus bar which would enable me to connect multiple batteries, add fusing, work with my Victron inverter and shunt and better enable me to better keep multiple custom built batteries in balance. I DO like the battery fuse idea and am seriously considering it.

If you do incorporate battery terminal protection with these, the lug/hole size issue & stress geometry issue might get resolved “all with the addition of these terminal fuse holders”.

Good point

 

[timselectric]

As stated
The only way to protect the wire, it to place the fuse between the wire and the source. The victron bus bars are nice. But its fuse location is better suited for an output.

 

[JJJJ]

Already on my buy list.

By the way, with flange nuts, are you using serrated or non serrated?

Thanks

 

[timselectric]

Already on my buy list.

By the way, with flange nuts, are you using serrated or non serrated?

Thanks

Serrated

 

[RV8R]

I wanted a solid brand bus bar which would enable me to connect multiple batteries, add fusing, work with my Victron inverter and shunt and better enable me to better keep multiple custom built batteries in balance. I DO like the battery fuse idea and am seriously considering it.



Good point

I ignorantly do not know the advantage of the Victron Lynx as incorporated into your system. I see there is a circuit board, but I am truly ignorant of the product as I have not had a need;

Here is my concern; If working around the Lynx in the “current” condition (say replacing a battery fuse), & your unprotected red wire brushes up against your (assumingely non-fused) negative bus bar that isn’t gonna help your batteries out much.

If that is the way it is, whenever doing any work I would disconnect the negative feed (probably at the battery terminals but in the least at the black negative bus bar 1st.

Judging from your recent posts I think you are sold on the idea of these battery terminal fuses. The Blue Sea is just an example & I would guess there are others out there to research and buy. Other than protecting your batteries & feed wires, the geometry of how you install them might overcome the issue you wrote about in your 1st post.

It might also rectify the oversized holes in your wire lugs that are reducing the terminal contact area ?‍.

Could be a win win win ?

 

[JJJJ]

Here is my concern; If working around the Lynx in the “current” condition (say replacing a battery fuse), & your unprotected red wire brushes up against your (assumingely non-fused) negative bus bar that isn’t gonna help your batteries out much.

Actually the system is well designed. The negative and positive terminals are kept separate by design. The negative lines are carefully tucked underneath.

Adding to this, the system will be stationary away from foot traffic. Appreciate your concerns however, very much appreciated!

Each battery will be attached to a blue seas switch. Before performing any maintenance, the batteries will be switched off before proceeding.

There will also be a redundant switch upstream from the distributor before it gets to the inverter.