custom made battery box for eve LF280K cells

[danmc]

Can anyone advise?

Background: I'm using LF280K EVE cells with the new double terminals, and as the EVE busbars or the ones provided with the mason aren't long enough to bridge the gap between the two rows I bought nickel plated copper bar from China planning to make my own.

The busbars provided by EVE seem to be 20mm x 2mm so I ordered the same in nickel plated copper bar, unfortunately what arrived does not appear to be 2mm thick. And even if it is it isn't as thick as the EVE busbars. Would it still be OK to use? Or do I need a plan B? How many amps would it need to be able to safetly carry?

Am I overthinking this? I have some 70mm cable left over. Should I just stick some lugs on it and use that?

 

[Sanwizard]

Can anyone advise?

Background: I'm using LF280K EVE cells with the new double terminals, and as the EVE busbars or the ones provided with the mason aren't long enough to bridge the gap between the two rows I bought nickel plated copper bar from China planning to make my own.

The busbars provided by EVE seem to be 20mm x 2mm so I ordered the same in nickel plated copper bar, unfortunately what arrived does not appear to be 2mm thick. And even if it is it isn't as thick as the EVE busbars. Would it still be OK to use? Or do I need a plan B? How many amps would it need to be able to safetly carry?

I would just use the calculator that was posted in this thread, and figure out if it will handle your peak load.

Busbar Current Calculator Online | Electrical4u

Enter the breadth and thickness of the busbar; do not enter the length of the busbar. Then press the calculate button, you get the aluminium or copper busbar

www.electrical4u.net

 

[danmc]

I would just use the calculator that was posted in this thread, and figure out if it will handle your peak load.

Busbar Current Calculator Online | Electrical4u

Enter the breadth and thickness of the busbar; do not enter the length of the busbar. Then press the calculate button, you get the aluminium or copper busbar

www.electrical4u.net

I did 48A according to that calculator.

 

[Ron-ski]

I did 48A according to that calculator.

Using the chart at https://www.copper.org/applications/electrical/busbar/busbar_ampacities.html it shows that the EVE busbars can cope with 141A., whereas the calculator shows 48A, bit of a difference, but even at 141A they are well under specced. Just measured my EVE twin bolt busbars and they are 20 x 2mm

If you're going across the pack, then a 20mm wide busbar is useless anyway, you ideally need a 35mm wide busbar, its 23mm between the outer edges of the bolts holes, and the terminal is 35mm wide.

Below is what I used, although it only allows for 10mm between the cells, the Seplos looks wider than this though.

Could you use two pieces of what you bought side by side, effectively it would be 40 x ~2mm then, which is more than the EVE busbars?

 

[danmc]

Using the chart at https://www.copper.org/applications/electrical/busbar/busbar_ampacities.html it shows that the EVE busbars can cope with 141A., whereas the calculator shows 48A, bit of a difference, but even at 141A they are well under specced. Just measured my EVE twin bolt busbars and they are 20 x 2mm

If you're going across the pack, then a 20mm wide busbar is useless anyway, you ideally need a 35mm wide busbar, its 23mm between the outer edges of the bolts holes, and the terminal is 35mm wide.

Below is what I used, although it only allows for 10mm between the cells, the Seplos looks wider than this though.

Could you use two pieces of what you bought side by side, effectively it would be 40 x ~2mm then, which is more than the EVE busbars?

View attachment 134648

If you think that will be sufficient that should be doable with some offset holes.



Massively regretting not buying cells with the old terminals now.

 

[Ron-ski]

If you think that will be sufficient that should be doable with some offset holes.

I'm no expert, but I'll explain my reasoning, EVE supplies 20 x 2mm busbars to go between the cells, so if that is acceptable, using two slightly thinner bars between the cells is going to be able to carry far more current than the single bar that EVE supplies. The cross sectional area of EVE busbar is 40mm2, if yours are 1.5mm thick the cross sectional area of two would be 60mm2, a 50% increase.

 

[danmc]

I'm no expert, but I'll explain my reasoning, EVE supplies 20 x 2mm busbars to go between the cells, so if that is acceptable, using two slightly thinner bars between the cells is going to be able to carry far more current than the single bar that EVE supplies. The cross sectional area of EVE busbar is 40mm2, if yours are 1.5mm thick the cross sectional area of two would be 60mm2, a 50% increase.

It's actually closer than that, around 1.9mm-ish. I think you've cracked it. Thanks very much.

 

[Ron-ski]

Massively regretting not buying cells with the old terminals now.

I think these cells are much better, the old cells have a single stud, which can fail, even the welded ones can snap off, the threads in these terminals are helicoiled, so much stronger, and there's two of them. Yes they cause some complications, but they can easily be overcome.

It's actually closer than that, around 1.9mm-ish. I think you've cracked it. Thanks very much.

Your welcome, glad to help, one thing to watch is its possible to screw the studs in to the top of the cell if your not careful. I used some 2mm plastic packers under the terminal, its enough to stop the stud turning when you tighten it, then just pull it out.

You can see my built pack here.

Please show me your EVE LF280K 2-hole packs

If you have built a pack using the new EVE LF280K cells featuring the new, dual stud, terminals, please show me some of your photos and are you using the standard bus bars that came with the cells or one of the flexible bar options from aliexpress? I just pre-ordered 8 cells from the next batch...

diysolarforum.com

 

[danmc]

Your welcome, glad to help, one thing to watch is its possible to screw the studs in to the top of the cell if your not careful. I used some 2mm plastic packers under the terminal, its enough to stop the stud turning when you tighten it, then just pull it out.

Thanks for the heads up. Knowing my luck that likely would have happened. Especially as I have a couple of bent terminals.

Do you know if there's a recommended torque for the screws? I've looked can't seem to find anything concrete. All I can find are recommendations for nuts and bolts.

edit: scratch that I've just seen your build, and you're using nuts. I'll ask Amy see if she knows. Looks good BTW.

 

[niktak11]

Using the chart at https://www.copper.org/applications/electrical/busbar/busbar_ampacities.html it shows that the EVE busbars can cope with 141A., whereas the calculator shows 48A, bit of a difference, but even at 141A they are well under specced. Just measured my EVE twin bolt busbars and they are 20 x 2mm

If you're going across the pack, then a 20mm wide busbar is useless anyway, you ideally need a 35mm wide busbar, its 23mm between the outer edges of the bolts holes, and the terminal is 35mm wide.

Below is what I used, although it only allows for 10mm between the cells, the Seplos looks wider than this though.

Could you use two pieces of what you bought side by side, effectively it would be 40 x ~2mm then, which is more than the EVE busbars?

View attachment 134648

The eve busbars are fine for 200A at least. That site just shows the ampacity for a very specific scenario (30C rise at 40C ambient).

 

[Ron-ski]

@niktak11 And that's where it gets complicated, there are calculators that tell us usually the lowest reading, then there are charts like the one mentioned earlier which are higher than the calculators, then there are the manufacturer ratings, which are normally the highest.

Why the difference?

I know the ability to disipate heat plays a big part in it, but surely a large part of that is dependant on the actual installation.

 

[niktak11]

@niktak11 And that's where it gets complicated, there are calculators that tell us usually the lowest reading, then there are charts like the one mentioned earlier which are higher than the calculators, then there are the manufacturer ratings, which are normally the highest.

Why the difference?

I know the ability to disipate heat plays a big part in it, but surely a large part of that is dependant on the actual installation.

The limiting factor for this application is probably the temperature of the terminals. If the busbars get to 200C+ then they'll be putting a ton of heat into the cells through the terminals. I'm not sure how hot is too hot for the busbars but at 200A it doesn't seem to be a problem at all, especially with the dual stud terminals with the large aluminum block.

 

[danmc]

I'm no expert, but I'll explain my reasoning, EVE supplies 20 x 2mm busbars to go between the cells, so if that is acceptable, using two slightly thinner bars between the cells is going to be able to carry far more current than the single bar that EVE supplies. The cross sectional area of EVE busbar is 40mm2, if yours are 1.5mm thick the cross sectional area of two would be 60mm2, a 50% increase.

It isn't the prettiest job, but it's the best I can do with the tools at hand. Should do the trick though.

 

[Ron-ski]

@danmc Looks pretty good to me, holes are a little big, but once its bolted down and the lids on it won't get seen, and most importantly it will do the job it needs to.

I'm not sure what the coating is on the terminals, but I cleaned all my terminals, and coated them in some silver grease.

 

[danmc]

@danmc Looks pretty good to me, holes are a little big, but once its bolted down and the lids on it won't get seen, and most importantly it will do the job it needs to.

I'm not sure what the coating is on the terminals, but I cleaned all my terminals, and coated them in some silver grease.

Cheers. Yeah the holes are a touch bigger than I would have ideally liked, but still smaller than the EVE busbar holes. As you'll likely already know the terminals aren't quite straight so I needed a little margin of error. Also as it's bare copper were it's been drilled I wanted to leave a little space between that and the aluminium.

They are a bit grubby and marked, I'm hoping it will wipe off, they came like that. Just pretty poor quality generally. I'm going to clean everything up with some isopropyl before connecting so hopefully it will come up ok. Also I've bought some Noalox due to the bare copper in the drill holes that should also help with conductivity. Hoping to be up and running this weekend all going well.

 

[Ron-ski]

Hoping to be up and running this weekend all going well.

Hope it goes well, my electrician should be coming next Tuesday to do the AC stuff, so hopefully mine will be fully running next week.

 

[danmc]

delete

 

[toluxa1]

I have 4 Seplos boxes stacked in parallel and these are their current state. Should the differences in SOC be this much? Isn't the variance too much? What should be done to correct this?

 

[Rossman]

I have 4 Seplos boxes stacked in parallel and these are their current state. Should the differences in SOC be this much? Isn't the variance too much? What should be done to correct this?

I've had that before but the BMS recalibrates periodically and they seem to come back into sync.

 

[Sanwizard]

I have 4 Seplos boxes stacked in parallel and these are their current state. Should the differences in SOC be this much? Isn't the variance too much? What should be done to correct this?

Were they all top balanced together prior to putting them in parallel as 48 volt batteries?