DIY Bus Bar

[Hedges]

You continue to reinforce the my belief that your in way over your head. 1000 amps is a 1000amps. This is why the wire size for 10amps of 12v is the same as 10a of 600v. yes the power delivery is different for those two, but that doesn't matter to the current that the wire/connections have to carry.

I'm out guys, I did my best.

That was an example of what happens if he (she?) has a cable come loose and start arcing.
1000A isn't all that much, less than CCA of two starting batteries paralleled for my pickup truck.
But in this case, needs to be lower resistance and higher ampacity so it can be done continuously.
Three, 4/0 cables properly torqued or otherwise terminated would do the trick. Question is what they go to.

 

[ghostwriter66]

Go to HomeDepot -- get a copper pipe plumbing tube -- take it home -- place it on the ground ... put a piece of long wood over it - DRIVE back and forth over it -- then take a 5 pound hammer and smash it totally flat ... cut the pieces to size you want -- drill holes -- DONE

 

[Jejochen]

just get a good piece of copper (big enough to handle the amps off course), drill holes in it and you're good to go

 

[Dzl]

Three, 4/0 cables properly torqued or otherwise terminated would do the trick. Question is what they go to.

I believe OP's thinking is to connect multiple battery packs in parallel to multiple inverters in parallel (split phase) (refer back to this thread). So theoretically the only component that would carry the full load is the busbar, I believe. Something in the ballpark of this maybe:

 

[Zil]

I hope you rethink your system. 1000 amps continuous is not to be trifled. Use commercial buss bars if you really must have 1000 amps. Could you link your inverter? Can you explain a bit of what your plan once you have the battery bank?

After i posted this, Dzl referred to the previous post. I have no more advice.

 

[Hedges]

just get a good piece of copper (big enough to handle the amps off course), drill holes in it and you're good to go
View attachment 22282

Yes, but I can still cut the temperature rise in half if I choose wisely where to drill the holes, and which cable goes where.

I believe OP's thinking is to connect multiple battery packs in parallel to multiple inverters in parallel (split phase) (refer back to this thread). So theoretically the only component that would carry the full load is the busbar, I believe. Something in the ballpark of this maybe:

Four batteries delivering 1000A to two inverters?
That's exactly what I was hoping for.
I can do that with a 250A busbar (without it breaking a sweat)
Just have to get rid of that silly chokepoint that is a shunt, otherwise I need a 500A busbar. Use 2 or 4 shunts and sum the values?

24V why? At 48V it would be half the current and 1/4 the power loss in wiring.

 

[Ampster]

24V why? At 48V it would be half the current and 1/4 the power loss in wiring.

He explained that as something to do with WAF (Wife Acceptance Factor) which is not part of Ohm's law.

 

[Deleted member 1888]

I believe OP's thinking is to connect multiple battery packs in parallel to multiple inverters in parallel (split phase) (refer back to this thread). So theoretically the only component that would carry the full load is the busbar, I believe. Something in the ballpark of this maybe:

This is the blueprint im using, I still need a few more fuses but ill get there, thx again for it.

 

[Deleted member 1888]

He explained that as something to do with WAF (Wife Acceptance Factor) which is not part of Ohm's law.

I need to remember that acronym now lol.

 

[Hedges]

This is the blueprint im using, I still need a few more fuses but ill get there, thx again for it.

So if you did this:



Under normal conditions, a busbar with cross section sufficient for 250A would do it.
Problem is if some battery fuses blow. If one on the end blows, remaining three batteries fused at 400A each can still deliver 1200A total, enough for both inverters. Now you've got 500A flowing through some parts of the busbar.

So maybe a 500A busbar would be the safe way to get away with smaller than 1000A busbar. Think through other failure modes before betting (your wife's?) house on it.

Still need to figure out what to do about the shunt. I would consider putting a shunt in each battery path and summing them in analog (because I used to be a digital guy but not any more.) The extra shunts will probably cost you more than the 1000A busbar, though.

 

[Deleted member 1888]

So if you did this:

View attachment 22294

Under normal conditions, a busbar with cross section sufficient for 250A would do it.
Problem is if some battery fuses blow. If one on the end blows, remaining three batteries fused at 400A each can still deliver 1200A total, enough for both inverters. Now you've got 500A flowing through some parts of the busbar.

So maybe a 500A busbar would be the safe way to get away with smaller than 1000A busbar. Think through other failure modes before betting (your wife's?) house on it.

Still need to figure out what to do about the shunt. I would consider putting a shunt in each battery path and summing them in analog (because I used to be a digital guy but not any more.) The extra shunts will probably cost you more than the 1000A busbar, though.

Have any likes to good bus bars?

 

[Hedges]

Have any likes to good bus bars?

I got mine from this guy and enlarged holes for my bolts:

1.5" x 7" C-110 Copper Busbar Power Distribution Bus Bar Terminal Block | eBay

The Busbar is made from C110 Copper. The Busbar / Ground Bar is insulated using "Eriflex" insulators rated at 600 volts. Ground / Bus Bar Kit. They are drilled for 1/4" bolts to attach the insulators and 0.201" holes for mounting.

www.ebay.com

I haven't checked math and the cross-section, but he says 600A.
I'm sure he could do other lengths. This one was about right for my 1 battery string, 4 inverters. Note that I only used every other hole due to size of my terminals.
Of course, DIY would cost you less.

You could use two busbars and put two 500A shunts between them.
Is the shunt just for your monitoring, or does it need to feed into any of the equipment to track state of charge?

How was one 1000A shunt supposed to connect to the two busbars in original drawing? Obviously not with a single 4/0 cable! Maybe two in parallel?
4/0 and "designed for 375A" suggests 750A is the continuous load, since one cable each to two inverters.

 

[Dzl]

To clarify, that is not OP's schematic, that is a quick and dirty example (attempt) at drawing one version of what OP may want (which is yet to be completely defined) but the two main parameters are < 24V and a goal of 15kW AC output. The schematic is not what OP is building necessarily, simply an example of something in the same ballpark.

Four batteries delivering 1000A to two inverters?
That's exactly what I was hoping for.

Not necessarily, that is just one example of the concept OP is pursuing (multiple inverters + multiple battery packs). The number of inverters and packs may differ, but I believe this is the general design they are shooting for. It was meant to illustrate a concept, and play with the numbers, not be a final design. Please see the other thread for context.

I can do that with a 250A busbar (without it breaking a sweat)

Is that safe/advisable/leaving enough margin? Particularly in the case of battery packs going offline due to BMS disconnection or other issues?

Just have to get rid of that silly chokepoint that is a shunt, otherwise I need a 500A busbar. Use 2 or 4 shunts and sum the values?

That is certainly an option. the schematic is not OP's design, just one quick and dirty example. I don't know much about large systems with parallel packs, Shunts could be per pack or per system, Victron makes shunts upto 2000 or 3000A I think, so either option is feasible. I used 1000A shunt assuming 1000A busbar so it wasn't a limitation in that scenario. Personally I think I would want Bank level SOC, but like I said in the previous post, multi-pack designs are much outside my experience or comfort zone designing.

24V why? At 48V it would be half the current and 1/4 the power loss in wiring.

Read the other thread. Short answer is treat it as a design constraint, OP has been advised multiple times 48v makes more sense for such a high power requirement, but has his reasons not to go that route (and is aware that it is not ideal to stick to 24v).

You could use two busbars and put two 500A shunts between them.
Is the shunt just for your monitoring, or does it need to feed into any of the equipment to track state of charge?

Shunt is for the example only, not one of OP's stated design requirements.

How was one 1000A shunt supposed to connect to the two busbars in original drawing? Obviously not with a single 4/0 cable! Maybe two in parallel?

If it were me (and since I drew the example, I suppose it is me), I would use copper bar to connect the shunt to the busbars directly (similar to this or this. I suppose 2 x 4/0 could work but its not what I envisioned), alternatively something like the Victron Lynx system (which was the inspiration for that part of my design, an which I'm sure is not cheap--but a 24v 15kw system is not going to be cheap) would accomplish the same goal and be safer and simpler.

4/0 and "designed for 375A" suggests 750A is the continuous load, since one cable each to two inverters.

Correct, 750A is a rough (and slightly conservative) estimation of OP's max power requirement (15kW)

15,000W / 0.85 inverter efficiency / 24V = 735A

It is also roughly the current each remaining battery pack would have to handle if 1/2 of them go off line.

But again, all these details are mine not OP's, his design requirements were 15kW on the loads side, and 24v system voltage, multiple parallel battery packs. The diagram is not meant to be a blueprint but more of a rough concept sketch of one maybe-possible solution (see previous thread).[/QUOTE]

 

[Deleted member 1888]

Wow so much info to consider, it may be safer just to buy one rather then try to make my own. I still don't understand how I could get away with a 250 amp or 500 amp bus bar. IF my inverters are pulling 15000w thats 625 amps(if im doing the math right, I don't get the inverter efficiency) so would not a 500a bus melt? I picked 1000 amp bar to give over head room for surges.

 

[Dzl]

This is the blueprint im using, I still need a few more fuses but ill get there, thx again for it.

Just remember, and really take to heart my disclaimer when I first posted that example drawing:

First a DISCLAIMER up front that, I haven't built, designed, or even ever really considered or thought about a (1) a high current / high power system, or (2) a more complex multi-pack system.

It seemed like a fun thought experiment. Bearing in mind I am in no way someone you should be taking advice from on this, here is one example system I came up with, that gets you to your ballpark AC output, keeps the system at 24v, and is (at least intended to be) somewhat conservatively designed. I am certain there are errors, omissions, or things that could be done better, and I had to make some assumptions about the system which may not accurately reflect your system.

It is not meant to be taken as a blueprint, just an example, and I'm not someone you should be taking specific advice from on this.

And my topline advice is the same as in past threads, work on significantly reducing your power consumption as best you can, this will be cheaper and safer and easier.

 

[Deleted member 1888]

Just remember, and really take to heart my disclaimer when I first posted that example drawing:



It is not meant to be taken as a blueprint, just an example, and I'm not someone you should be taking specific advice from on this.

And my topline advice is the same as in past threads, work on significantly reducing your power consumption as best you can, this will be cheaper and safer and easier.

Don't worry you will not be held liable in any way, this is all me and ill mess up along the way thats just how things are.

 

[Dzl]

Wow so much info to consider, it may be safer just to buy one rather then try to make my own. I still don't understand how I could get away with a 250 amp or 500 amp bus bar.

I haven't really thought it through hard, but I think that 250A would not be compatible with the above design, if BMS disconnections or maybe imbalances are considered (which I think they should be). 500A maybe (fuses would should blow at 400A), if @Hedges advice is accurate and advisable. In terms of overall system cost, a chunk of copper that can handle 1000A may not be cheap, but seems like a small cost. I like his idea of designing in a way to intelligently reduce current, its a very smart idea, but even following that advice, may as well get copper capable of the full current. OR the best option may just be to buy a properly sized commercially available busbar.

IF my inverters are pulling 15000w that's 625 amps(if im doing the math right, I don't get the inverter efficiency) so would not a 500a bus melt? I picked 1000 amp bar to give over head room for surges.

750A. Don't exclude inverter inefficiency because you don't get it.
But to briefly explain it, inverters are not perfectly efficient. So the input Watts must be higher than the output Watts. If an inverter is 85% efficient (this is the ballpark I use) and you need 15000 on the output side, 15000 / 0.85 will give you the input power, divide this number by 24 to get the input current.[/QUOTE]

 

[Hedges]

Other forum was closed to posts, but,

Psychotic Waif said,

"don't know what my power needs are yet so im just aiming at 15kw as it would power a 50amp RV plug with room to spare. I am slowly building up to it so I will not need the money all at once. As for why im staying on 24v for now is my wife dues not want me to go 48v as she is afraid ill get electrocuted. She has been with me on learning solar and likes the idea its just the 48v that scares her. So im stuck between a rock and a hard place as I need to keep her happy or there will be hell to pay. I know 48v is the best and I would love to but she is not on board with it. Maybe in the future I can convince her and at that time ill only need to get a 48v inverter and im good.

Thank you all for the help so far, im surprised you all remembered me so far. "

I think I may have a solution, splitting hairs or at least lawyering words.

Same thing I was going to recommend to colleagues at a certain federal research lab, but got canned before I could.

They wouldn't let their electrical engineers with advanced college degrees use a 50V bench supply. "Too dangerous!" they said. "You might get electrocuted", they said.

They still let someone get shocked by a vacuum system. AFTER I told them what was missing from their voluminous safety rule book.

There were plenty of dual 30V supplies around. 30V + 30V = 60V, and I've got banana cables. (shhhh!)

Now for your application: Just put two 24V batteries in series. Ground the midpoint. Now you're playing with +24V, and you're playing with -24V, but not 48V unless you use both hands. Fuse both positive and negative, so if either shorts to ground nothing bad happens.

Same thing we do for AC in the US: We have +120V and -120V, and some of our appliances run on 240V. But we would have to make two mistakes at the same time to get bit with 240V. Over in Europe, they have 220 coming out of the outlets.

So get 48V Sunny Island like me, and call it +/-24V. You can stack them from 5.75 kW to 23 kW. DC coupled PV if you want, but you can hang 2x as much AC coupled PV on the output for a peak of 69 kW continuous power at peak sun.

 

[Hedges]

Wow so much info to consider, it may be safer just to buy one rather then try to make my own. I still don't understand how I could get away with a 250 amp or 500 amp bus bar. IF my inverters are pulling 15000w thats 625 amps(if im doing the math right, I don't get the inverter efficiency) so would not a 500a bus melt? I picked 1000 amp bar to give over head room for surges.

If you put two 10 gpm sprinklers on the end of a hose, it has to carry 20 gpm.

If you put a "Y" adapter on the faucet and use two hoses, one sprinkler on the end of each, the hoses each carry only 10 gpm.



That's all I'm doing. Putting the faucet (one battery) in the middle and feeding two sprinklers (two inverters), one at each end.
That's my system.
Yours may be the reverse, two batteries feeding one inverter.

But you do need to consider if one battery fuse opens and the remaining batteries supply all the current, feeding the busbar from just one end not both. That's why I came up with 500A not 250A busbar requirement for 2 inverters, 4 batteries.

 

[Dzl]

If you put two 10 gpm sprinklers on the end of a hose, it has to carry 20 gpm.

If you put a "Y" adapter on the faucet and use two hoses, one sprinkler on the end of each, the hoses each carry only 10 gpm.

That's all I'm doing. Putting the faucet (one battery) in the middle and feeding two sprinklers (two inverters), one at each end.
That's my system.
Yours may be the reverse, two batteries feeding one inverter.

But you do need to consider if one battery fuse opens and the remaining batteries supply all the current, feeding the busbar from just one end not both. That's why I came up with 500A not 250A busbar requirement for 2 inverters, 4 batteries.

I think 500A would fit within my (arbitrarily chosen) design goal/assumption where 2 of 4 banks should be able to disconnect and still be able to (barely) deliver full power without overloading any part of the system.