How many amps for busbars?

[MartyByrde]

Hi this would be a massive battery build from 160 3.2v 280ah LiFePo4 batteries. The busbars would need to be custom copper. Would they need to be wide/thick enough to carry 2800amps?

Also if this was connected to a busbar with 4 Growatt SC48120 each with 120A, 4x120=480. Would that busbar need to be wide/thick enough to carry 3280amps?

Is that the correct way to calculate width/thickness/amps when making custom bars?

 

[rhino]

Maybe this would help: https://www.copper.org/applications/electrical/busbar/busbar_ampacities.html

 

[acdoctor]

I would avoid this configuration completely. 16S10P 16 48 volt batteries with individual cell protection, each battery with its own fuse protection all feeding common power buss. Have physical separation between batteries to avoid losses in a failure of a cell.

 

[Ampster]

Hi this would be a massive battery build from 160 3.2v 280ah LiFePo4 batteries

I am a fan of parallel cells but there has to be a practical limit? There is no BMS that I know of that could keep a pack that big balanced.
This is starting to look like a crypto mining dream.

 

[740GLE]

I’d wager 5 BMS are in order, double the cells per string, then connect each BMS to your heavy duty bus bars.

Also what sort of peak current demand/load are you anticipating?

 

[Ampster]

Also if this was connected to a busbar with 4 Growatt SC48120 each with 120A, 4x120=480. Would that busbar need to be wide/thick enough to carry 3280amps?

If I understand it correctly the total for 4 Growatts is 480 Amps. That is all you need. Is there a reason you want this all to be one battery? What will be charging this pack? What is your experience level? Have you considered the impact of NEC2020 and any building code or fire code requlations?

 

[SparkyJJO]

I am a fan of parallel cells but there has to be a practical limit? There is no BMS that I know of that could keep a pack that big balanced.

I’d wager 5 BMS are in order, double the cells per string, then connect each BMS to your heavy duty bus bars.

Also what sort of peak current demand/load are you anticipating?

Either multiple BMS, or a super fancy (expensive) BMS can do that I think.

 

[Ampster]

Either multiple BMS, or a super fancy (expensive) BMS can do that I think.

I have a 3P16S pack and use a 2 Amp active balancer. I have a "super fancy" BMS designed for EV conversions and it has very weak balancing current so I turned off the balancing function and use it for control and reporting. It can operate a 500 Amp contactor.

 

[Wet1]

I'd be inclined to do traditional16S 48 volt packs, each with it's own BMS feeding into a large common busbar. This way you not only have better pack control, redundancy, but also much lower current through each pack. Then again, going high voltage makes sense, but finding the equipment to control it all might be problematic and expensive... not to mention potentially dangerous voltage levels.

 

[MartyByrde]

I'd be inclined to do traditional16S 48 volt packs, each with it's own BMS feeding into a large common busbar. This way you not only have better pack control, redundancy, but also much lower current through each pack. Then again, going high voltage makes sense, but finding the equipment to control it all might be problematic and expensive... not to mention potentially dangerous voltage levels.

What size amp busbar?

 

[MartyByrde]

I would avoid this configuration completely. 16S10P 16 48 volt batteries with individual cell protection, each battery with its own fuse protection all feeding common power buss. Have physical separation between batteries to avoid losses in a failure of a cell.

What amp size busbar?

 

[Wet1]

What size amp busbar?

How many amps do you need it to carry?

 

[Ampster]

What amp size busbar?

The busbar should be sized to your loads not the capacity of your pack(s). Are you going to be running crypto mining machines 24/7 and each growatt at max? Does your proposed rental building offer 3 phase power? I saw on another post some numbers that indicated nothing has yet been finalized. We don't know what size array or if the landlord will permit solar panels mounted on the roof. Focusing on the bus bar size when other more important issues of system design need to be resolved is simply a distraction. How likely is this project going to come together? Have you made a preliminary budget and have the cash or secured financing?

 

[timselectric]

Is this "how to build a LiFePo4 bomb" ?

 

[Ampster]

Is this "how to build a LiFePo4 bomb" ?

Are you referring to my crypto mining comment? I have seen a lot of these crypto mining schemes and nobody does the fundamental math on the amortized capital equipment cost to do all that crypto mining. Then there is the volatility of the currency that is mined.

 

[timselectric]

Are you referring to my crypto mining comment? I have seen a lot of these crypto mining schemes and nobody does the fundamental math on the amortized capital equipment cost to do all that crypto mining. Then there is the volatility of the currency that is mined.

No, just the battery.
Not very familiar with the whole mining stuff.
Other than the physical mining companies that I work for. lol

 

[RV10flyer]

I would avoid this configuration completely. 16S10P ***THIS IS WHAT I HAVE>>>>16 48 volt batteries with individual cell protection, each battery with its own fuse protection all feeding common power buss. Have physical separation between batteries to avoid losses in a failure of a cell.

My pos and neg busbars are 1/4" x 2.5" tin plated copper. They can handle 800+ Amps. 3/0 copper cables from each end of my 6' long pos and neg busbar running to my two Sol-Ark 12K's. 10 batteries, separated by 1/4" cement board and 1/4" ceramic fiber mats, connect to busbars with 2 ga x 24" cables, through 100A breakers, 10 ea 100-250A BMS's (8 different brands). The max current is 185A limited by each of my two Sol-Arks entering through a 250A breaker from each end of busbars. Max Amps that I've noted from each individual battery is 37A +/- 2A. (185 x 2 = 370A) All 10 vary slightly during charge/discharge cycles. Typically 0-25A. Totally off grid 3+ months and loving it.

 

[Ampster]

I think Alace's calculation is right for the current. For 16S10P pack, the bus bar need to handle 1C x 10 = 280A x 10 = 2800A

He is only correct that the batteries could discharge at at a rate of 1C if there was a 2800Amp load. He never said there was going to be a 2800 Amp load.

If you use calculation according load current, it will cause big problem in case there some high current appears.

High current doesn't just appear. It moves to a load or through a short circuit. That is what fuses and circuit breakers are for. The transformer on the pole outside my house is capable of thousands of Amps but my house is protected by a 200 Amp circuit breaker. My battery pack is 840 Amp hours but the circuit breaker is 125 Amps and the most my inverter can charge my batteries is 80 Amps.

Some worse situation the inter-connection will melt like fuse due to high current.

Yes if he dropped a metal tool on the bus bars the tool or the busbar would probably melt. Oversizing the bus bars would only cause the tool to melt before the bus bars. I put a Lexan sheet over my pack so I don't have to worry about a metal tool dropping on my bus bars.
In any event this is just a hypothetical battery Alace is dreaming about building to make money mining Crypto.

 

[Shimmy]

I would avoid this configuration completely. 16S10P 16 48 volt batteries with individual cell protection, each battery with its own fuse protection all feeding common power buss. Have physical separation between batteries to avoid losses in a failure of a cell.

I would say it a little differently. I would go for 2x 16s5p, each system feeding two inverters. You could put a paralleling switch, but that is really dangerous. (But if it was me, I would actually do 4x16s2p and save a little money.)

With a single bus, generally you would design the busbars so that you mix sources and loads along the length-- in the 16s10p scenario you would have:
[ Batt1 - Batt2 - SCC1 - Inv1 - Batt3 - Batt4 - SCC2 - Inv2 - Batt5 - Batt6 - SCC3 - Inv3 - Batt7 - Batt8 - SCC4 - Inv4 - Batt9 - Batt10 ]

With that connection scheme I would design the busbar for 4x your battery string fusing. (I would fuse the battery strings at 150A personally.) Assume 1 square inch of copper = 1,000A, so about 2.5x0.25".

 

[houseofancients]

I suggest you do new design and choose new inverter. 48V is not suitable to such high power system. You need to choose more higher voltage for the system. Too high current flow will cause big potential problem.

no so much..
i would parallel after the bms though.
it would then basically be something like 6 eg4 batteries
you do want individual cell monitoring.
if you spend this much on cells, it makes non sense to save on a safety device like a bms.

as for the busbar, that is pretty easy to calculate based on above posted links