How many amps for busbars?

Shimmy

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Feb 22, 2022
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486
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".
 
Last edited:

indalecio

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Oct 26, 2021
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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.

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.

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.
Nice comments.
 

houseofancients

Photon Sorcerer
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Nov 29, 2019
Messages
1,279
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
 

Alace

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May 16, 2022
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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.
:ROFLMAO:
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.

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.

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.
Thanks for the info. Not sure where the crypto mining came from, but it does involve computers and equipment.

It would be about a 10,000 watt continuous load, running 240v at the panel. So if I was to base it on load am I right with assuming a 300amp busbars to connect the batteries would be safe given:

10,000 / 48v = 208 x 1.25 = 260
 

Alace

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May 16, 2022
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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.
I think this will be the way. The large common busbar then would need 2800A correct?
 

Shimmy

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Feb 22, 2022
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486
Thanks for the info. Not sure where the crypto mining came from, but it does involve computers and equipment.

It would be about a 10,000 watt continuous load, running 240v at the panel. So if I was to base it on load am I right with assuming a 300amp busbars to connect the batteries would be safe given:

10,000 / 48v = 208 x 1.25 = 260
I would add another 125% personally if it is really a continuous 10kW load. You also need to account for the inverter efficiency which would add another ~5%, or about 1.5x0.25".
 

sergea

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Dec 15, 2020
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I always rate my busbar at least x2 my charge/discharge inverter capacity. if you expect all 4 inverter to charge/discharge at max rate at the same time (4x120=480A=> x2 = 940A) in this case I would use 1000A busbar.

But to be honest I would rather use 2 x DEYE 12-16kW inverter and stack of individuals 16s batteries to keep everything manageable.
 

Warpspeed

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Jun 11, 2021
Messages
331
Agree.
Four separate inverters using four individual batteries allows some redundancy.
The way it is now, any fault anywhere is going to turn the whole thing into a very large expensive bonfire.
 

kromc5

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Jul 2, 2020
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Massive bank we will need lots of pictures if you go this route. I have two 4p16s in parallel for the large loads, soon to be 3. I used 1.5 inch by .25, and 3 inch by .25 to allow room to tap for connections. Before the solar additions it would top out around 380 amps for the charge rate. I would think it would be better to go with at 5p dual setup. If one pack fails I can still keep the system running if there should ever be an issue. Even at 11,600w nothing gets warm at all.
 

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Warpspeed

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I would think it would be better to go with at 5p dual setup. If one pack fails I can still keep the system running if there should ever be an issue. Even at 11,600w nothing gets warm at all.
Definitely worth thinking about.
The ability to shut down and isolate half of the battery for maintenance or repair, while the other half is still on line is the only practical way to build a very large system.
 

indalecio

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Oct 26, 2021
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Massive bank we will need lots of pictures if you go this route. I have two 4p16s in parallel for the large loads, soon to be 3. I used 1.5 inch by .25, and 3 inch by .25 to allow room to tap for connections. Before the solar additions it would top out around 380 amps for the charge rate. I would think it would be better to go with at 5p dual setup. If one pack fails I can still keep the system running if there should ever be an issue. Even at 11,600w nothing gets warm at all.
For now the connection is fine. You need to check again after the system run for weeks. You can not imagine what will happen during such high current operation.
 

kromc5

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Jul 2, 2020
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For now the connection is fine. You need to check again after the system run for weeks. You can not imagine what will happen during such high current operation.
The dual 4p banks have been up for over 6 months and its stayed so stable that the bms is hardly ever is needed.
 

kuranaga

Solar Enthusiast
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Sep 24, 2021
Messages
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rule of thumb: around 1mm^2 for each 10A of current. so you would need around 280mm^2 cross section to carry such current. Maybe you should try to increase the voltage instead
 
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