How big can you go?

Hedges

Photon Sorcerer
I have a fairly big grid-backup system.
Four SI-6048US wired 2s2p. Pass-thru from grid is 112A 120/240V
Continuous rated inverter output 4 x 5750W = 23kW, surge 4 x 11kW = 44kW for 3 seconds
Each has 2/0 cable to 48V battery. Battery is way undersize at 400 Ah, but inverter settings support up to 100,000 Ah.

With one or more inverters and/or one or more battery strings in parallel, busbar doesn't carry full current through it's cross section. On negative side, my busbar has 3 holes with battery in middle and 2 inverters on either side. Positive side two cables branch off to fuses.

11kW x 4 / 42V / 90% x 112% = 1300A. Split two ways, 650A for 3 second surge; continuous would he half that.
(112% is my ripple factor, battery current follows sine wave because capacitors can't supply. RMS current is 12% higher than average)

I have about 12kW of AC coupled Sunny Boy. If off-grid (so doesn't overload relay), can support 48kW of Sunny Boy. With PV array split and oriented for morning and afternoon sun, about 80 kW STC of PV would be a good fit.

If you want a larger system, go three phase. Each cluster is 3x SI-6048US and its own battery. Then you connect several clusters.

 
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HRTKD

Boondocker
There are a few vendors that are adjusting their specs on the 48v limit. Blue Sea Systems is one of them. They're now saying that their 48v limit is a hard limit (I'm paraphrasing here based on my DIY knowledge), not a description of what system it would go into. So you can't run 48v devices in a system that routinely spends most of its time above 50 volts.
 

Short_Shot

Solar Enthusiast
There are a few vendors that are adjusting their specs on the 48v limit. Blue Sea Systems is one of them. They're now saying that their 48v limit is a hard limit (I'm paraphrasing here based on my DIY knowledge), not a description of what system it would go into. So you can't run 48v devices in a system that routinely spends most of its time above 50 volts.
Is that due to the whole "50 volts and up is unsafe" thing?
 

Hedges

Photon Sorcerer
There are a few vendors that are adjusting their specs on the 48v limit. Blue Sea Systems is one of them. They're now saying that their 48v limit is a hard limit (I'm paraphrasing here based on my DIY knowledge), not a description of what system it would go into. So you can't run 48v devices in a system that routinely spends most of its time above 50 volts.

Electronics? Fuses with an AIC rating? Or just copper busbars?
Have any links to examples?

Is that due to the whole "50 volts and up is unsafe" thing?

Could be an issue of slipping under regulatory limits for testing and access control. Did you pay NRTL to test it with a mechanical finger?
 

Hedges

Photon Sorcerer
Circuit breakers, voltage matters in terms of sustaining an arc.

Busbars don't care about voltage and you'd be hard pressed to build insulation where 50V mattered, so probably just because they can't keep fingers off. Inside a box accessible by tools (e.g. PV combiner) should address that, while most battery busbars would be exposed.
 

Short_Shot

Solar Enthusiast
I was going to agree with you, but the Blue Sea bus bars do have a 48v rating limit:


I thought that the common bus bars I bought had a much higher voltage limit, but they don't. 250 amps at 12v, which is well within my expected use.
I believe that's due to this or something like it:


In that, it specifies 50 volts and above as unsafe requiring appropriate safeguards.

Which I believe itself is an extension of the IEC SELV which states 50vac and 120vdc as the maximum "safe" voltages in that they won't kill you should you touch it, but it might still hurt.

And I think internationally speaking there may be similar governing bodies which set < 50v as touch safe.

I know with industrial controls stuff that was a hard limit at least as of 40 years ago as we have 48 volt controls on some old machines but the way older ones are 110v controls.

The newer standard is pretty well unified at 24 volts, but it's all in relation to that "safety" aspect.
 

Pyrofx

Flux capacitor builder
I don't know if I would trust those cheap high amp fuses on ebay etc.

I would like to go big for a few reasons.
1. I own a small farm with plans for a lot of greenhouses. Grow lights, pumps, fans and HVAC add up.
2. Large over sized arrays help the batteries last longer.
3. E peen, the biggest.
Start small. Sell your first 20 pounds . Then but enough Sma product to run your needs.
Better be a leagle grow though. We just took down 80 operations. Give or take 1.9 BILLION in lost product. Grow braids are scheduled every day , 6 months out .
 

Short_Shot

Solar Enthusiast
Start small. Sell your first 20 pounds . Then but enough Sma product to run your needs.
Better be a leagle grow though. We just took down 80 operations. Give or take 1.9 BILLION in lost product. Grow braids are scheduled every day , 6 months out .
Oh I bet you've got some fun stories.
 

chrisski

Solar Addict
Once you get much past 350a though that's when I would need/want to take even more precautions but it's easy enough to stay under that on any one circuit.
IMO 350 amps is way too much to be recommending the average build be done for. If you're going to go above 100 amps constant draw with some forays into 200 amps, you really need to know what your doing and that should not be your first DIY build.
I have a fairly big grid-backup system.
Four SI-6048US wired 2s2p. Pass-thru from grid is 112A 120/240V
Continuous rated inverter output 4 x 5750W = 23kW, surge 4 x 11kW = 44kW for 3 seconds
Each has 2/0 cable to 48V battery. Battery is way undersize at 400 Ah, but inverter settings support up to 100,000 Ah.

With one or more inverters and/or one or more battery strings in parallel, busbar doesn't carry full current through it's cross section. On negative side, my busbar has 3 holes with battery in middle and 2 inverters on either side. Positive side two cables branch off to fuses.

11kW x 4 / 42V / 90% x 112% = 1300A. Split two ways, 650A for 3 second surge; continuous would he half that.
(112% is my ripple factor, battery current follows sine wave because capacitors can't supply. RMS current is 12% higher than average)

I have about 12kW of AC coupled Sunny Boy. If off-grid (so doesn't overload relay), can support 48kW of Sunny Boy. With PV array split and oriented for morning and afternoon sun, about 80 kW STC of PV would be a good fit.

If you want a larger system, go three phase. Each cluster is 3x SI-6048US and its own battery. Then you connect several clusters.
Obviously with what Hedges says, this 100/200 amp limit I mention can be exceeded, but this is on a well designed system with someone that knows what they're doing. I can understand most of what he says, but I can not picture in my mind the actual components and placement I would use to install a system like that.

Blue Sea typically rates there DC products at no more than 48 volts: https://www.bluesea.com/products/2127/MaxiBus_250A_BusBar_-_Four_5_16in-18_Studs and also the Battery Switch 9003e https://www.bluesea.com/products/2127/MaxiBus_250A_BusBar_-_Four_5_16in-18_Studs. Those busbars and switches being limited to 48 volts were part of the reason I did not upgrade to a 48 volt battery bank that I'd charge to 56 or 57 volts. My 1000 amp busbars are rated to 150 volts, but it does not say AC or DC. https://www.bluesea.com/products/1992/PowerBar_1000_-_8_5_16in_Terminal_Studs
 

Short_Shot

Solar Enthusiast
Yeah. I didn't say it should be a first time build lol

Nor did I say it's an average build or recommend it.

I'm constantly amazed by how many people can read the words and still get the context entirely wrong.

In fact in that very post that you clearly didn't read I explicitly stated that knowing your limits is a good thing but that you learn along the way.
 

Hedges

Photon Sorcerer
I was going to agree with you, but the Blue Sea bus bars do have a 48v rating limit:


I thought that the common bus bars I bought had a much higher voltage limit, but they don't. 250 amps at 12v, which is well within my expected use.

Maximum Voltage300V AC
48V DC

If I consider the large ripple voltage I've measured, can I call it AC?

Busbars don't know voltage.
People who touch it do.
The insulators need to withstand voltage, and perhaps "treeing" of breakdown through the dielectric with DC is an issue?
Then there is sustaining/breaking an arc. No switch contacts, but if you dropped a screwdriver that bounced off, maybe it would strike an arc which just continues under DC?
 

chrisski

Solar Addict
Busbars don't know voltage.
Then there is sustaining/breaking an arc. No switch contacts, but if you dropped a screwdriver that bounced off, maybe it would strike an arc which just continues under DC?
I don't know why 48 VDC is set as a limit for DC Busbars, both for Blue Sea and for others I've looked at. I'm assuming that an uninsulated or poorly insulated busbar becomes an arcing hazard, but don't know for sure. I would like to see what a reputable manufacturer says is a busbar rated for up to the mid 60 volts in the DC range for an equalization for 48 VDC FLA.
 

Short_Shot

Solar Enthusiast
I don't know why 48 VDC is set as a limit for DC Busbars, both for Blue Sea and for others I've looked at. I'm assuming that an uninsulated or poorly insulated busbar becomes an arcing hazard, but don't know for sure. I would like to see what a reputable manufacturer says is a busbar rated for up to the mid 60 volts in the DC range for an equalization for 48 VDC FLA.
I posted the reason for that above.
 
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