Hello?My 12v setup

[Dadoftheturkeykids]

Keep in mind, 2400W of output is 2880W of battery draw.

Thanks for pointing that out

What was the inverter you had on 24v, and what kind of problems did you have with it?

It was a 24v 4kw. This one

https://www.amazon.com/gp/aw/d/B0BGH897Q8?psc=1&ref=ppx_pop_mob_b_asin_title

Same company I got my 12v 3kw inverter from that performs very well. But the 24v scared me, I felt like it was going to start a fire.

It made all my lights flicker with a light load, and also made a loud alarming clicking sound In harmony with the flickering, my shunt monitor was fluctuating from
45watts-500watts rapidly in microseconds. It did this with just my lights thar should be drawing only 20watts, I added my fridge circuit to that, which still did the similar thing while only supposed to pulling 160ish watts. When I added my furnace circuit making the total draw 750-800 watts it kind of evened out the fluctuations and the ticking noise become more quiet. But I could still see my lights flicker very very fast like a strobe effect.. I didn't trust it, so I pulled it out of my system and went back to my steady but low voltage system of 12v

 

[Dadoftheturkeykids]

while your sharing, images of your panels and panel mounts would be sweet.

Tommy
SE Wisconsin

My original mounting/installation was kind of less than ideal. I was still learning and experimenting, but I will be removing these and installing my new trina 545s in place of these with actual rails and clamps.

 

[Supervstech]

So that the MRBF fuse blocks and wires do not apply excess pressure against the posts?

It is in the insteuction sheet not to mount directly to battery.

 

[Supervstech]

My original mounting/installation was kind of less than ideal. I was still learning and experimenting, but I will be removing these and installing my new trina 545s in place of these with actual rails and clamps.

Interesting.
The trinas look like they have a 1" rail.
Are your panels just laying on the roof?
Keep in mind, if you mount to rails, both the rails and thw panels need to be tied to the case of the inverter, and a ground system in your house panel.
If your inverter is similar to the one you linked i would be skeptical.

I am NOT a fan of those inverters that have a universal outlet on them.

It is good your 12v one is working for you though.

 

[robbob2112]

Thank you for your kind advice, and links!
And the warm welcome
As for kid safety, this cabinet is located in my bedroom, which has a lock and key. High voltage warnings on my door, and a high shrieking alarm if my door is opened. I do have 4 fire extinguishers located around my house, and 1 nearby in my room. I will get some smoke detectors as you have suggested. Thanks for that.

I definitely like the idea of MRBF fuses, I tried to keep my cable lengths the same per battery of combing the length of positive and negative wiring.
i.e.1 long 1short or 2mediums. Will just a couple inches make a difference?
I will only ever draw 50amps from each battery if my math is correct of only drawing 200amps max from my inverter, I have yet to run a load over 2000watts@120v. Which is how I based my 200amp breaker to the load line.
Yes all of my battery connections are with 4/0 copper welding wire along with the cables to the inverter.

As for ventilation that is a thought of mine too, if you look to the right of my inverter I have a DC fan that runs at 6watts, it's not installed yet but I intend on cutting a hole out the back and installing it near the inverter there and plugging it in to the usb port on the inverter while running it. But also, I leave that side of the cabinet open while in operation.

The bus bars I used are these.

https://www.amazon.com/gp/aw/d/B0BYMNL4YX?psc=1&ref=ppx_pop_mob_b_asin_title

Since then I have acquired some nice copper bus bars that came out of a 600amp main shutoff breaker.. they are 1 1/2" wide and almost 1/2" thick! And over 2 feet long and already predrilled. I obviously will cut them to the desired length.
You mentioned using a bus bar for my input to the shunt as well. Is there any problem with stacking the lugs as I did? Wouldn't there be less resistance stacked as opposed to having more conductor to travel through?

I used that 200amp breaker as a main cutoff, which I probably will replace with a class T as per your suggestion. I will also install a main cutoff switch on the negative side, I was always confused on where that should be installed. Thank you for clarifying

Thanks guys for the positive input, I was scared at first to post here thinking I would possibly be ridiculed

You misunderstand the suggestion for the same length of cables - We mean you use the exact same length of cables for all batteries and polarities. That means 4 red cables 2ft long and 4 black cables 2ft long (or whatever makes sense for your run). The idea behind that is that it has exactly the same resistance so all batteries have exactly the same charge on them. It doesn't take much to get them out of balance and then one is providing slightly more power out and taking slightly less charge.

As you will read over and over, fuses are to protect wires, not equipment. That is why you take what you can pull and add 20%. 3000/12*1.2=300. You are protecting from a short that will cause wires to melt. You can downsize the fuses, but realize they don't blow instantly.

In the event of a dead short you can have a fuse blow and and arc bridge the gap and keep current on. In the case of these type of batteries they typically have 7000amps when shorted so that is what your fuses have to interupt and exstinguish. The MRBF are rated for 10,000amps (AIC). The class T act much faster and are capable of interupting 20,000amps. You have 4 batteries in parrallel which mean they can provide 35,000 amps in theory if there was a short. You should probably read up on AIC and how to interupt it. And realize the AC and DC behave differently when it comes to AIC. There is a good video on testing class T fuses... they are full of sand so when the elements burn through the arc has to fuse the glass while trying to complete the circuit.

For the MRBF I would use 200amps just because no battery should put out more because the BMS limits to that. For the Class T I would use 300amps.

I would look at two things on your buss bars - first the back, are the bold heads exposed so they go all the way through? If they aren't take one out and unscrew it from the plastic backer and see if they are only kept from spinning by the plastic or if they are actually threaded all the way down and locked to the bar. If they spin verse being locked and you try to torque down the bolts they can twist out of the plastic and not get tight enough. One other bit, if they spin freely in the bar and the stars aligned so the bolts carried any signifigant amount of current (say a bit of heatshrink under your lug), then a loose bolt would be carrying a good amount of current and the steel to copper interface means lots of heat fast. The same as if you put a steel washer under a lug. If everything is right the current is passed from the lugs directly to the bar and the bolts are only there to keep them tight together.

One reason everyone does higher voltage batteries is because you run 1/4th the current at 48v than you are at 12v. Smaller wires and less amps. It is the amps that will kill you and the voltage that overcomes your skin resistance. So you need to dismis the idea that 12v isn't dangerous and treat it all like it is a live main panel in the house or a downed powerline. Deenergize the circuit if you are gonna work on it at all. With your setup I wouldn't be surprised if you could draw a 6inch arc if you started the conductors close and slowly moved them apart.

DO NOT MOUNT THE FUSES ON THE BATTERY POSTS!
connect them to the buss bars.

Oh wise one, please explain that reasoning to me? Note my question is for learning purposes, not to argue.

I have read a ton and never have seen an explaination of WHY people like them like that other than put them closest to the voltage source, i.e. the battery post? Is it in this specific setup that you don't want torque on the posts? If that is the case wouldn't the fuse holders provide that support since they are about 2.5~3 inches long and flush with the surface of the battery? (note I use a rubber cover over the battery wire end verse the silly cover that comes with the MRBF mount that holds it above the battery surface.)

On this spec sheet from Blue Sea they show them mounted directly on a battery post - at the bottom

Cautions When Using 2007/2008 MRBF Terminal Fuse - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

and another

https://www.electricalhub.com/media/catalog/product/pdfs/3080/fuse_blocks_blue_sea.pdf

 

[Supervstech]

You misunderstand the suggestion for the same length of cables - We mean you use the exact same length of cables for all batteries and polarities. That means 4 red cables 2ft long and 4 black cables 2ft long (or whatever makes sense for your run). The idea behind that is that it has exactly the same resistance so all batteries have exactly the same charge on them. It doesn't take much to get them out of balance and then one is providing slightly more power out and taking slightly less charge.

As you will read over and over, fuses are to protect wires, not equipment. That is why you take what you can pull and add 20%. 3000/12*1.2=300. You are protecting from a short that will cause wires to melt. You can downsize the fuses, but realize they don't blow instantly.

In the event of a dead short you can have a fuse blow and and arc bridge the gap and keep current on. In the case of these type of batteries they typically have 7000amps when shorted so that is what your fuses have to interupt and exstinguish. The MRBF are rated for 10,000amps (AIC). The class T act much faster and are capable of interupting 20,000amps. You have 4 batteries in parrallel which mean they can provide 35,000 amps in theory if there was a short. You should probably read up on AIC and how to interupt it. And realize the AC and DC behave differently when it comes to AIC. There is a good video on testing class T fuses... they are full of sand so when the elements burn through the arc has to fuse the glass while trying to complete the circuit.

For the MRBF I would use 200amps just because no battery should put out more because the BMS limits to that. For the Class T I would use 300amps.

I would look at two things on your buss bars - first the back, are the bold heads exposed so they go all the way through? If they aren't take one out and unscrew it from the plastic backer and see if they are only kept from spinning by the plastic or if they are actually threaded all the way down and locked to the bar. If they spin verse being locked and you try to torque down the bolts they can twist out of the plastic and not get tight enough. One other bit, if they spin freely in the bar and the stars aligned so the bolts carried any signifigant amount of current (say a bit of heatshrink under your lug), then a loose bolt would be carrying a good amount of current and the steel to copper interface means lots of heat fast. The same as if you put a steel washer under a lug. If everything is right the current is passed from the lugs directly to the bar and the bolts are only there to keep them tight together.

One reason everyone does higher voltage batteries is because you run 1/4th the current at 48v than you are at 12v. Smaller wires and less amps. It is the amps that will kill you and the voltage that overcomes your skin resistance. So you need to dismis the idea that 12v isn't dangerous and treat it all like it is a live main panel in the house or a downed powerline. Deenergize the circuit if you are gonna work on it at all. With your setup I wouldn't be surprised if you could draw a 6inch arc if you started the conductors close and slowly moved them apart.




Oh wise one, please explain that reasoning to me? Note my question is for learning purposes, not to argue.

I have read a ton and never have seen an explaination of WHY people like them like that other than put them closest to the voltage source, i.e. the battery post? Is it in this specific setup that you don't want torque on the posts? If that is the case wouldn't the fuse holders provide that support since they are about 2.5~3 inches long and flush with the surface of the battery? (note I use a rubber cover over the battery wire end verse the silly cover that comes with the MRBF mount that holds it above the battery surface.)

On this spec sheet from Blue Sea they show them mounted directly on a battery post - at the bottom

Cautions When Using 2007/2008 MRBF Terminal Fuse - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

I am not sure, but likely the warning was not to mount the fuses themselves to the battery posts without a fuse holder.

I just read the warning on the fuse website.

 

[robbob2112]

I am not sure, but likely the warning was not to mount the fuses themselves to the battery posts without a fuse holder.

I just read the warning on the fuse website.

Now that I can get behind. Sure enough someone who KNOWS everything would decide to stack it... washer, naked MRBF, washer, lug, washer, lock washer, long bolt so they can strip their threads and if they are lucky and the bottom out go through the cast terminal. On any normal battery that would cause issues, but on these where they terminal is just think with a wire soldered to the bottom he would get away with it until there was a fire and he would sue and make a million.

 

[robbob2112]

HA HA, I went looking and it didn't take but a second to find someone wanting to do basically the same thing https://forums.sailboatowners.com/threads/mrbf-fuse-on-busbar.196061/

 

[robbob2112]

Oh, one more note, class T fuse holders are not all alike. In blue sea they are a different size for over/under 300 amps... and the cheapo knockoff class T are different sizes than the originals.

And buy extra fuses in case you blow one by accident. I did some experiments with ANL fuses and blew them with some mock ups.

 

[Hedges]

You misunderstand the suggestion for the same length of cables - We mean you use the exact same length of cables for all batteries and polarities. That means 4 red cables 2ft long and 4 black cables 2ft long (or whatever makes sense for your run). The idea behind that is that it has exactly the same resistance so all batteries have exactly the same charge on them. It doesn't take much to get them out of balance and then one is providing slightly more power out and taking slightly less charge.

Ohms in series with each battery being the same is all that matters. Doesn't matter at all if you have 10' red cable on positive, 1' black cable on negative of one battery, then 1' red cable on positive, 10' black cable on negative of other battery.

Maybe if there was a data cable between the batteries, then it would matter. But not 2-terminal devices (just a positive and negative terminal, no data ports.)

 

[Supervstech]

Ohms in series with each battery being the same is all that matters. Doesn't matter at all if you have 10' red cable on positive, 1' black cable on negative of one battery, then 1' red cable on positive, 10' black cable on negative of other battery.

Maybe if there was a data cable between the batteries, then it would matter. But not 2-terminal devices (just a positive and negative terminal, no data ports.)

This system has nothing in series...
It is all parallel...

 

[Supervstech]

So, ALL negative cables need to be the same length.
And ALL positive cables need to be thw same length.

Negative and positive can be different length.

 

[Hedges]

So, ALL negative cables need to be the same length.
And ALL positive cables need to be thw same length.

Negative and positive can be different length.

I disagree.
For each battery, positive cable + negative cable needs to be same total length as each other battery's cable.

For some physical configurations (like OP's), you can use less total cable length by making each (pos + neg) the same length, but no two (pos) are the same and no two (neg) are the same.

This system has nothing in series...
It is all parallel...

Each battery is in series with one positive cable and one negative cable. Then 4x of those in parallel.
Therefore cable lengths matter.

If all four batteries had been in series (4s) for one 48V system, then no cable length would matter.

 

[robbob2112]

With the design he has, I would put a MRBF mount with 200a fuse on the positive post of each battery. Then I would put buss bars at the bottom and measure the longest length for positive and negative. Then I would cut the wires and put lugs on with heat shrink and boots. Then connect to the buss bars (should be 5 stud or more). Using all one length for everything would be simplest (battery to buss bar). Using all 1 length per color would be simple. Using a single overall length for the round trip would look the neatest.

 

[Supervstech]

I disagree.
For each battery, positive cable + negative cable needs to be same total length as each other battery's cable.

For some physical configurations (like OP's), you can use less total cable length by making each (pos + neg) the same length, but no two (pos) are the same and no two (neg) are the same.



Each battery is in series with one positive cable and one negative cable. Then 4x of those in parallel.
Therefore cable lengths matter.

If all four batteries had been in series (4s) for one 48V system, then no cable length would matter.

I dont understand what you are saying is in series...

I see 4 batteries paralleled to two bussbars.

Parallel positive cables all need to be the same length to a bussbar.
Parallel negative cables need to all be the same length to a bussbar.

What are you explaining, and where did you get the method...

 

[robbob2112]

I dont understand what you are saying is in series...

I see 4 batteries paralleled to two bussbars.

Parallel positive cables all need to be the same length to a bussbar.
Parallel negative cables need to all be the same length to a bussbar.

What are you explaining, and where did you get the method...

I see what he is getting at, say the total cable length is 20 inches..

4in -> battery1 +> 16in
8in -> battery2 +> 12in
12in -> battery3 +> 8in
16in -> battery4 +> 4in

Seems like the impedance per battery would all match. For simplicity assume each battery is 1ohm and each inch of cable is 1 ohm. Add up all and to the charge circuit the same. Is a variation of 6 inch red and 14 inch black for cables.

From a pure ohms perspective it works. I think in reality it would take testing with equipment I don't have. With battery cables and connections and order being important I just dunno. For now I would stick to equal length cables for all or equal for polarity.

Maybe a new project for Will.

Put 14v across them and they would all take the same charge and would discharge at the same rate.

How do we flag Will to look at something?

 

[Hedges]

The batteries are in parallel. They each have internal resistance.
All that matters regarding wiring is for each battery to be in series with the same wire resistance. Doesn't matter at all how much of that series resistance is connected to positive terminal vs. negative terminal. Therefore individual wire lengths don't matter, just total positive plus negative length.

If you don't believe me, work it out long hand by Ohm's law (remember, that's a law, not a suggestion.)
Or run SPICE.

I'd say build a test circuit, but battery differences may dominate. You could do one with dry cells and resistors.

 

[Dadoftheturkeykids]

Interesting.
The trinas look like they have a 1" rail.
Are your panels just laying on the roof?
Keep in mind, if you mount to rails, both the rails and thw panels need to be tied to the case of the inverter, and a ground system in your house panel.
If your inverter is similar to the one you linked i would be skeptical.

I am NOT a fan of those inverters that have a universal outlet on them.

It is good your 12v one is working for you though.

In the one photo I had them laying upside down across two loose 2x4s in the other photo they were laying on cardboard which I can't see I guess. The trinas just have a normal aluminum frame and wide busbars going across the center of each panel. I was wondering about the grounding too, so if i understand what you are saying, can I run a
continous (sort-of) wire linking to each of the solar panels, all the rails, and the inverter case and ties into the ground wire from the transfer switch to my main panel ground/neutral buss?

 

[Dadoftheturkeykids]

I see what he is getting at, say the total cable length is 20 inches..

4in -> battery1 +> 16in
8in -> battery2 +> 12in
12in -> battery3 +> 8in
16in -> battery4 +> 4in

This... was my exact logic

 

[robbob2112]

The batteries are in parallel. They each have internal resistance.
All that matters regarding wiring is for each battery to be in series with the same wire resistance. Doesn't matter at all how much of that series resistance is connected to positive terminal vs. negative terminal. Therefore individual wire lengths don't matter, just total positive plus negative length.

If you don't believe me, work it out long hand by Ohm's law (remember, that's a law, not a suggestion.)
Or run SPICE.

I'd say build a test circuit, but battery differences may dominate. You could do one with dry cells and resistors.

I get it, I really do, but sometimes the real world surprises me with stuff I think should work another way.

I do not have spice or enough free batteries to run it and test. Can get resistance of the wire from the mfg. But, I don't know how to measure the resistance in the battery. I suppose it can be figured but not with what I have.