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diy solar

Help with final purchases of wire and fuses

TheCoachStone

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Joined
Feb 12, 2021
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Birmingham, AL
I have collected all the big pieces for my solar setup. I am just hoping that someone can make sure my calculations are correct for wire sizes and fuse sizes.

8 145w, Imp 2.38A, Vmp 61V panels in parallel

40a circuit breaker/ 10 gauge

EPEVER 40A MPPT

50 a circuit breaker / 8 gauge

WZRELB 1500W 24V

20a circuit breaker / 8 gauge

2 Ampere Time 12V 100Ah wired to 24v

Main fuse - 250 and 6 gauge to terminals?

I am sort of following the attached pic.

EDIT: each panel has a 10a fuse on the power side.
 

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Panels in parallel need a fuse for each panel. Protection from many panels feeding back to one or two panel in failure. Someone else will do the calculation, but my hunch is 15 amp fuse on each panel.
You don't need the 40 amp breaker between the panels and CC, but you should have a good quality switch.
I use these BusBars; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs
Here is Blue Sea circuit wizard to calculate the wire gauge inputting different temperature rating insulation. I plug 10000 into the spot for battery CCA when sizing for LiFePo battery. That will get the fuse recommendations.
I don't like the main fuse. it is so easy to buy a cheap ANL fuse. They are everywhere.. I do like Class-T fuses for LiFePo battery main fuse. Main fuse needs be close to battery positive. The fuse protects the wire after the fuse. Fuses protect wires. Size fuses to ampacity of the wire.
 
Panels in parallel need a fuse for each panel. Protection from many panels feeding back to one or two panel in failure. Someone else will do the calculation, but my hunch is 15 amp fuse on each panel.
You don't need the 40 amp breaker between the panels and CC, but you should have a good quality switch.
I use these BusBars; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs
Here is Blue Sea circuit wizard to calculate the wire gauge inputting different temperature rating insulation. I plug 10000 into the spot for battery CCA when sizing for LiFePo battery. That will get the fuse recommendations.
I don't like the main fuse. it is so easy to buy a cheap ANL fuse. They are everywhere.. I do like Class-T fuses for LiFePo battery main fuse. Main fuse needs be close to battery positive. The fuse protects the wire after the fuse. Fuses protect wires. Size fuses to ampacity of the wire.
It looks like 8 gauge comes out ok for all of it. For the main breaker, I get everything from 60a to 225a.
 
Panels in parallel need a fuse for each panel. Protection from many panels feeding back to one or two panel in failure. Someone else will do the calculation, but my hunch is 15 amp fuse on each panel.
You don't need the 40 amp breaker between the panels and CC, but you should have a good quality switch.
I use these BusBars; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs
Here is Blue Sea circuit wizard to calculate the wire gauge inputting different temperature rating insulation. I plug 10000 into the spot for battery CCA when sizing for LiFePo battery. That will get the fuse recommendations.
I don't like the main fuse. it is so easy to buy a cheap ANL fuse. They are everywhere.. I do like Class-T fuses for LiFePo battery main fuse. Main fuse needs be close to battery positive. The fuse protects the wire after the fuse. Fuses protect wires. Size fuses to ampacity of the wire.
Are these the fuses to avoid? https://www.amazon.com/Skar-Audio-S...647265562&sprefix=250+anl+,aps,61&sr=8-3&th=1
 
I bet they are from china and are the typical shit quality fuses available in most audio shops.
 
TheFuseShop.com has Eaton Bussman ANL fuses at a very good price - about $9. They are tin-plated copper instead of aluminum, and don't fail prematurely. Personally I like the Spartan Power holders, but there are other decent ones. If you're going to connect a lifepo4 battery there then a class-T fuse is recommended. Don Rowe is a good source, Best RV Converter is another. That's a good place for a BlueSea master cutoff switch so you can isolate your battery for service or maintenance.

A switching breaker to SCC is common, but again an Eaton Bussman brand at a minimum - the rest tend to create a lot of resistance and can overheat. Some of the really cheap ones are really junky. Also convenient to be able to disconnect your controller from the system.

A mini din rail breaker works well as a PV disconnect and is recommended, unless you can easily get to the the main MC4 connectors to cut your panels off. Maintenance and servicing convenience again.

What is the inverter capacity? Wire gauge is based on current - generally a 1000w inverter has the potential to pull 100A DC, so 4 gauge wire is minimum, some brands will recommend even larger than that, up to 2/0. Main battery wires should be minimum 2G IMO.

If your panel array indeed does need fusing, inline type are convenient, or they can be in a combiner box. Since you didn't indicate how your array is configured it's hard to say.

A 40A mppt should have 6G wire per the installation manual.

Here's a good wire size chart - use the 3% drop values:

DC_wire_selection_chartlg.jpg
 
With parallel panels the total amperes will feed into the bad panel. That at best will short the panels so there is no charging. At worst it could cause a fire by overloading the bad panel.
 
TheFuseShop.com has Eaton Bussman ANL fuses at a very good price - about $9. They are tin-plated copper instead of aluminum, and don't fail prematurely. Personally I like the Spartan Power holders, but there are other decent ones. If you're going to connect a lifepo4 battery there then a class-T fuse is recommended. Don Rowe is a good source, Best RV Converter is another. That's a good place for a BlueSea master cutoff switch so you can isolate your battery for service or maintenance.

A switching breaker to SCC is common, but again an Eaton Bussman brand at a minimum - the rest tend to create a lot of resistance and can overheat. Some of the really cheap ones are really junky. Also convenient to be able to disconnect your controller from the system.

A mini din rail breaker works well as a PV disconnect and is recommended, unless you can easily get to the the main MC4 connectors to cut your panels off. Maintenance and servicing convenience again.

What is the inverter capacity? Wire gauge is based on current - generally a 1000w inverter has the potential to pull 100A DC, so 4 gauge wire is minimum, some brands will recommend even larger than that, up to 2/0. Main battery wires should be minimum 2G IMO.

If your panel array indeed does need fusing, inline type are convenient, or they can be in a combiner box. Since you didn't indicate how your array is configured it's hard to say.

A 40A mppt should have 6G wire per the installation manual.

Here's a good wire size chart - use the 3% drop values:

DC_wire_selection_chartlg.jpg
Ok, so this 250a fuse - https://www.bluesea.com/products/5118/Class_T_Fuse_-_250_Amp
This fuse holder - https://spartanpower.com/product/300a-500a-anl-fuse-kits/
Is my 50a breaker ok for the inverter? https://www.amazon.com/gp/product/B07GFCNN7T/ref=ewc_pr_img_3?smid=A28LQLUGKI63QO&th=1
Cut off switch - https://www.amazon.com/Blue-Sea-Systems-Circuit-Battery/dp/B000MMC914?ref_=ast_slp_dp&th=1
Here is my inverter - https://www.amazon.com/gp/product/B07SGXHXMZ/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&th=1
Each of my panels has an inline 10a on the + side.

Is it ok that the wires connecting the batteries to each other (+ to -) and to the fuse and ground bus bar are 2 gauge and the rest are 6 gauge?
 
For your main fuse consider a class-T if you're going to connect a lifepo4 battery. This is something implored by the experienced advisors here on the forum. Something about the potential of 20K volts in a direct short circuit, that an arc can jump across a lesser fuse and weld itself together. Photo below if my pack with a class-T and a master cutoff switch before it gets connected to my 12V system.

So it's either or. ANL fuses are common to chargers and inverters, sized appropriately. Class T for a primary fuse.

For the 50A switchable breaker to your solar controller, consider one of these:

Yes, Bussman breakers cost more, said to be higher quality internals with much less incidence of failure or resistance.

Your BlueSea switch is a good one, their heavy duty model. This one would also work, might be easier to manage/install in your space:

For your inverter - you're doing a 24V system? I'm probably not the one to advise on a 24V system - everything I work with is 12V.

Panels are fused - good there. I don't think they're needed on a single pair.

A 1500W inverter will pull 150A in 12V - 75A in 24V. #6 wire is probably okay, other inverter manufacturers recommend at least #4.

I used #2 wire for mains as I'll never pull more than 100A on this one. My inverter is 600W. 230Ah prismatic cells:



On the left side here, ANL fuse to charger and inverter. The right said neg connects to a smart-shunt for a battery meter. Everything goes to a main buss connection point on the 12V system for loads with #2 wire. BMS is 120A max.

 
You are a life saver. I have attached my cart - I have terminals and heat shrink. I also have 4 and 8 gauge wire.

Amazon does not seem to stock a 250a t-fuse. I'll order it from somewhere else.

Also, your setup is really clean. What is the case it is in?

EDIT: do I need 2 50 amp breakers - one for the controller and one for the inverter?
 

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The cell compression casing is starboard - it's a DIY pack from cells.

For a main fuse, 250A might be a little high - it should be sized based on projected max current @125%. So if your inverter pulls up to 150A x 125% = 187.5, a 200A might be more appropriate. Can also be based on ampacity of your wiring.

Donrowe.com is a good source for fuses, I got mine here, link to 200A class T with holder:

I would also invest in proper lug terminals, copper is okay but tinned is better, and a proper crimp tool, adhesive shrink wrap. Some of your terminals look decent, those yellow pvc insulated ones are probably not adequate. A proper crimp literally cold-welds the strands into the lug.

Since I'm fairly low amp I got by with a Temco hammer crimper:

A lot of the guys here really like a die type crimper, hydraulic tool. They are kind of expensive for one-time use. Others prefer die-less crimps - and those are cheaper - the hammer crimper is dieless. You don't have to worry that your crimp isn't sufficient from an incorrectly sized die. Die type crimps are more uniform and prettier for sure. For high-amp systems they are likely well worth it.

I cut one of my crimps apart to verify they are 'cold-welding'. There shouldn't be any air space between the strands for moisture to get in and resultant corrosion. The most common problems with these circuits are from poor/bad connections. Here you can't tell where the lug terminal ends the copper strands start - it's all welded together solid. Then you put a piece of shrink wrap tubing over the wire insulation/lug joint - the adhesive type is more more durable than standard shrink tubing:



Building the DIY battery pack:



 
Oh, that pic is from Mobile Solar - I am just using it as a guide. I have attached my pic.

I think this is the crimper I own - Amazon
 

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