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Correct size Wires for Batteries

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kashxpert

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I have 2 x 51.2v LFP batteries connected via Busbar to Growatt SPF5000ES.

I want to check if I am using the correct wire sizes. Currently I'm using 2 AWG (33.6 mm2) rated for 188A.

I am about to add a Class T fuse between Busbar and the Inverter and realised the total potential is 200A, I got a class T fuse rated for 250A.

Question is that, should I also be upgrading the wires from Busbar to the inverter as the current wires are rated for 188A? Is that right?
 
hwy17 said:
250 amp fuse should go on 1/0 wire or larger.
Click to expand...

And you should fuse each battery with a class T rated at 125% of amps. In your case 125a as close to bus bar as possible. This is if your wires from battery to bus bar are more than 7" long.

Also your wires between batteries and inverter should be pure copper welding wire, windy nation is a good brand.

From the output of the inverter to panel should be THHN, assuming your inverter goes to a panel verse just having a poug on the back.
 
Could I use 1/0 cable from the busbar to the fuse then use same 2AWG from the fuse to the inverter? And downgrade the fuse from 250A to 200A?
 
kashxpert said:
Could I use 1/0 cable from the busbar to the fuse then use same 2AWG from the fuse to the inverter? And downgrade the fuse from 250A to 200A?
Click to expand...

#2 welding wire rated 105c is good for 208amp, that is from the windy nation chart. 1/0 is good to 285 amps. You need to use 1/0 all the way to the inverter and leave the fuse alone.

wheelman55 said:
What wire size does Growatt recommend?
Click to expand...
Good point, check the size the mfg recommends so you have a good fit. Also they will list a fuse size most of the time.

So if that information conflicts with what we said post back before buying.
 
Thank you, I did check the manual of Growatt and they recommended 2AWG so I bought wires we have locally called 2B&S 32mm rated for 188A at 30 degree Celsius.

I have been using system with these wires and haven't had any issues, Growatt didn't list breaker size but recommended to have one.

I checked the data I have been collecting via Victron smart Shunt and the max amps follow we have recorded is 68A.
 
If you stick with Growatts recommendation of 2 AWG copper wire, buy a less than 188 amp fuse, plus an extra and you should be good to go.
 
188a is good enough.

I looked at the wire on the website and I am not sure I have exactly the right one you bought. It quotes it as 250~300amps at 30c which doesn't match what you posted. It is listed as automotive wire which means battery wire in that size.. Either way it works.

I would put in a 175amp Class T + holder with cover

NOTE - this is not ideal wire for hooking up batteries to an inverter because it lacks flexibility, but for a stationary install it is just fine.
 
robbob2112 said:
188a is good enough.

I looked at the wire on the website and I am not sure I have exactly the right one you bought. It quotes it as 250~300amps at 30c which doesn't match what you posted. It is listed as automotive wire which means battery wire in that size.. Either way it works.

I would put in a 175amp Class T + holder with cover

NOTE - this is not ideal wire for hooking up batteries to an inverter because it lacks flexibility, but for a stationary install it is just fine.
Click to expand...
Thank you, these are 2B&S which is 2AWG and rated for 188A at 30 degrees.

It's for a stationary installation we did 6 months ago and have been working fine. All potential loads it never exceeds 70A. It's for a Tiny House.

I'm thinking the same, I will get 175A Class T fuse and place it between the busbar and the Inverter using the same cables.
 
ScrotusGobbleBottom said:
That is right where my tiny house sits :) 70 amps. I have a 100 amp fuse after my buss bar.
Click to expand...
I saw on YouTube then since total potential is 200A combined two batteries then I should have fuse 200 x 125%. I don't understand why. I agree that if our usual load won't exceed 100A then why have a buffer up to 250A. Does that make sense to you?
 
kashxpert said:
I saw on YouTube then since total potential is 200A combined two batteries then I should have fuse 200 x 125%. I don't understand why. I agree that if our usual load won't exceed 100A then why have a buffer up to 250A. Does that make sense to you?
Click to expand...
Not sure that makes sense.
The context is wrong.

That statement came from someone who wanted to be able to max draw their batteries. You and I are not looking for that. We have a different situation.

I dont fuse the total output of the batteries...
I fuse the wire that I selected to use for the load.
My lightest wire is 2 Awg / 35mm so I use 100 amp fuse to protect the wire from my decided max load of 100 amps.
 
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