0 AWG into 2AWG slot?

Hi There

Firstly, I have a EASun 3kv 24v all in one.

The only thing I've noticed is, it can only take a 32mm cable (or 2 AWG cable) into its input.

Ideally, from all the reading in these forums, sounds like 0 AWG would be alot better fit.

So question - What do others do. This is the same connectors on the MPP etc. so what everyone else do?

Also the daly 250a BMS only has 2AWG cable anyway. so it there any point in going larger?

Thanks in advance.

So if I can decipher your question; should my cable (wire) be 2 AWG or 0 AWG?
Is this correct?

Wait, but, you tell us your unit can only fit 2 AWG wire.

"IT there any point is going larger"; what are you asking, should I spend more for 0 AWG (which won't fit) or what?
maybe it's a "alot better fit."

Sorry I am confused. Glad this is the only thing you've noticed.

Ryang said:

Also the daly 250a BMS only has 2AWG cable anyway. so it there any point in going larger?

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Voltage drop across the cable might be the point. If the components of the system are unavoidably spread out the drop can be compensated by using heavier wiring. A well designed system should have all the high current paths as short as possible. If your device can only accommodate 2 AWG max wire size then all else being reasonable, that's fine.

If you do need to have longer runs of heavier wire you can do it a few ways. One way is to connect a short 2 AWG wire to some connecting thing, a bolt, a bar, what ever, then attach your 0 AWG there and continue on. That thing could even be a fuse holder. You could also trim down the 0 AWG so that it fits in the 2 AWG terminal on the device but beware, the heavier wire could mechanically overload the terminal, ie break its solder joint etc. Current through the thinned part won't be an issue since the device is designed to work with 2 AWG so thinned down as little as possible the 0 AWG is not going to be any worse than 2 AWG.

Ryang said:

Hi There

Firstly, I have a EASun 3kv 24v all in one.

The only thing I've noticed is, it can only take a 32mm cable (or 2 AWG cable) into its input.

Ideally, from all the reading in these forums, sounds like 0 AWG would be alot better fit.

So question - What do others do. This is the same connectors on the MPP etc. so what everyone else do?

Also the daly 250a BMS only has 2AWG cable anyway. so it there any point in going larger?

Thanks in advance.

Click to expand...

Well... 3000W at 24V is 125A.

times 1.25 is 156A

156 amps SHOULD be 2/0 for minimal losses, #2 should only handle 80A

an article on a dc wire calculation site says this...



In conventional home electrical systems (120/240 volts ac), wire is sized primarily for safe amperage carrying capacity (ampacity). The overriding concern is fire safety. In low voltage systems (12, 24, 48VDC) the overriding concern is power loss. Wire must not be sized merely for the ampacity, because there is less tolerance for voltage drop (except for very short runs). For example, a 1V drop from 12V causes 10 times the power loss of 1V drop from 120V.

Might be time for the relevant pages of the device's manual to be posted in case it actually says 2/0.

AWG 2/0 2 is good for 175A in free air with 75c or higher rated insulation. Ambient conditions not withstanding. This would be for 100% duty cycle, ie always carrying 175A. If current flow is intermittent you can push more amps through provided sufficient time is allowed for everything to cool back down otherwise the insulation is up in smoke.


*edit to fix incorrect wire gauge*

Ryang said:

The only thing I've noticed is, it can only take a 32mm cable (or 2 AWG cable) into its input.

Click to expand...

I think @Ryang is saying the maximum wire guage that the mechanical lugs on his device will accept is 2 awg.
You could use reducers https://www.amazon.com/Premium-Reducer-Gauge-Cable-Input/dp/B08GLVC4JM
Not sure of the quality of that specific one but something like it.

Sorry I was out.

Thanks everyone for your input.

Yes smoothjoey is correct in that I am saying the mechanical lugs (and manual) suggest 2 AWG.

I wanted to go larger, atleast 0.

My original question was, if you go bigger cable, how do you fit it into the mechanical lugs, and, secondly, is there any point (does it create a bottleneck effect anyway). is this therefore SAFE?

As Supervstech says, ideally it should be 2/0.

That all said, the BMS is only 2 AWG wire aswell, and ita a 250amp rated daly bms.

So I am a little confused between why the bms is 2 AWG, the Inverter suggests 2 AWG, but the suggestions say larger. And if so, how do you fit a larger cable?

I hope I am making more sense.

FYI - cable runs will be 50cm. As short as possible.

It comes down to the environment. Certain assumptions are made with where you will be putting the wiring and that affects the insulation temperature. If you put a wire in a conduit the amp rating will have to be derated compared to if it's in free air because it can't get rid of the heat it produces as effectively.

This causes a whole bucket of confusion because usually this detail isn't mentioned. One web page says X amps, another says Y and no explanation of why is given.

gnubie said:

It comes down to the environment. Certain assumptions are made with where you will be putting the wiring and that affects the insulation temperature. If you put a wire in a conduit the amp rating will have to be derated compared to if it's in free air because it can't get rid of the heat it produces as effectively.

This causes a whole bucket of confusion because usually this detail isn't mentioned. One web page says X amps, another says Y and no explanation of why is given.

Wire Size Chart for Conductors in Free Air

Wire Size Chart: Allowable Ampacities of Conductors in Free Air - 30C

wiresizecalculator.net

Click to expand...

Thanks

so is it worth going larger and finding a reducer, or just shaving the wire off at the crimp?

With your wire length and assuming it's not covered up / in conduit etc, I'd be happy to use 2 AWG myself. In fact, I do! You also need to consider the loads you have on your inverter and how long you expect to be at full power. If you only find yourself at 3000W for 10 minutes every now and then you have even more space to breathe. Pay attention to the insulation temperature rating though, you don't want it going soft and able to be deformed / pushed through.

I'm not an expert, just a semi-retired technician, but I can still read spec sheets etc and put 2+2 together. If someone can present a good argument for you having to use heavier wire, pay attention.

Find the biggest crimped ferrule that will fit your inverter input.

Remove strands from the 0 AWG until you can fit it in the ferrule, then crimp and insert.

I’m betting this will have more ampacity than what is connected to the other side of that inverter input inside the box..

gnubie said:

With your wire length and assuming it's not covered up / in conduit etc, I'd be happy to use 2 AWG myself. In fact, I do! You also need to consider the loads you have on your inverter and how long you expect to be at full power. If you only find yourself at 3000W for 10 minutes every now and then you have even more space to breathe. Pay attention to the insulation temperature rating though, you don't want it going soft and able to be deformed / pushed through.

I'm not an expert, just a semi-retired technician, but I can still read spec sheets etc and put 2+2 together. If someone can present a good argument for you having to use heavier wire, pay attention.

Click to expand...

Will the smaller wire handle the load for short times? Sure.
Will it waste precious energy? Absolutely.
DC solar wiring shouldn’t always just be what the insulation can handle. It is about voltage drop from conductor resistance.

Will there be significant power loss across a 50cm piece of wire?

Let's find out.

Voltage drop across 50cm (two 50cm cables) of 2 AWG at 148A, 0.076V. Power dropped, 11W. 11W compared to the power flowing, 3.5kW. I think anyone here can live with that.

Will the smaller wire handle the load for short times? No. It will handle it indefinitely in the situation described, that is 2 AWG insulated (as in the 'plastic') wire in free air with ambient 30c, using 75c rated insulation. Sure it will get hot but it is rated to do it indefinitely. For ever. 24 x 7. You can do the maths if you like to work out the rate of temperature rise and ultimate temperature too if you can get the thermal resistivity of the insulation.