Unable to get 4/0

[Famous_addit]

Hello

I am currently located in Italy and my set up calls for 4/0 to connect my battery and inverter. Unfortunately in Italy they use mm2 as the unit of measurement and I am only able to procure 95mm2 cable unless I ship it in from the states. The latter obviously takes more time and money.

With a 5000w inverter can I get away with 95mm2 cable. This roughly translated to 3/0 though the conversion to metric isn't exact.

Many thanks

EDIT: this is a 12v system

 

[HRTKD]

Can you run two smaller cables instead of one larger cable? My inverter has two posts for each leg.

 

[Struc]

You forgot to mention the voltage of the inverter. For needing that size cable, I would suspect 12v?

 

[Famous_addit]

You forgot to mention the voltage of the inverter. For needing that size cable, I would suspect 12v?

yes , sorry. It's 12v.

 

[Struc]

If you can't get it, I tend to agree with @HRTKD and see if you can use 2x2/0 cables or something like that.

 

[rmaddy]

5000W on a 12V battery! Really? That's up to 500A being pulled from the battery. That's a ridiculous amount of current. That needs wire much larger than 4/0AWG. For 5000W you really should be at 24V or 48V, not 12V.

What does the manual for the inverter suggest for wiring?

 

[chrisski]

This set up will likely end up in the “danger zone—> up in smoke” if built at 12 volts and run at several thousand watts for any period of time.

 

[Famous_addit]

Thanks all. I have decided to return the inverter and reconfigure the system to 24v. I appreciate the input.

 

[Hedges]

Mobile system or stationary?
Many of us use 48V equipment.

 

[12VoltInstalls]

Mobile system or stationary?
Many of us use 48V equipment.

have decided to return the inverter and reconfigure the system to 24v.

I’m an advocate of and personally use the heck out of 12V but there’s a limit to where 12V is practical.
I’d consider 48V as suggested.

 

[73powerstroke]

5000W on a 12V battery! Really? That's up to 500A being pulled from the battery. That's a ridiculous amount of current. That needs wire much larger than 4/0AWG. For 5000W you really should be at 24V or 48V, not 12V.

What does the manual for the inverter suggest for wiring?

Some serious stuff here. Definitely 24v would be so much easier, or 48v.

 

[ericfx1984]

We are getting by at 12 volts.. and we often times are running 1500 to 2,000 Watts continuous off of the batteries...

 

[Famous_addit]

Mobile system or stationary?
Many of us use 48V equipment.

It's a stationary set up. The only reason for running at 12v is I can get very cheap 200ah batteries but only in 12v. After seeing the advice above I was planning on running 2 of these in series as per Will's video on how to do this correctly.

- Q1) Can this be done safely with 4 in series to run @ 48v? (in which case I would be looking at one of these inverters: https://www.vevor.it/invertitore-so...-caricatore-solare-50a-con-lcd-p_010485988472 )

- Q2) The safety booklet that came with the batteries specifically says not to run them in series. Is this just standard text to prevent people doing so without guidance?

 

[ericfx1984]

The only reason for running at 12v is I can get very cheap 200ah batteries but only in 12v. After seeing the advice above I was planning on running 2 of these in series as per Will's video on how to do this correctly.

So I just want to make sure you understand something...

200(ah) x 12v = 2.4 kWh
100(ah) x 24v = 2.4 kWh
200 (ah) x 24v = 4.8 kWh
50(ah) x 48v = 2.4 kWh
100 (ah) x 48v = 4.8 kWh
200 (ah) x 48v = 9.6 kWh
200(ah) x 3.2v = 0.64 kWh

Hopefully this illustrates that you are not actually getting anything for cheap in order to really understand the storage capacity of a battery it needs to be calculated in either what hours or kilowatt hours

I mean if this statement were accurate it would mean that all the companies making 24, 48, 72, 96 volt batteries were just wasting their time.. why not just make a 3.2 volt battery and run everything at 3.2 volts? You have to look at the total capacity which would be amp hours multiplied by voltage

 

[Famous_addit]

So I just want to make sure you understand something...

200(ah) x 12v = 2.4 kWh
100(ah) x 24v = 2.4 kWh
200 (ah) x 24v = 4.8 kWh
50(ah) x 48v = 2.4 kWh
100 (ah) x 48v = 4.8 kWh
200 (ah) x 48v = 9.6 kWh
200(ah) x 3.2v = 0.64 kWh

Hopefully this illustrates that you are not actually getting anything for cheap in order to really understand the storage capacity of a battery it needs to be calculated in either what hours or kilowatt hours

I mean if this statement were accurate it would mean that all the companies making 24, 48, 72, 96 volt batteries were just wasting their time.. why not just make a 3.2 volt battery and run everything at 3.2 volts? You have to look at the total capacity which would be amp hours multiplied by voltage

Sorry, you seem to misunderstand me. I'm aware of the above.

What I mean is a) I can get 200ah 12v batteries for like 800 euro, delivered in a day or two. I can't get 24v or 48v batteries at all, let alone that cheap or quickly.

B) because I am running a full off grid system I would prefer to run 24v or 48v.

Hopefully that clarifies.

 

[rhino]

I didn't see link or even type of battery those 200Ah batteries are you are referring to.. but there is no issue putting 12V lead acid batteries in series to have a 48V nominal battery bank. If they are 12V LiFePO4 batteries which will have a BMS you'd have to verify they can be put in series to form 48V battery since some BMS's don't support that.

 

[Hedges]

As Rhino said.

In addition, if you are able to connect 4x 12V lithium batteries in series (because their FETs can handle the voltage from other batteries when BMS disconnects.), imbalance in state of charge will develop. Eventually, one 12V battery will have to disconnect for high voltage while others still haven't charged past the knee.

Probably you can observe that developing before it happens with volt meter or reading BMS, and use 12V charger on low batteries.
Much nicer to have a single 48V 16s BMS.

48V is the way to go for larger systems, like whole house. For a component system rather than AOI, one can look for things that support multiple voltages, for instance batteries, fuses, and charge controllers, so later if replacing a 12V or 24V $500 inverter with a 48V $3000 one nothing else has to change.

If you can start with a 48V inverter and have option to add more of same inverter, that could be better.

Maybe start with the 12V batteries you can get, and in the future open them up, connect a 48V BMS?
Those sound like "drop in" lithium replacements for lead-acid. Quality and performance vary.
Can you get "server rack" batteries? Quality and performance also vary there.
In either case, make sure its current output can support inverter draw. And look into having a resistor precharge circuit, to avoid inrush current when connecting inverter (which contains capacitors.)

 

[stienman]

For those referring to this thread in the future looking for thick cable, look towards welding suppliers in your country. Every country has welders and welding supply, and you should be able to ask them to supply the 120mm2 or 300MCM cable needed when your electrical suppliers don't want to carry it.