Can anyone help with wire sizing

[Whome]

I bought 10-100 watt solar panels, a 3000 watt Victron Multiplus Inverter/Charger, Victron MPPT 150/85 Charge Controller and 4-100 amp hour Battle born batteries.

My question is what gauge wire do I use to connect all this. I watched a lot of videos but was even more confused.

 

[svetz]

Take a look at What wire gauge should I use? and see if that helps...

 

[Justin Laureltec]

@Whome, where did you purchase your Victron equipment? All authorized Victron distributors are strictly required by Victron to provide technical support for the components they sell - technically this is only for the Victron equipment, but that is generally interpreted to also mean advising on what wire gauge and fuse sizing is required and other things like that. Now, all of the minimum wire gauges and fuses are also included in your user manuals for every one of your components, however, so my advice is: 1. Read your user manuals. 2. If you still have questions, contact the authorized Victron dealer or distributor from whom you purchased the components.

 

[dobol-lb]

Good Afternoon,

I need an expert check on wire sizing. I need to know if I am applying correctly the methodology on this website to determine the appropriate wire gauge using 3% voltage drop ( https://www.altestore.com/howto/wire-sizing-tool-for-12-24-and-48-volt-dc-systems-a106/ ). The other thing is if I am correctly applying the wire length in the methodology.

Methodology Example - Is this correct?
Installing a 20Amp DC-DC charger (made by Renogy) between the vehicle's 12V battery/starter and the 12V LiPO4 parallel connected solar batteries, I estimate approximate one way cable length to be 30-feet (length of vehicle of 22-feet + 8-feet for change in directions). Applying the methodology:

VDI = (Amps x Feet) / (%Voltage Drop x Voltage) = (20x30)/(3x12) = 51.55. This would require a 0 gauge wire - HUGE!!

I will still need a 0 gauge wire even if I assume a vehicle battery voltage of 12.5V so its still a little over 12V when it gets to the battery. I get a 2 gauge wire if I want to live on the edge by assuming a cable length of 25-feet.

Wire Length Example 1:
Continuing with the DC-DC charger example above, even if I place the DC-DC charger in the middle of the 30-ft run between the vehicle battery/starter and the solar batteries, the wire sizing still needs to use 30-feet and not 15-feet correct?

Wire Length Example 2: Sizing cable between solar batteries and bus bar.
The cable between the solar batteries and bus bar will carry both inverter load and DC loads. To keep the example simple, suppose I have no DC load and I have a 4,000 Watt inverter. I know that the inverter will never see 4,000 Watts but only about 3,500 Watts maximum when the induction cooktop (1800W), water heater (1440W) and other misc items + inverter losses. So to size the cable between the bus bar and inverter, does the cable length in the calculation needs to be all the way to the inverter or just to the bus bar?

Thanks again for your wisdom,
Noel

 

[Oddball]

I calculated it and only got a 4awg for 30ft. Also using a different formula and table though. Unless you're using building wire below 1awg the wire is probably rated for much higher Temps than the section of the table they are using.

Voltage Drop Calculator | Southwire

www.southwire.com

This is a link to the southwire calculator I use most of the time.
Generally you want to calculate total run of wire and within total systems you would generally use 5% total drop from service to point of use as max acceptable. This is also part of why higher voltage is used due to the cost/efficiency advantages. It may quickly become an advantage to use a higher voltage with a step down converter at the end due to wire size.

 

[Supervstech]

Keep in mind the circuit entire length is needed to calculate wire size and voltage drop.
30’ between components is a 60’ run length.

 

[Oddball]

The calculator I linked takes that into account. I haven't seen the other calculation method before. That page doesn't take into account the allowance to use a higher temp range for some of the calculations or over a certain size.

 

[mapguy525]

@Whome, where did you purchase your Victron equipment? All authorized Victron distributors are strictly required by Victron to provide technical support for the components they sell - technically this is only for the Victron equipment, but that is generally interpreted to also mean advising on what wire gauge and fuse sizing is required and other things like that. Now, all of the minimum wire gauges and fuses are also included in your user manuals for every one of your components, however, so my advice is: 1. Read your user manuals. 2. If you still have questions, contact the authorized Victron dealer or distributor from whom you purchased the components.

Agree with the above as a starting point. Pay close attention to the Owners Manual guidance regarding wiring size and Over current protection -especially on the battery to inverter charger cables. Proper operation and use of the Multiplus requires larger cabling than most anticipate due to the power boost function, surge function, and load support function.

Personally, 3% voltage drop is to much for me on critical circuit wiring.

 

[Zil]

I look for 1% or less in charging circuits.

 

[Mex Rider]

@Whome, where did you purchase your Victron equipment? All authorized Victron distributors are strictly required by Victron to provide technical support for the components they sell - technically this is only for the Victron equipment, but that is generally interpreted to also mean advising on what wire gauge and fuse sizing is required and other things like that. Now, all of the minimum wire gauges and fuses are also included in your user manuals for every one of your components, however, so my advice is: 1. Read your user manuals. 2. If you still have questions, contact the authorized Victron dealer or distributor from whom you purchased the components.

Hi Justin, bought my Multi 3000 from you. Can you please recommend a wire size for the chassis ground? Can't find it in the service/installation manual or operators manual. Have some questions about the AC side, thought of using a Blue Seas 3 panel... will call you at work on Monday. Anyway, thanks