2000 W inverter wire and fuse size

[TiKiMaTT]

Is wire size and fuse calculated based on the Continuous Power specifications (2000 W renogy pure sine), or the Peak Surge, which is 4000 W, listed in the specs.?

Im assuming that the same size wire would also be used to connect the batteries together? (2 renogy 100 Ahr LiFePo4 in parallel)

What is best practice, to go directly to the inverter, or to a bus bar that will also be used for distribution to a DC fuse block.

 

[John Frum]

Continous

As far as best practice there is no consensus.
I say yes to busbars but others say no.

2000 ac watts / .85 conversion factor / system_low_voltage_cutoff = max_continuous_dc amps
max_continuous_dc amps * 1.25 fuse_factor = fuse_amps
fuse_amps must be less than or equal to wire_amps

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[TiKiMaTT]

Thanks. That’s the first I’ve seen the low voltage cut off used. Inverter in question lists 10.0V +-.5.
Any preference on fuse type? I’m thinking either ANL fuse or a MRBF terminal fuse?

 

[John Frum]

Thanks. That’s the first I’ve seen the low voltage cut off used. Inverter in question lists 10.0V +-.5.
Any preference on fuse type? I’m thinking either ANL fuse or a MRBF terminal fuse?

Mrbf
The low voltage cutoff should be based on the battery chemistry. 3.0 volts per cell for lifepo4.
Because your inverter is 2000 watts you should consider 24 system volts.

 

[RCinFLA]

How long is the line length from your batteries to inverter? For 12v inverters it is all about voltage drop..

 

[TiKiMaTT]

Mrbf
The low voltage cutoff should be based on the battery chemistry. 3.0 volts per cell for lifepo4.
Because your inverter is 2000 watts you should consider 24 system volts.

Unfortunately the renogy lifepo4 that I have can only be combined in parallel.

 

[TiKiMaTT]

How long is the line length from your batteries to inverter? For 12v inverters it is all about voltage drop..

line length is short, round trip approx. 6ft.

 

[John Frum]

Unfortunately the renogy lifepo4 that I have can only be combined in parallel.

That's ok I was thinking of diy cells.

 

[RCinFLA]

At 200 amps which is about what you will approach for 2000 watts output at lower end of battery voltage.

3 foot run from battery to inverter

#2/0 gauge = 20 watts of wire power loss (warm cables), 0.10 v drop
#1/0 gauge =25 watts of wire power loss (warm cables), 0.126 v drop
#1 gauge = 32 watts of wire power loss (very warm cables), 0.16 v drop
#2 gauge = 40 watts of wire power loss (very very warm cables), 0.20 v drop
#4 gauge = 63 watts of wire power loss (hot cables), 0.32 v drop, Not recommended
#6 gauge = 101 watts of wire power loss ( very hot cables), 0.51 v drop , Don't even think about using #6

 

[RCinFLA]

Unfortunately the renogy lifepo4 that I have can only be combined in parallel.

That is because of the BMS MOSFET breakdown voltage used in their BMS.

 

[TiKiMaTT]

At 200 amps which is about what you will approach for 2000 watts output at lower end of battery voltage.

3 foot run from battery to inverter

#2/0 gauge = 20 watts of wire power loss (warm cables), 0.10 v drop
#1/0 gauge =25 watts of wire power loss (warm cables), 0.126 v drop
#1 gauge = 32 watts of wire power loss (very warm cables), 0.16 v drop
#2 gauge = 40 watts of wire power loss (very very warm cables), 0.20 v drop
#4 gauge = 63 watts of wire power loss (hot cables), 0.32 v drop, Not recommended
#6 gauge = 101 watts of wire power loss ( very hot cables), 0.51 v drop , Don't even think about using #6

just for my understanding...
2000 Watts/.85 conv. factor/ 12 V = 196 A

is there a disadvantage to using #3/0?

im just thinking of the potential 4000 W peak draw.

 

[RCinFLA]

just for my understanding...
2000 Watts/.85 conv. factor/ 12 V = 196 A

is there a disadvantage to using #3/0?

im just thinking of the potential 4000 W peak draw.

Yes, the bigger the better but you have to deal with the inverter terminal lugs at some point. You can always make a neck down connector.

By the way, the numbers I quoted are wires only. You need to add some for connectors. That dependents on quality of connectors. Do yourself a favor, do not use cheap connectors made of thin gauge metal. You would be surprised how much resistance they have from inside end of crimp tube where wire stops to where flat lug begins.

#3/0 gauge = 16 watts of wire power loss, 0.08 v drop

Only thing to worry about 4kW surge is low voltage trip. You are limited by batteries on surge current and its BMS voltage drop.

 

[TiKiMaTT]

Yes, the bigger the better but you have to deal with the inverter terminal lugs at some point. You can always make a neck down connector.

By the way, the numbers I quoted are wires only. You need to add some for connectors. That dependents on quality of connectors. Do yourself a favor, do not use cheap connectors made of thin gauge metal. You would be surprised how much resistance they have from inside end of crimp tube where wire stops to where flat lug begins.

#3/0 gauge = 16 watts of wire power loss, 0.08 v drop

Thank you very much for the input.... I’ll be getting connectors from the local marina shop here. A little bit on the high end as far as price, but all quality goods.

 

[John Frum]

Since we are talking about connectors and resistance.
I'm planning on using aluminum mechanical lugs and noox.
Any thoughts?

http://www.tnb.ca/en/pdf-catalogues/power-connection-and-grounding/mechanical-connetors/dual-rated-mechanical-connectors.pdf

 

[Zil]

I have a 2000w Samlex inverter on 12 volts. The largest draw is my 1000w microwave. Then I draw 150 amps from battery. Cables from battery fused at 300 amps to bus bar fused 250 amps to inverter. I use Blue Sea Powerbar and MRBF on the bus bar. I have a measured 1% voltage drop on the battery/inverter circuit when on full power. I don't know the inrush current, but my 2/0 can carry 300 amps continuous and much more for shorter time.
parts; https://www.bluesea.com/products/2104/PowerBar_600A_BusBar_-_Four_3_8in-16_Studs https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

 

[Zil]

I'm planning on using aluminum mechanical lugs and noox.
Any thoughts?

I am comfortable with 2/0 crimped and heat shrink terminals on my low volt stuff. Especially DC. I use FTZ lugs with the FTZ tool. On marine grade tinned copper cable.

 

[John Frum]

My idea is to use these

https://www.waytekwire.com/wps/myportal/en/products/!ut/p/z1/

With fuses for the positive busbar.
And without fuses for the negative busbar.

 

[JoeHam]

Since we are talking about connectors and resistance.
I'm planning on using aluminum mechanical lugs and noox.
Any thoughts?

http://www.tnb.ca/en/pdf-catalogues/power-connection-and-grounding/mechanical-connetors/dual-rated-mechanical-connectors.pdf

First thought: Don’t do it. Just use properly crimped copper lugs.

Second thought: If you do proceed that way check for heat production and other signs of a conduction “bottleneck” when under max current use.

 

[John Frum]

Second thought: If you do proceed that way check for heat production and other signs of a conduction “bottleneck” when under max current use.

I plan to stress test and examine every connection point with an Infrared Thermometer.

 

[RCinFLA]

Since we are talking about connectors and resistance.
I'm planning on using aluminum mechanical lugs and noox.
Any thoughts?

http://www.tnb.ca/en/pdf-catalogues/power-connection-and-grounding/mechanical-connetors/dual-rated-mechanical-connectors.pdf

Just that aluminum will have about 58% higher resistance then same sized copper. Also watch out for corrosion when mating dissimilar metals but the ones you point to have tin plating to address that.