12v wire thickness

[timelinex]

I have a 2kw inverter and will be getting a 100a converter for my 2 100ah lifepo4 batteries. Currently I'm just using whatever ga wires came with everything (a bix of 4/6/8).

I am planning on changing everything to connect through a BUS BAR and upgrade all the cabling to heavier ga. I want to future proof it to handle a 3kw inverter.

It's been REALLY confusing figuring out what wires I need. ALMOST everything online "(forums and articles) tell me I need something like a 4/0 guage, which is HUGE. That makes sense considering 3kw can reach 200-250 amps. Except the fact that no OEM items come with something nearly this thick.

I think the reason all these recommendations may be wrong is they do not account for length of wire being very short in our use cases.

Can anyone confirm?

I've found this site, which DOES take into account length:

http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/

It looks like considering everything is definitely under 4ft, I won't need anything over 4ga. On the other hand, I'm pretty sure that ampacity is over max 4ga rating when you look it up.

Using this calculator: https://baymarinesupply.com/calculator I get 2ga for my 2kw and 1/0 minimum for the 3kw. If this is the case I would likely go with 2ga to save money and more importantly because I don't even think the 1/0 would fit in the current inverters lugs.

Can anyone make any recommendations based on actual knowledge and not just heresay or making best guesses?

[CA_Traveler]

Voltage drop is absolutely dependent upon wire size and length. A 5% drop for 12,7V is 0.6V which means a 12V battery would be 12.1V. More than I'd want.

There are various wire calculators availabke.

[1995brave]

I'm running 2awg from my 2-200ah Lifepo4 batteries to a buss bar and then from there 2awg to my 2kw inverter. Then I'm running 8awg for the solar panels, DC-DC converter, fuse panel and charger. Also to the leveling jacks.

[wa8yxm]

I used 2/0 on my 2000 watt.. Still do in fact.> Though I'm no longer in an RV. it's the emergency supply here in my apartment these days.. WORKS too had a 13 hour power fail a few weeks ago.. Ran the fridge off the 2KW inverter along with a bunch of other stuff.. Ran the tiny aux freezer off another inverter. Nothing thawed.