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?

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.

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.

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.

You adapt to the situation. For example my 3x serial solar panels at 92V and with 62' of 10ga wire have a 0.4% voltage drop to the controller. One of the reasons I didn't wire them in parallel.The second major reason is shadow performance which is another topic.

12v wire thickness | Good Sam Community

wa8yxm
Explorer III
Oct 18, 2023
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.
1995brave
Nomad
Oct 18, 2023
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.
CA_Traveler
Explorer III
Oct 18, 2023
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.
CA_Traveler
Explorer III
Oct 18, 2023
deleted
CA_Traveler
Explorer III
Oct 18, 2023
You adapt to the situation. For example my 3x serial solar panels at 92V and with 62' of 10ga wire have a 0.4% voltage drop to the controller. One of the reasons I didn't wire them in parallel.

The second major reason is shadow performance which is another topic.
Chum_lee
Explorer
Oct 18, 2023
timelinex wrote:
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.

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.

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

Look at the cables/connectors from your chassis battery to the starter motor. What size/material/insulation are they? It's quite normal for your starter motor to draw well over 250 amps @ 12 volts (nominal) to start the vehicle. Granted, it's usually for only a short time, but when you need it, . . . . you need it. It's not just the size of the wire, the connectors are important too, since over time, often (not always) they initiate the failure of the wire.

Chum lee
CA_Traveler
Explorer III
Oct 18, 2023
Especially unseen corrosion on connectors near flooded batteries.
Grit_dog
Navigator
Oct 18, 2023
For a short run, to power a 3000W inverter, 1/0 is sufficient.
4/0 is ridiculous unless you were hooking it up across the street.
Boomerweps
Explorer
Oct 18, 2023
Read the reviews on Amazon. Most complain about the wires supplied with inverters is TOO small, mostly 4 AWG.
Use at least 1/0awg or better yet, 2/0awg. If making your own, ask for the given gauge welding cables at your electrical supply store. Welding cable is very flexible with many smaller wires.
Another consideration is that many, myself included, decide that a given inverter is a little small and get a higher power unit. If the wiring is extra thick for the smaller inverter, it can support the larger unit.
IMO, the inverter should be directly connected to the battery bank with only a fuse or circuit breaker on the positive cable.
ktmrfs
Explorer II
Oct 18, 2023
go to a welding shop and buy the length of welding cable in the gauge you want and have them put logs on it for you. Many shops can do that.

Otherwise you'll need a hybraulic crimper. And based on what I've done I'd suggest and least 2/0 wire if not 3/0. Most inverters have a low voltage shutoff and a few tenths of a volt drop can make the difference in inverter running and inverter shutting down.

And make sure you use the correct fuse to the inverter. they are big, bulky but meant to protect under the high load conditions.

Welding cable has lots of very fine wire so it is very flexible and easy to route.

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