Wire gauge seems extreme

Seedsca · June 2012

I have recently bought a Xanrex ProSine2 inverter/charger. I am setting it up in an off grid scenario on a 5th wheel. My problem is that on page 49 of the manual (on the link) it states that I MUST use a 250MCM cable size to go between the inverter/charger to the batteries. This seems obscene! I can't even find someone that carries anything over 0/4 ought cable. When I ask people if they carry it, I get the strangest looks. My brother that works as a lineman and builds power plants is telling me it seems a bit much.

People I talk to say 0/4 is way more than enough, but then I read on forums people saying that you should ALWAYS follow the manufacturer's recommendations. Is this just a liability thing? Last thing, the inverter charges at 100 amps and it does mention it peaks at 600. I am only going to set it to charge at 75 amps. Do you think I can get away with a smaller gauge or is this a golden rule and I should go with the 250 MCM?

niel · June 2012

Re: Wire gauge seems extreme

welcome to the forum. i think if it were me i'd go with 4/0 cable if you can keep the length of each wire 5ft or under. this will have a v drop loss % of about 1% calculated with a 200a draw. the inverter will pass about 2000w to the loads, but will also draw a good bit of power for itself to operate and 200a x 12v = 2400w giving a 400w leeway for inverter self consumption. usually people do not run inverters at max power and if they do it's often for short periods. also, charge at whatever current level you want to.

waynefromnscanada · June 2012

Re: Wire gauge seems extreme

Hi Seedsca, just wondering about you're overall system - - you don't mention what you have for batteries, how you plan on keeping them charged, or what you plan on powering from the ProSine 2.
We always love to pass opinion on those things.

ywhic · June 2012

Re: Wire gauge seems extreme

Um.. 2000w inverter.. I'm buying the Xantrex SW2000 sine inverter. I'll be running with some 3/0 wire I had here (free)..

My loads will be below 100 amps (1000w) usually.. and the inverter is 1800 or 1900 w constant..

Some numbers I found on the web..

AWG AMPS
4/0 302
3/0 239
2/0 190
1/0 150

Your length of cable to the batteries from the inverter will be the deciding factor..

225 amps at 5 feet will be 0.97% loss for a 12v system..

Go here and try the calc.. this is the one I use..

Cariboocoot · June 2012

Re: Wire gauge seems extreme

Page 3-3 of the manual says: "DC cable, sized appropriately for load and application."

It's a 2kW 12 Volt inverter. 2/0 AWG will handle it if the runs are short (under 5') 4/0 AWG if they're longer. Like Niel said, it will not be at max Wattage all the time. Just be sure the fuse/breaker is appropriate (no more than 250 Amp).

I'd guess they're basing their 250 mil wiring on the 600 Amp surge current potential.

This is the major reason why 12 Volts is not suitable for heavy loads: the current involved is difficult to handle.

john p · June 2012

Re: Wire gauge seems extreme

We have a rule of toe .neatly written in sand..
IF YOU CALCULATE YOU NEED CABLE FROM BATTERY TO INVERTER LARGER THAN #4 DOUBLE THE VOLTAGE.
Its very difficult to make"perfect" connections with cables above #2 with out the use of hydraulic lug presses.Even the slightest corrosion on the battery terminal can cause considerable losses between it and the battery terminal clamp.

James · June 2012

Re: Wire gauge seems extreme

I'm running my Prosine 2k sinewave inverter with 3/0 with no problems.
5 feet of cable.

I have maxed inverter a few time with no issues.
I'd say 3/0 is ok, but 4/0 is better if you can afford it.
Bigger is better with wire, but in this case the 250 MCM wire is overkill IMHO, unless you are going some distance to the batteries.

2manytoyz · June 2012

Re: Wire gauge seems extreme

I have a Xantrex 2000W inverter as well.

Here's the recommendation from Xantrex. Note the line under the chart:

I'm using 4/0 cable. It's NOT that much more money. An undersized battery bank, OR and undersized set of cables, can cause an under-voltage condition when the inverter puts a heavy load on the battery bank. The inverter will shutdown. People on Amazon have given this inverter bad reviews, and I fully believe it's from improper installation. Some even claimed it couldn't operated a 1000W load. I put a video on YouTube a year ago showing mine running a 1500W heatgun. Have run higher loads since. Zero issues, but I have a 900AH battery bank, using bus bars, and the inverter is feeding from 4/0 cables.

Here's where I buy mine (no affiliation): http://www.wesbellwireandcable.com/Welding/Welding4_0.html

This is very flexible cable, with very fine strands. I've cut it (carefully) on a bandsaw, but now prefer to cut it with a wood chisel and mallet.

Keep the inverter as close to the battery bank as possible, use FAT cables, enjoy the full capacity of your hardware worry free. Compromise on the wire, you might end up having to buy fatter cable after buying the other smaller wire.

vtmaps · June 2012

Re: Wire gauge seems extreme

john p wrote: »

We have a rule of toe .neatly written in sand..
IF YOU CALCULATE YOU NEED CABLE FROM BATTERY TO INVERTER LARGER THAN #4 DOUBLE THE VOLTAGE.

For the Magnum inverters (which cannot double their voltage), Magnum doubles the cables. Apparently that is OK by code.
Can that be a solution for the OP?
--vtMaps

Seedsca · June 2012

Re: Wire gauge seems extreme

I am at a loss for words. I got home today hoping I had a reply to my question. I would not have imagined there would be so many replies with such good advice. Thanks, you guys.

I have two 2'6" 0/2 terminated cables I got for free and also a 300 amp class T fuse I bought thinking ahead for when I got the 250 mcm cable. I know Cariboocoot mentioned using a 250 amp fuse, but could I use these cables with that fuse? Not really, right? The fuse is provably too big for that cable. I am planing on building a battery box and having the inverter/charger right next to it, so it would be very close. I should use the same gauge cable to interconnect the batteries right?

If I get the cable from 2manytoyz's link, how do I terminate the ends? I have found a local battery place that will special order the cable and will put the ends for me at about $6 per foot and $4 per cable end.

waynefromnscanada:
I did not mention my system because it's a work in progress. I plan on soon adding some panels, but for now I'm trying to keep my marriage running smooth. I am just charging the batteries from a generator every other day or three and keeping it really light on the energy usage. We just recently moved, quite ill-equipped I might add, to a fifth wheel on a 10 acre off grid site off of the Malibu coast in California. It needs work and we are only renting for now, but we have plans for our own spot in the not too distant future.

The setup:
Kipor Sinemaster 6000 watt generator I just bought on Craigslist, but it has no spark... looking to fix that soon.
Honda EM2500 generator doing the trick for now.
Sears battery charger, this is until I get the Xantrex inverter/charger hooked up.
4 Interstate GC2-XHD-UTL 6v batteries for a total of 464ah, right?
All this on a 25' 1990 Fleetwood Prowler in excellent condition.

Too much info?

niel · June 2012

Re: Wire gauge seems extreme

remember robert that the prosine is wanting 250mcm cables for the 2kw. imho 4/0 is fine if not too long. those using 3/0 are probably fine too if they don't keep it high ended in watts for very long or have high surges and keep the wire short. i doubt the prosine is that radically different in its draw than the xantrex you have and they list 4/0 as acceptable. those mentioning the 3/0 were not telling him to go that low, but that it isn't as critical as the prosine instructions make it sound.

vtnaps,
it is an option should he wish to take it.

seedsca,
with each 2/0 wire only being 2.5ft for a total of 5ft this does work out to be a 1% v drop at the rated fuse value of 250a, but the nec states minimum wire sizes for the current passed and 4/0 is minimum for 250a.

2manytoyz · June 2012

Re: Wire gauge seems extreme

niel wrote: »

remember robert that the prosine is wanting 250mcm cables for the 2kw. imho 4/0 is fine if not too long. those using 3/0 are probably fine too if they don't keep it high ended in watts for very long or have high surges and keep the wire short. i doubt the prosine is that radically different in its draw than the xantrex you have and they list 4/0 as acceptable. those mentioning the 3/0 were not telling him to go that low, but that it isn't as critical as the prosine instructions make it sound.

vtnaps,
it is an option should he wish to take it.

seedsca,
with each 2/0 wire only being 2.5ft for a total of 5ft this does work out to be a 1% v drop at the rated fuse value of 250a, but the nec states minimum wire sizes for the current passed and 4/0 is minimum for 250a.

I have a Prosine 1800W, and the Prowatt SW2000. I was initially scratching my head of why Xantrex, same company for all three of these models, would recommended even fatter wire for the Prosine 2.0 model.

Looking closer at the specs, the surge for the Prosine 1800 model is 2900W. The surge for the SW2000 is 3000W. For the Xantrex 2.0, the surge is 4.5kW for 5s.

"A-HA", says I. So if he needs to start some monster load, by all means go with the recommended wire. Otherwise, it's only going to run the same items these two inverters will run with the 4/0 wire.

FWIW, the video I put on YouTube with the SW2000 running a 1500W load, was using 2 gauge wire on the inverter. So I agree, not as critical. I've since upgraded to the 4/0. Lot less loss, and no worries of the inverter shutting down due to a low voltage spike. However, if he doesn't own the wire already, now's the time to think hard about whether the cost difference is worth it.

I don't run my inverter often near the capacity, but I do start motors/compressors with it. My Prosine 1800W inverter will start loads my Yamaha EF2400iS generator cannot.

Wire gauge seems extreme

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