installing a 6000 watt inverter

[michaelrj9]

Hi all,
I have a few questions about installing a 3000 continuous 6000 peak inverter the correct way.
I am Installing 2 6v trojan deep cycle batteries in series for the inverter which will give me almost 9 hours of operation at a 25 amp draw.

Also will be using a battery isolator.

1.)Do you have to use a "marine inverter"
or can you use a standard one as long it is fused properly. and the battery isolator? or will the coast guard not aprove it?

2.)It says 2/0 cable no longer than 3 feet long.
Does anyone know a online calculator that would tell me what size wire i would need if I need to go more than 3 feet. more like 10-15 feet.

3.) I would still like to have this battery attached to the "battery switch" so it can be easily turned off in needed to be.I will need to use the 2/0 or larger for this correct? Will the "battery switch" hold that much power?

Am I missing anything?

Thanks

Michael

 

[Dunaruna]

Re: installing a 6000 watt inverter

[colour=blue]What appliance are you planning on using with the inverter?

Google is your friend d

http://www.stealth316.com/2-wire-resistance.htm

http://www.gorhamschaffler.com/wire_size_calculator.html

You will find these sites helpful also..........

http://www.donrowe.com/inverters/inverter_faq.html

http://www.jobsite-generators.com/power_calculators.html

A few musings to ponder..........
Even though you are not using the full 6000w, your wiring will need to be up to the task. A 6000w inverter can get very hot, good ventilation is the key.
Inverters are not efficent units, calculate a 10-15% overall loss when working out loads and demand.
Most inverters have a safety cutoff to protect the batteries from going below 50%.
The stated reserve capacity on batteries are calculated for ideal conditions, play it safe, deduct at least 10%.

 

[bamadave]

Re: installing a 6000 watt inverter

25 amp draw, what the heck are you powering? Why not use 2 12v batteries in parallel instead of 2 6v?

 

[bjcsc]

Re: installing a 6000 watt inverter

Most of the guys around here running that kind of power are running lights for graining, but all in all, a small Honda generator ends up being what they all eventually go to.

 

[michaelrj9]

Re: installing a 6000 watt inverter

25 amp draw, what the heck are you powering? Why not use 2 12v batteries in parallel instead of 2 6v?

I hope not to use all 25 amps. But a/c is almost 10 amps,microwave even a small one is almost 7-10 amps,tv,dvd,couple laptops etc...obviously not everything at one time.

For the price I could not find 2 12v that would have at least 265 min each to receive the 530 I am getting with the 2 6v's

Stil looking on some input if you have to use a "marine"inverter to be coast guard approved? I have been looking on google with no luck.

Thanks for all your help everyone...

Michael

 

[Dunaruna]

Re: installing a 6000 watt inverter

[colour=blue]If you have 2 x 265amp 6 volt batteries and connect them in series to make 12volts - you still only have 265 amp reserve, NOT 530.

 

[bjcsc]

Re: installing a 6000 watt inverter

Dunaruna is correct. Serial connections do not change the reserve, but add the voltage. Parallel connections add the reserve, but not the voltage. To get what you're after with those 6Vs you would need four wired in series-parallel.

 

[michaelrj9]

Re: installing a 6000 watt inverter

[colour=blue]If you have 2 x 265amp 6 volt batteries and connect them in series to make 12volts - you still only have 265 amp reserve, NOT 530.

You are correct.

The 6v batteries I am looking at are 530 minute reserve each.I was just saying I would need (2) 265 minute 12v batteries to get the 530 reserve of the 6v batteries.
For the price It was cheaper to go with the 6v's than 2 12v's.
Here is the specs.

nullurl]http://www.trojan-battery.com/Products/ProductSpec.aspx?Name=T-145[/url]
Michael

 

[Texasmark]

Re: installing a 6000 watt inverter

Another thing on wiring batteries.

If you have batteries in series, their internal resistance adds; in parallel it halves. Internal resistance is what determines the terminal voltage under load. The lower, the higher the voltage for your appliance and as batteries age, internal resistance usually rises as the batteries sulphate up.

Not familiar with your batteries physical size but a really good battery at a really good price is a size 31 OTR truck battery (about the same physical size as the size 27 trolling motor battery) rated 12v at 950 cca. We can buy them here for around $65, they are sealed, ruggedized, and have 3/8" studded terminals. A couple of these babies and you should be able to run a long time.

On current, 25 amperes is miniscule as compared to a 2/0 wire. 2/0 is entrance service conductor size for 200 ampere house wiring.

For 25 amps running 10-15 ft, #10 is rated for 30 amps....like if you have a 30 amp electric clothes dryer you can run it off #10. I don't have the code book handy, but that's what we used to use. If you want some margin go to #8.

Beins you're in a marine environment, weight is usually a prime consideration so I'd go for the smaller wire personally, but I don't know your situation.

HTH

Mark

 

[michaelrj9]

Re: installing a 6000 watt inverter

Another thing on wiring batteries.

If you have batteries in series, their internal resistance adds; in parallel it halves. Internal resistance is what determines the terminal voltage under load. The lower, the higher the voltage for your appliance and as batteries age, internal resistance usually rises as the batteries sulphate up.

Not familiar with your batteries physical size but a really good battery at a really good price is a size 31 OTR truck battery (about the same physical size as the size 27 trolling motor battery) rated 12v at 950 cca. We can buy them here for around $65, they are sealed, ruggedized, and have 3/8" studded terminals. A couple of these babies and you should be able to run a long time.

On current, 25 amperes is miniscule as compared to a 2/0 wire. 2/0 is entrance service conductor size for 200 ampere house wiring.

For 25 amps running 10-15 ft, #10 is rated for 30 amps....like if you have a 30 amp electric clothes dryer you can run it off #10. I don't have the code book handy, but that's what we used to use. If you want some margin go to #8.

Beins you're in a marine environment, weight is usually a prime consideration so I'd go for the smaller wire personally, but I don't know your situation.

HTH

Mark

Hi, The inverter is 6000 watts total which is about 500 amps @ 12 dc So would need at least the 2/0 cable
no way anything smaller going to the batteries. The inverter is only going to put out 120v @ about 26 amps Ac which on the Ac side I can go with 12-14 ga wire each outlet (each outlet is a max of 15 amps not the 26 amps)

Thanks
Michael

 

[Dunaruna]

Re: installing a 6000 watt inverter

[colour=blue]Correct. Need to treat the 12v side of the inverter differently to the 120v side. Totally different wiring requirements.

I'm curious, what type of boat is this seeing that it is capable of carrying a microwave, A/C, TV etc....
Are you sure that you will have adequate amp storage? I've done some very quick calculations - 4 x 6volters would be closer to the mark for your power requirements, maybe even 6.

 

[Boatist]

Re: installing a 6000 watt inverter

500 amps on the 12 volt side is correct if the unit is 100 percent effecient but it will be more like 80 percent so it will be over 500 amps by 20 percent or 600 amps.

On the AC side a 12 guage will carry 20 amps. A 10 guage wire will carry 30 amps.

 

[Texasmark]

Re: installing a 6000 watt inverter

I'm sorry. I wasn't thinking about that part of the circuit. Was thinking about your ac output ckt.

I can get you the resistance value of 2/0 at 20C if you want (have to go out back to the shop and get the numbers if you want) and you can calculate your voltage drop/power loss for that 500 ampere run if you choose.....just to touch base on where you are with your heat on that load.

Also, ventilation has a big part in heat rise (as I'm sure you well know) and if you can separate the wires out they run much cooler.

2/0 service entrance has a real tough poly jacket and beins you are only running 12v you won't have to put it in any kind of raceway.

On the load side, My EE handbook says that 2% loss for feeder ckts is tops (max).

Says to 33a on #6 @ .403 ohm/1000ft. 2% 120v = 2.4v

so 20' @33a =.265v. If temp doubles, rule of thumb they say (actual calculation is involved) is that res will follow temp or double also.

To 26a on #8 & you have .6408 ohms/1000 ft for .43 v drop @ 20C.

Running the 12-14 that you mentioned is a no brainer for the 15 ampere loads.

Want more, ask.

If you could up the input to a 24 v source, you would do yourself a lot of good. Being heat is Current squared x res, halving the current is 1/4 the loss.

I know you know this but just a little brainstorming.

If you are pushing 500 amperes thru the cable, the heat of the cable/ft will not change only the voltage drop due to a short run. So your 3ft will only affect the drop.

Also 500 a is 2.5x the entrance service rating for that wire.......I do realize it is in a conduit if in entrance service so I agree that it would not need that rating if conductors were singled out and not sitting out in the hot sun in a steel pipe.

However, doubling the voltage would allow you to run 1/0 at less of a thermal stress beins the loss would drop to 1/4 the 12v loss and the res of the wire would only be 2x. But, for 3' you probably don't care; not that much of a weight difference.

Just curious. The batteries I mentioned won't put out 500 amperes. If you aren't going to charge these batteries while they are putting out this kind of power they must really be some whoppers.

Another thought; if not being charged, and you are running this kind of load, they will obviously discharge significantly. That puts you in the realm of deep cycle for any battery life. Is that where you are headed?

Mark

 

[jason176]

Re: installing a 6000 watt inverter

SE cable ain't allowed anywhere near my house and definetly near my boat. I would probably use a good automotive/marine grade power cable to feed the inverter and use crimp connectors and the correct crimping tool to install the connectors. Also I am confused as to why everybody is using the peak value for this inverter? Don't worry about peak values only average, if you run the inverter at peak regularly it would definetly shut down in a short period of time, and you are only wasting money if you size your wire according to that value. Use this chart to determine the size of wire for your batteries ( your draw will be 250A): http://www.crutchfieldadvisor.com/learningcenter/car/cable_gauge_chart.html.

DO NOT try to size household or 120v wiring by this chart, that is a totally different ballgame. Also I may be incorrect but, are you sizing your batteries off of your AC draw or your DC draw, you need to use your dc draw for this. No offense meant towards anyone but this post is probably a little overly technical, lets just make sure he gets the inverter installed correctly and not try to re-engineer the wheel,heck, I got confused reading this post.

 

[jason176]

Re: installing a 6000 watt inverter

Crud, that chart doesn't go that high give me some time to either do the math or find you another chart. Fiance is nagging me to go to bed.

 

[ZmOz]

Re: installing a 6000 watt inverter

I hope not to use all 25 amps. But a/c is almost 10 amps,microwave even a small one is almost 7-10 amps,tv,dvd,couple laptops etc...obviously not everything at one time.

You are measuring your amps on the wrong end. 25 amps at 12 volts is only 300 watts. That is barely enough for a laptop, and nowhere close to enough for a microwave or AC. 25 amps coming out of your inverter means over 250 amps going in from your batteries. Your batteries would only last about half an hour at this rate. You simply cannot run AC without a gas generator.

Also I am confused as to why everybody is using the peak value for this inverter?

Because that is the correct way to do it. The inverter is capable of pulling more than 6000 watts, there fore, your cables must be capable of providing that - whether it's 6000 watts continuous or not doesn't matter. If the peak is 6000 watts then the cable needs to carry that much safely.

 

[jason176]

Re: installing a 6000 watt inverter

Been doing this a long time and never used a peak power value to size cable and I have installed amplifiers that big as well. Read the paragraph above the chart that I posted the link to, size the wire to the peak value and you might as well take the money in the front yard and burn it. That inverter isn't designed to carry more than 3000 watts for any extended period of time, as with motors there is a high inrush current on the start up but you don't size the wire according to inrush current because the wire is capable of higher ampacities for short periods of time. Everybody seems very knowledgeable in here, does anybody remeber the difference between peak power and rms power?Here is a link to a handy calculator for sizing wire:
http://www.powerstream.com/Wire_Size.htm

According to this link you are gonna need some hefty cable so definetly keep it as short as possible. As far as running all of this stuff its gonna be tight, give me more time and I will calculate the actual dc draw on your batteries given the loads you indicated to find out whether it is feasible to do this or not, I am a little rusty with my formulas.

 

[Gone]

Re: installing a 6000 watt inverter

Even RV's running full inverter power are using 4 batteries and an automatic gas/diesel generator to charge the batteries. Even the 3KW inverter models. Pay close attention to ventilation of the inverter, the derating curve vs temperature (up and down) is quite dramatic.

CD

 

[Dunaruna]

Re: installing a 6000 watt inverter

[colour=blue]Jason, I take your point and agree to a certain extent, but......
It's a boat - no room for error. Or more to the point - no room for hot wires.
That aircon could concievable cycle on/off regularly. Ever time it turns on, BIG amp draw.

CD has hit the nail on the head.

 

[jason176]

Re: installing a 6000 watt inverter

If the air conditioner cycled on and off enough to heat the wire enough to do damage chances are you would burn up the motor in the ac unit before you would ruin the wire. I am telling you guys, if you size the wire properly to the rms draw you will be more than good. I have installed audio amplifiers in this power range and everytime the bass hits you hit that peak number but the wire WILL NOT fail as long as it is properly sized to the rms value and of good grade.I think peak numbers are pretty much useless and just a ploy by manufacturers to sell their products as being more powerful than they are. Ever see a product marked with the rms value and not the peak? I bet his inverter has a big 600 watt sticker on the front of it, not that there is anything wrong with that, its just a marketing strategy. I guess in the end we have to agree to disagree, but I have never seen an installation (and I have seen and done alot) where they size the wire according to peak numbers.