inverter wire gauge question

rick danger · 08-18-2015, 02:35 PM

Installed 1500 watt PSW Ramsund. Used 0 gauge stranded copper for a 3 1/2' run on the 12v dc side to batteries. . Question: I have 6 gauge connecting the two batteries. About 8 or 10" long. Will this be OK? Or should I get heavier gauge for the Bat. to Bat. connection?...Oh, and I used 10 gauge direct burial romex for a 20' run on the 110v A-C supply side to a receptacle next to shore power cord.

hoppers4 · 08-18-2015, 03:11 PM

#6 NM-B or UF-B is rated at 55 amps or 660 watts. You're going to have to decide if the battery to battery current draw will be more than that. I'm using #10 for a run from my 200 amp service 60' to my outside 30 amp outlet. It's adequate to run the AC as the voltage at the rig is still 115VAC when running.

rick danger · 08-18-2015, 03:30 PM

Quote:

Originally Posted by hoppers4

#6 NM-B or UF-B is rated at 55 amps or 660 watts. You're going to have to decide if the battery to battery current draw will be more than that.

is that rating over any particular given distance? I'm wondering if it makes a difference that the initial draw from the inverter will be adequate from the one battery (with the proper 0 gauge to the inverter) and the second battery will leak over slower to make up the current loss to the first battery. Or will the inverter draw from both right away. In which case maybe the 6 gauge will be inadequate at the full 1500 watt load

hoppers4 · 08-18-2015, 06:26 PM

Actually the chart I drew from doesn't include distance in the ampacity. Here's the site I went to.
Ampacity Charts
I can't imagine where you would ever go to the full 1500 watt draw. Those batteries would last no time at all. I would hope the #6 is large enough. Current draw from each battery would be approximately equal. The battery that the load is hooked to would get a slightly larger draw because of the line loss of the wire between the batteries but not enough to make any difference.

rick danger · 08-19-2015, 04:15 AM

Great, thanks. I guess I'll give it a real world test here at home. The bigger loads I would use it for would only be for a short time. Like the coffee maker or a few minutes on the microwave. Most of the time will be just the television and reciever box for a few hours plus an electronic sound machine after that. digital clock, and maybe charging a cell phone and computer. I'm anxious to see how long it takes the converter to get the batteries back up the next day. Gen. run time.......Also, do you agree with what someone said about not mixing older and new batteries? The one I have is about 6 months old and the other a year or more. I would add 2 6 volt golf cart batteries to them http://www.batteriesinaflash.com/dee...ud0aApRD8P8HAQ But they say the new batteries would take on the age of the older ones. Or that the older ones would decrease the life of the new ones? I wouldnt want to do that to fairly expensive batteries.

rick danger · 08-19-2015, 05:47 AM

OK, seems to be a problem. Just tried out the inverter. (1500 watt) Microwave pins the led watt meter on the inverter and the blue "on" light turns to red and the inverter beeps. Than resets. (auto reset breaker?) OK, thats fine. Even with microwave set at half power it does that. I dont really need the microwave. But heres the real problem, the coffeemaker (small 5 cup) does it too. And the kicker is the led watt meter is only reading 750. It trips and resets about three or four times as the coffee brews. ...Any idea why it should trip when the watt meter is only reading 750? Seems to do it when the inverter cooling fan come on. Batteries are at full charge (13.5v )........update: coffee maker draws 650 watts which is what the led bar reads on the inverter. So why does it trip and reset? Converter breaker is off. If anything else was drawing in the camper wouldnt it show on the watt meter?

mike837go · 08-19-2015, 05:58 AM

I ran into the same difficulties on my old trailer.

The solution was to place the 1,500W inverter under 12" from the battery. Very short, heavy leads. I think I used #4 wire.

The 750W microwave could warm up (room temp to drinkable) an 8oz cup of coffee in 1 minute on the inverter. 30 seconds on shore power.

Forget about running a coffee maker on batteries! 8 minutes @ 700W. The CO detector will complain about low volts before the pot is brewed.

rick danger · 08-19-2015, 06:26 AM

I used 0 gauge wire for a 3 1/2' run to batteries. Why wont it run a 650 watt coffee maker for 4 minutes with two freshly charged batteries? Its a 1500 watt unit. I read some reviews of this on amazon (BTW its $80 cheaper now and I bought it a week ago) and someone had the same complaint. Is the inverter just a POS?

mike837go · 08-19-2015, 06:54 AM

Quote:

Originally Posted by rick danger

I used 0 gauge wire for a 3 1/2' run to batteries. Why wont it run a 650 watt coffee maker for 4 minutes with two freshly charged batteries? Its a 1500 watt unit. I read some reviews of this on amazon (BTW its $80 cheaper now and I bought it a week ago) and someone had the same complaint. Is the inverter just a POS?

Do the math: How many amp-hours in your battery?

650 watts @ 12V is over 50 amps per second.

So 50 times 60 seconds in a minute times 4 minutes equals 13,000 amp minutes. Divide by 60 minutes in an hour about 217 amp hours are needed to do a batch of coffee.

The problem isn't the inverter, it is in how much absolute energy can be stored in a battery. Gasoline is over 300 times more energy dense. Propane is close at 270x.

Why do you think electric cars are so pointless in this era of cheap hydrocarbons?

If you want to make coffee and don't have access to lots of electricity (grid, genset, etc.), buy a stovetop unit.

But keep the inverter. I haven't found a 12V coffee grinder yet.

Seann45 · 08-19-2015, 07:28 AM

My batteries are tethered together with 0 ga.. no sense having a choke point

Flapper · 08-19-2015, 07:32 AM

While your batteries will not last long, as pointed out, the Inverter should be able to supply the power while they do last. Your #6 wire is close to capacity with the coffee maker, and so may be causing a voltage drop that is making the inverter work harder/overheat as it is getting a lower than expected voltage. Beef up that wire and try again. If it is still a problem, then the inverter isn't meeting spec, and it's time to get with the manufacturer. A volt meter to measure voltage at the battery, and then again at the inverter input would help tell the tale.
But you'll still kill your batteries really quickly trying to brew coffee......
Another thought - it seems as you may have a mix of older/newer batteries. If so, one may be bad and not putting out full voltage (especially under very heavy load), which again would give a reduced supply to the inverter. Again, a volt meter will tell the tale.

hoppers4 · 08-19-2015, 08:22 AM

Like Flapper said, you'll need a meter to tell the story. You need to take a voltage reading right at the input to the inverter. 650 watts at 12V is 54 amps and the inverter should be able to handle it. That 3 1/2' wire run may have enough drop to cause your problem.

The relatively small difference in battery age shouldn't matter.

**Mustang65** · 08-19-2015, 10:24 AM

I have an older version of the same inverter. I have 0AWG from the batteries to my DC distribution point (4 feet). I have 2 Trojan T145 batteries that are rated at 260Ah, which do the trick.

1st thing change your weakest link which is the cable that connects the 2 batteries together. It is like using a 3/8" fuel line from the gas tank to the fuel pump and then using an 1/8" fuel line from the fuel pump to the carburetor (old style) normal use will not affect anything, step on the gas (load) and that is when you find out that the smaller diameter will restrict the flow. Same idea here.

I very seldom use the coffee pot on electric for coffee, we boil water and I have a Tupperware plastic cup with small holes in the bottom that sits in the electric coffee pots grounds basket. I pour the hot water into the Tupperware cup and it runs through the filter.

Microwave, that is another killer. I only use it when it when the sun is shining brightly and the solar is pumping out the amps (19.5Amps), which helps the batteries.

The inverter has a 10.5VDC cut off voltage, so if the batteries voltage drops to that point it will trip the breaker, and then reset. Monitor your voltage while making a pot..

Ok, what is the TRUE battery voltage when the coffee pot is on? You can actually watch the battery voltage drop as the coffee is brewing, that is how much of a drain it is on the batteries.
Is it on an extension cord or your interior outlets? If on your interior outlets is your TT's battery charge controller turned off?

What is your AC voltage when the coffee pot is on?
Are your terminal connections tight?
Are the lugs on the ends of the cables crimped tight?
Do they get hot when the coffee pot is on?

How does everything work other than the coffee pot or microwave? TV, fans, radio...?

What batteries do you have? Interstate 85Ah? Trojan T105's?

Are the two batteries identical as far as manufacture and dates? IF the batteries are not the same date, the weaker battery will draw down the stronger battery to its level.

Don

rick danger · 08-19-2015, 11:59 AM

Well, heres the deal so far. The battery bank power isnt any problem .I brewed two pots, ran the microwave for 4 minutes had the tv and the lights for half hour and the batteries were at 12.69 volts. They charged up to 13.5 in one and a half hours. Maybe quicker ,but I went to the store. .....The problem is when the coffee pot is going the inverter cuts out a few,or more than a few, times. It just seems to trip some internal breaker and come back on instantly. As this happens it beeps and the blue "on" light turns red for a split second. I beeps once in a while weather there is a load or not. ......just another quick question: when the coffee pot is going ,the voltage drops to 11.7. As soon as the pot turns off it goes back to 12.6. That cant be bad for the batteries? For 6 minutes?

Ela1948 · 08-19-2015, 01:27 PM

I haven't read all of this thread yet, but what you are experiencing is a preset shut down by the inverter. You say that it goes to 11.7 volts when making coffee. Your batteries are not really at 11.7 volt. Your voltage is only as strong as your weakest link. Meaning somewhere in your system there is a break down. If your inverter is hooked up to positive on one battery and negative to a second battery, then you probably have an issue with the connecting cables between batteries. Your batteries are just like a chain. look for the weak link. My inverter is wired to just one battery with the rest of the batteries hooked in parallel. The voltage on the inverter will go down to 11.7 or a little more but has never went into the red zone or reset. Like you said they bounce back to 12.5 volt as soon as the coffee maker shuts down. You either have a battery that is faulty or a cable that is too small or a bad connection somewhere. It sounds like the inverter is acting exactly like it should when the voltage is low.

rick danger · 08-19-2015, 02:35 PM

Thanks for the input. The inverter is wired with o gauge to one battery on a 3 1/2' run. The other battery is connected in parallel with 6 gauge and an 8" run. The converter (and ac and all big draw things) have the breakers off. I ran 10 gauge romex (on 20' run) From the inverter to an outlet next to the shore power cord (like I did the gen.) so I can plug into either gen. power or inverter power. I did a check by plugging the coffee maker directly into the inverter and it works fine. I thought that maybe the inverter was thinking that the coffee maker was a direct short because of the heating coil. (which it really is I guess, but so is anything thats a load) . Im baffled.

rick danger · 08-19-2015, 04:38 PM

Quote:

Originally Posted by Mustang65

I have an older version of the same inverter. I have 0AWG from the batteries to my DC distribution point (4 feet). I have 2 Trojan T145 batteries that are rated at 260Ah, which do the trick.

1st thing change your weakest link which is the cable that connects the 2 batteries together. It is like using a 3/8" fuel line from the gas tank to the fuel pump and then using an 1/8" fuel line from the fuel pump to the carburetor (old style) normal use will not affect anything, step on the gas (load) and that is when you find out that the smaller diameter will restrict the flow. Same idea here.

I very seldom use the coffee pot on electric for coffee, we boil water and I have a Tupperware plastic cup with small holes in the bottom that sits in the electric coffee pots grounds basket. I pour the hot water into the Tupperware cup and it runs through the filter.

Microwave, that is another killer. I only use it when it when the sun is shining brightly and the solar is pumping out the amps (19.5Amps), which helps the batteries.

The inverter has a 10.5VDC cut off voltage, so if the batteries voltage drops to that point it will trip the breaker, and then reset. Monitor your voltage while making a pot..

Ok, what is the TRUE battery voltage when the coffee pot is on? You can actually watch the battery voltage drop as the coffee is brewing, that is how much of a drain it is on the batteries.
Is it on an extension cord or your interior outlets? If on your interior outlets is your TT's battery charge controller turned off?

What is your AC voltage when the coffee pot is on?
Are your terminal connections tight?
Are the lugs on the ends of the cables crimped tight?
Do they get hot when the coffee pot is on?

How does everything work other than the coffee pot or microwave? TV, fans, radio...?

What batteries do you have? Interstate 85Ah? Trojan T105's?

Are the two batteries identical as far as manufacture and dates? IF the batteries are not the same date, the weaker battery will draw down the stronger battery to its level.

Don

Well, I have the cut out (and instantly back on ) problem with the coffee maker and the microwave. Happens about three or four times in five minutes. The inverter beeps once in a while no matter what is on. OK, heres the answers: Voltage brewing coffee or useing the micro is 11.9 while brewing. Once done its back to 12.6....One battery is about a year old, and the other is 6 months. They are deep cycle marine. Not true golf cart deep cycle. I'm still waiting for my ac volt meter and didnt check with my handy amprobe. The led strip on the inverter was saying about 110. not below. I know its not accurate. ....Lugs a very tight. Nothing gets hot. Not even the 8" run of 6 gauge that tie the batteries together. Converter breaker is off .As well as the ac. I dont see whats wrong with using the coffee maker or micro if the voltage after using them is 12.5v. And if they dont draw more than 1500 watts. Even if the wire connecting the batteries were to thin ,or one battery was older, If the voltage was there why is it a problem? Thanks, im just frustrated......oh its on my interior outlets. When I plug the coffee maker directly into the inverter there is no problem. I would put in a switch to disconnect my 12v to the converter panel, but I would lose my lights and heat (furnace) fan

hoppers4 · 08-19-2015, 07:36 PM

Your last explanation puts a different light on the problem. You're still using the converter for power distribution just not to charge the batteries. To narrow down the problem, pull all the 12VDC fuses and turn off all of the AC breakers except the one needed for the micro or coffee pot. Insert fuses and turn on breakers one at a time until problem appears again.

**Mustang65** · 08-19-2015, 08:26 PM

You need to get the TT's battery controller out of the circuit. The battery controller sees the voltage dropping and figures it needs to send more voltage /amps to the batteries, which puts more drain on the batteries because they are trying to charge themselves with their own power.

The only solution is to disconnect the controller's AC power source, turn its AC breaker off, and see which AC items are affected.
Or run everything off the inverter with an extension cord.

Don

rick danger · 08-20-2015, 03:51 AM

Quote:

Originally Posted by hoppers4

Your last explanation puts a different light on the problem. You're still using the converter for power distribution just not to charge the batteries.

Right, the breaker for the converter was turned off. Is it still somehow involved because its tied into the power distribution? I did pull these two reverse polarity 30 amp (DC) fuses and it made no difference. I did turn off all the ac breakers except the ones for micro and coffee maker, but there are some other things on their circuits. Refridge for example. But I made sure it was off. When I pull the main 12v hot wire off of the dc distribution panel I think it solved the problem. but I lose lights and heat fan. I'll double check that again today ,and do what you suggested with removeing the dc fuses and replacing the ones for lights and heat. Thanks

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