Inverter Questions.

[happykraut]

Been reading about inverters for the last 2 hours and still couldn't find the right answer. I want to mount one in the basement and run one receptacle(on a extension cord) off of it to run a little fan and brew a cup of coffee in the morning while camped at a Walmart. I have a 1200W and a 2500W inverter and 4/0 cables. For a given load ie. the fan, do both converters draw the same amount of power from the batteries? Guessing the 2500 draws more, but how much more? I'm thinking that there might be an occasion where I need more power and go with the 2500, but it is more important to me not to run the batteries down over night when just running the fan. I have two Group 27 batteries. Final question, what do I use for a ground since chassis ground in an RV really isn't ground? Do I use the neutral bus bar?

 

[jnbhobe]

Bernie, I would go with the 2500W, your coffee pot may draw more than 1500W. Not sure on the guage wire required for the 2500W but 4ga may be OK. Hook the ground directly to the battery ground, and you probably should run one to the frame.

 

[happykraut]

Jon, the pot draws 800W, but if I only get 50% efficiency(so I read), then I'll be drinking Frapuccinos instead.

 

[murry135]

I believe and may be wrong but if you look at the labels on your appliances and add up the wattage that they state for each item that should be the wattage of your inverter. Coffee pot watts + fan watt's = Watts needed for simultanous startup or Inverter output. Hope this helps calculate your needs.

 

[hoefler]

I would use a 12 volt fan instead using one to go through the inverter. A 1500 watt coffee pot will draw approximately 125 amps on the 12 volt side. This will be a continuous load as long as the coffee pot is on. I don't know how you plan on charging the batteries, but they will not fully charge off your tow vehicle. I would look into a 12 volt coffee pot or use a stove top method.

 

[brianharrison]

For a given load ie. the fan, do both converters draw the same amount of power from the batteries? Guessing the 2500 draws more, but how much more?

Two inverters with the same technology (ie fast switching conversion to AC) will draw the similar power from the batteries - inverter efficiency may create a small difference. Inverters have a typical efficiency curve - here is one for 4000 and 6000W Xantrex. They are usually less efficient at low outputs (ie less than 10% output compared to max output). Drawing 1000W on a 1200W or 2500W will be similar inverter efficiency. Note the internal power consumption of the inverter (power boards, switches etc) are low, comparative.

More importantly - starting current (or inrush) needs to be taken into account - My rule of thumb, is total up the power requirements for simultaneous loads at operating conditions - and add 50% for inrush. For your scenario running fan and coffee pot (1000W) - I would select the 2500.

Environmental conditions also affect the inverter - ie it gets hot with use, battery voltage drops, etc - these affect the ability for the inverter to provide it`s maximum output. A 1200W rated inverter for a 1000W continuous load is undersized in these conditions.

Here is a inverter sizing article from an expert with Xantrex.

I'm thinking that there might be an occasion where I need more power and go with the 2500, but it is more important to me not to run the batteries down over night when just running the fan. I have two Group 27 batteries.

You would need to calculate the amp draw that your specific fan will require times the hours you want to run it to determine if your battery bank will support running the fan overnight - It is a good rule of thumb to not draw down your batteries greater than 50% of their total AmpHour (Ah) capacity.

Final question, what do I use for a ground since chassis ground in an RV really isn't ground? Do I use the neutral bus bar?

The inverter will typically have a ground (green) connection requirement - follow manufacturers recommended installation instructions (ie size of ground wire recommended, etc). I have run my inverter ground to the trailer bus bar.

Brian

 

[dewwood]

This is not about an inverter but this is what we have started using for coffee. http://www.amazon.com/Coleman-5008C...74932488&sr=8-1&keywords=coleman+coffee+maker
It uses only a flame to perk the coffee and I actually like the coffee better. I turn the heat down and let it perk slowly and it makes a more robust flavor. We use it even when we have hookups.

 

[pegmikef]

We use the Endless Breeze 12 Volt fan when we boon dock or are without power. I use two Trojans for boondocking and the fan runs all night with no problem. I run one of the Hondas a couple of hours every day just to charge the batteries.

http://www.amazon.com/s/?ie=UTF8&ke...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_4iul9jyl25_b

. . and believe it or not, we use our old camping coffee pot exclusively for coffee. We dug it out the first time we went boondocking and have been using it ever since. I like the coffee better

 

[scottyb]

Bernie, I did almost exactly what you described. I mounted a 3000W inverter to the front basement wall on the door side. That put it within 3' of my batteries in the front generator compartment. I'm not sure about your rig, but my Cyclone has the BR dresser directly above the basement. I followed the plumbing for the W/D and came up in the void behind the drawers, through the foam. I then mounted a wall recepticle on the end of the dresser facing the living room. I used romex but I installed a male plug on one end to plug into the inverter.

My inverter is inexpensive (Whistler) and was just an experiment to see what direction I want to go. My 2 GC-2 6V batteries will run the TV and Dish receiver for a few hours in the evening, then run a fan all night, but will not run a 1100W coffee maker the next morning. Could be due to the lack of efficiency, so I'm told.

 

[happykraut]

Thank you for all the responses. Heartlanders are the greatest. Just got back from the RV lot. Left this morning before I had a chance to read all the responses. I mounted the 1200 on the wall of the basement, the input is within 3 feet of the batteries. I ran 12ga wiring up underneath the BR dresser and installed a receptacle on the side of the dresser(exact same setup as yours, scottyb. Put a plug on the other end of the wiring which will plug into the inverter. Of course now that I've read all the good advice, I'll go back to the lot after the flea market tomorrow and swap out the 1200 for the 2500. I did look at the 12v fans, but I think I'll get more use out of the inverter. Hoefler since I'll be using it between campgrounds for one night at a time, I am relying on my truck to charge the batteries again, even though they won't get fully charged.

 

[evolvingpowercat]

I have a 1500 watt inverter with what is called 'modified sine wave output' that is able to generate a clean enough signal to run my microwave oven. Coffee pot is just a resistance heater load and will work with about any kind of inverter that can put out the wattage required. The 4 cup drip coffee maker I bought at Wal-mart only draws about 800 watts and works great with it. Others will draw as much as 1500 watts.

You will need very large gauge wires and very large fuse to handle the 12 volt amps the inverter will require. And it is best to have VERY short 12 volt wire runs. Also you can use up all the stored power in your 12 volt batteries VERY quickly and may find that you use too much and won't be able to close your slides without recharging your batteries if you use the inverter too much when boondocking.

 

[marvmarcy]

I did some research and chose a Magnum 2800 full sine inverter charger. I use four large 6v batteries connected with 0000 gauge pure copper welding cables (more batteries would be better). The batteries are in a custom vented box next to the inverter. My control panel is where the Onan genset control panel was prewired. When in dry camp, I turn on the inverter when needed. It automatically recharges the batteries when I start the genny at dinner time. I could leave the inverter on all the time as it would automatically start a genset when needed. That way we would have 120VAC all the time, but we seldom need it. It can also be attached to solar panels for more flexibility.

 

[scottyb]

I did some research and chose a Magnum 2800 full sine inverter charger. I use four large 6v batteries connected with 0000 gauge pure copper welding cables (more batteries would be better). The batteries are in a custom vented box next to the inverter. My control panel is where the Onan genset control panel was prewired. When in dry camp, I turn on the inverter when needed. It automatically recharges the batteries when I start the genny at dinner time. I could leave the inverter on all the time as it would automatically start a genset when needed. That way we would have 120VAC all the time, but we seldom need it. It can also be attached to solar panels for more flexibility.

That's my goal. I have been looking at the same Magnum and also an Outback the same size. I am adding 2 more 6V batteries next week to make 4. Does the Magnum have 1 or 2 outputs? Do you have it wired to the panel or did you install a sub panel?

 

[porthole]

I recently added my Xantrex PRO1800 inverter. Mainly to keep the TV's, ice maker and cooler fridge on steady power. Was hoping to be able to run the coffee pot but to no avail.

I'm using a Keurig. Xantrex says it probably doesn't work because of the "flash heat" technology the Keurig uses.

I think it doesn't work because the Xantrex digital meter reads .6 - 1.2 volts lower then my actual battery pack and is artificially cutting the inverter out early.

A cheap 2500 watt inverter will not work anywhere near as well as a quality 2000 watt inverter.

There is a reason the Magnum's, Xantrex's etc, big boy inverters cost upwards of $1500 and weigh 30-60 pounds.

I am using two gel cell 6 volt batteries at 180 amp hours. rated. That means I could theoretically run a 9 amp load for 20 hours

Amp hours	Hours	Amps
180	20	9
180	10	18
180	5	36
180	2.5	72
180	1.25	144

My 1500 watt heater will draw about 130 DC amps off the battery, so in theory my battery bank is just big enough that I should be able to get coffee.

80-90 % efficient is about normal with the better units getting up around 95%

Bernie - are you really using 4/0 cable or 4 gauge? 4/0 is almost a 1/2" diameter of copper. That is a good way to start.

My inverter will run the lighter loads at low voltage (TV's cooler, ice maker) but the coffee pot is a no go. Bummer. I was hoping to be able to get coffee without firing up the genny.

I use the Fan-Tastic 12 volt fans. Much more efficient then using an inverter to power the air flow.

 

[happykraut]

I just noticed that the 2500 that I'll be installing in the morning has two DC inputs and three AC outs. Why two inputs and which one do I use? Thanks.

 

[brianharrison]

If you could post the make and model we could search for an online manual and help with figuring out the two DC inputs.

Brian

 

[marvmarcy]

That's my goal. I have been looking at the same Magnum and also an Outback the same size. I am adding 2 more 6V batteries next week to make 4. Does the Magnum have 1 or 2 outputs? Do you have it wired to the panel or did you install a sub panel?

The Magnum 2800 can be wired in several ways. I wired it DI/DO. I have it wired between the main 50A panel and a 30A subpanel. I moved breakers for all outlets, the microwave, central vac, and ceiling fan to the subpanel. I do not power the ac, wh, w/d, converter, or fireplace with inverter. The Magnum 2800 can be programmed to protect your generator and batteries. It is a great setup but cost about $4,000 just for materials - I installed everything myself. It is not a diy project unless you have extenive electrical experience.

 

[happykraut]

I've had this thing for several years and never looked at it before. It is a Roadpro RPPI-2500W and it does have a little owner's guide with it. The booklet states to hook the red cables to the red input terminals and the same for the black cables. I'm guessing it's a way to increase wire size without going to a much larger cable.

 

[brianharrison]

A preliminary check to an online manual indicates to only use the cables that came with the inverter - I think you are correct; the two terminals allow two runs of smaller wire to carry the current to support the 2500W inverter. On another webpage they talk about a 2 times 4AWG runs, about 4 feet long. I see no issue running a larger cable and connecting to one terminal; I suspect the terminals are in parallel. Remember to use a Class T DC fuse rated for the wire size you select. I have run 2/0 cable with 300 DC amp fuse for my 3000W inverter.

Brian

 

[happykraut]

Well, the inverter install is completed minus the fuses. Looks like you have to take out a loan to buy a 300A class T DC fuse plus the mount. Don't know what I'm going to do yet. I ran a fan and then a vac in the bedroom and they worked great. One problem though. The checker shows an open ground which goes back to my original question. I noticed the minus side of the battery is connected to the white bus bar and that is what I used for the minus side of the inverter. There is no ground on a RV until you hook up to shore power. So, do I just live with it??