inverter advice

ltypd · 07-09-2011, 03:15 PM

Hi everyone, just ordered a new georgetown 373 and would like to add an inverter. do I need to add to the two coach batteries that come standard ? how large an inverter do i need? id like to be able to power the ac outlets, tv, maybe brew a pot of coffee. any advice would be greatly appreciated.

**Herk7769** · 07-09-2011, 03:25 PM

Quote:

Originally Posted by ltypd

Hi everyone, just ordered a new georgetown 373 and would like to add an inverter. do I need to add to the two coach batteries that come standard ? how large an inverter do i need? id like to be able to power the ac outlets, tv, maybe brew a pot of coffee. any advice would be greatly appreciated.

The "brew a pot of coffee" is a deal breaker on inverter power. A 1500 watt 120 VAC coffee maker will pull 125 amps from your battery while brewing. It will be less (about 900 watts) when keeping the coffee warm.

Inverter size is based on anticipated power draw and you should have at least 25% over your anticipated draw in watts. Remember you will need battery capacity equivalent to output required and correctly sized wires and fusing for the DC side of the inverter.

I am including some light reading to help you along.

ltypd · 07-09-2011, 03:54 PM

Quote:

Originally Posted by herk7769

The "brew a pot of coffee" is a deal breaker on inverter power. A 1500 watt 120 VAC coffee maker will pull 125 amps from your battery while brewing. It will be less (about 900 watts) when keeping the coffee warm.

Inverter size is based on anticipated power draw and you should have at least 25% over your anticipated draw in watts. Remember you will need battery capacity equivalent to output required and correctly sized wires and fusing for the DC side of the inverter.

I am including some light reading to help you along.

how do you know the capacity of the coach batteries ? i was thinking of a 1000 w prosine inverter eliminating the coffee maker from the equation.

jsutherl · 07-09-2011, 04:02 PM

Yes you'll need to install new batteries, which will mean a new battery tray (welding shop), and an inverter sub panel (electrician), and the inverter itself with it's control panel (RV tech). I did it myself, except for the welding. Total cost to do it myself:

Interter $550
Batteries $550
Battery tray (welding shop) $150
AC Wire $75
DC Wire $75
Sub-Panel $25

Those prices are hardware only, no labor. Since I did it all myself. If you're not comfortable doing electrical work then you should pay somebody to do it. I do inverter power systems as part of my job. Really big ones that run hundreds of computers.

Lou is right, brewing a pot of coffee takes a bunch of power. Coffee pot pulls the same power as about 12 100watt light bulbs. A percolator on the gas stove is a much better way to do that. Or start the generator while the coffee pot is on. Once the coffee is made pour it into a dewar flask of some kind to keep it hot.

Don't get me wrong you can brew a pot of coffee on the inverter. You'll just need a good size battery bank and you won't be able to do it very often. Certainly not every morning for a week or anything. I regularly run my microwave on my inverter to heat up corn dogs or whatever. It pulls about the same amount of power as a coffee pot but only runs for a minute or two to heat something up. The coffee pot will run for a while longer.

The documents that Lou linked are a great primer if you want to try this yourself. I especially like "The 12 volt Side of Life"

jsutherl · 07-09-2011, 04:08 PM

As an example I have a 480A/hr battery bank installed. That's a pretty good sized bank of batteries, about 400lbs worth of batteries. Four large batteries, 100lbs each, about the largest a healthy young man can lift.

Recently we dry camped for 5 nights. We had lights on at night, used the laptop for maybe four hours that week. Charged up the RC car a couple of times. Charged the camera and gigapan batteries several times. Heated stuff up in the microwave half a dozen times. Made meals, did dishes. Regular living, minus any TV watching.

At the end of the trip I had used about 350A/hr's of juice. I had run the generator twice. Once because I was working on it and once to run the AC for a while. If I hadn't run the generator that whole time my batteries would have been pretty flat at the end of that fifth day.

jsutherl · 07-09-2011, 04:11 PM

OFF TOPIC: In case you don't know what a gigapan is, here's the one I took while we where camping:

gigapan: 2011 Laidlaw Sutherland Family Campout

Zoom in as far as you want. That's the beauty of a gigapan, you can zoom way way in. I'm the guy in the red Coke shirt.

That image took an hour to take and is comprised of 711 images stitched together.

ltypd · 07-09-2011, 04:14 PM

thanks for the advice. i was hoping to add an inverter without adding to my battery pack. is that possible with a smaller capacity inverter?

**Herk7769** · 07-09-2011, 04:16 PM

I have no idea what your coach batteries capacity is!
I was speaking in generalities.

You would need to look at the batteries and write down the manufacturer and model number and do some research online.

A 1000 Watt pure sine inverter is a perfect size for our needs (less high draw items like: Microwave, Air Conditioner, Heaters, Irons, Coffee Maker, blenders, Hair dryers, curling irons, Toasters, etc.) It will power your computer, TV sound system; charge phones and other battery powered appliances that have AC chargers like laptops and do it all pretty much at the same time for as long as your batteries last.

The article I sent you about battery capacity explains how long that will be based on amp draw over time.

If you use the inverter at its max draw (84 amps) and "normal" Camper usage, say an average of 10 amps (fridge, lights, Propane detector, and water pump), and your battery bank turns out to be, say, 160 amp hours; you should get about 120 minutes out of your house batteries before they needs a total recharge. Less amp usage will not only give you longer battery life, but MUCH longer battery life since charge consumption is not linear. If you look at the chart in the previous post you will see that your capacity drops pretty fast the more amps you demand at once.

For example, if you have a 100 amp hour battery bank; it is way better to pull out 10 amps for 10 hours that to try and get 100 amps for 1 hour. Due to the capacity reduction of about 50% (to the inability of the battery plates to release electrons at that rate) you would only get about 30 minutes of battery life at a 100 amp draw.

jsutherl · 07-09-2011, 04:19 PM

Quote:

Originally Posted by ltypd

thanks for the advice. i was hoping to add an inverter without adding to my battery pack. is that possible with a smaller capacity inverter?

Heck yea, lots of ways you can do it. Even plugging an inverter into a cigarette lighter and running small things works great.

Or mounting an inverter with an outlet on it inside your coach and running good wires to the battery bank. Just plug in what you want to run. Run an extension cord to the TV. Cheap and easy.

You'll just have to be careful what you run and for how long you run it.

ltypd · 07-09-2011, 04:20 PM

thanks herk, im beginning to see things clearer now. i will have to get info on my coach batteries and do some math.

jd-ford-hd · 07-09-2011, 04:22 PM

Quote:

Originally Posted by jsutherl

OFF TOPIC: In case you don't know what a gigapan is, here's the one I took while we where camping:

gigapan: 2011 Laidlaw Sutherland Family Campout

Zoom in as far as you want. That's the beauty of a gigapan, you can zoom way way in. I'm the guy in the red Coke shirt.

That image took an hour to take and is comprised of 711 images stitched together.

Very cool...! I like the Gigapan pic.

**Herk7769** · 07-09-2011, 04:28 PM

Quote:

Originally Posted by ltypd

thanks for the advice. i was hoping to add an inverter without adding to my battery pack. is that possible with a smaller capacity inverter?

The inverter is not the issue. A 600 - 1000 watt pure sine inverter is totally worth the money. I spent way more on the wiring, switches, second battery and battery monitoring system than the inverter cost.

I screwed up thinking I could just drop a 2400 watt inverter into the camper and I could "run the air conditioner" whenever I wanted!

What a Dufus I was! Until I actually started to dry camp and ran the coffee maker the first morning I could not believe my battery was dead by noon.

I had a single Deka DC-24 "Dual Purpose" battery as my "house battery" - Total Amp Hour Capacity ----> 75 amp hours

Talk about drinking from a fire hose!

I found out my "stock" battery was damn near useless for dry camping but only after I had spent another hundred bucks buying a second one (they have to be matched and changed in 12 volt cell pairs). Now I have 150 amp hours. Sheesh!

Currently saving my spare change for a couple of 12 volt deep cycle Trojans. It may take a while. $$$$

**Herk7769** · 07-09-2011, 04:30 PM

Quote:

Originally Posted by jsutherl

OFF TOPIC: In case you don't know what a gigapan is, here's the one I took while we where camping:

gigapan: 2011 Laidlaw Sutherland Family Campout

Zoom in as far as you want. That's the beauty of a gigapan, you can zoom way way in. I'm the guy in the red Coke shirt.

That image took an hour to take and is comprised of 711 images stitched together.

What were the blacked out items?

polkatronron · 07-09-2011, 05:52 PM

I had an inverter in my last mh and found I never used it. It seemed the generator was much more of a plus so I would never invest in an inverter again.

jsutherl · 07-09-2011, 10:26 PM

Quote:

Originally Posted by herk7769

What were the blacked out items?

The government made me do that ... Just kidding!

The black places are where the camera decided not to take a picture for one reason or another so I replaced the missing picture with a blank black one to keep everything else in it's place.

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