Let's talk about converters (make that inverters!)

[Lesherp]

I don't seem to be able to find any posts dealing specifically with inverters.

I have a 400 watt inverter that I picked up from a garage and used to charge my computer on the first trip with my solar panel using the lighter plug-in. I had more than enough charge from the panel to bring my batteries up to full charge and am now considering installing a inverter permanently wired to the battery to take advantage of any additional power I might have. We will always need to charge the computer and have a 900 watt espresso machine we would really like to be able to use. It seems like something mounded permanent directly to the battery would be best.

I am wondering just how large a inverter I should install. I am not sure how much additional electricity I will have with 2- 6 volt batteries and a 150 watt panel but it seemed like we had quite a bit on this first trip. I have a few questions someone might be able to shed some light on.

Do larger inverters use more electricity or is it just dependent on what you are running?

My batteries are in the back of the TM. I am thinking of mounting it next to the converter in the TM. Has anyone done this? Is there enough air circulation under the tub area for the inverter fan and heat the inverter might generate? I know the bathroom vents out of there somehow. It seems like I could mount it on the floor in there and cut a hole in the wall to plug into. Any suggestions that might work better?

I am considering a 1600 or 2000 watt inverter. These two get good reviews on Amazon. It seems like for an extra $50 the 2000 might be the way to go.

http://www.amazon.com/gp/product/B003R7AJ4K/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

http://www.amazon.com/Whistler-Pro-2000W-Watt-Power-Inverter/dp/B003R7M6CS/ref=pd_sim_lg_3

[ShrimpBurrito]

I think you are talking about inverters -- they convert DC (battery) power to AC power that you can use to power devices that you plug into the wall at home.

Converters convert AC power to DC power -- that's what is built-in on every TM by the bathroom.

Generally, you don't want to use an inverter any larger than required for your intended usage because larger units will waste some energy in being able to supply extra capacity. However, with your solar array, that overhead is probably not particularly significant. If you want to run your 900 watt expresso machine, and that is the biggest power draw, then I would get a 1600 watt inverter. A 2000 watt unit would be fine too, but if you're not going to use it, I wouldn't get it; it is also probably physically larger, which may be an issue depending on your mounting location. Note that the wattage numbers specified are sometimes surge capacities, not continuous, so be sure you know what you're looking at. The ratings for the ones you referenced are continuous.

Dave

[Lesherp]

Your right I meant inverter. For some reason was thinking they were called converters. Can't change the title of the post but tried to correct in my post.

I was considering the 2000 just in case I might find there is something down the road I want to run that is larger than 1600 as I have just begun to get used to having more electricity than I need. I know DW has a hair dryer she would like to use that is about 1800. I have been thinking that could be too much of a draw on the batteries though. If not then why not run a small electric heater. I just have no idea how much extra electricity I may have at this point.

Looked at the area next to the converter and nothing is going to fit there. The wall of the battery compartment extends into this area about 3 inches. It looks to me like the storage area under the bed is the only place to put it.

[Bluegrass]

I had a 1800 on my houseboat and it ran all the appliances including the microwave just fine. Hair dryers are a bit much and they get run longer which eats up battery power. We sure loved the convenience when anchored out for extended periods.

For sure you'll want a battery monitor. Take a look at the West Marine website. They used to have a lot of good info on inverter usage.

Keith

[ShrimpBurrito]

Keith / Bluegrass is right -- running anything that generates heat, like a hair dryer, is a huge energy sink. You DEFINITELY don't want to run an electric heater off batteries -- you'd have no battery power in short order, regardless of whether you have 1 or 4 batteries.

Your wife's 1800w hairdryer will draw 150 amps without taking any inverter inefficiencies into account. If you have 2 Trojan T-105s, for example, you have about 220 Ah, of which half that (110 Ah, or maybe more depending on your comfort level), is usable. But that is the 20 hr rate, which is the capacity quoted if you have a constant power drain that will exhaust the battery in 20 hrs. But with the hair dryer, the rating time period would be much less -- less than 1 hour in fact, and since batteries have less capacity the faster you draw power, you would get FAR less than 110 Ah. Considering 8 hr rates are typically at least 20% less than 20 hr rates, you might not even get half the batteries' rated capacity -- maybe 50 Ah.

So the hair dryer completely depletes your fully-charged 2-battery bank in 20 minutes.

Dave

[thewayneo]

You might also want to look into "Modified Sine Wave" vs "True Sine Wave". Sometimes they're called "Pure Sine Wave." Both of the inverters you're looking at are MSW. MSW will run most things but it's hard to know which appliances don't like it until it's too late. From personal experience, one older brand of bread machine worked great, and one new digital readout brand burned out the first use. I think that items like a charger for a rechargeable drill don't like MSW. MSW has worked fine for me to power a laptop and cell phones. My 2500 MSW could run a small microwave but the power draw was huge and now I leave the micro at home.

I currently have 3 MSW inverters in different places for different uses.

Also from personal experience, go for the most watts you can afford! TSW if you can afford it!

wayne

[Lesherp]

Thanks for the advise. I decided to just install the 400 watt inverter and see how it goes before investing in a larger inverter. This one will do everything I really need except run the espresso machine. It would be hard for me to justify the prices I saw for true sine wave inverters. I checked with my computer manufacture and they said modified sine wave is fine for it.

[Riwright]

I have a 2000 watt inverter that came with the camper. When we tried the wife's hair dryer the inverter did not overload, but the batteries could not keep up. You could see the voltage fall quickly until the low voltage shutoff kicked in and turned the inverter off.

The batteries just don't put the electrons out fast enough to support it. We have two 6 volt golf cart batteries.

Anything that generates heat will have a very high current draw.

I carry a generator too. If the wife wants to dry her hair I hook it up.

You could install the inverter in the rear storage area with the batteries. You want the cables to the inverter to be short. DC current (what you input into the inverter) does not carry well over long distances, AC (what the inverter outputs) is much better for distance.

An inverter draws a little bit of power when it is turned on. You need access to the switch.

[Lesherp]

I mounted mine in the storage area under the back bed. Not too long a run from the battery there and easy to plug into. I know about the problem of sending DC over long distances from the Edison/Tesla controversy. I have read that the first electric chair was Edison's idea to help persuade people that AC was just too dangerous.

I think it is interesting that everyone gives credit to the lights we use to Edison and the radio to Marconi and few have ever heard of Tesla. Conspiracy theorists claim the government confiscated all of Tesla's research papers upon his death and they have never been seen again.

[scrubjaysnest]

Older thread but still valid.

Here are some numbers to think about. Brought over from the solar-electric forums.

Daily WH usage based on battery bank, I used our two 105 AH stowaways

• 210 AH * 12 volt * 0.85 AC inverter eff * 1/1 days storage *0.50
maximum discharge = 1071 WH per day (RV/Boat)

• 210 AH * 12 volt * 0.85 AC inverter eff * 1/2 days storage * 0.50 maximum discharge = 535 WH per day (off grid cabin)

• 210 AH * 12 volt * 0.85 AC inverter eff * 1/3 days storage * 0.50 maximum discharge = 357 WH per day

12 volt is used above as the not charging battery voltage.


Charging wise--Based on a 5% to 13% typical rate of charge. 5% is OK for weekend/seasonal use, 10% or above is recommended for full time off grid charging (and if you have "significant" day time inverter/battery loads:

• 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.05 rate of charge = 198 Watt array minimum(this is 10.5 AH rate or 5.25 amps per battery; about the c/20 rate)
Marginal for our batteries with 160 watt of solar and why I added the 120 watt panel

• 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.10 rate of charge = 395 Watt array nominal( this is a 21 AH rate or about what is best for GC-2 batteries)

• 210 AH * 14.5 volts charging * 1/0.77 panel+charge controller derating * 0.13 rate of charge = 514 Watt array "cost effective" maximum

14.5 volts is a typical bulk or boost charge voltage.

The above calcs are from BB aka Bill over on the solar-electric forums.

The drip coffee maker we have at home is 975 watts and for two hours use that is 1950 watts or almost 2 times our daily capacity.

[Bill]

The drip coffee maker we have at home is 975 watts and for two hours use that is 1950 watt[-hours] or almost 2 times our daily capacity.Your post made me curious, so I made some measurements. Results are interesting, and maybe even useful.

Our coffeemaker here at home is a Mr Coffee 12-cup unit. The label says 900 watts.

It seemed to me that a coffee maker has two states - brewing, and keeping the pot warm. I plugged it into nifty little Kill-A-Watt meter so I could see actual electrical consumption. I saw

o During brewing (about 2 minutes), electrical consumption is about 910 watts.
o When brewing is done, the heater cycles on and off to keep the pot warm, averaging about 127 watts.

We don't have an inverter, or a big battery, so instead we heat water on the stovetop (propane) and then let it drip through our French press. Total electric usage zero. But to each his own.

Bill

[scrubjaysnest]

We have the 12 cup Black and Decker seems to be hotter coffee then the Mr Coffee. Takes about 10 minutes to brew then does the cycle thing. I need to pick up a Kill-a-watt meter. Coffee in the TM is down on the gas stove and is really hot.:D

Thought folks here might be interested in some numbers dealing with inverters and solar charging based on battery bank size. Some of the solar values seem unrealistic for a TM when you look at roof area for panel placement.

[Padgett]

Key to remember is that the watts just increase about 15% but the amps required to dreate those watts are x10 for 12v vs 120v. Any inverter over 160-180w is probably going to be too much for a standard cigarette lighter socoket. Larger inverters need to be hardwired on their own circuit. Also the stock battery has a 30 amp fuse which is maxed at about 360w.

Hope to get my two 100W solar panels installed today since going to be dry camping for a week but for the Keurig or A/C will need to fire up the Pred.

[rickst29]

(1) Buy one of the flat-bottomed "Mr. Coffee" permanent filters. Also buy a pari of food-safe tongs, if you don't already have one.

(2) In a saucepan, on the gas stove, boil water at a height which will not exceed the lip of the coffee filter. While water comes to a boil, grind the coffee, and load the FRESH coffee into the filter.

(3) When boiling: Turn stove heat way down, or take it off the burner completely. Set the filter into the saucepan, using tongs. Drag it around the bottom of the pan, using the tongs, coffee is done. While brewing, enjoy wonderful coffee smells. :)

(4) Remove filter by grabbing the edge with tongs. Pour the coffee into cups or thermos.
- - - - - - -
This is a modern variant of "cowboy coffee" (done in paper towels). Really good coffee. No need for a massive inverter and 4-gauge wiring, no massive battery drain,, and no French Press "crunchies" in your Juice.