Installing An Inverter

[predvers@gmail.com]

I have a Class C Fourwinds Citation. I am installing an inverter. I expect to be camping more in parks than boondocking, but I feel I want to use my TV and computer when doing overnight or short term boondocking.

I bought a 1750 watt modified sine wave inverter. I did not want to go the inverter/charger route. I don't want to get involved in changing the current set up in my unit in any way. I just want to have AC power for those occasions when shore power is not available.

The inverter I have has 3 power points. I am thinking of mounting it inside the cabin, in a location keeping the line from the battery to the inverter as short as possible. I will run extension cords to the TV, coffee pot etc as needed. I will ensure the inverter is off when not in use.

Any comments or suggestions would be welcome.

Paul

[wolfe10]

Paul,

That will work-- consider it a semi-permanent installation (vs one wired into the house 120 VAC system).

Be sure to fuse the positive lead at the battery and use the correct (read that LARGE gauge) cable from battery to inverter.

Brett

[tbutler]

Use extreme caution when using extension cords. They are always a trip hazard and in a motor home where space is limited they will have a tendency to be under foot occasionally if you aren't careful. Also, a coffee pot is a large load on an extension cord. Be sure to get a 12 gauge or maybe a 14 gauge extension and then check when in use to see if there are hot areas in the cord indicating pending failure. These usually occur at the ends of the cord but with use they could develop anywhere the cord is repeatedly bent.

[predvers@gmail.com]

Thanks for the comments.

The inverter installation guide makes a point of setting out the correct gauges. As to extension cords, a heavy gauge, high quality cord is a must, and should be replaced when it gets nicked or cut. The coffee thing may best be solved using the gas range, a kettle, and a french press or drip cone. I will not camp on instant coffee.

We have not done any significant motorhome camping yet. Our previous experience was a tent trailer and camp stove outdoors. Showers depended on the weather. From a few weekend trips, plus all I am reading on the net, its clear that energy management is a key to traveling beyond camping parks and using the motorhome to its limits.

Any suggestions on energy management would always be welcome.

Paul

[wolfe10]

Paul,

Energy management can be as basic as adding up all your electrical draws (in amps) times the time they run to give you total AMP-HRS of consumption.

Then look at your battery capacity, again expressed in amp-hours. IF in like new condition and IF fully charged, you can reasonably discharge deep cycle batteries to 50% of their capacity. Said another way, a 200 amp-hour battery (or multiple batteries tied into one large battery bank) can theoretically provide you 100 amp-hrs before you need to recharge.

If you need to run the generator to recharge (i.e. you are dry camping) most efficient use of generator time is to recharge from 50 to 85%, discharge to 50%, recharge ........ Once a week or so they will need to be fully recharged, but it will take longer to go from 85% to 100% than from 50% to 85% and the amps the charger puts out diminish as the battery becomes charged.

Can you find expensive automatic power (amp-hr) meters that do this for you-- sure?

Brett

[dogpatch]

I've been told that you should not use a modified sine wave inverter with use for LCD or LED TV's or for laptops. That's why I put in a Pure sine wave inverter. Your thoughts Brett?

[wolfe10]

I've been told that you should not use a modified sine wave inverter with use for LCD or LED TV's or for laptops. That's why I put in a pure sine wave inverter.

Your thoughts Brett?

Yes, some electronic equipment is sensitive to AC wave form. Best advice is to contact the manufacturer of the device you wish to run on the inverter and ask them about MSW vs pure SW inverter use.

Brett

[Koliver]

In my experience laptops don't care what the form of the AC power is. The laptop power cord takes whatever input it gets (within the parameters on the little box, but it can handle European 240v 50 cycle, North American 120v 60 cycle, and lousy, cheap inverters) and converts that to DC in a range of voltages, as stated on the individual unit. The one I am using right now says:output 19v...4.74A.

I have used a little 175 watt inverter and more recently a 300w inverter, neither have any pretensions of putting out a sine wave, both put out a square wave, for 15 years on my boat with no issues at the laptop.

What I would like to know, is; will the laptop operate on 12v DC instead of 19v DC. I have heard of some who plug directly into the 12V of the house battery power, but I haven't tried it, and would like to know if those who have, have a laptop that also operates on the more usual 19vDC. then you eliminate the 15% loss of efficiency thru the inverter, and if you have no other loads, can turn the inverter off and eliminate the 5A minimum draw on your batteries from the inverter's internal losses.

I should add that recharging battery packs, for tools, from a square wave inverter or even a modified sine wave inverter is prone to a fryup in the battery pack. Pure sine wave inverters will do it OK.

[Guest BillAdams]

I have been using a modified sine wave inverter for all of the above listed items (have not installed a LED/LCD TV yet but use an LED/LCD computer monitor) plus the Hughesnet satellite internet modem, GE Profile household refrigerator and anything/everything you can think of that a full timer might need including my rechargeable toothbrush!

[tbutler]

We use a heated mattress pad as a way to warm the bed before crawling in at night. Sometimes DW likes to keep it running all night long. These are Sunbeam (Mfg. in China) and we're on our third or fourth because we forget to unplug before going on the inverter. It isn't the heating element but the electronic controls that won't deal with a modified wave inverter. They even go out if we haven't turned on the heat, if they were plugged in when the inverter was on they were fried. We haven't risked using it on the sine wave inverter we installed two years ago. We've become very careful not to leave it plugged in when we aren't plugged in to shore power. There are some electronics that won't tolerate the modified wave power.

[desertdeals69]

A few points to consider. I always recomend a pure sine wave because you never know what sensitive equiptment might be plugged in. With regard to recharging batteries most converters charge capacity is in the 30-40 amp range with an effective charge rate of only 15-25 amps. With a battery bank of 440 amp/hr discharged 50% you can see how long it would take to recharge even to 80%. Back in the 70's before inverter/chargers we had to build 100 amp chargers to use with then available pure sine wave only inverters. We recomend a battery bank would consist of 4 6 volt golf cart 110 minutes @ 75 amp draw, wired series/parallel for 220 minutes @ 75 amp draw. A modern inverter/charger could be simply wired with a 30 amp outlet which you plug in the shore cord. Since every thing would be connected care must be taken as to not to turn on the air conditioner, fridge, etc. however there be no extention cords required. Battery recharging would be done in a much shorter time period.