Power/Inverter Questions

[SoCalCamper]

Thank you to all posters who generously offer advice on this forum.  It has been a pleasure to "steal" all of this information and put it to immediate use.   :p

As a relatively new PU camper, I have a few questions concerning dry camping, power inversion, and battery life.

A little context:
I just bought a Black and Decker power inverter rated at 750 watts.  Since my wife and I are making our first attempt at dry camping this weekend, I need to transfer my PU's deep cycle power into AC.  

Needs/Wants:
* House lights
* TV/DVD
* Various battery charging devices (cell phones, laptop)
* Hair dryer
* Radio/CD player

Questions:
1.  Will this power inverter have trouble running any of the above?  Can it run them simultaneously?
2.  Should the inverter be turned off when no power is in use?
3.  How much life can we expect from the battery without recharging?  (We are camping two nights.)
4.  Most importantly, how do you recharge your battery?  I heard that the PU's brake system (when plugged into the car) will recharge the PU battery if the car is running.  Is that true?  How long should the car be left on?
5.  Please feel free to drop any other advice.

Thanks!

[AustinBoston]

As a relatively new PU camper, I have a few questions concerning dry camping, power inversion, and battery life.

A little context:
I just bought a Black and Decker power inverter rated at 750 watts.  Since my wife and I are making our first attempt at dry camping this weekend, I need to transfer my PU's deep cycle power into AC.  

Needs/Wants:
* House lights
* TV/DVD
* Various battery charging devices (cell phones, laptop)
* Hair dryer
* Radio/CD player

Questions:
1.  Will this power inverter have trouble running any of the above?  Can it run them simultaneously?

By "House lights," do you mean the lights that are built into the pop-up, or are you bringing more along?  If you are talking the camper's lights, those already run off 12V, so they will not use the inverter.

You can probably forget about using the hair dryer.  Most have too high a wattage to be practical on battery power.

The best way to answer this question overall is to check the wattage on each device.  (it's usually right on the device near the power cord).  If they add up to more than 750 watts, you can't use them in combination.  But see below.

2.  Should the inverter be turned off when no power is in use?

Yes.

3.  How much life can we expect from the battery without recharging?  (We are camping two nights.)

This depends on a number of factors.  How many lights will you have on at a time?  For how long?  What's the campacity of your battery? How long do you plan on watching TV?  Most of us would not give two nights a second thought, but you can drain a battery dry in less if you use it a lot.

4.  Most importantly, how do you recharge your battery?

We plug in our pop-up at home and use the built-in converter, but our converter is a replacement converter and much better than the converters of 4-5 years ago (or the cheap converters of today).  A three-stage smart charger is generally the best way to go.

I heard that the PU's brake system (when plugged into the car) will recharge the PU battery if the car is running.  Is that true?  How long should the car be left on?

This is a gross miss-statement of the facts.  The brake system will not charge the battery.  If you have a 6-way or a 7-way electrical connector, there is probably an independent "Aux" or "Charge" line that is usually wired to charge the battery.  While it is possible to charge the battery when connected, it can take a loooooong time, sometimes as much as 4-5 hours, depending on a number of factors.  The whole time, you would need to leave your tow vehicle running.  When you figure wear and tear on the tow vehicle engine, it is generally cheaper to buy and use a generator.

5.  Please feel free to drop any other advice.

Unless you have wired it with some very big cables, I don't think you will really be able to get 750 watts from your inverter.  Assuming 100% inverter efficiency, 750 watts means more than 60 amps at 12V.  You would need 6 gauge wire or larger directly between the inverter and the battery to avoid overheating the 12V wires (or blowing a fuse/breaker).  10 gauge wire would max out at 360 watts, 12 gauge at 240 watts.

Dry camping works best when you minimize battery load instead of maximize the conveniences of home.

Austin

[wavery]

We actually have 2 inverters in our camper. We have the 750w one, like you do. I plug that into our 12v electrical socket and use it for charging 12v devices and running the laptop computer. When not using it in the camper, we use it in the car for the same purpose. I would never put more than a 200w draw on it, for the reasons mentioned above. A small TV shouldn't be a problem. However, you will need at least 2 batteries if you plan on watching much TV. You may also have to wire in a special 12v socket with larger wiring. I would suggest using 12 gage wire. That will cut down on the resistance which will lower your actual power usage and keep the wires from getting hot.

We also have a 2500w inverter. This is a much more serious inverter and can be used to run a hair dryer and most electrical tools. We mostly use it to run our microwave.

I put the 2500w inverter on a bracket & lock system that I installed under the bed platform, just above the batteries. It is wired to that batteries with "00" gage battery cables. It is mounted in a way that I can reach it from inside the camper to turn it on & off while using by sticking my hand through the tent side and reaching under the bed platform.

I also have 2- 27 group, deep cycle batteries wired together. This is essential to keep the battery from over-heating. We use the inverter quite a bit during "Quiet hours" and usually don't have to recharge over the weekend. However, I always carry our generator, just in case.

[garym053]

My experience with charging the battery while driving has been completely different than those stated here! I can dry camp for two days running lights and furnace as needed. (No TV's, Computers, etc that's what I'm escaping from!)
Anyway, after 2 days of dry camping, my Jeep will recharge the battery to 100% in 1 1/2 to 2 hours on the interstate. Even after disconecting and waiting for the charge to stabilize it still reads 100% charge.
I always carry a multimeter and check the batteries daily while camping. (I have sleep apnea and run my CPAP through an inverter, so we COULD be talking life or death here!)
I carry 2 Group 27 batteries, one just for the CPAP and the other to run the camper. I have a pigtail wired so I can place the CPAP (Gel Type) Battery in the back of the Jeep and charge it as we sight see, or drive to and from hikes or paddles.
Have dry camped 8 days straight on the coast of Maine with this arrangement and did not run out of power or need a generator. Granted it was in the summer so the furnace was only used two mornings to take the chill off.

[dthurk]

I found (and bought) a 12 volt hairdryer and curling iron for DW.  It keeps her happy.  We use 2 6 volt golf cart batteries in series and could go 3 days before recharging using the furnace, water and lights at will.   We have a  Black and Decker 400 watt inverter and wired that directly to our original Group 24 battery that came with the camper, to help save the main batteries.  We also use battery operated flashlights and lanterns indoors when we can, rather than the on board 12 volt lights.  We will be installing a solar system to recharge batteries, and probably a large inverter to be able to run the microwave after that.

[tlhdoc]

One thing no one has touched on is that your vehicle has to have a "hot" line wired in order to do any charging of your battery.  If you don't have a hot line you will not be able to charge your battery at all with the vehicle.

[gypsy_soul]

In todays world, You should be able to find just about everything you need in the 12 v. range Except for Microwave. You can get a decent solar charger on ebay for about $65.oo or pick up an inexpensive generator from Wally-world.
Coleman 1850 under $500.00. And you'll be good to go.

[Brauma]

Just to razz you a little, are you sure want to camp or don't you think you should get a motel room?    Just kidding.

I'm an old backpacker/tent camper recently turned pop-up camper. So I still have that "ounce counting" primitive camping mentality. I like to go with just the basics and get away from the TV and cell phones and laptops and Blackberries when I camp.

We've been to a few state parks and its been ok, but its just a little crowded for me. I have felt that we have to talk low to each other because the next camper is so close. I'm afraid that I might burp or pass gas and offend the next door neighbors. Thats just a little too close. I like to get out away from people and enjoy the outdoors when I camp. Nothing will be as free as backpacking but Im trying to share camping with my kids. They're a little too young for backpacking yet. I hope they will be into it one day though.

So Ive been doing my research (mostly on this board) and gearing up my setup for dry camping. This post is very helpful so please don't be offended. I just had to razz you a little about the hair dryer and laptop.  

[Steve-o-bud]

Anytime you can avoid using an inverter, by using devices that run directly from 12 volts DC, the better off you are. This is because inverters are inherently inefficent, generally in the 50% range. The higher quality inverters, which are designed to provide a clean sinusoidal (sine) wave output, are more efficient than the cheaper units, which produce a dirty 'square' wave output.

The cheap and dirty inverters are most suited for non-motor type (non-inductive) loads such as lights, heating, etc. They will also work for electronics.
 
AC motors requires sine waves to work most effectively. When selecting a high quality inverter, it is important to ask what the inverter's 'inductive' load capacity is. On cheaper units, it will be lower than it's 'non-inductive' load capacity.

[fritz_monroe]

I don't know how I missed this discussion.  This is great stuff.

We've only had the pup since March.  We always camp in state parks, and about half the time we have electric.  We did camp in April without electric and the group 24 battery lasted the entire weekend.  We made sure we turned off the lights when not needed, and when ww played some cards at night, we used a battery powered lantern for light.  We also used the furnace somewhat sparingly, but were never uncomfortably cold.

I've since adapted the lantern so I can plug into the 12V system if we have hookups.  We are also going to get a group 27 or larger battery, we will either connect the group 24 in parallel, or just keep it as an emergency spare.  Eventually, we will probably get a small, quiet generator to allow us to charge the battery if needed, and run the fridge at home in case of power outages.

[dademt]

Not sure if it will be any help to you if you decide to add more battery capacity but I just installed a second battery on my trailer and put individual disconnects for each battery.  For a change I actually took pictures and I believe the captions to each one tell more information about what they were mounted on and how.  

http://community.webshots.com/user/dademt
 
Or click this link to see where I discussed it further.
http://www.arveeclub.com/showthread.php?t=60248

[wavery]

Not sure if it will be any help to you if you decide to add more battery capacity but I just installed a second battery on my trailer and put individual disconnects for each battery.  For a change I actually took pictures and I believe the captions to each one tell more information about what they were mounted on and how.  

http://community.webshots.com/user/dademt
 
Or click this link to see where I discussed it further.
http://www.arveeclub.com/showthread.php?t=60248

No offense intended here but that looks like it could be a pretty scary modification.

If someone drops a tool, bunk support rod, crank handle or anything metal on that, you may have a fire. Once a metal object shorts from your frame to one of those connections, it may instantly weld itself, become red hot and that wood could easily catch fire. If someone touched the item to remove it, they would be severely burned in an instant.

I would recommend using your ground wires for your your disconnects, if you want to do it that way. It does the same thing, only safer.

They make a switch for exactly what you are doing there (safely):
http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/3094/0/0/battery%20switch/All_2/mode+matchallpartial/0/0

[wavery]

Not sure if it will be any help to you if you decide to add more battery capacity but I just installed a second battery on my trailer and put individual disconnects for each battery.  For a change I actually took pictures and I believe the captions to each one tell more information about what they were mounted on and how.  

http://community.webshots.com/user/dademt
 
Or click this link to see where I discussed it further.
http://www.arveeclub.com/showthread.php?t=60248

No offense intended here but that looks like it could be a pretty scary modification. I don't see any fuses. I hope that they are inside the battery boxes.

The way that it looks (not fused), if someone drops a tool, bunk support rod, crank handle or anything metal on that, you may have a fire. Once a metal object shorts from your frame to one of those connections, it may instantly weld itself, become red hot and that wood could easily catch fire. If someone touched the item to remove it, they would be severely burned in an instant.

I would recommend using your ground wires for your your disconnects, if you want to do it that way. It does the same thing, only safer.

They make a switch for exactly what you are doing there (safely):
http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/3094/0/0/battery%20switch/All_2/mode+matchallpartial/0/0

[wavery]

Not sure if it will be any help to you if you decide to add more battery capacity but I just installed a second battery on my trailer and put individual disconnects for each battery.  For a change I actually took pictures and I believe the captions to each one tell more information about what they were mounted on and how.  

http://community.webshots.com/user/dademt
 
Or click this link to see where I discussed it further.
http://www.arveeclub.com/showthread.php?t=60248

When I first saw this I thought that it looked like it could be a pretty scary modification.

If those were positive battery wires (which they don't appear to be) and someone drops a tool, bunk support rod, crank handle or anything metal on that, you may have a fire. Once a metal object shorts from your frame to one of those connections, it may instantly weld itself, become red hot and that wood could easily catch fire or worse, melt through that propane hose. If someone touched the item to remove it, they would be severely burned in an instant.

However, after looking at it again, it looks like you are using your ground wires for your your disconnects.

I just wanted to be sure that no inexperienced person saw that (as I did at first) and tried it using positive wires because the wires that you used are red someone could misunderstand that. The typical color coding for campers is white=ground and black=positive. In automotive use, red=positive and black=ground.

They make a switch for exactly what you are doing there (safely):
http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/3094/0/0/battery%20switch/All_2/mode+matchallpartial/0/0

or, if you like the individual switches and want to keep the price down:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92688

They have these on sale for about $3 each, quite often. If your battery box has enough room, you can cut a hole in it and mount the switch so that the handle is on the outside and the connections are on the inside.

[dademt]

Thanks, you did bring up a very valid point that I failed to explain, in my situation this is mounted on the front of a tt and as such there is not much risk of poles or anything else coming in contact.  Furthermore, these are fairly resessed to help prevent anything laying on top or hitting them from the sides.  Those are the positive connection disconnects ( matching the red positive that was existing on the trailer ), not negative, as you can see it goes up to the exposed positive connection that came stock on the trailer.  I had thought of placing the disconnects on the negative instead but considered that a larger potential problem of having a charged vehicle with no ground to the battery.  I had considered your idea also as we use that type of setup on the ambulance but I didn't want to build an enclosed box to mount it on.  The disconnects I chose are the same ones as designed for under-the-hood applications where caution would be observed.  In time, I plan to build either a wood cover or some other protection to prevent something from laying across the top.  Another idea I had was to actually put a rubber coating on the tongue of the trailer but as the weather was bad, I had never completed my work in either method.  

As with anything, people need to take caution in what they do and never assume that someone else's solution will work for them.