Free Standing 12v Power Inverter

[RichAFix]

Okay, still working on the plans (I know just jump in and do it already, I did order metal and will start the trailer frame this week). Ever since I decided to build this thing I have been struggling with the power part of it (mainly because electricity really intimidates me as I don't understand it in the least). I have always thought I would like to have power when off in the boonies somewhere, but I don't see that would be the case too often. For the most part (I would guess about 80% of the time) I will be where I have access to electrical power.

So, my newest brainstorm is why not just build the camper for 110 volt using things like LEDs to minimize my power usage. Then what if (and this is the part where you chime in and tell me it is a silly idea) a guy makes some sort of box that can be brought along when you know you will not have access to power that is self contained that holds the battery/inverter and a plug that just plugs into the shore power so you don't have to bring all the extra weight when you know you will have power, but still be able to have a free standing camper if you are in the boonies.

Am I off my rocker? Seems like a really obvious solution (especially because you wouldn't have the precious space/weight used if you knew you would be somewhere that has power) and couldn't I just steal the battery out of our extra car that would be left at home on those weekends anyways. All I would need is a decent inverter, a box to put that and the battery in and a plug to plug into the trailer. I would make it so it could be secured in some way as one draw back by this being free standing is that this thing would be real easy for someone to borrow.

Does this make sense? What else would a guy need to make this work? Thoughts? Criticism (come on I can take it)?

[starleen2]

Why Not? seems like a good idea - maybe use the tow vehical to charge the batterry when drained low

[Trackstriper]

Sounds like a plan if that is what you wish to do.

Two things to keep in mind. An inverter will only be 80-90% efficient so you will lose some of the power of the battery (a fixed quantity) by taking 12v up to 110v. That may not be a big deal depending upon what you will be using the power to run.

The other item is that you won't want to use the battery from your second car. You will need a deep cycle battery rather than a standard automotive starting battery....they are two different animals. Even if you used the other car's battery, it might not have the juice to start the car upon returning the battery, break out the jumpers. Sounds like a lot of work switching thing around. Better to buy a simple deep cycle battery for $70 and keep it charged with a small charger/maintainer.

I have an inverter in my work van. I replaced the standard starting battery with a hefty sized dual purpose "marine" battery from Walmart. It handles the semi-deep cycle work load just fine and starts the van to boot. You could possibly try that scheme if you think that you'll be using that battery very seldom. The problem is the size of the battery. A battery that large won't fit in most cars, but you might have space.

There are some really inexpensive inverters available if you're not trying to run a heavy load. A heavy load will drain your battery resources quickly.

It seems that most folks will to run 12v in the trailer and keep the deep cycle battery permanently on board. Then a suitably sized on board inverter can make 110v for the items that need it.

[RichAFix]

So how would one go about recharging that battery from the tow vehicle? I guess my thought is that one thing I really like about this idea is that this unit could move from vehicle to vehicle easily, so I wouldn't necessarily want to have to do something with a the wiring on the tow vehicle to accommodate the charging. I agree, for $70 it seems to be best to buy an additional battery (deep cell) then I wouldn't have to goof around with switching batteries from car to car. If I am just powering indoor dome lights at night prior to getting into bed (especially if they are LED's) and perhaps charging the cell phone/iPod what kind of life does one get out of this sort of system before having to charge? I know that is a tough question to answer, but I am trying to figure a cost for this thing and not sure what kind of inverter I would want. Does it make sense that I could just plug this unit into the shore power on the trailer then just use my normal lights and without having to have separate 12v and 110 outlets?

My main thought for this entire thing is weight/storage savings. I have a sister/brother in law that own a Camp Inn and they have a battery on board and all the lights are run on 12v plus it has 12v outlets, but does anyone out there really buy new appliances (12v) when you already have what you need in 110? I don't even recall seeing 110v outlets in there Camp Inn (although I could be wrong, it really is a beautiful camper could just be that I haven't got past the beauty of it to really look at how it works). I don't know if I would ever even run any sort of appliances so what is the point in even having the outlets/battery on board? To me it seems odd to convert everything to 12v when you already have and most of the time would use 110? Right?

[RichAFix]

Sorry, just realized I probably should have posted this under the electrical section.

[brian_bp]

I think the "portable power" plan make some sense, and I actually did essentially this with a rental tent trailer a few years ago. Since then, I have used the power pack mostly for boosting cars with dead batteries.

The easiest way to go is to just buy the thing: packs with an AGM battery, inverter, small charger, and usually stuff like booster cables, lights, and even air compressors are readily availalble. Many are made by Xantrex, who sells them as Powerpacks and supplies them to various retailers to sell under their house brands. Most have quite small batteries, but some are larger (e.g. XPower Powerpack 1500). Cheaper brands are available from the usual Chinese product retailers.

Do-it-yourself is practical too, and would allow the selection of a larger battery, more suited to the job. The limit is what you can reasonably lift.

To me, this approach would only make sense if most of the camping was at serviced sites, and for most trips it would be known that the pack would not be required and could be left at home.

[Trackstriper]

Brian hit the nail on the head if you are looking at minimal power drain. If your concerns are running LED lights, and charging a cell phone or ipod a relatively small powerpack would probably do the trick. He mentioned Xantrex. The Power Pack 1500 is quite spendy and fairly heavy but the smaller units would give you a fair amount of juice. Here's a sample from eBay of one of the larger powerpacks (don't know anything about the seller!):

http://cgi.ebay.com/Xantrex-XPower-Powerpack-600HD-Portable-Backup-Power_W0QQitemZ220338115476QQcmdZViewItemQQptZCar_Electronics_Parts_Accessories?hash=item220338115476&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

This type of unit will have its own battery, inverter, built-in charger, etc., all you might need if it has enough battery. You could charge your cell phone with your car charger if you have one, either from your car or this unit's 12v outlet. It appears that you can charge this unit back up from your car, which you could do if you ran any local errands/day trips while you were camping.

[Wimperdink]

I did quite the reverse of what your talking about. Since my trailer came prewired for 12volt for everything, I planned for it. I have rewired a computer power supply that puts out clean 12.3 volts. I added a marine trolling motor battery and wired in an automotive relay so that when I plug in a power cord, it automatically stops taking power from the battery and the computer power supply starts powering the trailer. When unplugged it drains from the battery. The battery lasts me 5 to 6 days one 1 charge. I've been going to throw a small battery charger into the mix so that everything is 100% automatic when I plug a power cord in it starts charging too.

I have a charge pack and found that my trailer was out of power in 1.5 - 2 days. It might be due to the low quality pack though.

I made this lil graphic to explain this in another thread awhile back so here's another chance for it to shine. There is no charger in the diagram but its just connected to the battery and hardwired into the 110 coming into the trailer.



I forgot to mention I have two normal 12v lights inside and one outside of each door, and I'm running this exact stereo. (walmarts cheapest) It has an aux jack for plugging in my ipod, and it also has a usb charge jack built into the stereo. Cant be beat for charging phones, ipods, nintendo ds, etc etc.

[bbarry]

I did quite the reverse of what your talking about. Since my trailer came prewired for 12volt for everything, I planned for it. I have rewired a computer power supply that puts out clean 12.3 volts.

Interesting!

From what little I know, most computer power supplies put out current in a variety of voltages, including 12v, 5v and 3.3v. Did you just isolate the 12v supply and wire that into your circuit?

Brad

[firemaniac]

Wimperdink, how long has the power supply system been installed? How is it holding up to the power demands? And any complaint's or should have done's?
I don't anticipate using AC power often, but when I am plugged in such a system would be perfect for light's and tunes.

[Wimperdink]

Interesting!

From what little I know, most computer power supplies put out current in a variety of voltages, including 12v, 5v and 3.3v. Did you just isolate the 12v supply and wire that into your circuit?

Brad

They do put out those voltages yes... The wires are color coded. The yellows on mine put out 12v, the reds put out 5v and I forget the color of the 3.3v.

I cut them all off close to the board except the yellows as I don't need the other voltages.

Wimperdink, how long has the power supply system been installed? How is it holding up to the power demands? And any complaint's or should have done's?
I don't anticipate using AC power often, but when I am plugged in such a system would be perfect for light's and tunes.

I've had it in there for at least 6 months now and it stays plugged in. Mine had a switch on it so I can turn it off at will which I havent done. There's a constant blue glow from the display on the stereo but I don't leave the lights on.

As for the only thing different, is that I still need to add a charger. I'm looking closely at the chargers made for boats that are onboard chargers that stay connected to the battery always. They come in a small lightweight package that just stays connected. I have yet to install the electrical pass through, but I will use a marine plug in for that and hardwire the charger and power supply direct to the 110 pass through. Doing what the drawing shows, will do three things at once when you plug into 110. Remove 12v draw from the battery, Turn on the charger, and turn on the power supply that will now supply your 12 volt. When you unplug the cord you get the opposite. unplugging will shut off the charger and the power supply and redirect draw from the battery again.

As for it holding up, I have cranked up the radio, turned on all 4 lights and turned on my vent fan. The lights dimmed slightly when I hit the fan but nothing to be concerned about. Using all LED's would help lighten the load significantly.

[tinksdad]

I did quite the reverse of what your talking about. Since my trailer came prewired for 12volt for everything, I planned for it. I have rewired a computer power supply that puts out clean 12.3 volts. I added a marine trolling motor battery and wired in an automotive relay so that when I plug in a power cord, it automatically stops taking power from the battery and the computer power supply starts powering the trailer. When unplugged it drains from the battery. The battery lasts me 5 to 6 days one 1 charge. I've been going to throw a small battery charger into the mix so that everything is 100% automatic when I plug a power cord in it starts charging too.

I have a charge pack and found that my trailer was out of power in 1.5 - 2 days. It might be due to the low quality pack though.

I made this lil graphic to explain this in another thread awhile back so here's another chance for it to shine. There is no charger in the diagram but its just connected to the battery and hardwired into the 110 coming into the trailer.



I forgot to mention I have two normal 12v lights inside and one outside of each door, and I'm running this exact stereo. (walmarts cheapest) It has an aux jack for plugging in my ipod, and it also has a usb charge jack built into the stereo. Cant be beat for charging phones, ipods, nintendo ds, etc etc.

I like the idea of using a computer power supply to supplement the 12V side of the equation.

Correct me if I'm wrong. I know the old XT power supplies were connected direct to the power switch on the case so that when the switch was flipped the power supply turned on and sent power to the motherboard. The newer AT/ATX mother boards are wired to the case switch, so I am assuming somehere in the 20/24 wire connector from the power supply to the mother board there are a couple of wires that would have to be jumped/crossed/connected to fool the power supply into thinking there was a motherboard attached.

[bg]

I like the idea of using a computer power supply to supplement the 12V side of the equation.

Correct me if I'm wrong. I know the old XT power supplies were connected direct to the power switch on the case so that when the switch was flipped the power supply turned on and sent power to the motherboard. The newer AT/ATX mother boards are wired to the case switch, so I am assuming somehere in the 20/24 wire connector from the power supply to the mother board there are a couple of wires that would have to be jumped/crossed/connected to fool the power supply into thinking there was a motherboard attached.

AT power supplies still used a master switch
ATX power supplies have a pin on the motherboard connector that must be connected to ground.
Basically you jumper out the "ps_on" (pin #14, typically a green wire) wire to ground. Test an ATX power Supply

[Wimperdink]

AT power supplies still used a master switch
ATX power supplies have a pin on the motherboard connector that must be connected to ground.
Basically you jumper out the "ps_on" (pin #14, typically a green wire) wire to ground. Test an ATX power Supply

BG has it right. And I stole the idea from Jamesm. There was a thread in the electrical section on this board with a conversation about how to convert it. Mine is an atx supply with a power switch built in and yes I put my green wire to ground. You can do a search here for power supply conversion... or google has a great deal of info with pictures on how to do it.

or click to see this thread....
http://www.tnttt.com/viewtopic.php?t=22592&highlight=convert+power+supply