Powering a laptop computer while off the grid

[Bluesail20]

I have a small camper trailer (2008 Casita) that has an in-house converter (Parallax series 7300). I like to go camping off the grid, and can do so for a week to 10 days without any trouble. That is, unless I try to recharge my laptop computer from the in-house battery using an inverter. A single charge to the laptop drains the in-house battery. I'd like to solve this problem with a solar power solution.

The laptop is a Dell Inspiron N411z. The inline adapter/converter on the laptop's power cord outputs 19.5V DC at 3.34A for a 65W power draw.

My inverter is a PowerBright PW1100-12. One of my questions is: when you have an 1100W inverter, and you plug in a 65W load, does it draw 1100 watts out of the 12V battery and waste whatever is not being used? The fan on the inverter runs constantly when I use it, and I never have anywhere near 1100 watts hooked up. For convenience, I have connected the inverter to the battery terminals exposed on the converter panel rather than to the battery terminals on the battery itself. Does it make any difference?

But the real question is : how to set up an efficient, elegant, solar power solution just to power my laptop computer without spending more money than I really need to.

What I don't want to do is to plug the laptop, with it's inline converter, into my oversized inverter, which is connected to the in-house converter, which is connected to the battery, which would be connected to a controller, which would be connected to a solar panel. I mean, there just has to be a better way.

Can I connect the computer directly to a controller/regulator of a solar panel? I'd like to take an appropriate cable (say, 8 gauge) with a barrel plug that matches my Dell Inspiron N411z on one end, and (somehow) connect the other end directly to the output of a controller (which is connected to appropriately sized solar panels), if the controller is smart enough that you can set it to exactly what voltage and amperage you want to come out of it, while it provides thermal overcurrent protection somehow (like with a thermal circuit breaker?). Since the laptop's inline adapter turns AC input power into 19.5V, 3.35A output, I want a controller that will take the solar panel's energy and deliver it at precisely that power profile.

Of course, it would be nice to have the flexibility to recharge the camper's battery as needed too. I might also like to power a bluetooth speaker (12VDC, 2A) and recharge my cell phone as needed.

I am new to solar power, and have only rudimentary knowledge of electricity/electronics so all of this is guesswork. Any helpful advice would be greatly appreciated.

[Sunking]

Never mind, I am not going to touch this one.

[Bluesail20]

Never mind, I am not going to touch this one.

Hm... What's that all about?

[Mike90250]

When you turn on the 1Kw inverter, it starts pulling 50 watts, or more, out of the battery. Add your 65 watts, and another 20 watts of more loss, and you are over 100w of draw from your house battery. I'd look for the $50 car adapter for the laptop and use that.

Or look for a highly efficient inverter - I like the morningstar suresine 300. Very low draw, and efficient. but pricey. In solar, you pay for quality, or go cheap and have dead batteries.

[PNjunction]

Ok, I'll give it a shot. There are just a LOT of variables involved, so I'll generalize. In the meantime, read the stickes and faqs to get up to speed in the shortest time possible.

I have a small camper trailer (2008 Casita) that has an in-house converter (Parallax series 7300). I like to go camping off the grid, and can do so for a week to 10 days without any trouble.

Part of that equation means that for a successful solar setup, you'll want to know the solar-insolation hours of where you are going. These differ from mere sunrise to sunset hours, and NREL charts are available online. Basically, a system designed for Albequerque, NM is going to suck in Fairbanks, AK !

A single charge to the laptop drains the in-house battery. I'd like to solve this problem with a solar power solution.

Sounds like the first thing to solve is determining if your battery is in fact good in the first place.

The laptop is a Dell Inspiron N411z. The inline adapter/converter on the laptop's power cord outputs 19.5V DC at 3.34A for a 65W power draw.

That's usually at full power, AND recharging a dead battery at the same time. If it takes 4 hours to finish a charge, then when running while on and drawing 3.34A, that would be about 13A, which requires a minimum of double that capacity in battery storage because recharging it is not 100% efficient.

One of my questions is: when you have an 1100W inverter, and you plug in a 65W load, does it draw 1100 watts out of the 12V battery and waste whatever is not being used?

No. You are only drawing 65W through it, and theoretically it can supply 1100. This kind of a large mismatch usually means the inverter is operating inefficiently, but it is not wasting 1040W. Not only that, but if you WERE able to pull 1100w through it, that would mean pulling 91A through the cabling between the battery and the inverter. Sure hope you have short and fat cabling. In reality, this rating is only convenient for instantaneous and short pulls, say from a motor startup. Ideally, you'd want a smaller inverter to operate more efficiently, about 100 - 150w perhaps. Oh, and then you'd want pure-sine wave, and not modified-sine-wave.

For convenience, I have connected the inverter to the battery terminals exposed on the converter panel rather than to the battery terminals on the battery itself. Does it make any difference?

It very well could be. The general rule of thumb to help avoid voltage drop losses is to connect inverters directly to the battery.

Can I connect the computer directly to a controller/regulator of a solar panel?

No. Panels and charge controllers are designed to be used with batteries - that is not directly to laptop batteries. It is a logical conclusion for beginners that you don't need a battery, but it just doesn't work that way. This is one reason for some returned solar charge controllers that "dont work", simply because the newbie hooked it up to a panel without a battery, measured the voltage at the controller output, and sees nothing.

Of course, it would be nice to have the flexibility to recharge the camper's battery as needed too. I might also like to power a bluetooth speaker (12VDC, 2A) and recharge my cell phone as needed.

Uh oh, more loads. Cell phone is easy. Grab a 14w Anker folding solar panel with built-in usb regulator. Optionally get an external Anker battery, which you can also charge from the panel if that is more convenient.

I am new to solar power, and have only rudimentary knowledge of electricity/electronics so all of this is guesswork. Any helpful advice would be greatly appreciated.

To stop it from being guesswork, read, read, read my friend, and be sure to close your wallet first.

The key is to actually determine how much power you are going to use in a day. A P3-Kill-A-Watt meter or dc ammeter is handy for this.
This will determine the size of the battery you need, which is at least double your power draw.
From that, you can figure out how much panel power you need, BUT that has to take into account the solar-insolation hours from where you are located.

[jony101]

I got 3 laptops and can power 2 of them from a 400 watt modified wave inverter, my gaming laptop i have to use a 150 watt pure sine inverter otherwise the power adapter for the laptop cycles on and off.

As far as running the laptop from the solar charge controller directly (I had a pwm and mppt and both had load out where you can connect 12 volt loads) The problem that i notice with this is that the power coming from the load out is not consistant, it goes up and down. when I have a fan connected, I can tell when a cloud is passing overhead by the fan rpm throttling down, also if its cloudy and the sun suddenly comes up, the voltage will shootup and the controller will shut off power to the load out to keep it under 14 volts. i would not hook up inverters to the load out, even the low wattage ones.

My advice is get the biggest panel that you can fit on your roof of your camper trailer. For only a laptop you need at least 120 watt panel (which gives you about 6 amps charging power) , you can get a pwm charge controller on ebay for 20 dollars, I used the wincong brand 20 amp model and it proved very reliable when connected to a kycora 120 watt panel.
You dont need to spend alot of money, I would stay away from the small harbor freight type of panels, you can get good large used panels for a good price.

I rely 100 percent on solar and had no problem running my giant gaming laptop off a 75 ah battery and 120 watt solar panel but only when the sun was out, at night I always use my netbook.

[Sunny Solar]

If you can get away with using a netbook and not a laptop your supply needs will drop dramatically. you will still need a 100w tsw inverter and battery but 100 ahr deep cycle battery be more than adequate and a 100w panel.

[Wy_White_Wolf]

Battery going dead that fast might be on it's last legs.

Get a car adaptor for you laptop. That will reduce a lot on tha wasted poer from th inverter. I really see no reason to go from DC to AC to go back to DC.

Then get a solar panel to mount on the trailer. use the basic formula of 1 watt of panel for every 1 AH of battery with an MPPT controller. If you want to use a PWM controller then up that to 1.2 Watts of panel.

Now the down side is you have to park in the sun instead of parking the trailer in the shade to stay cool.

WWW

[Sunking]

Now the down side is you have to park in the sun instead of parking the trailer in the shade to stay cool.

That would be full sun with clear view of the horizon to the east, west and south. No shade allowed. Good news is you will not need lpg or fire wood for cooking in warmer months. Just take the food out of the cooler, leave it in the camper, and it will cook itself.

[Bluesail20]

Update 1

Many thanks to all of you for your input. I'm now looking at several strategies:

1) Using the tow vehicle to charge the laptop and phone while driving. But the problems with this are:

a) the 12 volt outlet in my tow vehicle is defective. It blows the fuse whenever I connect an inverter to it, even a small (25W) one. I don't know how to trouble-shoot the problem, but I'm going to start by replacing the socket receptacle with this item from Amazon. I've not done something like this before and might have to take the car panel apart. Yikes.
-- Then, if I do manage to get the 12v outlet working, I will get a Laptop DC/DC Converter such as the PST-YD100W from Powerstream.
b) I don't do a whole lotta driving around once I've setup camp. I like to stay put out in the remoteness. My fridge holds up on propane for at least a week, so I don't have to go anywhere. Additionally, I'm frugal and my vehicle is a gas guzzler (2001 Infiniti QX4 4WD, gets @15 mpg), which discourages unnecessary driving.

2) Upgrade my tow vehicle wiring and harness to supply a charging line to the camper battery. As of now it's only wired with a 4-pin harness for the basic lights on the camper trailer. The I have 7-pin receptacle and plug in my possession, plus 12 feet of 12 gauge "auto wire." I watched a youtube vid on this and think I can do it.

3) Buy a second battery for the laptop as a power supply extender. Because I am a software programmer and reading addict, I need my laptop, all the time. I'd like to charge the laptop battery while the computer and I are asleep, finally, in the wee hours of the night/morning. Not sure how I will charge the battery that is swapped out, though.
-- I'm also thinking of upgrading to a SSD in my laptop, since they are supposed to be more power-efficient.

4) I'm looking at purchasing flexible solar panels from eBay, like these. I might get 2 of the 50 watt panels. These are supposed to be more efficient, lightweight, and compact, which are important features for me (since my camper is small, my tow vehicle isn't big, and I'm not as strong as Wonder Woman). Then I would need a controller, and long cabling so I can set the panels up in an optimal spot, away from the camper if necessary. I'm not keen on mounting them in a fixed position on the roof of the camper because it limits the options for optimal charging.

Any further input from you all is more than welcome. Should I go ahead and order the socket receptacle, or is there some trouble shooting I can do first? I do own and know a little bit about how to use a digital multi-meter.

Happy Trails!