portable solar inverter

System

i'm trying to decide if making a portable solar power inverter is fesable. i am not very knoledgable in this area. i would greatly appriecate any help on this subject. thanks

BB.

Re: portable solar inverter

That is a pretty generic request...

What specifically are you looking for... I just purchased a 150 watt AC inverter + USB charger for $23 or so... And it is much smaller than a paper back book.

And there are generators that use an internal inverter for fuel efficient operation over a wider range of electrical loads--and a very solid frequency output.

Then there are the bigger inverters... 12-48 VDC input standard, some include battery chargers and internal transfer switches. You can make a "whole house" UPS out of them by just adding a large battery bank.

In gernal, the inverters are pretty small and reliable these days... And the True Sine Wave ones are really nice to use with electronic equipment, motors, and energy efficient devices.

It is the "power source" (batteries, solar panels, generator motors, fuel storage) that add size and costs to the installation.

Are you looking to build a trailer sized portable power system?

Even with the trailer--the solar panels are glass, the batteries are lead weight, and the only way that solar PV panel powered systems usually make sense as a primary power source is if you are using them ~9 months of the year or more.

For short term use (summer weekends, 1-2 season cabin, emergency power trailer, etc.), you have to look hard at the application to justify the size/cost/maintenence overhead (batteries have a life--even in storage) to make sure it meets your needs...

-Bill

System2

Re: portable solar inverter

i'm trying to develope an idea. i go off roading with some friends along with primitive camping. i was looking for a way to make a unit that would incorpate an inverter to run an electric impact wrench as well as an halogen work light arount 300 to 500 wats.

i would try to convert a tool box that would house the battery and inverter ( fan cooled of course ) and a solar pannel around 15 watt for recharging purpose. i just wasn't sure if it would be practial or not. this would make the unit portable enough to move from one location to another. via carring handle.

( cost of inverter, deep cycle battery, and solar panel.) i have only come across a few mfgers. who make theses items.

whats you opinion ?

BB.

Re: portable solar inverter

In general--The two weak spots would be the battery and the solar panel.

For example, just picking round numbers. Say you want to run the halogen light for 1 hour. And a 1kW impact wrench for 15 minutes. And, there is nice weather and 5 hours of sun per day.

Use a big old 1,500 watt inverter 12 volt inverter--assume 85% efficient. And a flooded cell deep cycle battery at 80% efficient. And a 15 watt solar panel.

Total Energy:

P=V*I
Work=P*Time (in hours)

Work=500 Watt Light * 1 hours + 1,000 watt tool * 15 min/60minperhr=500WH + 250WH = 750 Watt*Hours of load.

Run this through an 85% inverter:

750 watt*hours * 1/0.85 = 882 Watt*Hours of "battery work"

Drain battery to 50% maximum (50% state of charge) for longer life:

Work-batt=882WH / 0.50 = 1,764 WH...

Now, in reality, the storage battery should probably probably have a C/5 (5 hour) discharge cycle--more than that--the battery will overheat.

So, 5*882 WH = 4,410 WH...

Batteries are typically rated in AH which is just WH/battery voltage:

1,764 WH/12 volts = 147 AH (2-5 hour rate)
4,410 WH/12 volts = 368 AH (5 hour rate)

So--your battery should be somewhere between 147-268 AH--A pair of "golf cart" batteries would be 2x 6 volt 225 AH or 132 lbs of lead...

Regarding the solar panel... 15 watt panel and 882 Watt*Hours of load would take this long to recharge after 1 hour of "use":

882 Watt*Hours / 15 Watt * 0.77 (panel+charge controller losses) = 76 hours of sun (5 hours per day = 15 days to recharge)

In reality, the 15 watt panel is only about the right size to "trickle charge" the two golf cart batteries. You would need somewhere around 150 watts or more of solar panels--at a minimum.

Your better bet--get a Honda eu1000i generator (900 watt) or eu2000i (1,600 watt) generator. Probably something like $700-$900 each. And they weight 30-50 lbs. Add a gallon of gas and you have somewhere around 10+ hours of power for your needs on 1 gallon of gas of pretty quiet power.

If you are still looking at a battery+inverter--look at power conservation... Use a 23 watt or 65 watt CFL out door fixture instead of a 300-500 watt halogen. The power tool (large amounts of power for short time periods) will probably less of a "power hog" vs the 300-500 watts of halogen (less power, but on 100% of the cycle).

There are other recommendations that can be made (AGM / Sealed Batteries and such)--but the basics issues are still there unless you change to something like a lithium ion battery to reduce your weight (I am sure not practical for cost reasons alone).

-Bill

PS: A 175 watt solar panel is 31"x68" and weighs 34 lbs and is made of pretty thin 1/8th inch thick tempered glass--not really a rugged item. And it costs ~$800 each by themselves.

System2

Re: portable solar inverter

thank you for your information. i guess this is why theres not any companys making them. i wasn't sure if it would work.

i knew if i was to post it here someone with alot more knowledge would help me out. again thank you for you help.

i'm not sure that lugging around a generator in the back of my jeep would be practical, as well as dangerious.

BB.

Re: portable solar inverter

The eu1000i is a really small device (under 30 lbs dry). And they have sealing gas caps and auto-off fuel valve (or fuel pump). And the small one only holds 0.6 gallons of fuel. Bring a siphon for more fuel from the vehicle tank.

Personally, I have a healthy fear of a large battery / battery bank. There is no way to "shut down" a battery if the wires/terminals get shorted--and the heavy currents tend to weld switches and shorts together (unless there is a working switch or fuse somewhere you can get at). Not to mention the sulfuric acid.

If you assume you have a running vehicle engine--there are various options out there for belted alternators (in the "olden days" there were kits that could switch your alternator from 12 vdc to 120 vdc) or PTO driven devices--and just attaching an inverter to the battery (with alternator to keep the charge up)...

-Bill

n3qik

Re: portable solar inverter

Look into a battery powered impact gun. This will allow you work on other stuff that breaks with out the cord getting in the way. Also a battery powered gun can be used if you get stuck water crossing or mud pit. A 115 AC gun is just going to electrocute you. This should fit into your trail box also.

Cariboocoot

Re: portable solar inverter

I've been all over this issue for different reasons; attempting to maximize the return from a very expensive investment in solar that basically only gets used 6 months of the year. I was going to mount the whole deal on my trailer (which I drag back and forth anyway). Somewhere on this board was a thread with a title like "An idea that came too late" in which we delved into the practicality of it. It wasn't very practical.

My son-in-law and his buddies go recreational 4x4ing, and dragging along a small generator is always done. It is the most practical way to have lots of AC power in the bush. Some of them have tied inverters to their truck's DC system, but you have to run the truck to keep the battery up during use. If the truck is not running, you're stuck if alone (never go out there alone).

I second the idea of the battery impact wrench. I've got an 18v Ryobi one, and it is every bit as useful as the 120 VAC versions but much, much smaller and lighter. Almost as good as an air wrench (some of the trucks have "on-board" air for this purpose).

When you examine the power usage requirements you see that solar doesn't work well for short-term, high wattage uses.

BB.

Re: portable solar inverter

Here is the thread that Cariboocoot started:

An idea that came too late

-Bill

mike95490

Re: portable solar inverter

Here's my "Lugable" (barely portable) solution:
http://forum.solar-electric.com/showthread.php?p=26606&highlight=monolith#post26606

Now linked to my facebook page, which is open access to this album:
http://www.facebook.com/album.php?aid=2074858&id=1196643274&l=7e66e96c3c