Thursday, February 14, 2008

Power Problem - Inexpensive Solution

As you might recall from the article “Power Problem” I have been looking for an inexpensive, mobile power solution to run the lights and some small electronics at my retreat cabin on weekends.

The plan was to fully upgrade and replace the existing power system in March of this year. Unfortunately the cabin was broken into and thieves made off with most of the existing power system. Since the break in have decided not to keep anything of value at the cabin and to put off the upgrade until I am living at the site in June. This leaves the problem of no power until then so a small mobile power system is needed to fill the gap.

An additional requirement was that I not purchase anything now that I could not use later. I have decided to scrap this one and use the mobile power system in the camper after upgrading the cabin.

I thank everyone for their input on this and here is what I have come up with. This should work for anyone.

Here is what you are going to need. Everything is available at Wal-Mart.

2 Deep Cycle Marine Batteries (Group 27) $60 apiece
1 Black and Decker 400 Watt Inverter $30
1 Cheap Battery Charger $30
2 Battery Cables $10
2 100 Foot Extension Cords $20 apiece

Take the two 115 amp hour batteries and connect them in parallel with the battery cables. (Positive to Positive/Negative to Negative) This creates one 12 volt 230 amp hour battery. You should never discharge a battery below 80 percent so we actually have around 46 amps in our power pool. Connect the 400 watt inverter using the supplied clamps and the systems is ready to go. I like this small invert because the cooling fan only comes on when the system is hot thus conserving power.

Run the extension cord to the house and plug into a power strip mounted near the ceiling in the center of the room. Hang your clamp on work lamps with compact fluorescent (CF) bulbs around the house with the cords plugging into the power strip.

This basic system will comfortably power five 23 watt CF bulbs. So here is the high end of the power draw:

115 watt total for five 23 watt CF bulbs
10 watt overhead for the inverter
125 total watts divided by 120 volts
1 amp roughly per hour of use

Actually it is slightly more than 1 amp but that’s ok. So if we were to run all 5 bulbs for 12 hours through the night it would only be 12 amps pulled from our 46 amp pool of available power. In reality you will only run one or two lights for no more than six hours nightly so our two batteries should easily deliver four night worth of light without charging. There should be plenty in reserve for the laptop.

When you get home just plug in your charger overnight and top off the batteries. To be really elegant mount a couple of cheap solar panels on the top of your camper and keep the batteries fully charged all the time.

I will be using the system this weekend and will let you know how it goes on Monday.


Anonymous said...


That will work and it is cheap .
Will you be able to use those batteries in your main system later on ?

BigBear said...


Will not be able to use them in the bigger system. They are not true deep cycle batteries but I can use them in the camper or on the ridge in the small cabin.

theotherryan said...

Getting stuff that will work later is wise. I approve.

Blue Skye said...

Using a marine deep cycle battery might be better economics. They cost more like $100 but are designed for 50% depth of discharge, meaning you'd get more amp-hours for your buck.

Remember to turn the inverter off when you're not drawing power.

Will be interested in the results of your experiment. Good luck!

Dragon said...

good post.

off topic question: have you had any permit issues with power or the composting toilet or building issues...I seem to be running in to all sorts of problems where I'm shopping for land...

the texan said...

You could also wire your batteries into your pickup electrical system so they charge while you are driving to and from your cabin. I like your blog.

The Hermit said...

The Texan was thinking exactly what I was... charge the batteries on the way down to your cabin during your commute!

Congrats on finding a solution!