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Author Topic: DIY DC Homekit help please?  (Read 3198 times)

Offline Airthumbs

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DIY DC Homekit help please?
« on: 19/10/2011 13:50:14 »
I would like to have a small set up for a DC lab.  I will have a solar panel, or two, a small wind generator, LED 10mm white lights and several old phone chargers, less then output 4v.

I have a small voltmeter but I have a feeling I am going to need more stuff.  What do I need to get as a minimum in the way of equipment to allow me set up a self contained DC system?  Old nuclear submarine batteries are hard to get so what is the best can of battery to store the electric charge?

I also will be making several LED light packs to send to Africa, about a hundred or so to start with.  I want to use a re-charageable battery connected to small solar panel providing electricty for one or two LED's.  Anyone have any ideas to the best and the simplest way of doing this? 


 

Offline CZARCAR

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DIY DC Homekit help please?
« Reply #1 on: 19/10/2011 15:15:12 »
deep cycle lead/acid battery is best for slow discharge,AKA marine battery
 

Offline CliffordK

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« Reply #2 on: 19/10/2011 17:45:52 »
As far as batteries, there are a few different sources.

In Kansas City, I found a battery recycler that would sell previously used batteries for the value of scrap lead. 

Forklift batteries are excellent Deep Cycle batteries.  Some people have found a few with a little life left, but most of the ones I've seen have been pretty well abused before they hit the used/scrap market.

You may also find some used UPS/Telco batteries.  Some may be the size of car batteries.  Some may be bigger.  They often come in 2.1V individual cells which makes dynamic configuration easier,  and you can move bad cells out of your array.

Unfortunately, you will find it cost prohibitive to ship used Lead Acid batteries anywhere.

If you are making a small system, I would prefer going with DC, and not requiring an inverter.  You should be able to buy 12V DC Compact Florescent or LED bulbs.  I find using the Edison Base is easiest.  It may be confusing since it is shared with your 110V/220V lamps, but it is the widest supported.

Depending on the size of your system, you will probably want a charge controller, or a MPPT charge controller.  This is especially true if the voltage of your panels are significantly different from the voltage of your battery bank.

Solar Panels --> Charge Controller --> Battery Bank --> LED Lights.

In some situations, you may be able to get away with a simple Diode to prevent battery drain at night, rather than a full charge controller.

Solar Panels --> Diode --> Battery Bank --> LED Lights.

Fuses might not be a bad idea too.

I'd encourage adding an inverter for electrical power needs to increase the flexibility of your system.  A simple 700 Watt (or so) inverter is pretty cheap, and can run a PC and some other devices.  You can also buy larger inverters if you need to run power tools.  Perhaps 10,000 Watt inverters imported from China for a few hundred bucks.  Modified Sine seems to be sufficient, and you generally don't need "true sine".

If you are going with a DC system, one thing you will have to do is to deal with "Wall Warts".  You may be able to wire some 12V DC small appliances directly to your battery system.  However, keep in mind that 12V is just an "estimate" with the system providing as little as 10V or 11V during discharge cycles, and as much as 15V or so during charge cycles.  Most appliances can deal with small voltage shifts, but perhaps not as high as the battery packs encounter.

There are a number of 12V DC adapters available for cell phones and computers.

An excellent forum resource for Do-it-yourself home power is:

www.fieldlines.com

Although they do tend to be somewhat biased towards making one's one wind generation system.

A few issues that occur with wind generation that don't occur with solar is a much higher variability of voltage output.  A solar system can be disconnected from your battery bank if the batteries are fully charged.  A windmill should always have a "load", unless it can be turned out of the wind.  So, many people also incorporate a "Dump Load", usually from a converted space heater.
 

Offline Airthumbs

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DIY DC Homekit help please?
« Reply #3 on: 19/10/2011 19:13:54 »
Thank you for the information CliffordK, very useful and much appreciated.
 

Offline SeanB

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« Reply #4 on: 19/10/2011 20:20:04 »
As an aside, I bought some real cheap LED garden lights from Makro. At under $2 each, you get a solar panel, a 600mAH AAA NiMH cell and an inverter to drive a single white LED. You could buy a batch of these, and either just send as is ( place outside to charge and collect in the evening to get a few hours light) or place into a different casing with a switch to enable you to switch it off.
 

Offline CliffordK

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« Reply #5 on: 20/10/2011 08:28:15 »
Good Point. 

If you are just wanting lights, you could go with something simple.  Solar LED Spotlights often have a small panel separate from the base, so theoretically you could install the panel on the roof, and the spotlight inside a building.

I've used single 3W or 5W CFL bulbs as lighting.  They are good enough to easily navigate around in a house, but I seem to have problems reading fine print under low-light conditions.
 

Offline CZARCAR

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« Reply #6 on: 20/10/2011 18:31:55 »
would a handcrank generator do the trick?
 

Offline CliffordK

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« Reply #7 on: 20/10/2011 19:15:16 »
would a handcrank generator do the trick?


No, not really.
I've had hand-crank radios and flashlights.  They are a big pain.  Especially since the &^%&U^%O(!!!! Chinese junk never works quite right.  Ever tried to hold a flashlight while cranking the crank, and holding tools, and trying to do work, all at the same time?

A pedal powered gen might do a bit better.  However, solar is pretty extraordinary.  You get (a portion of) the solar panel rating, all day long, every day without having to do anything.

I have planned to couple my washing machine to a bicycle though.   :D
Solar Hot Water is great for a sunny environment.  Use the resources that are available.

I suppose a lot also depends on your budget  If your budget is $100 per installation, that will guide you in one direction.  If your budget is $5000 per installation, it will guide you in another direction.
 

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DIY DC Homekit help please?
« Reply #7 on: 20/10/2011 19:15:16 »

 

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