Energy Options > Solar Power

Ease my way in to Solar

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It is not a bad way to start at all. It is an excellent way to have emergency back up power and build a system that may later be solar powered.  Being able to sleep at night without the generator noise is a real plus, your neighbors will also thank you.  The battery charger will keep your battery bank topped off and ready to go.

You can generally add batteries to your system for up to maybe a year (just a rule of thumb), you just don't want to add a new battery to a very old set. 

I use golf car batteries, series parallel combinations to get the capacity I want. My cabins golf car battery bank, replaced last year was over 7 years old, not bad for inexpensive batteries.

One thing to consider about a battery charger is how long it will take to recharge the battery bank.  This comes down to generator run time if there is a power failure.  I am afraid the solution is expensive, as quality, high current chargers are not cheap.  This is something you can upgrade later, you just need to know the trade off.  You will want an automatic battery charger of some type, something you can connect and forget.  The charger should have several charging levels, from trickle charging to full current, determined by the battery banks state of charge. 

Consider the following example to illustrate the problem.  Say you use 100 amp hours from your battery bank.  With a cheap 10 amp charger the recharge time would require 10 hours of generator run time, ouch.  If you had a 20 amp charger the generator run time is cut in half.  If you can afford it maybe even a 40 amp charger should be on your wish list.  Note, batteries are complex, and are not perfect, so they take more time and current than simple calculations would indicate.

Having a hand held volt meter is a wise purchase to monitor the batteries state of charge. It is a good way to start as you will need the meter anyway.  When you can afford to add bells and whistles, I would add a battery meter, like a gas gage, a "Bogart Engineering, trimetric meter" will set you back about 160 bucks. You can Google to locate their web page and download a manual to see how they work and see if you are interested.  Xantrex makes a battery meter but is about twice as expensive.  These meters will give you a moment by moment indication of how much capacity remains in your battery bank, plus a lot more.

Last, remember battery rule number one," batteries don't die they are murdered", ha.  You should try not to use more than half the rated capacity of your battery, 50 percent of the capacity.  If you have golf car batteries, typically 6 volts at 220 amps. You should not count on using more than say 100 amp hours of the capacity in normal use.  Using more than 50 percent of the batteries capacity will reduce the batteries life. The point is to double the capacity you calculate you need.

Good luck with your back up power system.

You guys wouldn't happen to have links to some good sites for getting started, would you?  I'd really be interested in information about how to figure out your required capacity.

Part of my interest is that one of the houses we want is wired without grounds run everywhere.  Since I have to re-wire some of the house anyway, why not run some DC power as well?  What gauge wire would need to be run?  Would a DC breaker panel be required?  I'm thinking that if I ran the DC also, I could start converting over to DC lights and appliances while I'm reducing my electrical usage.  Then when I'm able, I could convert over to an alternative energy source.

Home Power magazine is a good source, their earlier issues are better as they focus on smaller systems.  These days they tend to do million dollar system articles, its turning into a coffee table magazine.  You can download a free copy of an older issue at their web site.  I would check with your local library to see if they have some old issues. the topic of system sizing is covered in many of the issues. 

As for rewiring an older house...

My suggestion would be to do three things, first, to add the ground wiring to bring the house up to code as required.

Second, while rewiring, group the "critical circuits" and place them in a separate small circuit breaker box.  These are the items like refrigerator, water pump, furnace blower etc.  With all the "must have circuits" in this box, it will be easy at a later date to wire this to a manual transfer switch giving you the option to power them from a generator, or maybe solar in the future.

Third I would add a few DC circuits.  if nothing else being able to plug your ham radio, CB, or 12 volt coffee pot into a circuit on your kitchen counter maybe very convenient at some point.   I will put more on a second post with a few more details that may help, don't want to make these post so long they are unreadable.

Advice on house DC wiring.....

Typically you would want to use 10 Gage wire to the 12 volt circuits, as the current is much higher to get the same power to the load.  I would try to keep the length of the wiring reasonable short to keep the voltage drop as low as practical, under 40 ft (one way) if possible.   You can Google "voltage drop calculator" and use one of the online calculators to determine if you are doing OK, try to keep the drop in the range of 3-5 percent.  if you have a long distance to wire then go to 8 gage or whatever your budget will allow.

Next, as the type of plug and socket to use.  Avoid automotive cigarette lighter plugs and auto fuses etc.  Cigarette lighter sockets are good to a maximum of about 8 amps before they become problematic.  You want your wiring to be "idiot proof" so you want to use plugs and receptacles that can not accidentally be connected to regular grid power.  I recommend using (NEMA type 6-15R or 6-20 R).  These are single receptacle 240 volt outlets rated for 15 or 20 amps. You can Google an image to see that they are different.  Verify you can find them at a local home improvement store.  You can swap out this type connector on any 12 volt appliance you may buy to make them match. The advantage to this series, is that no modern house has a 240 volt appliance that will operate on a current this low, thus they are idiot proof a selling point to your local inspector if you have one.  make sure to observe polarity while wiring, read that as wire them all the same, and double check with a volt meter to verify you got it right before plugging in. 

Now, on to circuit breakers, use Square-D, type QO series, as they are not only rated for regular AC circuits, but are also DC rated up to 48 volt circuits.  if your wiring has to be code compliant this will get you there. 

General suggestions.
Wire your DC circuits to a separate low voltage circuit breaker box, no 120 or 240 volt wiring in that box.  Since you are using Square D then you might look at their 6 circuit breaker box, they have both indoor and outdoor (type 3-R) boxes available, the box is about 20 bucks.

 and third to group the electrical circuits such that all of your critical loads, refrigerator, pump, maybe lighting in one room are pulled to a smaller box.  The critical loads would be those you least want to be without.

Hmm, If there is interest I can post a description for a do it your self manual transfer switch that is 100 percent code compliant, even better it allows you to choose between more than two power sources as is the case with a regular transfer switch.  This is a DIY project, you have to be able to use a screw driver to make it work, ha.

Hope this helps.


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