Top Navigation  
U.S. Flag waving
Office Hours Momday - Friday  8 am - 5 pm Pacific 1-800-835-2418
Facebook   YouTube   Twitter
 Home Page
 Current Issue
 Article Index
 Author Index
 Previous Issues

 Kindle Subscriptions
 Kindle Publications
 Back Issues
 Discount Books
 All Specials
 Classified Ad

 Web Site Ads
 Magazine Ads

 BHM Forum
 Contact Us/
 Change of Address

Forum / Chat
 Forum/Chat Info
 Lost Password
 Write For BHM

Link to BHM

Get Powered Up! Certified Energy Manager Jeff Yago answers your alternative energy questions

Wondering about a great new energy-saving device
you found on the Internet? Then CLICK HERE!

Sorry. Jeff no longer answers questions online.
This will remain as a searchable
resource for all BHM website visitors.

Archive for the ‘Backup’ Category


Batteries usage

Thursday, February 12th, 2009

Dear Sir,

I have 4 or 5 12V batteries similar to the Vision CP1270 Battery (that style).  I want to put 2 of them in my truck to run any emergency items or simply to charge various items.  I am going to have them charge from the regular system, but I need assistance on how I should run the wires.  I am going to connect one DC to AC converter to them as well, to connect a laptop or other item.  Can you provide information to or explain how I will want to wire them?

I am also investigating what it would take to use the other 3 to have as “backup” power to a small amount of items in my home and I am curious if you can give some advise as to how best utilize them for that if it is possible.

Thank you!

Jon Webb


The information you have provided is not detailed enough for me to provide a specific answer, and our web site is not intended to provide free detailed system designs.  However, I have published many articles in Backwoods Home Magazine that cover systems like you are planning and I suggest you check these articles which you can read on line:

Solar power 101: Batteries

Solar Power 101: Batteries

Add solar power to your truck camper

Solar power trailer: Part 1

Solar power trailer: Part 2

Hope this helps,

Jeff Yago


Cross check my design

Saturday, November 15th, 2008

Hi Jeff,

I am impressed on your publications and answers you do give to questions on Energy problem.

It will do me good if you attend to mine own question/solution to my need.

I have the need to have a back up power for my data center active devices, servers and other equipments and in the addition to the provision of a generator I still need a Battery Power back up that will take over on emergency.

By my load evaluation on the equipments running for 12 hours per day and working for two days with out charging, an average total watt-hour per day of 49,964.57wh/d.

I have in mind of using a 48v, 200Ah battery for my battery bank. Taking this into consideration I have an average amp-hour/d of 1,040.93 Ah/d.

The sum of all the power ratings of the equipments is approximately 16KW, and I intend deploying a single 20Kw inverter with thirty 48v,200Ah battery or in other have have six 3kw inverters with six same battery for each inverter and balance-distribute the loads among them.

This is exactly what I have in mind and I want to know your view to it. Also which brand of inverter and battery will you recommend? In each situation, how long will take to charge the bank?


Chekwube Kamah


Based on your description of system capacity, this is a very large and very expensive backup power system. Any casual review of your plans with the limited information you have provided is not possible to address on a “free advice” web site.

Since just the inverter alone will cost as much as $35,000.00, not to mention thousands of dollars for batteries, I am quite sure you can spend a few thousand dollars more for the assistance of a solar system designer which you clearly will need.

If you thought you could do all this for a few hundred dollars and free design services you are going to be in for a real surprise.

Good Luck,

Jeff Yago


Back-up power for off-grid

Saturday, September 6th, 2008

Dear Jeff,

Having recently bought some land in Missouri that is located out the the sticks and very much at the end of the power grid. I have pretty well deduced that I will need some back up power.

Recently I have discovered the website and a number of your articles. As one who is not totally familiar with alternative power like wind and solar, everything I read seems only to confuse me more.

With interest I have read about l-16 industrial batteries for a battery bank in some articles. In an article about adding a solar cell to a truck camper a RV/marine battery is recommended. Since RV/marine batteries are easy to find and will take to repeated charging wouldn’t they be logical choice for a battery bank vice the harder to find L-16?

I have noticed too that with wind power most often suggested is a dc wind generator that requires upwards of 6 or 7 knots of wind to operate. In searching around I have found a source for a AC wind generator that begins operation in the sub 7knot range. AC generators have to best of my knowledge a big advantage over DC generators and that is in size of the cable between the transmission line from the tower to the battery bank. An ac generator can use a standard ac power cord and suffers no loss in current between the tower and batteries.

I have to admit that my understanding of the way a ac generator works is taken from the following website: On the opening page there is a photo of a customer using 9 ac wind generators on his farm in Wisconsin. Although wind power as such is confusing to me I believe that this ac system must be quite good or the farmer who had added to it and bought these generators would not be doing so if they weren’t efficient.

Perhaps you can give some insight into battery banks and DC versus AC generators in a future story. Also the battery bank issue of l-16 versus marine batteries is very confusing to a novice seeking information like myself.

Any information you can provide along these lines would be greatly appreciated.

Thank You

Keith McElroy


Lots of questions! Actually you are talking about “L-16” batteries, not “I-16”. When I suggest using an RV/Marine battery, you will find that it is for a small 12-volt DC system that does not have a large load that would fully discharge it each day. These batteries are much heavier duty than a typical car battery, and most have re-combiner caps and do not need to add water. However, they will NOT hold up to a daily deep charge/discharge cycling like a solar powered home or cabin. For these larger loads and system sizes, the lowest cost battery designed for a heavy charge/discharge cycling each day is a 6-volt golf cart battery ( T-105 size). These are less than $100, and can be found at most big box stores during the summer months. They are about the same size as a car battery, but because they are 6-volt, the plates are very thick and very heavy.

For a 12-volt system you will need two 6-volt batteries wired in series, and for larger systems you will need 4, 8, or 12. When you start getting above 8 batteries of any size, its better to switch to a larger amp-hr battery and stay less than 16, as this can cause problems with un-even charging and dis-charging when you have multiple strings of parallel batteries.

I think you are caught up in the AC or DC debate as a marketing ploy. There is no engineering difference in the amount of wind it takes to turn a wind turbine based on AC or DC output voltage. Wind energy is a “cubic” function of the area of the blades, and below around 7 MPH I think you will find most small-scale generators will not provide any real power, although the blades might turn. There are now both AC and DC wind turbines and each has its advantages, but only in wiring and additional equipment that will be required.

A 24 or 48 volt DC output wind turbine is very easy to add to an existing solar-power system, and some models have built-in charge controllers and can be hooked directly to the batteries. Yes, this will require a larger wire size since the voltage is lower, but the ease of wiring is its real advantage. Also, unless you are talking about some huge wind machine on a 150-foot tower, the difference in wire costs would most likely be less than 50 cents per foot for the larger wire caused by using a lower voltage DC model. An AC wind turbine can use a smaller wire size since the voltage is higher, and these are usually designed for grid-connect systems without batteries. There are a few other issues, but you cannot say an AC unit works better than a DC unit having the same size and blade design, and the reverse is also true.

Good luck!

Jeff Yago


Simulating a grid on a grid-tied system

Wednesday, August 6th, 2008


I have a Fronius 5100 inverter on a grid tied solar system. When the grid goes down, I lose all power to my house even though the solar panels are working.

Is there a way to simulate the grid so that when power goes down I can still utilize my solar energy?


Mike Emmons


I can’t believe this was a surprise to you, and I sincerely hope the installer made it very clear that ALL grid-tie solar inverters are designed to shut down in the event of the loss of grid power.

If they continued to operate after a power outage, they could be energizing a downed power line that the utility crew would not realize power was being supplied from the wrong end of the line which they may not check. Keep in mind that any power you are sending back to the grid at 240 volts AC goes through the transformer on the power pole in reverse and will go out onto the power lines at 480 or higher voltage which is deadly.

All inverters must pass a very strict testing process to make sure their design will not allow this to happen, and proof of meeting this safety requirement must be provided to the local utility before they will allow you to install the inverter on their grid. The equipment label will note – “UL 1741” and “IEEE 929” to indicate this.

Yes, there is a way to make a grid-tie inverter “think” the grid is still operating and not shut down, but this requires a second inverter with battery backup. In addition, since the first inverter is now being fooled and continues to operate, your system must isolate the output from the utility grid, and include enough electrical loads in your home that are operating to consume this excess power being generated or you will have a system error in the inverter that will shut the system down.

I do not want to give out too much information on this subject as you really need to work with an experienced solar installer to make this conversion due to several safety concerns, but it can be done.

Good Luck,

Jeff Yago



Copyright © 1998 - Present by Backwoods Home Magazine. All Rights Reserved.