Jeff

Rodger Newgreen

Roger,

Although it’s always best to match all solar modules in any array for the best performance, it’s possible to mismatch wattages in smaller systems under certain conditions.

The key is not the “wattage” of each module, its the “voltage”.  You want all modules to have the same nameplate voltage ratings under open, short, and peak power.  If the voltages match and they are all wired in parallel, the current for each will be based on each module wattage.

If wired in series, you may have problems if the smaller wattage module cannot handle the amp current passing through from the larger modules.   There is also the possibility that the lower wattage module in the circuit will “draw down” the other modules so and reduce their output, much like what happens when you install one old battery in series with two new batteries.

Good Luck,

Jeff Yago

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Posted in Solar panels | Comments Off on Mismatched solar panels

Jeff,

Sam Allen

Sam,

Your question is actually more complex than you probably thought since there are several different charging issues involved. If you read the fine print on any new deep-discharge battery, it will give its warranted life in a fixed number of total discharges. In other words, a battery with a 6 year warranty may only last 2 years if deeply discharged more times in the shorter period than warranted. This means a battery that is discharged 25% every day then recharged will normally last much longer than the same battery that gets discharged 75% one day each week. However, on the other side of this debate, a deeply discharged battery can take a huge charging rate which charges much faster if using a generator or solar array without out-gassing which will increase the need to add more distilled water more often.

The other re-charging issue relates to a large battery capacity matched to a small solar array. Typically what happens is the first day the battery starts out at 100% full, then is discharged 20%. The next day the solar brings it back to 90%. Again, the next day the battery is discharged another 20% so it now is at 70%, and the days solar adds another 10% leaving it to start the next day at 80%. This cycle continues until the battery keeps cycling in the 30 to 50% charged state and never gets fully recharged. This type situation will damage the battery because when the lead plates are never brought back to 100%, the surface area will soon develop a layer of calcium or other minerals which become insulators between the acid and the lead which reduces the plate area exposed to the acid and this means battery capacity is reduced. In many cases, this damage cannot be reversed.

The real answer to your question is based on how the battery is being re-charged. If you have a quality 3-stage battery charger that will “back-off” the charge rate as the battery reaches full charge to avoid gassing, then you should get the best battery life by shallower daily discharge and re-charge cycling regardless of battery capacity.

Hope this helps,

Jeff Yago

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Posted in Batteries, Charging, Deep cycle | Comments Off on When to recharge a deep cycle battery

Jeff,

Do you have any experience with propane refrigerators? If so, what model small refrigerator do you recommend for a small cabin that will be used year-round?

Thanks so much,

Tex

Tex,

We have included propane refrigerators and freezers on many solar off-grid homes, but since most are based on heating a gas to cause the cooling cycle, I would not use them in an application where the home is not occupied for many parts of the year like a typical weekend cabin. After the first few years there are some maintenance issues that you need to take care of to keep them operating properly, and they do use a lot of propane.

We have switched to the 12/24 VDC small 50 liter refrigerator or the larger 8 cu.ft. top load freezer by SunDanzer that operate from solar charged battery. They require very little solar power to operate due to their very heavy wall insulation, and do not use a flame like the propane units. I think if properly installed they are a much safer and offer a longer life solution, although they are more expensive.

Good luck,

Jeff Yago

Jeff,

Tex

Tex,

SunFrost and SunDanzer both make really great super-efficient DC refrigerators and freezers.  All SunFrost models are stand-up designs, and all SunDanzer models are top load.   You may like the stand up version better, but they are pricey.

I have worked with both for almost 15 years and each has their advantages.  Up until this year, the SunDanzer units were in the 8 cu.ft. range which is fairly large.   This spring they came out with a 50 liter unit which I found to be perfect for a week-end cabin type application due to the small size and very small battery usage.  However, it’s a top load and must be ordered either as a freezer or a refrigerator, but not both.

When we say “VDC” we mean “volts DC”.

Click Here for ome other useful solar terms
Hope that helps.

Jeff

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Posted in Cabin, Propane, Refrigerator | Comments Off on Propane refrigerator for cabin

Jeff,

I came across an add for the Power Save 1200. Electricity flow “cleaner” with a 1K solar panel to connect without batteries. We are on the grid and looking to waste less and minimize our “footprint”. http://www.power-save1200.com/1200.html. They have an assortment of interesting products.

Donna

Donna,

Even if we installed wind and solar equipment for free, no labor charges at all, just the hardware costs for either system would easily exceed many thousands of dollars, so anyone that claims they can do this for $299, tells me there may be more to the story. For example, the web site you referred me to is very interesting as it discusses in detail their solar grid-tie system, but no costs or sizes are given, and a grid-tie wind system, but no costs or sizes are given, then the ad goes into describing this power saving product with a $299 price, as if it included all the solar and wind features that were also listed as if this was all the same product.

Based on the very limited information provided as to how this “black box” can save up to 25% of your home’s utility usage, a figure I highly doubt, it appears to me this is just another capacitor bank with an added whole house surge suppressor. Yes, there are times when large motor or transformer loads on an electrical system can cause the voltage and current to be out of phase more than 90 degrees as required for maximum power conversion. However, I do not know any utility companies that measure this power factor penalty except for large commercial clients since this requires installing a separate power factor meter. It is highly doubtful that even if you had an extreme case of all kinds of motor and transformer loads in your home, odds are this is not being metered or is not enough to cause the type of added savings being claimed by this device. The only time we install equipment like this is for a large retail store with thousands of fluorescent lights, or a large industrial facility with all kinds of large motor loads.

As far as the mentioned benefit for having a surge suppressor, yes this can save your appliances from damage if there is a major voltage surge on the utility line like lightning nearby, but you can buy a whole house surge suppressor at Lowes for about $40.00.

I suggest that you first contact your local utility to see if they even measure power factor on their residential meters, and if they do, ask them what this added utility cost is. If it is not metered by the utility, the only benefit I can see to adding a capacitor bank would be if your power factor was so bad that it was increasing the actual VA metered usage, and for that you would need a whole house-full of motor and ballast loads to realize these kinds of savings.

I say read the small print on anything like this since the basic information being offered before the sale is too limited to actually know what you are buying, how it works, and how they are measuring their very high utility savings. Odds are this sample case is nothing like your home.

Buyer beware,

Jeff Yago

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Posted in Capacitors, Electricity, Save energy | Comments Off on Power Save 1200 or similar products

Dear Jeff;

I have a 14 year old double wide trailer. The insulation in the ceiling was to suppose to be 12″ blown in. While having a metal roof installed I was able to place my hand inside the roof vents. There was only about 1″ laying in there.

I would like to have this re-done. I have been told that there is a type of blown insulation with a glue content added. This is supposed to keep it from settling.

What are your suggestions or comments about this type of insulation?

Sincerely,

Bill Constantine
Bill,

Sounds like you have several issues to deal with. First, most of the trailers and RV’s I have had experience had at most about 3″ of insulation in the attics and walls, so if you were told yours would have 12″ I would say that was an option and you should have documentation that you paid extra for this. If that is true, I would be calling the dealer and demanding to have them pay to re-insulate since you clearly did not get what was advertised or told you would get.

My second concern is space. When we build a conventional house there is either an attic space or large roof trusses that create a space above the ceiling for wiring, ductwork, and insulation. There is always some kind of attic trap door to allow access to this area which usually has several feet of space for repairs, which makes it easy to blow in more insulation if needed. However, all of the trailer-type construction I have seen had only a few inches of access space above the ceiling which would make it impossible to access for adding more insulation. Although double-wide construction should follow more traditional home construction methods, I would not be surprised if there is limited space above the ceiling to access. This may make it very difficult to add more insulation unless added holes are installed to reach areas not near access doors or vents.

Most of the blown-in insulation for attics is “fluffed” by the blower before it goes down the pipe and into the attic so I have not heard that there is a need to add a “glue” to this. They do add water to blown in cellulose insulation for walls which makes it “stick” between the studs and dry before the drywall is added, but I have not heard of anyone doing this for attic insulation. What I would be more concerned about is getting good and uniform insulation coverage over the entire ceiling area, and for that I think you will need a professional installer. I would ask how they will guarantee to reach all areas in this confined space and you can say you are going to rent a thermal scanner the next winter to scan the ceiling for cold areas that may not be properly insulated, which should convince the installer to take extra care. As the say, out of sight, out of mind.

Good luck,

Jeff Yago

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Posted in Insulation | Comments Off on Blown Insulation

Jeff,

Any update since the issue #98 article on picking the right emergency radio?

I’m leaning toward a crank job, but when I read reviews on Amazon, etc., they’re all over the field. Add to that that every schlock outfit that can cobble together a radio sells them with all kinds of useless do-dads. One criticism of the Sangean was that it runs for progressively shorter durations after cranking each time it runs down.

Thanks,

Rob Wagner

Rob,

All of the hand crank radios I have tested have not been very good with many broken cranks and other failures.   I have, however, tested many small radios that require very little battery power and it’s just as easy to keep a pack of spare batteries nearby.

I am not a big fan of rechargeable batteries as then tend to play out when you really need them and the older they are the shorter they hold a charge.

The Sony radio I have shown in several articles has AM, FM, Weather, and TV-sound bands and will fit inside your fist.  Since it can use an earphone, it requires very little battery power to operate for very long periods.  A spare pack of batteries should give you weeks of operation during an extended power outage.

When I buy LED flashlights and other battery powered equipment, I try to standardize on only 2 battery sizes, then its easy to keep refreshing my spares as the older ones get used for everyday use.

I’ll take a Sony earphone radio and a pack of 16  AAA copper-top batteries any day instead of one of these hand-crank specials with no batteries.

Hope this helps,

Jeff Yago

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Posted in Electronics, Hand-crank, Radio | Comments Off on Emergency Radio

Jeff,

I have a deep cycle battery which we use with an inverter at craft shows to power the credit card machine and sometimes lights or fans. After using it all day and before going to the next show, I would like to be able to check the battery level.

How can I check the battery level?

I plan to get a second battery as a backup since we do multiple day shows and can’t afford to lose function of the credit card machine, but it would be good to know how much drain has occurred after a day’s use.

Thanks for your help.

Sam Allen

Sam,

Knowing how much amp-hour charge is remaining in any deep cycle battery has been a problem still waiting for a solution, as there is no perfect meter that can tell you this. The only way to know the exact charge level of a lead-acid battery is to insert a calibrated hydrometer with temperature correction into each cell. Obviously that’s not going to happen, so you could take a voltage reading with a digital volt meter.

The problem is the volt meter will not give a true voltage reading while the battery is under load, as it will read too low, but it will also read too high when there is no load and the battery is at rest or was just charged. Many companies make a battery amp-hour meter that keeps track of how may amp-hours you put into the battery when charging, then will subtract from this total during discharge, but this also has to keep correcting itself due to temperature changes and how the “rate” of discharge can affect this reading and these meters cost several hundred dollars.

You did not say what inverter you are using, but many will include a battery volt meter which will give you a rough idea of battery charge.

Here is my suggestion. Buy a volt-meter from Radio Shack for about $15 that provides a digital display. Set for the lowest DC voltage range it has that can easily read in the 8 to15 volt range, but not more than 50 volts.

Add a “small” load to the battery. Nothing large and do not connect the inverter. Maybe a small 12 DC light or small DC fan you indicated you had, just enough to pull off the surface charge but not enough to start drawing down the voltage.

Note the voltage reading and compare with the following:

20 to 30% charged – – – – 11.60 volts

30 to 50% charged – – – – 11.90 volts

50 to 60% charged – – – – 12.20 volts

60 to 70% charged – – – 12.45 volts

80 to 90% charged – – – – 12.50 volts

Over 90% charged – – – 12.66 volts

The above chart is just a starting point for you. Once you take a few voltage readings and then see how long your equipment will run, you will be able to customize this chart for your specific battery. Please also note this chart is based on your battery being at 77 degrees F. If the actual battery temperature is higher or lower, this voltages will shift some, but not major until it is over 90 degrees or below 50 degrees.

Good Luck,

Jeff Yago

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Posted in Batteries, Charging, Deep cycle | Comments Off on Checking a deep cycle battery

Jeff

I am looking at replacing a traditional fireplace with a wood stove insert that can be used in a hydronic floor system.

I looked over your article on the fireplace you installed in your home and have spoke to and web searched for wood stoves that circulate water for heated floors and find only the “long burners” for outside or commercial “furnaces”, nothing that would be appropriate for a great room/ranch application.  Can you point me toward manufacturers that have this type of product?

Thank you.

Mark J. Bechtel

Mark,

Jeff Yago

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Posted in Heating / Cooling, Radiant heat, Safety, Wood, Wood stove, Wood-fired heater | 2 Comments »