Alternative energy advice from Ask Jeff Yago. Volume #22

Ask Jeff Yago
Solar & Energy-Related Issues

By Jeffrey Yago, P.E., CEM
Jeff Yago

Sorry. Jeff no longer answers questions online

Alternative battery charging

Hi Jeff,

I don’t know if you will respond, but I have had trouble finding people that can answer some seemingly obvious solutions to recharging batteries that could be used to power a electric vehicle (scooter etc) or whatever.

I am unfortunately required to drive quite a bit. When I think of the energy lost in the driving of a car it amazes me. Here are some questions or ideas: mini electric generating turbines: that could be easily mounted in the front grill etc. that could recharge batteries brake conversion kit- turn your car brakes into hybrid vehicle type brakes that would generated electricity that could recharge batteries

Sun blocking solar shields similar to what people use to keep the interior from heating up (I live in Florida)

So, lets say I buy an electric scooter. Instead of just recharging the batteries using my home plug, wouldn’t it be possible to have some sort of easy system of using my car to charge either a bank of batteries in the trunk, that could then be used to recharge the scooter (easiest solution) or having two sets of scooter batteries and recharging the batteries each time I drive?

I would imagine that this already exists, but when you think of all the energy that is lost involving a car….. kinetic, wind, solar, friction, heat, etc its amazing. I feel that our society is in this black and white way of thinking – using fossil fuels, or using alternative energy. Why not simply harness all the energy that is lost in a vehicle and use it to charge energy storage units such as batteries? In a way hybrids do this, but it is still very inefficient when I hear hybrids getting 40 mpg. There are plenty of gasoline vehicles that get that in Europe, and diesel that get 50 mpg. But if an energy efficient vehicle is completely harnessed, I do not see why 60 plus is not possible. I’m straying from my original question.

I hope you respond


Daniel Buisson


Lots of questions!

Let me address your main points and perhaps this will help on the others. Yes, if you use dynamic breaking you can do some extra battery charging from this waste energy each time you slow or stop a car. All of the battery-electric and hybrid cars on the market today already do this. Yes, if you dark tint your car windows you can reduce the cooling loads, and most cars sold in hot climates already include tinted windows.

However, until somebody can void the laws of physics, anything you do to a car to charge a battery will require more engine power and in turn, more fuel. Adding a “wind turbine” to generate electricity will cause an equal amount of wind drag on the car which will lower the mileage. Adding a battery charger to re-charge scooter batteries in the trunk will not only require more horsepower to turn the car’s alternator to generate this charging energy, but the added battery weight will lower the mileage.

Making a vehicle go 100 miles on a gallon of gas is easy. Just get rid of all the weight, and decrease wind and rolling resistance by making it very small. However, you will always end up with a small flat box having no interior space, no crash safety, no heating or cooling, and with no acceleration.

Since I am asked this type of “free vehicle energy” question many times each year, I have a simple answer that may help you understand the concept of physics involved, and why this never works – Just take your 26″ bicycle and replace the front tire with a 16″ tire, then your bike will always be going downhill and you will never need to pedal!

Hope this helps,

Jeff Yago



I read your “overview” on bio diesel kits and the general process. I think it was important for you to mention the necessity of finding sources of waste vegetable oil before one were to begin his or her own processing station. However, I wonder with the escalating prices of crude oil if the interest in bio diesel will become more prevalent for people interested in defraying the cost of home heating oil, and or diesel for their vehicles. With this being said is there a possibility for myself to secure waste vegetable oil sources only to find a hidden market evolves, and find others who want to make bio diesel like me become competition only to outbid me for the waste vegetable oil at my sources? The basis of this inquiry is to ask if I could skip the middle man and buy virgin vegetable oil in bulk to process for bio diesel?

Eric Brown


I mentioned at the close of this article that as the price of diesel fuel goes higher and higher, more and more people will be trying to take the “free” waste oil from the same fast food outlets and this could be a problem.

In larger cities with lots of restaurants, I think you will soon see the existing waste management trucks hauling this waste oil away to their own central storage tanks where they will start selling this back to people wanting to do what you are doing. In smaller cities and rural areas, until the demand exceeds the supply, I think there will be room for each bio-diesel maker to stake out their own specific restaurant without fighting over it with others.

However, I think you will find that buying any virgin oils to make bio-diesel will cost as much as buying diesel at the pumps. In the end, the small bio-diesel users will still make their own from waste oils that are free, and the larger users will be buying waste oils from a bulk waste management company at much lower costs than buying new un-used oils of any type.

Good luck!

Jeff Yago

Battery for the home?


What type of Battery for the home would I need to plug in a computer, electrical heater, refrigerator, and Television. I live in New York City

Alvin Alexis


Your battery would need to be the size of a Ford SUV. Since I have a daughter living in New York City and am very familiar with living costs there, I am going to assume you live in an apartment about the size of a postage stamp and do not have room for a battery this big. Also, the tenants below your apartment would complain when their ceilings started to sag from the 4 tons of added battery weight.

Seriously, I do not know anybody with a battery backup-power system that are using it to provide electric space heating.

If you delete the heating, a more realistic system could be installed to power the remaining computer, television, and refrigerator, but you did not indicate how long the backup power needed to operate so I have no way of sizing a battery for you. A system that provides backup power for a one-day power outage would have much fewer batteries than a system that needs to operate for a week. You can estimate that a sealed gel 6-volt golf cart battery will store 1 kWh of backup power. You will need at least 2 to make 12 volts DC which is what a small inverter will require, and you need the inverter to convert the battery power into 120 volts AC for your appliances.

This means the smallest system you could install would have a 2 kW capacity. This is 2000 watt-hours, so if your television is 150 watts and your computer and monitor are 200 watts, this backup system could power these appliances for about 6 hours 2000 / (150 + 200) Your refrigerator will require more power than this, but it will cycle on and off several times each hour and is harder to estimate without knowing its size and how new (efficiency).

This should give you a rough idea. Also, I was showing both the computer and television operating at the same time which may not be the case. Just read the watts on the nameplate for any appliance you want to power, and multiply by the number of hours you need each to operate during a power outage. Multiply the watts times the hours for each and this will give you a rough idea of power required. Divide total watt-hours by 1000 and this will give you the number of batteries you will need. Round up to an “even” number of batteries.

Good luck, but if I were in your situation, I would buy a box full of canned or pre-packaged foods that have a long shelf life and do not require a refrigerator. If you delete the refrigerator, buy a laptop, several LED type flashlights, and flat screen TV, and your electrical demand will be so low you could go for days on a very small system.

Good luck!

Jeff Yago

12 volt light


Where can I get a 13-watt 12 volt light for making a flood light at my barn, as described in your article? None of your links provided this type of light. Also, I have looked around and cannot find a DC photocell. Do you know where I can find one of these?

Thank you.

John in Michigan


These are standard products for the solar industry and any RV outlet. There are several advertisers in BackWoods Home magazine that I know can provide this type 12 volt DC hardware, and these are stock items for any RV outlet and they are located in every major city.


Good luck,

Jeff Yago

Batch solar water heater tanks


For several years I have been reading up on building a Batch Solar Water. I have decided to go ahead with this project and have decided to build it to the best of my abilities and budget.

On almost all of the articles I have read the tanks used are 40 gallon, glass-lined, electric water heater tanks. I am having a problem with this part. A pretty important part too. The area that I live in (just South of St. Louis, MO) has hard water. All the tanks that I have been able to get have a heavy mineral deposit in them.

I have been trying to find a source for “new,” 40 gallon, glass-lined, electric water heater tanks minus the outer shell, insulation and heater rods.

My question is, “Do you know of any source for tanks like this? Or can you point me in the direction to where I might find information on this?”

Thanks for your help.

Lonnie Miner


In this day of recycling everything you may not like my advice, but here goes. The exterior sheet metal housing and the insulation are a very small part of the cost to make any hot water tank. The real cost is the actual tank, its steel fabrication, welding the inlets and outlets, adding the glass lining, and testing each one to make sure it holds the pressure safely. Since a new electric hot water tank is not that expensive to begin with, I suggest buying a new tank and removing the exterior shell and insulation.

Perhaps you can unroll this sheet metal and insulation and use to make the back of your home-made batch heater. A 50 gallon tank will have a sheet metal exterior that is almost 30 sq.ft. of painted metal. The new heating element and thermostat can be saved for spare parts in your backup electric hot water tank or given to a friend for theirs. Be sure to look for a tank that is tall and skinny, not short and fat to get the best solar results.

Good luck,

Jeff Yago

Battery question


First I must thank you for all the wonderful information, especially concerning batteries. It has been a big help to my scratch-built solar installation. A year ago, I knew nothing of DC electric or solar power. Now I have a small 12v solar system that I�ve put together to supplement my AC power usage. I continue trying to add on to the system when I can, which is why I am contacting you today. I have recently scoured the internet trying to find the answer to a question regarding batteries, but have had no luck finding the information I need. I�m hoping you can help me.

My question relates to batteries for solar-energy storage. I currently have a 50ah battery I purchased to get me started. I want to add to this capacity with another battery. If possible, I would like to get a larger battery. I understand that when linking the batteries in parallel configuration, you must have batteries of the same voltage. However, I am not sure if you must use batteries of the same capacity (amp-hours) or if I can safely link my 50ah battery to a newer, larger battery, say in the 75-100ah range. Is this acceptable practice, or must I continue adding on with more 50ah batteries, or alternately just make the switch to a new size of larger capacity batteries?

Hoping very much you can help me out here. Best wishes,

Mike D., Bear


Yes, you can wire two different amp-hour sizes of batteries of same voltage in “parallel”, but I do not recommend it as the charger will sense the smaller battery reaching its re-charge level very fast and shut off charging before the larger battery gets re-charged. Also, anytime you connect a newer battery in series or parallel with an older battery, you will have the same problem and the battery bank will “assume” the lower charge level of the weaker battery very quickly.

Considering the battery you have now is very small, why not just replace it with a larger capacity battery and forget about re-using. Although many lead-acid batteries can last for many years, after about 3 years they start to have reduced charge capacity, will start using more water, and will “waste” some of the solar charge you are trying to put into them.

Good Luck,

Jeff Yago

Building an ice box


We want to buy or build an Ice box for our cabin, but I can’t find any information online to do this.

Coolers tend to fill with water and waterlog our food.

Any suggestions on building an icebox?

Dan Lieffring


Yes, you can build your own DC refrigerator. My first suggestion if you are low on cash is to buy a small propane powered RV or boat refrigerator/freezer. These are small and do require manual defrosting, but will use very little propane and no electricity. However, their freezer sections are very small so don’t expect much ice.

There are several companies that offer a 12 volt DC compressor and coils pre-plumbed and charged, and all you need to do is build an insulated box.

Here is one of many sources for these kits:

Good Luck,

Jeff Yago

Solar battery life


I recently discovered that Solar batteries have a limited life (about 25 to 30 years).

What is actually happening? Your response can be as technical as you like (I’m tough :-)

Does the rate of decay depend on how much Sun they get? Ie: will they still decay in a dark cupboard?

Does this differ for Crystalline and Amorphous cells?

I hope I haven’t asked too manny questions at once.




I think you mean solar “modules” not solar “batteries”, since you are referring to solar cells.

Many of the solar modules installed around 1979 as part of a large government demonstration project and later removed and sold as used modules are still working just fine after 28 years. These thousands of modules were left out in the desert sun for years after this project was abanded, and then finally removed in 1991 for sale to those of us in the solar business at that time. There were a few failed modules which were scrapped, but most still work just fine and the only problem is their original white backing behind the cells had turned yellow from the long exposure to the harsh sun.

Solar modules are made with silicon cells which do not wear out, do not loose their solar electric effect, and may last forever. These crystalline solar cells (or amorphous plating on the glass) are “sandwiched” between the tempered-glass front and vinyl backing material to hold the cells in place and protect the small foil wiring between each individual cell. Most solar modules fail when moisture begins to leak between the glass and backing when this backing material starts to breakdown. This corrodes this very-thin foil wiring and cell electrical inter-connects and the module finally looses the electrical connection.

I have also seen several solar modules fail when there is a flaw in the tempered glass front. The constant daily cycling from hot sun to cold night causes this flaw to crack and the entire module will look like a car window that was in a wreck. However, this type flaw almost always happens during the first year of operation, and if it makes it that long then this type failure usually will not happen after this initial break-in period.

There have been a few solar modules that failed due to manufacturing defects, but these also usually show up in the first few years of operation. An example was a new manufacture who was making very sharp 90 degree bends in the tiny foil “fingers” that connected one cell to the next, instead of the more common gradual bend. Many of these modules failed when the constant thermal expansion and contraction of this bend each day caused these bends to break.

Remember, all solar modules get very hot during the day and very cold at night and this constant thermal shock is what causes most of the long term problems with solar modules. Finally, to address your question about keeping them stored dark when not used – this will make no difference in module life. Most of the solar modules made in the US have very similar high-quality construction and most should last well past their 25 year warranties. I am concerned however, that there are now many solar modules being made in China which are just starting to enter our market. I know one or two of these manufacturers have been making solar modules for over 10 years and most likely have figured out all the above design flaws. However, most of these Chinese manufacturers are new and may not have all the kinks worked out. Buyer beware!

Good luck!

Jeff Yago

Vent pipe fins


In a previous house I bought aluminum fins that wrapped around the gas furnace vent pipe to reclaim waste heat. I would like to buy more but have not been able to find them. Are they available?

Ken Ladd


You are having a problem because most of the stoves and heating appliances built in the past 10 years are much more efficient and many no longer even require a metal flue pipe. Many use PVC plastic vent pipes because the exhaust temperature is so low, and therefore not much “free” heat to reclaim with the fins you are looking for.

The following link is for a really good supplier of “old timy” stoves and other hard to find non-powered household equipment. What you want may not be on their web site, but call as they may have this item or something that will do the same thing.

Good luck,

Jeff Yago

Old solar water heater


I have a solar hot water heater that hasn’t been hooked up in about 10 years. The pump went out and at the time because of money problems we had it disconnected. I would like if possible to get this hooked up again or at least find a use for my solar panels. Is the system worth fixing. Their are two panels about 4 foot by 10 foot on my roof. Any suggestions, the system was installed about 1984. Thanks in advance.



It depends on the materials. Many older-style quality solar hot water panels consisted of an aluminum box, batt insulation, a copper heat exchanger and copper piping, and tempered glass cover with high temperature rubber gasket. If this is what you have you may be in luck as these can last many years even if they have been sitting un-used.

However, newer modules used galvanized metal which is cheaper and will rust out from the inside due to condensation, newer foam insulations break down at the high temperatures inside due to the panel not having any water circulation and give off gases which “fog” the inside of the glass, this high temperature also destroys the gaskets if they are cheap, and some manufacturers switched to aluminum fins or even aluminum piping to save money and if this is what you have it will most likely be full of “pin-holes” after any anti-freeze protection has been lost.

If the panels look like the materials are in good condition and the piping is copper, then most likely it is worth putting back in operation, and you will only need the pump and a new diff. temp. controller. You should pressurize the system with a water hose to check for piping leaks and failed fittings fist before buying new parts. Also remember that the pump may be stainless steel if the system is water only, and you cannot use a standard lower cost cast iron pump if the system is not designed with a double-wall heat exchanger to keep the solar loop separate from the domestic water.

Good luck,

Jeff Yago

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