I decided to begin to look into this area a lot deeper since I became interested in – of all things – running my car audio system separate from the cars own battery. My brother has been doing this for his ham radio equipment for a short while using a solar panel on the roof of his car to keep a separate battery charged. Sounded intriguing so I queried him about it and he sent me the details of what and how.
Since before the industrial revolution energy storage and it’s use has been a major preoccupation of the human race. How to get energy, use it and save it for later. From the first use of fire for cooking and then for early metallurgy and of course warfare.
The use of wood and then hydro carbon compounds for generating heat and then chemical reactions to generate electricity. The first practical use of steam to power was Savery steam pump used in the pump water out of the mines in England. Followed by the Thomas Newcomen “Atmospheric Engine”.
Then came the improvements of James Watt and others.
Around this same time Benjamin Franklin had been experimenting with Leiden jars collecting the static charge in to s series of them he called a “Battery” as he thought them like a battery of guns. But static electricity proved not to be very useful. Then around the same time frame as Flanklin’s experiments, Alessandro Volta began his experiments based on the discoveries of Luigi Galvani and put together his Galvanic Cell or voltaic pile consisting of pairs of copper and zinc discs piled on top of each other, separated by a layer of cloth or cardboard soaked in brine.
Finally a way the generate electricity that was constant and consistent. And there were numerous variations on this battery developed. Including the first rechargeable battery, the lead acid cell which we still have today. In 1899 Waldemar Jungner invented the nickel-cadmium battery and then then nickel iron battery, which he failed to patent since he felt in inferior to the NiCad cell.
Edison picked up on the nickel iron battery in hopes of making a quick buck selling them for electric cars but electric cars fell out of fashion to be replace with gasoline engine cars. Edison lost money on the deal. The nickel iron battery was not dead yet though as it was very tolerant of abuse and found favor in the newly emerging telephone industry, military and even aviation areas because of this. Even though it did have drawbacks such as out gassing and thermal runaway.
But it was the invention of the battery that led to the discoveries of such people as Orsted and Faraday and Ampere and Hertz in the areas of magnetics and electromagnetics and magnetic waves. Giving us electric motors and transformers and radio and nearly everything we take for granted today. In fact even into the late 1940s people in rural areas not yet serviced by the electric grid relied on storage batteries for the radios and even lighting.
And today especially with the move away from carbon base energy systems to those that are more or less ecologically friendly and toward “off grid” personal systems – as well as electric vehicles – there is a major renewal in the interest in batter technology.
However batteries have a lot of draw backs. For one because they are electro-chemical IE base on a reaction between an electrolyte, an acid or base and some metallic electrodes – they have a limited life. Either failing completely or a fixed number of times they can be charged and discharged.
Also they fall into one of two different categories. Either constant voltage or constant current.
The Lithium and Nickle based batteries are constant voltage. That is you can draw current from them up to some maximum and the voltage available will not change but remain constant. Very good for today’s electronics which need a constant voltage to function properly. But there is maximum where if you attempt to draw too much current they will overheat and self destruct. Sometimes very violently.
The so called dry cells and alkaline batteries and lead acid types are constant current batteries. They have a constant amount of current you can draw from them and then the voltage drops. In fact the voltage drops the minute you begin to draw current but becomes more and more noticeable with the more current you draw. Their big plus is that they are less expensive to manufacture and with the case of AGM or Absorbed glass mat lead acid cells, do not out gas or leak and can be stored and operated in most any position. Unlike the so called wet cell lead acid batteries.
Current AGM batteries now can be deep discharged and float charged with little or no problems unlike in the past where these types of batteries could not be deep discharge and float charging them had to be highly regulated. Because of this they have become very popular for UPS systems and even solar powered off grid applications. Though for high current and high availability applications such as industrial sized UPS systems or large scale solar, the wet cell lead acid battery is still preferred.
Some of the newest battery technology is now the lithium iron phosphate battery. These have many advantages over the previous lithium ion batteries. Such as a longer life cycle and fewer environmental concerns. But like other Lithium based batteries they require an intelligent monitor system to make sure they are not completely discharged, or their internal chemistry changes and can no longer be charged. Or over charged or they will be damaged or that too much current is drawn or they overheat and self destruct. All of this makes them considerably more expensive than other cells.
However for a large number of applications they are the battery of choice with their smaller size and lower weight for a particular voltage and current. And in the case of the lithium ion phosphate battery, they have become very popular with the sport vehicle crowd and even as replacements for car batteries. There are even companies that offer them as single 3v cells with current rages up to a couple of hundred amps. Of course these require separate battery monitors for each configuration. This is making them look quite good for solar power energy storage.
All of which brings us back to Benjamen Franklin and the Leiden jars. Leiden jars being the first capacitors. Capacitors also store electrical energy but until recently very small amounts and were used mainly in various electronic circuits. But this technology has been advancing as well. Such that we now have what are called super capacitors. And the price of these are dropping like lead shot in a swimming pool. And because they are not electro-chemical devices, can be charged and discharged almost an infinite number of times. They can also deliver as much current as needed without any physical damage.
These super capacitors are now available up to 100s of farads. To give you and example of what this means, when I got into electronics a 10 micro farad [that's 0.000001 farads] capacitor was the size of small pop bottle. And had a finite longevity. They would go bad after a while. If you talked about a 1 farad capacitor, images of something the size of stem ship boiler came to mind and was considered impossible to build.
Now we have super capacitors that are reasonably small and relatively inexpensive. They are by no means a panacea but combined with new battery technology could make our quest for energy and better way to store and use it more and more feasible. The combination of these ultra capacitors and newest batteries together is making electric energy generation by means other than carbon based fuels look quite good indeed.