The X, Y, and Z’s of Batteries

Batteries.  Everyone uses them, but most people know very little about them.  What type is better than others?  What are the good traits of a given type of battery.  What are the worst traits of that type of battery.  All batteries have the same basic design – two different electrodes (an anode and a cathode) separated by an electrolyte.  All will be revealed…

 

Let’s start with batteries that are NOT designed to be recharged and that can explode if you decide that you know better about this!  One of the earliest designs is called the Zinc-Carbon battery.  One of its electrodes is powdered carbon and Manganese Dioxide and the other is Zinc.  The acidic electrolyte originally was zinc chloride, but a new and better formulation uses Ammonium Chloride as the electrolyte (these are often called Heavy Duty).  These are the cheapest variety of batteries available.  If you have some of this kind of battery you have either bought a real cheap gadget where the manufacturer has skimped on the cost of a damn battery, or you have discovered time travel and have just returned from the 1950’s with these awful batteries – if so, I would suggest you bring them back to 1950 and get a refund – they are quite awful.  It’s tough to decide which of their many poor traits makes them so awful.  They have the worse energy density of any design.  This means they get used up faster than any other type of battery.  Their internal resistance characteristics limits their ability to discharge electricity at a good rate, so they are usually recommended, if ever, for low drain or intermittent operation.  You can’t even rely on a steady voltage during their operation – its voltage falls during use.  It has a terrible shelf life and discharges while it sits in your drawer, before you can get a chance to use it.  And it often leaks!  There is nothing good about this design beyond its cheap cost to manufacture.  My advice is not to use them if at all possible!

 

Alkaline batteries, first introduced in the late 1960’s, are probably the most common variety people are aware of.  They are not too expensive and have very good, all around, battery characteristics.  This type of battery has a Zinc anode and a Manganese Dioxide cathode, and its electrolyte is made of an alkaline paste of Potassium Hydroxide.  It has a higher energy density (lasting three to five times longer than Zinc-Carbon) and longer shelf-life than Zinc-Carbon batteries.  This type of battery also has a voltage that falls during normal use.  This type of battery design also suffers from self discharge and a mediocre shelf life as well as a tendency to leak caustic alkaline material.  Don’t get this stuff on your hands, but if you do, wash it off with soap and water quickly!  This kind of battery can tolerate intermittent heavy loads.  This is the most popular variety of batteries, and makes up approximately 80% of the batteries manufactured in the U.S.

 

Silver Oxide batteries use Silver as the cathode and Zinc as the anode, with and alkaline paste of Sodium Hydroxide or Potassium Hydroxide.  They have a much greater energy density and shelf life than the previously mentioned battery types, but they are significantly more expensive!

 

Lithium batteries come in rechargeable and non-rechargeable design.  Right now, let’s discuss the non-rechargeable variety.  Lithium batteries, refer to a family of batteries with various cathode-anode materials.  The most common kind of Lithium battery uses Lithium metal as the anode and Manganese Dioxide as the cathode with a salt of Lithium acting as the electrolyte, dissolved in an organic solvent.  This class of batteries possesses the highest energy density of any commercially available non-rechargeable battery. Energizer Lithium cells use a Lithium metal anode and an Iron Sulfide cathode.  These batteries excel at high load conditions – they often last 2 ½ times longer than Alkaline Batteries during high load conditions.  They have an excellent shelf life of 10-20 years.  They are more expensive than Alkaline Batteries but probably worth it in high load situations.  Under low to medium load conditions you would be wasting your money on this type of battery unless you need that extended shelf life!

 

Those are the Usual Suspects, when it comes to available non-rechargeable batteries.  Now, onto those rechargeable kinds.

 

The great granddaddy of them all is the Lead-Acid battery. Invented in 1859 by French Physicist Gaston Planté, it is, by far, the oldest rechargeable battery.  Its design has been tweaked a little bit through the years and a few variations on the theme have been engineered, but the basic principles have remained the same.  Although it has a very low energy density, it is capable of supplying high surge currents which have kept it as the “go to” battery for automobiles.  They are relatively inexpensive and much more low maintenance than they were in the old days when you would have to top off the water level in them.  In addition to being used in automobiles and other vehicles they are used in Uninteruptable Power Supplies that are part of most well designed computer server racks.  Lead-Acid batteries come in two major categories – Starting Batteries and Deep Cycle Batteries.  The former are designed to supply massive amounts of short duration surge power, while the latter is optimized to survive more episodes of almost full discharge of the battery without degrading its lifespan too much.  They can also be divided into three types – Wet Cells, where the electrolyte is dissolved in water, Gel Cell Batteries and Absorbed Glass Mat (AGM) Batteries, which do not contain water and can be placed in any position without concern that the electrolyte would not work correctly.  AGM and Gell Cell batteries often cost twice as much as Wet Cell and may require different charging devices, they store better and do not tend to degrade as easily as Wet Cells.  AGM Batteries hold their charge better than the other varieties, and usually provide a longer life span.

 

When lead-acid batteries are allowed to be undercharged small sulfate crystals form.  As this condition persists these reversible small lead sulfate crystals develop into large irreversible crystals that impede the battery’s ability to charge, both by decreased total charge possible and charging at a slower and slower rate.  There are commercial gadgets that promise to “de-sulfate” batteries and reverse the irreversible.  How much of this is true or erroneous is not obvious to many at this time.  Lead-Cell Acid batteries can be summed up as “cheap”, “heavy”, “high capacity”, and “short life span”.

 

Then there is Nickel Cadmium Batteries (NiCd, or NiCad which is a registered trademark) – the “Zinc-Carbon” batteries of the rechargeable battery world.  They are a technology that has been eclipsed by much better designs, and is usually only seen in older gadgets at the bottom of your old gadget drawer.  Low energy density, limited number of recharge cycles, poor shelf life requiring regular recharges while it is sitting on your shelf unused, and the worst characteristic – its memory effect.  If you don’t fully discharge them, their charge capacity shrivels over time.  Ni-Cads are a dead-end technology these days.

 

Nickel Metal Hydride (NiMH) can have two to three times the energy density of their NiCd equivalent.  Each cell produces 1.25 Volts, lower than most other battery cell technologies, but today’s modern electronics often have no problem with this lower voltages.  One of their major disadvantages is their high rate of self-discharge – they don’t remain charged when sitting on the shelf, or inside your device with the power off.

 

Lithium based rechargeable batteries exist in numerous forms.  As a group they possess the best energy density of all the batteries mentioned here.  They are also some of the most expensive batteries and since they  use Lithium, some designs can be dangerously explosive (we have all seen videos of laptops “self destructing” due to the runaway failure of their lithium battery).  One of the things you should keep in mind about most rechargeable Lithium based batteries is that heat can destroy them, and “top off” charging all the way to 100% produces excessive heat in the cells (often leading to a swollen battery, or just plain failure).  The manufacturers of Lithium Batteries advise that batteries be stored in the 40-60% charge level and only fully charge the battery just before you need to use them.  This requires a degree of “fortune telling” on the part of the user – knowing when you will need a full charge, and when you won’t.  Lithium Iron Phosphate (LiFePO4) Batteries are starting to be released for Hams.  They are relatively light, with a relatively long lifespan and an excellent number of lifetime discharge cycles.  The problem, as I see it, is the extremely high premium over a routine Lead-Acid Cell battery system.  Prices may drop, or another technology might appear in our future.  Time will tell…

 

In closing, I just want to add something.  Many people get their battery types confused.  NiCd’s memory effect traumatized so many people, that they have taken that idea to other battery types that do not suffer from a memory effect.  Cycling Lead-Acid or Lithium batteries does not improve them, but prematurely ages them.

 

So, don’t cycle all your batteries, just for the sake of cycling them – just the ancient NiCd’s that you should think about retiring anyway.

 

-Roy, AC2GS- (I can be contacted at [email protected])