2.  WHY BOTHER?

Because only the rich can afford cheap batteries.....

A good quality marine or RV deep cycle lead acid battery will cost between $50 and $100 and, if properly maintained, will give you at least 500 deep discharge-charge cycles.  The purpose of a deep cycle battery is to provide power for trolling motors, golf carts, fork lift trucks, uninterruptible power supplies (UPS), and other accessories for marine and recreational vehicle (RV), commercial and stationary applications.  Dead batteries almost always occur at the most inopportune times such as across the lake, during bad weather, or on the 17^th tee.

2.1. How is a battery made?

There is an excellent description of how battery is made at the BCI (Battery Council International) web site at www.batterycouncil.org.  A 12-volt lead-acid battery is made up of six cells, each producing 2.1 volts and that are connected in series from positive to negative.  Each cell is made up of an element containing positive plates that are all connected together and negative plates, which are also all connected together.  They are individually separated with thin sheets of electrically insulating, porous material "envelopes" [labeled #3 in the diagram below] that are used as spacers between the positive (usually light orange) and negative (usually slate gray) plates to keep them from electrically shorting to each other.  The plates [#2 in the diagram below], within a cell, alternate with a positive plate, a negative plate and so on.  A plate is made up of a metal grid that serves as the supporting framework for the active porous material that is "pasted" on it or solid lead.

            

After the "curing" of the plates, they are made up into cells, and the cells are inserted into a high-density tough polypropylene or hard rubber case [#1 in the diagram above].  The cells are connected to the terminals [#5 in the diagram above], and the case is covered and then filled with a dilute sulfuric acid electrolyte [#4 in the diagram above].  The battery is initially charged or "formed" to convert yellow Lead Oxide (PbO or Litharge) into Lead Peroxide (PbO₂), which is usually dark brown or black.  The electrolyte is replaced and the battery is given a finishing charge.  Some batteries are "dry charged" meaning that the batteries are shipped without electrolyte and it is added and charged when they are put into service.

Two important considerations in battery construction are porosity and diffusion.  Porosity is the pits and tunnels in the plate that allows the sulphuric acid to get to the interior of the plate.  Diffusion is the spreading, intermingling and mixing of one fluid with another.  When you are using your battery, the fresh acid needs to be in contact with the plate material and the water generated needs to be carried away from the plate.  The larger the pores or warmer the temperature, the better the diffusion.

2.2. How does a battery work?

A battery is created by alternating two different metals such as Lead Dioxide (PbO₂), the positive plates, and Sponger lead (Pb), the negative plates.  Then the plates are immersed in diluted Sulfuric Acid (H₂SO₄), the electrolyte.  The types of metals and the electrolyte used will determine the output of a cell.  A typical fully charged lead-acid battery produces approximately 2.11 volts per cell.  The chemical action between the metals and the electrolyte (battery acid) creates the electrical energy.  Energy flows from the battery as soon as there is an electrical load, for example, a motor, that completes a circuit between the positive and negative terminals.  Electrical current flows as charged portions of acid (ions) between the battery plates and as electrons through the external circuit.  The action of the lead-acid storage battery is determined by chemicals used, State-of-Charge, temperature, porosity, diffusion, and load.

A more detailed description of how a battery works can be found on the BCI web site at www.batterycouncil.org.

2.3.  Why do batteries die?

When the active material in the plates can no longer sustain a discharge current, the battery "dies". Normally a battery "ages" as the active positive plate material sheds (or flakes off) due to the normal expansion and contraction that occurs during the discharge and charge cycles. This causes a loss of plate capacity and a brown sediment, called sludge or "mud," that builds up in the bottom of the case and can short the plates of a cell out.  In hot climates, additional major causes of failure are positive grid growth, positive grid metal corrosion in the electrolyte, negative grid shrinkage, buckling of plates, or loss of water.  Deep discharges, heat, vibration, and over charging accelerate the "aging" process.

The number one cause of premature deep cycle battery failure is sulfation. It is caused when a battery's State-of-Charge drops below 100% for long periods or under charging. Hard lead sulfate fills the pours and coats the plates. Please see Section 12. for more information on sulfation.  Recharging a sulfated battery is like trying to wash your hands with gloves on.  Using tap water to refill batteries can produce calcium sulfate that can also fill the pores and coat the plates.

Most of the "defective" batteries returned to manufacturers during free placement warranty periods are good.  This suggests that some sellers of new batteries do not know how to or fail to take the time to properly load test or recharge them.

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