A Basic Guide to Understanding Lead-Acid Battery Charging and Maintenance Requirements.
Many RV owners may not have the technical background to understand the operation of their battery charger. Sometimes they forget about the need to maintain the battery water level and to keep it fully charged when their RV is in storage. RV owners do however remember the consequences of improper battery charging and maintenance…a dead battery that is expensive to replace!
The following analogy uses the flow of water from a Charger Tank (battery charger) to fill (recharge) a Battery Tank (battery) to simulate a battery recharging cycle. The goal is to fill (recharge) the Battery Tank as fast as possible, while keeping water loss to a minimum. The same goal you have when recharging your RV battery. This analogy explains the need to constantly monitor and adjust the flow rate to prevent water loss. Battery chargers also require voltage adjustments during the recharge cycle to reduce water loss. The small leak at the bottom of Battery Tank represents the small internal current leak present in all lead acid batteries. This internal current leak self-discharges your RV battery approximately 4% per week, thus the need to charge your battery periodically when in storage.
At the start, both tanks shown below are at the same height, 12.6 feet; therefore, water (amps) in the Charger Tank will not flow into Battery Tank. Water will only flow if the height of Charger Tank is increased. Remember when recharging your RV batteries the charger voltage must also be higher than battery voltage to allow charging current to flow. Typical converters/chargers used in the RV Industry have a fixed output voltage of 13.6 volts.
As Battery Tank begins to approach the 90% Full Level the Charger Tank must be lowered to 13.6-Ft. (figure # 4) to prevent excess splashing and water loss over the top. The Battery Tank would then complete the fill at this slower rate.
In figure # 5 the Battery Tank is now full, but the Charger Tank continues to remain at 13.6-Ft. This causes more water to flow than required to maintain a full level in the tank. This excess water is lost as it splashes out the top of the Battery Tank.
To reduce water loss even more, once the Battery Tank is fully charged the height of Charger Tank must lowered to 13.2-Ft. This lower height reduces the flow from the Charger Tank so that it just equals water lost due to the leak at the bottom of Battery Tank.
As you have seen filling a Battery Tank as fast as possible with minimum loss of water, requires several adjustments to the height of the Charger Tank. First, it has to be raised to 14.4 feet to refill as fast as possible. Then it must be lowered to 13.6 feet to finish the fill with minimum water loss. Once the tank is full, you have to lower it again to 13.2 feet to reduce water loss even further.
Proper recharging of RV and Marine batteries also requires charger voltage adjustments during charging cycle to accomplish these same benefits. Unfortunately, most battery converter/chargers on the market today have a fixed output voltage of 13.6 volts and can not be adjusted.
It would be nice if someone created a robot called the "Battery Butler" that automatically came around every week to check and adjust your battery system. Well someone has, Progressive Dynamics developed a microprocessor based programmer-controller for our electronic power converters. This device proved to be so intelligent, we called it the Charge Wizard, because it automatically adjusts the charging voltage as required by the battery to ensure fast recharge cycles, with minimum water loss.
Now that you understand the requirements for properly filling a tank with water, it is time to learn more about the construction operation and recharge requirements of your RV and Marine lead acid batteries.
How do Lead-Acid Batteries Work?
The lead-acid battery shown below in Figure # 7 consists of a single cell composed of two lead plates. One plate is Positive and is made of Lead Dioxide. The other plate is Negative and made of Sponge Lead. These plates are surrounded by the electrolyte, a mixture of water and sulfuric acid. The cell shown is capable of storing a voltage of 2.1 volts once it is charged...THIS IS THE REASON LEAD-ACID BATTERIES ARE CALLED STORAGE BATTERIES, they store a charge.
Since a single lead-acid cell only produces 2.1; volts, six (6) cells must be connected in series to create the typical RV or marine battery (see Figure # 8 below). Six cells connected in series will provide a total voltage output of 12.6-volts. The standard RV battery (shown below) has an output voltage of 12.6 volts, when fully charged!
The Battery Discharge Cycle
In figure # 9 below, the battery is partially discharged and Lead Sulfate (sulfation) has begun to coat both lead plates. The output voltage of the battery has dropped to 12.3 volts.
In figure # 10 below, the battery has now been discharged to 50% of its total capacity. The Lead Sulfate (sulfation) is now covering more of the surface area of the plates. The battery voltage has dropped to 12.1 volts.
Figure #11 below illustrates a fully discharged battery and the voltage has dropped to 10.5 volts. Battery Management 101 now completely covers the surface of all plates. Initially the Lead Sulfate coating is soft, thin and easily reconverted into lead and sulfuric acid when battery is recharged. It is important to remember, The longer your battery remains discharged, the more it will begin to form hard crystals of Lead Sulfate…RECHARGE YOUR BATTERY AS SOON AS POSSIBLE! Once these hard crystals form, they are impossible to remove during a standard fixed voltage (13.6 volts) charging process.
Now that the battery is completely discharged it is time to discuss the recharge cycle. Remember, when recharging your RV battery the goal is to recharge it as fast as possible without excess water loss.
Recharging Lead Acid Batteries with the Charge Wizard
In figure # 12 below, the battery is in the process of being recharged. The Charge Wizard has detected the battery is very low and has automatically selected BOOST MODE (14.4 volts), of operation to return battery to 90% of full charge in 2-3 hours.
In figure # 13, the battery has reached the 90% of full charge level. The Charge Wizard has reduced charging voltage to 13.6 volts to prevent excess battery gassing and water loss. The remaining 10% of charge cycle will be completed at this lower voltage.
When the battery reaches full charge (figure # 14), charging voltage must be reduced to 13.2 volts. This lower voltage reduces charging current to 20 to 25 milliamps, enough to replace current lost through the internal leakage present in all batteries. The Charge Wizard knows this and automatically selects STORAGE MODE of operation and reduces charger voltage to 13.2 volts.
IMPORTANT - WHEN STORING RV OR MARINE BATTERIES FOR THE WINTER, KEEP THEM ON A CONTINUOUS CHARGE AT 13.2 VOLTS. CHECK WATER LEVEL AT LEAST ONCE A MONTH AND ADD DISTILLED WATER AS NEEDED.
When electrical current flows through water during the charging cycle, it breaks the water down into its original components, a mixture of Hydrogen & Oxygen. These two gasses are extremely flammable and can cause an explosion if the battery is not properly vented to the outside of the RV. This normal conversion of water into hydrogen and oxygen is part of the battery recharge cycle and is another reason you should check the battery water level at least once a month.
Other Battery Maintenance Problems Solved by the Charge Wizard
Even after receiving a full charge, notice that near the bottom of the battery, some of the Lead Sulfate has not converted back into lead and sulfuric acid. This remaining Lead Sulfate has formed hard crystals that can not be easily reconverted. These hard crystals are the beginning of BATTERY SULFATION, the leading cause of battery failure.
To remove the remaining Lead Sulfate, the battery must receive an EQUALIZING CHARGE (i.e. increase the charging voltage to 14.4 volts or higher periodically for a short time). This equalizing charge will eventually convert this crystallized Lead Sulfate into its components (lead and sulfuric acid).
Problem solved the Charge Wizard automatically provides an EQUALIZING CHARGE that increases charging voltage from 13.2 to 14.4 volts for 15 minutes every 21 hours, when operating in the STORAGE MODE. The Charge Wizard's EQUALIZATION MODE automatically eliminates BATTERY SULFATION BUILD-UP before it becomes a problem! Remember that the rate of SULFATION increases rapidly as a battery discharges…so keep your battery fully charged when not in use!
Now that you have seen what the Charge Wizard can do to improve battery recharge time, adjust charge voltages to reduce water loss, and eliminate sulfation, its time to eliminate the last of the battery plagues…BATTERY STRATIFICATION!
What is BATTERY STRATIFICATION? You learned previously that the electrolyte inside a battery is a mixture of water and sulfuric acid and like all mixtures, one component is heavier than the other is. In this case Sulfuric Acid is the heavy component and will eventually begin to settle to the bottom of the battery. This process is called STRATIFICATION! Stratification will increase build-up of lead sulfate and reduce battery capacity.
The way to prevent BATTERY STRATIFICATION is to apply an EQUALIZING CHARGE (i.e. increase charging voltage to 14.4 volts) to your fully charged battery for a short period at least once a month. This EQUALIZING CHARGE will cause heavy gassing. This heavy gassing mixes up the electrolyte and equalizes the water/sulfuric acid mix. Equalizing also breaks down lead sulfate crystals that may have begun to form. The Charge Wizard automatically Equalizes your battery for 15 minutes every 21 hours, when in the STORAGE MODE to prevent BATTERY STRATIFICATION.
As you have learned, the Charge Wizard is a very valuable addition to your battery charging system and it will eliminate battery problems. Charge Wizards are available at leading RV Dealers and Distributors, or you may contact Progressive Dynamics at 269 781 4241. ORDER YOUR CHARGE WIZARD TODAY AND ELIMINATE BATTERY PROBLEMS.TOP OF PAGE | BACK TO PREVIOUS
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Progressive Dynamics Service Department
507 Industrial Road, Marshall, MI 49068
Service Dept. Fax: 269-781-8729
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