Battery Management 101

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.


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.



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.


  • The Charge Wizard is built into the PD9200 Series converters.
  • The Charge Wizard is available separately as an add on to the  the PD9100 Series converters for Lead Acid Batteries.
  • The Charge Wizard is built into the PD4000, PD4500,  Series Power Centers for Lead Acid Batteries.

Answers to Common Questions about Batteries

Question ? !!!!! Use the search above to find an answer !!!!this column is hidden in CSS options
What Type of batteries are recommended?Wizard equipped converters.
Deep cycle Flooded Lead Acid, AGM , Gel Cell
Battery size should not be less than the converter size in AMPS.
Will equalization affect AGM batteries ? Equalization when applied in the conventional sense to LA battery chargers, means up to 15.5 volts for a period often exceeding an hour.
The equalization cycle that we use is mild, 14.4 volts for 15 minutes every 21 hours when in storage mode. This has been proven to be good at reducing sulfation in the Lead Acid Wet batteries. It also has no effect on AGM .
We have been reassured by AGM manufacturers that the profile we use is good for AGM batteries.
Do lead acid batteries discharge when not in use?All batteries, regardless of their chemistry, will self-discharge. The rate of self-discharge for lead acid batteries depends on the storage or operating temperature. At a temperature of 80 degrees F. a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125-amp hour rating would self-discharge at a rate of approximately five amps per week. Keeping this in mind if a 125 AH battery is stored for four months (16 weeks) winter without being charged, it will loose 80 amps of its 125-amp capacity. It will also have severe sulfation, which causes additional loss of capacity. Keep your batteries charged while not in use!lead acid
Do lead acid batteries develop a memory?Lead acid batteries do not develop any type of memory.lead acid
Do I need to completely discharge my lead acid battery before recharging it?No, in fact you should never discharge your lead acid battery below 80% of its rated capacity. Discharging it below this point or 10.5 volts can damage it.lead acid
When do I need to perform an equalization charge?Equalizing should be performed when a battery is first purchased (called a freshening charge) and on a regular basis (every 10 discharge cycles or at least once a month). Reduced performance can also be an indicator that an equalizing charge is needed.lead acid
What is an equalizing charge?An equalizing charge for a 12 volt battery requires that it be charged with a voltage of at least 14.4 volts for a period of at least one hour once a month, or every 10 discharge cycles. An equalizing charge prevents battery stratification and reduces sulfation, the leading cause of battery failure.lead acid
When should I add water to my batteries?How often you use and recharge your batteries will determine the frequency of watering. Also, using batteries in a hot climate will require more frequent watering. It is best to check your battery water level frequently and add distilled water when needed. Never add tap water to your battery. Tap water contains minerals that will reduce battery capacity and increase their self-discharge rate.

Warning - A brand new battery may have a low electrolyte level. Charge the battery first and then add water if needed. Adding water to a battery before charging may result in overflow of the electrolyte.
lead acid
What is the proper electrolyte level?Battery electrolyte levels should be just below the bottom of the vent well, about ½ - ¾ inch above the tops of the separators. Never let the electrolyte level to drop below the top of the plates.lead acid
Do I ever need to add acid to my battery?Under normal operating conditions, you never need to add acid. Only distilled or deionized water should be added to achieve the recommended electrolyte levels.lead acid
Can my batteries freeze?If your battery is partially discharged, the electrolyte in a lead acid battery may freeze. At a 40% state of charge, electrolyte will freeze if the temperature drops to approximately -16 degrees F. When a battery is fully charged the electrolyte will not freeze until the temperature drops to approximately -92 degrees F.lead acid
What are the most common mistakes made by owners of lead acid batteries?Undercharging - Generally caused by not allowing the charger to restore the battery to full charge after use. Continuously operating a battery in a partial state of charge, or storing the battery in the discharged state results in the formation of lead sulfate (sulfation) on the plates. Sulfation reduces the performance of the battery and may cause premature battery failure.
Overcharging - Continuous-charging causes accelerated corrosion of the positive plates, excessive water consumption and in some cases, damaging temperatures within the battery. Lead acid batteries should be charged after each discharge of more the 50% of its rated capacity and during or after prolonged storage of 30 days or more.
Under-watering - In lead acid batteries water is lost during the charging process. If the electrolyte level drops below the tops of the plates, irreparable damage may occur. Check your battery water level frequently.
Over-watering - Excessive watering of a battery results in additional dilution of the electrolyte, resulting in reduced battery performance. Add water to your battery after it has been fully charged, never when the battery is partially discharged.
lead acid
Can I reduce the need to add water to my battery by lowering the charging voltage to 13 volts or less?Lowering the charging voltage will reduce the need to add water, but this will cause a condition known as battery stratification. Battery stratification is caused when the sulfuric acid in the electrolyte mixture separates from the water and begins to concentrate at the bottom of the battery.

This increased concentration of acid increases the formation of lead sulfate (sulfation). To prevent stratification, your battery should receive a periodic equalizing charge (increasing the charging voltage to 14.4 volts or above).
lead acid
How do Lead Acid Batteries work?Battery Basicslead acid
How do I Take care of Lead Acid Batteries ?Battery Management 101lead acid
What size battery Bank ?RV Battery Bank Calculatorlead acid
What size battery bank for an inverter ?RV Battery Bank Calculatorlead acid

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Lead Acid Battery Discharge Cycle
Lead Acid Battery Recharge Cycle
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