The MPL Battery Charger - What is Sulphation? |
Battery Sulphation
Batteries have a finite life and cannot be expected to last forever, however it is possible to increase the life expectancy of the battery by following a few simple rules. During the normal discharge process, the sulphuric acid in the electrolyte reacts with the lead plate material to produce soft lead sulphate crystals in the pores, and on the surfaces of the positive and negative plates inside a lead-acid battery.
When a battery is left in a discharged condition, continually undercharged, or the electrolyte level is below the top of the plates, some of the soft lead sulphate re-crystallizes into hard lead sulphate. The hard lead sulphate cannot be reconverted during subsequent recharging process. This creation of hard crystals is commonly called permanent "sulphation".
It accounts for approximately 85% of the lead-acid battery failures that are not used weekly. The longer period over which sulphation occurs, the larger and harder the lead sulphate crystals become. The positive plates will be light brown and the negative plates will be dull, off white colour. These crystals lessen a battery's power capacity and ability to be recharged.
How the battery is used is important; this is because deep cycle and some starting batteries are typically used for short periods, vacations, weekend trips, etc., and are then stored the rest of the year to slowly self discharge causing sulphation. Car batteries are normally used several times a month, so sulphation rarely becomes a problem provided the car is in regular use.
As a consequence of parasitic load and natural self-discharge, permanent sulphation occurs as the lead-acid battery discharges while in long term storage. (Parasitic load is the constant electrical load present on a battery while it is installed in a vehicle even when the power is turned off. The load is from the continuous operation of appliances, such as a clock, security system, maintenance of radio station presets, etc.) While disconnecting the negative battery cable will eliminate the parasitic load, it has no effect on the natural self-discharge of a car battery. Self discharge is accelerated by temperature. Thus, sulphation can be a big problem for lead-acid batteries not being used, sitting on a dealer's shelf, or in a parked vehicle.
How Can I Tell If my Battery is Sulphated?
Chances are that your battery has some permanent sulphation, if it exhibits one or more of the following conditions:
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If your wet Standard (Sb/Sb)* or wet Low Maintenance (Sb/Ca) battery has been not been recharged for over three months, especially if the storage area was warm or hot. (Six months for wet Maintenance Free (Ca/Ca) or one year for VRLA AGM or Gel Cell.) |
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If the temperature compensated absorption charging voltage is correct and the battery is gassing excessively |
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Poor performance, or it will not hold a charge. |
How do I Prevent Sulphation?
Batteries naturally self discharge 1% to 60% per month (depending on the battery type and temperature) while not in use and sulphation will begin occurring when the State-of-Charge (SoC) drops below 100%. Cold will slow the process down and heat will speed it up. Storing batteries under 250 AH on concrete floors will not cause them to naturally self discharge faster than normal.
Physically inspect for leakage or damaged cases, remove any corrosion, clean and dry the tops of the batteries to remove possible discharge paths from dried battery electrolyte, and clean the terminals.
If the battery is in a vehicle, remove the negative connection from the battery to eliminate the additional parasitic (key off) discharge. Use a suitable tool such as the Gunson vehicle memory saver (4148) to prevent loss of security and or radio codes.
If the battery has filler caps, check the electrolyte (battery acid) level in each cell. If required, add only distilled, deionized or demineralized water to the recommended level, but do not overfill.
Fully charge and equalize levels in wet (flooded) batteries, if required, and recheck the electrolyte levels when the battery cools.
Store a battery in a cold dry place, but not so that it will freeze, and where it can be easily recharged. The freezing point of a battery is determined by the SoC and the higher it is, the lower the freezing temperature.
Do not use a cheap, unregulated "trickle" charger or a manual two stage charger which was not designed for "float" charging or you will overcharge your battery. A less desirable alternative to float charging would be to periodically test the State-of-Charge. When it is 80% or below, recharge. The frequency of testing and recharging will depend on the ambient storage temperature.
How Do I Remove Existing Sulphation?
The MPL charger from Traction Charger is designed to recover Sulphated batteries and restore as much of the capacity as possible.
At initial connection any charger must 'see' a battery is present before starting its charging cycle, this prevents damage due to reverse connection and sparking between charger clips and battery terminals. Most chargers need ‘see’ more than 8volts in the battery when connected to recognize that a battery is present and to start the charging process but the MPL will recognize a battery with only 1 volt. This means that the MPL charger will attempt to recover and charge a battery that is 'completely flat' whereas other chargers would not be able to start charging at all.
At the start of each charge the MPL charger tests the battery to determine if it is deeply discharged or if sulphation has occurred, and the correct recovery algorithm is automatically applied.
After the deep discharge test, the constant current charge provides the fastest possible return of energy to the battery. Even deeply discharged batteries can be recovered, in this way.
Partially discharged batteries are automatically limited to 50% maximum current in order to minimize plate surface charging and heating. When the battery reaches the preset gassing voltage, the charger switches to constant voltage mode. The calculated proportional timing ensures sufficient gassing to prevent stratification, mix the electrolyte thoroughly, and give a green hydrometer indication, but minimizes electrolyte loss and gas emission.
After the completion of charging, the MPL charger switches to the standby or float mode, which compensates for self-discharge and holds the battery at peak charge ready for use.
Using the MLP can dramatically improve the performance of batteries that have been stored and
reduce warranty costs along with improving customer satisfaction.
*Note: Ca = Calcium, Sb = Antimony
