The main cause of battery aging is considered to be the formation of insoluble crust of lead sulfate on the charging plates. The deposits reduce the concentration of ions in the electrolyte, increasing the internal resistance to charge acceptance. When they say “the battery is dead” the culprit is lead sulfate deposits in the cans. To remove the plaque is to desulfate the battery, to restore performance.
Desulfating an acid battery
When a battery gives up energy, it discharges by running a chemical reaction:
Pb +2H2SO4 +2PbO2 -> 2PbSO4 +2H2O
Pb is the lead plate
PbO2 is the active putty on the carbon lattice
PbSO4 – small crystals that grow to cover the plate
But when the battery is charged from a generator or mains, the reaction goes in the opposite direction, that is, the sulfuric acid lead decays into lead ions and an acidic residue. And everything would be fine, but some of the crystals, when the battery is chronically undercharged and deeply discharged, grow and do not participate in the reaction. The substance covers the plate with an insoluble grayish-yellow film, clogs the pores, and does not allow charged ions to pass to the conductive plates. This explains the rapid recharging of the battery and the instant discharge – no capacity.
It is possible to return the capacity to the battery if the putty has not crumbled and the plates are not destroyed – that is, the electrolyte in the cans is light, without suspended particles. The purpose of battery desulphation is to clean the plates mechanically, chemically or electrically, to restore or replace the electrolyte. Desulfation schemes have been worked out for years. There are methods of battery desulfation used in service centers and available at home.
How to desulfate a car battery
The natural process of battery aging due to the loss of capacity, due to the deposition of hard-to-solve salts can be postponed by timely desulfation of the starter or traction battery.
All methods can be classified by type:
- Exposure to electrical charge – low-value direct current, pulsed current, and repolarization.
- Chemical methods using sludge breakers followed by electrolyte replacement. Or dissolving the sludge in distilled water with a small charging current
- Mechanical – when the plates removed from the cans are restored by mechanical treatment.
As a preventive measure, additives are periodically added to the electrolyte to prevent the appearance of sulfate stone, but they destroy the plates, reducing the life of the battery.
A diagram for desulfating a car battery
Of the chemical methods of battery desulfation, the most commonly used is a compound of Trilon B and ammonia. These substances are available, but must be used according to the instructions and on strong batteries. Trilon B, the sodium salt of ethylenediaminetetraacetic acid, soluble in water, the sodium replaces the lead ion in the salt and the precipitate dissolves. But the active putty also dissolves.
The order of battery desulfatization by chemical method:
- Prepare a solution – take 60 g of Trilon B, 622 ml of NH4OH 25%, 2340 ml of distilled water for 3 liters. You can take a 10% ammonia solution of 1560 ml, 1140 ml of water and 60 g of Trilon B.
- Drain the electrolyte from the battery into a suitable container.
- Immediately not dried jars pour the prepared composition, and leave in the battery for no more than 60 minutes.
- Drain the contents and wash the cans 3-4 times with distilled water.
- Pour fresh electrolyte of desired density and perform charging on a full cycle.
The method should be used with caution. If car battery desulfation is carried out to remove a small amount of sediment, the exposure time is reduced to 30-40 minutes. Trilon B does not care what to dissolve – harmful sediment or active mass. At the moment of reaction there is heating and boiling of liquid. Work in the open air, use protective equipment.
Charger with desulphation for car battery
In industrial conditions, at motor depots, where the batteries are charged by trained workers, battery desulfation is carried out by a special charger for desulfation. Reversible pulsed currents are used to remove sludge from a heavily clogged battery.
Reversible current is alternating current, with different amplitude and polarity, repeated cyclically. Pulsed desulphation by charging and discharging acts on the battery softly, the temperature of the electrolyte does not rise, there is no gas release.
To create reverse currents, a special device, a reverse current generator, the cost of which is approximately equal to two batteries, is used. How to desulphate a battery using a reverse current generator?
The generator is used for medium sulfation of the plates with 0.5 to 2.0 A current for 20-50 hours. The process is over when the voltage and electrolyte density remain unchanged for 2 hours.
A severely clogged battery is cleaned using a distilled water desulfatization device in several steps. To do this, the battery voltage must be reduced to 10.8 V, the electrolyte must be removed, and the cans must be filled with distilled water.
Lead the desulfation of the battery with a small current, so that the voltage was up to 2.3 V. Gradually the sediment dissolves in the water, the electrolyte has a density of about 1.11 g/cm3. Replace the solution with fresh distilled water, and continue the process to a density of 1.12 g/cm3. The amperage is now set to 1 A and watch the voltage rise until the index stabilizes.
After the first stage of battery desulphation, raise the current to 20% of the discharge current, charge the battery for 2 hours, discharge, and so on to a constant density and voltage 3-5 times.
Bring the acid to a density of 1.21-1.22 g/cm3, charge the battery fully and after 3 hours correct the density, using the table. The method is labour-intensive, but the desulphation of the plates is complete. The battery regains its second youth.
Desulfating the battery with a battery charger
It is possible to get by with a cheaper way of desulfatization with a common battery charger. But the prerequisite is the ability to regulate the current and voltage. If the sludge occupies less than half of the plates so far, the following battery desulfatization scheme is applied:
- Bring the electrolyte level to normal with distilled water.
- Connect charger and set voltage 14 V, current strength 1 A. Charge for 8 hours. Measurements should show that the electrolyte density has increased, voltage has risen to 10 V. If the readings are lower, the battery can not be restored.
- For 24 hours the battery is resting, disconnected from the battery charger.
- Connect with voltage of 14 V and current of 2-2.5 A for 8 hours. Voltage should become 12.7-12.8 V. The electrolyte in the jars has a density of 1Y13 g/cm3.
- Discharge the battery to 9 V, with a high beam lamp for 6-8 hours.
- Repeat charge-discharge several times until electrolyte density is 1,27 -1,28 g/cm3. During the cycles desulphation process takes place, stone is dissolved, acidic residue SO4 strengthens electrolyte.
As a result, the capacity of the lead acid battery will be restored by 80-90%. But this is not the way to desulfate a calcium or gel battery.
Most often for desulphation with a battery charger use the “Vimpel” unit. It is affordable, and has the necessary adjustment. A blinker attachment or other electronic device can be connected to it to remove the lead stone.
In maintenance-free batteries, desulphation is effective only at the initial stage of scaling. It is done using a pulse charger. But it is necessary to know that the stone in a calcium battery contains gypsum, which is not destroyed by pulse currents. Therefore, maintenance-free batteries cannot be restored after 3 deep discharges.
Car battery desulfation device
Car battery plates are well desulphated under the influence of alternating currents with reversed polarity in high frequency. The industry offers battery desulfation devices and charger attachments.
The Kedr Auto-10 battery charger with desulfation mode belongs to the automatic battery chargers. It provides charging with a current of % A of the battery capacity, fast mode with a current of 5 A and cyclic – desulphation. The compact charger is affordable.
Desulfating chargers are chosen for a specific type of battery. The best products for servicing a single battery are considered to be:
- A single-channel device designed for car batteries;
- it is better to take a device with manual adjustment of charging current;
- study the possibilities of protection, interlocks and allowable temperatures;
- know the parameters of your battery, select a suitable device.
According to the technical indicators, the device with an adjustable voltage of 0-36 V, with different ways of desulphation will be suitable for the motorist:
- gentle – low current, constant voltage;
- intensive – cyclic pulse charging with asymmetrical current;
- cyclic charging with decreasing charging voltage.
Compatibility with a battery of your capacity is a must.
If you have purchased a desulfating attachment, it must be included between the charger and the battery, and its wires must not be thinner than others in the connection circuit. The charger must maintain the pulse mode.
Desulfating the battery at home
Often the desulphation of passenger car batteries is carried out with their own hands, guided by the schemes provided on various resources. Many of them are based on the use of an ordinary charger, but require a lot of attention. On average, manual sulfation with low currents and a few cycles takes more than 2 weeks.
Connecting a set-top box to the charger will speed up the battery’s desulfation mode. An example of a set-top box is a pulsed converter called a blinker because the LEDs signal the passage of alternating current. The device can be assembled with your own hands.
In front of you is a schematic diagram of the battery charger for car battery sulfation, called “blinker”.
The principle of the “blinker” is to pass 10% of the current of the battery capacity, the voltage is 13.1 – 13.4 V. The scheme represents the discharge by 12 volt bulbs and a relay switching on the charging at the end of the discharge. You get a blink of 4.3 seconds for a 1 A current discharge and 3 seconds for a 5 A current charge. The current pulses first loosen the monolithic film on the plate, then dissolve the small crystals.
We know that maintenance-free batteries are not good for desulphation. But if the battery is new, has not served more than 2 years, and the electrolyte level in the jars is low, you can try to restore the capacity. First you need to add distilled water to the jars and seal the holes with epoxy glue. Then try pulsed current charging. When the battery is desulfated, at the same time as the sulfated lead crust will break down the active putty. Capacity will be restored slightly and not for long.
Important to know!
The electrolyte corrodes the body and natural cotton fibers as well as concentrated sulfuric acid. The gases released through open battery plugs are harmful and explosive. Therefore, the place where hazardous work is carried out should be ventilated and inaccessible to children and animals. Bottles of electrolyte should not be placed in general access areas. Remember to wear safety glasses, rubber gloves, and use a rubber apron.
It may be helpful for you to watch the video provided on battery desulfation.