How to Repair a Closed Battery for a Car

Why the battery bank short circuits, and what to do in such a situation

It is difficult to imagine a modern car with an internal combustion engine without a starter battery. These batteries are installed on cars and trucks. The most common variants are designed to work with an on-board voltage of 12 V.

A shorted battery bank

The batteries are called 12-volt, although in fact a fully charged battery produces about 12.7 volts.

Structurally, the battery consists of six sections. Each of them produces about 2.1-2.2 volts. This allows you to get the necessary 12.6-12.8 volts in total. But it happens that one of the jars (sections) short-circuits. That is, it stops giving voltage. And even with a full charge the battery with a closed bank will show the voltage of about 10-11 V. With such a battery it is extremely problematic to start the engine, almost impossible.

Characteristic signs

Not everyone understands how to know whether the starter battery is closed or not.

To do this, it is necessary to know better the structure of the battery. Most batteries used in motor vehicles are one of the many variations of lead-acid batteries. Inside, there are multi-polar plates of lead that are coated with special alloying additives. This can be antimony, calcium, silver, etc. In addition to lead, the electrolyte plays a huge role. It is a mixture of sulfuric acid and distilled water.

Each of the 6 sections stores energy, which is due to ongoing electrochemical processes. These banks are connected to each other in series. Due to this their voltage is summed up. From each bank about 2.1 V is released, which gives a total of 12.6 V voltage in the battery.

Now to the question of how you can tell if the battery in the car is shorted. Shorting can occur as a result of the plates in the banks coming together, bloating of the walls, a drop in the electrolyte level.

A short circuit is a situation where the positively and negatively charged plates, which are structurally separated, come into contact under the influence of various factors. It is the connection of the plus and minus leads to a kind of short circuit.

This happens when a piece of lead falls off the plate, or the lead gradually crumbles, accumulates on the bottom and at a certain point acts as a jumper, shorting the plus and minus plates.

The motorist should know how to determine the short circuit in the battery. There are several ways to do this. A short circuit is indicated by several characteristic signs:

  • when the voltage is measured, it drops significantly compared to normal readings;
  • the battery case during operation and during charging gets very hot; does not give the desired result;
  • it is not possible to crank the starter.

Battery bank repair

If you list the signs of closed battery cans, you should also add to this back the appearance of an unpleasant odor. It resembles the smell of rotten eggs. It is associated with the release of hydrogen sulfide. But such a phenomenon is not always observed.

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If there is suspicion of battery malfunction, you should check the starter battery for short circuits. And it can be done with your own hands in the garage.

Unfortunately, a closed battery often leads to the same ending. This is the need to dispose of and replace the battery. Therefore, even if you manage to check by yourself whether one or another bank of the car battery is short-circuited, there is no guarantee that the battery will be able to return to work.

If you notice at least one of the signs discussed above, you should start checking.

Why does it happen?

The question logically arises: why in the car battery starter type sometimes closes one or another bank.

This is mainly due to the actions of the motorists themselves, who trivially do not follow the manufacturer’s prescribed instructions for the use of power sources.

The plates are located close enough to each other, but separated, which provides a stable flow of electrochemical reactions. But if the operating rules are violated, the plates begin to crumble, the electrolyte level drops, and the oppositely charged plates come into contact with each other.

There are some causes of possible shorting of the starter battery. But they are not all related to car owners:

  1. Factory defect. It is possible that the battery plates may be short-circuited due to the fault of the manufacturer of the battery. These causes do not occur as often if you buy batteries from proven companies. But nevertheless, there is such a possibility. The manufacturer should be responsible for the consequences, since the closure of the cells as a result of a factory defect is a warranty case.
  2. The physical impact on the body. This is possible in collisions, as a result of serious traffic accidents. As a result, the plates are displaced and a short circuit occurs.
  3. Chronic overcharge and undercharge. It is this reason that occurs in practice more often than others. Basically, motorists operate the battery, which is in a state of constant undercharging. This provokes sulphation, shattering of the plates with all the ensuing consequences. Constant overcharging is possible due to problems with the alternator, diode bridge and voltage regulator.

Shorted battery cans

Regardless of the causes, further action can be divided into 2 options. This is either disposal of the battery and the purchase of a new battery, or an attempt to restore the battery and extend its life.

Checking the battery for short circuits

Now specifically on how you can identify a closed bank in a battery. The easiest way is to contact a professional. They will take the battery for testing for a certain fee and give you a verdict within a while.

But to check the battery for a possible short circuit is quite realistic by your own, using almost improvised means and a standard set of tools available to every motorist. There are several ways, how to check yourself if the battery is short-circuited. Each option has its own features and difficulties in terms of independent implementation:

  1. Technical way. Simple, but at the same time very effective. The essence is to check the starter battery for shorting, using a multimeter. The old batteries and even allowed to make measurements of voltage on each bank. The structure of modern batteries does not allow to do this. Therefore, it is necessary to make general voltage measurements. This is done at the end of the charging procedure. If the multimeter shows 10-11 V, one of the banks is probably short-circuited.
  2. Visual method. When the battery is fully charged, but it continues to receive the charge voltage, the electrolyte begins to boil. That is, gas is released, bubbles are formed. If 5 cans are boiling, and one is “silent”, it means that it is the problem section of the tested battery.
  3. Diagnosis by color. This option of checking is mainly suitable for serviced batteries. After all, you can unscrew the plugs and look into all the banks, thereby determining the color of the electrolyte there. A short circuit is indicated by a dark, black, or cloudy color of the working fluid. Since modern batteries are mostly maintenance-free, you can look at the condition of the electrolyte only with a transparent part of the case. By putting the battery to the light, you can potentially see that the color of the electrolyte in one of the jars is different from the others.
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It also happens that the check shows the presence of a closed jar. At this point, motorists have a legitimate question about what to do next.

Repairing the battery jars

It is possible to restore the battery. But it is actual mainly for specialists and in workshops with the appropriate equipment.

At the same time, car enthusiasts who like to dig in the car, have found a way to reanimate the battery with a closed can with their own hands.

There is no guarantee that the presented method of restoration will help. The motorist does it at his own risk, taking full responsibility.

To engage in restoration or not, is a personal matter.

How the restoration is carried out

The following is detailed about what to do if one bank of the battery is short-circuited.

Usually in such a situation, it is advised not to try to reanimate the batteries, but to search for a new battery. After all, the probability that it will be possible to successfully restore a closed bank is not so great.

But there are those who are ready to eliminate the consequences on their own, not rushing to the disposal and purchase of a new battery. In practice, plate shorting is not the final verdict for the battery. But much depends on the specific cause:

  • if the case is damaged, it is extremely dangerous to engage in restoration;
  • if it is a factory defect, the battery should be returned to the seller, to demand a refund or exchange for a new battery without surcharge;
  • If the battery is chronically undercharged or overcharged, you should first eliminate the cause of this phenomenon, and then try to restore the battery.

It turns out that it is possible to restore the battery, which shorted, only in one situation. And here each motorist must decide for himself what to do in this situation.

To eliminate the consequences of a shorted section of the battery, it is necessary:

  1. Determine which particular bank is not functioning, using the proposed diagnostic methods and based on the characteristic symptoms.
  2. Then it is necessary to completely drain the electrolyte from the problematic bank. All other sections do not need to be touched. Drainage is not performed by turning the case upside down, because it is dangerous. It is better to use a syringe or similar device to pump out all the electrolyte.
  3. A piece of plastic should be cut out from above the problem section so that the plates can be removed through the hole.
  4. The jumpers with adjacent sections should always be disconnected. Some people simply cut them.
  5. Then the package of lead plates is carefully removed. Not with your bare hands. The plates should be rinsed under running water, remove any acid residue.
  6. Now carefully examine the condition of all the plates. This will give an indication of exactly where the short circuit occurred. If this was the result of sediment accumulation, it will be necessary to wash out all the debris at the bottom.
  7. After the plates are restored, they are lowered back into place. The electrolyte is poured and the cut out plastic cover is closed. It must be soldered, achieving tightness.
  8. Then you only have to charge the restored battery.

If after charging the voltage is restored to the required 12.5-13 V, you can continue operating the battery.

Short-circuiting the battery bank does not always put an end to its further operation. But it is important to be prepared for the fact that the resuscitation will not give the desired result, and the battery will have to be recycled.

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Shorted battery bank – what to do?

The car battery is a store of electrical energy, the renewable supply of which is due to the electrochemical reaction in several cells. Each bank provides an equal amount of energy. The cells are connected in series, the voltage in the battery is equal to the sum of the resulting potential differences of all the banks. If one cell fails, the battery becomes unusable. How do you know the cause of the malfunction – is the battery jar shorted or there was a break in the circuit?

Shorted battery banks – symptoms

The structure of a lead battery

You are looking at a classic lead acid battery, consisting of 6 cans. Each is made up of pairs of differently polarized plates. Their contacts are assembled into a common collector, connected in series and two terminals lead to the cover. Modern banks have a different design, but the scheme of completing the banks, the cells, is the same.

When connected in series, the voltages of the cells are summed, and the capacity is determined by the jar which is the most jammed. To charge the battery, the voltage is applied to the terminals, and the current flows through the vaults. Why do the jars in a lead battery short out? If for some reason the plates in the can have come closer together, the walls have blown up, you get a jumper, the cell is closed. Sometimes a piece of crumbled putty or scale creates a contact bridge.

How can you check if a battery bank is shorted? When you measure the voltage on the terminals, you will find a sag. For example, a 12 V battery consists of 6 cans with a total voltage of 2.1*6=12.6 V. The voltage has dropped to 10.5-11.0V – look for a closed can.

One of the plates inside the can is lead, and the other has a layer of active ingredient. If the electrolyte level is disturbed, overcharged, the mass can crumble and close the plates.

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Mechanical damage from the outside can cause deformation. The battery case may have swollen, and then internal shorting of the plates in the cans is not excluded. This can occur when the electrolyte freezes and from overcharging an unattended battery.

Symptoms of a shorted battery bank are loss of voltage, warming of the battery case. The battery does not charge to 12 volts, unable to crank the starter, requires replacement. Sometimes you can hear the smell of rotten eggs when charging – hydrogen sulfide gas is released.

Signs of a closed battery bank

Finding a dead battery

As charge is redistributed inside, the battery case warms up, which is one of the signs of an internal short circuit. If the battery is serviceable, a shorted battery can be detected during charging. At the moment the voltage rises, the plugs on the cans are open, hydrogen is released, and the cans are boiling. If one jar does not show any sign of life, it is a shorted jar. You can check and find the cause of undercharging in a ventilated room or outdoors.

If there is a voltage drop in the maintenance-free battery, the device does not charge to operating voltage, how to determine if the bank is shorted, or another reason. Specialists advise to close the contacts for 1-3 seconds. From a non-working bank will begin abundant release.

Even a maintenance free battery allows you to see the level of electrolyte in the jars through the translucent walls. Signs of a closed can will be a reduced electrolyte level – boils out, sometimes a change in color to black is noticeable.

How to Detect a Closed Battery Jar

Deformation of the battery plates

Technically you can determine the closed battery by measuring the voltage on each bank separately with a voltmeter. To measure the voltage at each bank, you must use a load fork. Under load, the voltage of the bank below 1.7 V indicates a defect.

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The most reliable way of testing is carried out on a fully discharged battery. The battery should give a voltage of 12 V. A reading less by a multiple of 2 will determine how many cans are defective. It will then be necessary to determine why the bank is shorted. If the battery is expensive and new, used less than 3 years, it can be resuscitated. But to do this you need to have locksmith skills, tools and follow safety procedures.

Causes of shorting of the jars in the battery

Shorted battery

The main problem lies in non-compliance with the instructions for the operation of the car battery. Tightly spaced plates, active putty on the grids, are precisely designed to work under flooding, with voltage, within the allowable limits. Crumbling mass, sulphation, sharp impact on the case is a prerequisite for contact between the plates and opposing charges. If one bank works with overload, it discharges faster, sulphates, and the first will fail.

What should you do to avoid shorting the battery bank and make it work for a long time? Keep the battery clean, avoiding unnecessary self-discharge currents. Do not leave a discharged battery for a long time without recharging. A discharged battery will freeze in the cold because it has a weak electrolyte. Often you have to scrap the whole battery because of 1 can of battery. From what it can short-circuit – there are several reasons:

  • Factory defect – a warranty case.
  • Severe impact on the case.
  • Chronic undercharge and overdischarge – the most common cause of malfunction.

Recovering a closed battery bank

Repairing the battery after a short circuit

After it was possible to understand that the banks of the car battery are closed, it is necessary to evaluate the work to restore the cell and compare it with the purchase of a new device. If more than one bank is shorted, there is no point in wasting time and effort on repairs. How do you know if other cells are still jumpered? They can manifest themselves if you break the layout of the case, loosen connections.

Step-by-step instructions on how to repair a closed battery bank.

  1. Identify the failed battery bank by the listed signs.
  2. Remove the electrolyte using special tools, wearing goggles and rubber gloves.
  3. Cut the plastic around the cell from above.
  4. Disconnect jumpers from adjacent cells and carefully remove the plate pack, rinse them of the acid.
  5. Identify the location of the closure – a particle of metal, a bent plate, remove sediment on the bottom.
  6. Put the construction in place as it was, pour the electrolyte, fix the lid with glue.
  7. Charge the battery fully.

This is how lead batteries of older models and those manufactured in Europe are restored. Maintenance-free batteries must be protected from deep discharge. It is difficult to repair them with your own hands.


It is better to see once, how specialists eliminate the consequences of a shorted battery bank. How to repair a shorted battery bank, watch the video.

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