How to Bring a Deep Cycle Battery Back to Life

Written by John Ho on September 24, 2020
How to Bring a Deep Cycle Battery Back to Life 2020

If you are stumbling around to know, how to bring a deep cycle battery back to life, you are at the right place. I will explain to you in detail, how you can repair an old battery so that you can use it for some more couple of years instead of buying a new one.

Deep cycle batteries are specially designed lead-acid batteries, known for maintenance-free and longer life span.  A normal car lead-acid battery gives a quick burst of current for ignition or other purposes. In contrast, deep cycle batteries are capable to provide steady current for a longer duration. Hence, deep cycle batteries are preferred in off-grid or hybrid solar power systems.

If a battery is left unused for a longer duration, it produces sulphate crystals on the plates of battery cells. The sulphate crystal minimizes acid contact with the cell plates, resulting in rapid charging and short discharging time. This makes the battery ineffective or sometimes useless.

Going straight away to buy a new battery is not a good option all the time. It will need an investment in new battery which is an expensive solution. In many conditions, you can recover the battery or enhance battery life for some more years.

In a battery, there may be a sign of not holding a charge, or even not taking a charge, you can try to repair it to get more out of it. A series of steps are given here which you can follow to get your battery back to life.

Precautionary Measures

Before starting off with the repairing procedure, you must take these points in mind,

  • Strictly follow the precautionary measures where discussed in the procedure.
  • Use proper or appropriate tools for every job done with the battery.
  • Battery inspection is very important procedure, do not overlook it in any case.
  • While caps of the battery cells are open, try to avoid contact with electrolyte (water) inside the battery as it is acidic in nature.
  • While charging the battery for the first time, pay attention to it regularly for first couple of hours. If body of the battery is too hot to touch, disconnect the charger immediately.

Tools and Materials needed for the Repairing Process

These tools will be used in repairing process while performing different steps.

  • Battery charger
  • Battery Desulfator
  • Battery Load Tester
  • Flathead or Phillips head screwdriver
  • Dry rag or a piece of cloth for cleaning
  • Baking soda
  • Distilled Water
  • Wrench or spanner for battery clamps

Preliminary Inspection and Cleaning

You will need to thoroughly inspect the condition of the battery. Check for any leakage in the battery because water level may go down due to leakage. Remove the battery terminals if they are connected. You should have two wrenches or spanners of correct size to loosen the battery clamps. In some designs of the battery clamps, you may need to use a flat head or Philips head screwdriver to remove the clamps.

Battery terminals get corroded as the battery ages or due to environmental conditions. A white or greenish-blue powder forms at the terminals. You should use gloves and safety goggles while doing the cleaning as the powder is toxic. First, clean the battery using a dry rag or any piece of cloth. Add 3-4 tablespoons of baking soda in a glass of water. Then, use the solution to clean the battery surface with a piece of cloth.

Inspect for the battery cell condition

Open the cover or caps from the cells of the battery and check for the water level in each cell. If there is no or little water, then inspect for the condition of the cells as well. They should be at least moist, otherwise, there are chances of the battery destroyed. Look into each cell for the accumulated debris at the bottom. When the battery is dried off too much, the stuff from the plates is shed off and accumulated at the bottom. This stuff shorts the bottom of the cell plates and charging this battery is dangerous.

Pour water in each cell of the battery

Now, the time is to add distilled water in the battery. If the condition of cells is good, pour distilled water in the cells up to the given mark. If there is no mark given, try not to overfill the battery and leave some space at the top. Do not use tap water or water from any other source, no matter how clean it is. The reason is that tap water has different salts dissolved in it depending on the source of water. These salts enhance the process of corrosion in the cells.

Put the Battery to Charging

For first charging after the above treatment, use a slow charger of 1-2 Ampere to avoid any damage to the battery. If you do not have a slow charger, you can use a regular charger with precautions. Some intelligent chargers have a safety feature not to charge a deep-discharged battery as they consider a battery below 10.5 V as defective.

Use a good battery in parallel if needed

To deal with such intelligent chargers, you will need a good battery with voltages above 12 V and battery jumpers. Using jumper cables, connect the repaired battery in parallel with the good one i.e. positive with positive and negative with the negative terminal. Now, connect the batteries to the charger. The charger will sense the voltage of the good battery and will start the charging process.

Keep an eye on the battery while charging

Let the battery charging continue for about an hour. During that time, keep an eye on the battery if you hear any kind of hissing sound (gassing) from the battery. DISCONNECT IMMEDIATELY if you hear any hissing sound. After an hour, check whether it is slightly warm or hot to touch. If you feel that the body of the battery is hard to touch or hot, DISCONNECT THE CHARGER IMMEDIATELY. If it is slightly warm, then let the charging process continue. Batteries become a bit warm while charging.

Remove the good battery if voltage improved

If you applied the method of paralleling the good battery with the repaired one, remove the second battery (the good one) after 3 to 4 hours if your main battery’s voltages go above 12 V. To check the voltage, disconnect both batteries from the charger and disconnect them from each other as well. Now, using a voltmeter, measure the voltage on the repaired battery. If voltages are above 12 V, reconnect only the repaired battery to the charger. Let the battery charge for 24 hours. After that, disconnect the battery from the battery charger and measure its voltage again if they are satisfactory or not.

Use Battery Desulfator to Remove Sulphate Crystals

While performing the above charging procedure, if you find that the charging process is very slow or no charging at all, you will need a battery desulfator. Alternative names of battery desulfator are battery resuscitator, battery rejuvenator, or battery reconditioner. As it is explained earlier, if the battery is dried up too much or deep-discharged, sulphate crystals are formed on the surface of the plates of battery cells. We need to remove this sulphate from the battery cell’s plates.

A battery desulfator is a device that enhances the capacity of an old lead-acid battery and extends the life of the battery. It provides pulses of high voltages or high frequency (depending on the technology used in the device) to the battery causing a current flow that reverses the crystallization process of lead sulphate. The desulfation process takes one day to three weeks depending upon the duration of the battery remain unused or damage caused to the battery due to the deep discharging.

Perform Charge and Recharge Cycle

It is a practice of experienced people to do the desulfation or charging/discharging repeatedly. Let me explain it to you. If you are doing the desulfation process, keep the battery on desulfator for two days, give it a rest for one day, and repeat the process. Measure the voltage at the end of each cycle and note if there is an improvement in the voltage. Repeat the desulfation process until you see no further improvement in battery voltage. Remember that disconnect the battery from the battery charger before measuring the voltage to get an accurate reading. In the same way, if you are charging the battery, charge it completely up to the limit possible and discharge with a load. This charging and discharging process help the battery to recover.

Perform the Load Test

In battery load testing, current produced by a charged battery is measured. We use this method to measure the health of a battery. First, you need to charge the battery until you get output voltage equal to the labelled voltage indicated on the battery. The voltmeter reading should be in the range of 10 percent of the labelled voltage. Connect the battery to the load tester and press the button to test the battery health. If the needle remains in the healthy (green) zone, the battery is in good condition.

If you do not have a load tester, you can connect the battery to a random load like 12 V street light or headlamp of a car. The brightness of the light should not go down too early.

Conclusion - How to Bring a Deep Cycle Battery Back to Life

The recovery chances of a battery are 60 to 80 percent. The recovered battery can give an extended life of 6 months to 2 years depending on the amount of sulphation or damage to the battery due to overcharging, deep-discharging or battery heat up. A deep cycle battery does not need regular watering, a regular inspection is still recommended. It is recommended to use modern and efficient chargers, charge controllers or solar inverters which have options to care about the health of the battery.

Article written by John Ho

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