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How to charge a dead lead acid battery

How To Charge A Dead Battery


Charge A Dead Lead Acid Battery


Often a car battery will die on us and it seems like nothing we try can bring it back again. A conventional battery charger may not be able to recognize that a battery is even attached due to the voltage being too low. But sometimes you can recharge a dead auto battery, even if it seems hopeless.

If you do not have a so called "maintenance free" battery that is sealed, you may be able to pry off the lids on top and check the fluid level. Batteries will lose fluid with time due to heat and charging. The water boils off and evaporates.


Check battery water levels

How to charge up a dead lead acid battery



Wash the battery fully and wipe it dry with paper towels before proceeding to the next step. You do not want any dirt or filth getting into your battery cells. This can damage the battery.

If you do have removeable lids on the battery top, carefully pry them off with a screwdriver. Have some baking soda nearby in case any acid comes out. Baking soda will neutralize the acid.

Check the water levels inside the battery cells. If the water is not visible above the tops of the lead plates, then the water needs to be topped off. Use distilled water only and carefully pour water into each cell until the water level is above the lead plates.

Put the lids back on the battery cells and let it sit for about 20 minutes.

If your battery is maintenance free, proceed to the next step. You may still be able to charge your battery.



Check your battery with a volt meter. It may already be improving and can be recharged with a normal battery charger at this time.

If the batter will still not take a charge, do not give up yet. If the battery is lower than about 10 volts, then the charger may not be able to recognize that a battery is attached to it. A battery charger will try to sense if a battery is attached for safety reasons. If it does not see a battery, then it will not put out any energy.

There is a trick to get your battery charging.


Put a battery in parallel with a dead one to connect to charger


Get another battery that is good and has a charge. Place it next the dead battery and connect them together in parallel. Plus to plus and minus to minus. Let the batteries sit like that for about 5 or ten minutes to stabilize.

Now hook up your charger to the pair of batteries as if they were one single battery. The charger should recognize the batteries and start charging. Disconnect the charger every few hours and separate the bad battery from the good one. Measure the voltage. If it is increasing, then the battery is taking a charge and may be possible to revive. Try connecting the battery charger to it and see if the charger will recognize the battery. You may need to hook up the other good battery in parallel again. But eventually, if the dead battery is taking a charge, it should be able to be charged alone.

If all of this fails, there is still hope to restore your old, tired battery. See our Homemade Battery Restorer for details.

Feel free to ask any questions or get help with your project on our Support Forum.

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Troy Reid


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