How to Fix and Restore Gel Batteries

by Stephen BenhamUpdated July 12, 2023
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Gel batteries are generally the same as regular lead-acid batteries you use to start your car, except the battery cells contain a gel rather than a fluid. Gel batteries are considered to be safer than lithium-ion batteries, because if the casing gets damaged the gel doesn't spill, but fluid-based batteries can leak sulfuric acid if the casing gets damaged because of corrosion or other chemical reaction. Gel batteries are sealed batteries, so unlike fluid-based batteries you cannot access the cells. Because of this, their lifespan is long and they are supposed to be “maintenance free” with little reason for battery charging or deep discharge. But again because of long life, you may need to fix this type of battery at some point to avoid having to get a new battery for your automotive in order to power your alternator and inverter fully.

The best way to fix and restore a gel battery is to discharge it as much as possible and then charge the battery slowly. This kind of reconditioning will act as a regulator for the battery and extend the life of the battery through the charging voltage. A gel cell battery is typically a 12-volt battery, but the battery capacity can vary depending on what kind of car battery it is, if it’s a deep cycle battery, or if it’s in another vehicle like a golf cart or off-grid vehicle – then it might be a 6 volt battery.

1. Use all the energy left to refurbish the cell structure

Use whatever energy is left in the lead-acid gel battery. This process helps refurbish the cell structure. If there's not enough energy to power equipment requiring a lot of energy, turn on lights. Leave the battery to self-discharge for a period of time until the lights are very dim and the power supplies are obviously low enough to call it a dead battery or at least a very low battery voltage with amps that won’t damage the AGM battery.

2. Clean

Before your recharge the battery, clean any residue left on the outside of the lead plates with a mixture of baking soda and distilled water.

3. Prepare your battery charger

Place your battery charger near your lead-acid gel battery. Check your battery charger for a low charge setting such as "trickle charge." Some battery chargers have a setting for "Gel." It's important the battery receive a slow charge as charging it fast will damage the battery beyond repair. If your battery charger doesn't have a slow charge rate, obtain or borrow a trickle charger that has a slow charging current that will be able to deliver a long charge time with the correct amperage and a voltmeter to measure it.

4. Select lowest setting or Gel

Select the lowest charge setting on the battery charger. Use "Gel" if it has the setting. Connect the two battery cables attached to the charger to the lead-acid gel battery terminals. Use the clamp on the end of the red cable and attach it to the positive terminal "+" of the battery. Use the clamp on the end of the black cable and attach it to the negative terminal “-” of the battery.

5. Turn on your battery charger

Turn on your battery charger to begin charging the lead-acid gel battery. The slow charge rate on a totally discharged gel battery allows the cell structures to repair themselves without sulfation, desulfation or gassing. Leave it for five to six hours and then touch the side of the battery with your hand. If it is charging correctly, the battery is getting warm. Leave it for another five or six hours then touch the battery again and you should find it is warmer, but not hot. If it is hot, turn off the charger immediately and let the battery completely cool before restarting the charge.

6. After 12 hours, turn off the charger

Turn off the charger after a total of 12 hours. Don't leave it too much longer, as unlike regular lead-acid batteries you can overcharge a gel battery. Disconnect the battery charger cables.

7. Repeat once or twice a year

Use your lead-acid gel battery in the usual way and it should hold a full charge. Repeat the steps at least once or twice a year to prolong the life of a lead-acid gel battery.

Helpful Video

Helpful comments from the video:

  • I hope you didn't throw out that small battery. All you have to do is jump it with a larger battery and some jumper cables. Let it try to equalize with the larger battery for a few minutes , then remove the jumper cables and connect your charger to the small battery. This tricks the charger into working because the small battery is now reading voltage rather than completely dead. (It drew some charge from the larger battery as it was trying to equalize to the larger battery's voltage.) Your desulfator may be able to bring it back. They work best on smaller batteries like the one from your light. Good Luck. Chris B
  • Wrong about one key thing - That Optimate will not charge, or start to charge, a fully flat battery - It needs to receive a small input from the battery to be charged. So, with this type of charger you need to find a way to get the Optimate to kick off (which is worth it because the desulphation or saver mode is worth a go). 2 ways of doing it, either connect another battery to your flat battery with some leads OR use another non microprocessor type charger to get a bit of voltage into it (just for maybe 30 seconds or so or even while still connected to your other power source) and then connect your Optimate. You can then carry on as with the rest of this video. I've pulled back from the abyss a few batteries using this type of charger, but they won't kick off a dead flat battery without help.

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