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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, because if the casing gets damaged the gel doesn't spill, but fluid-based batteries can leak sulphuric acid, if the casing gets damaged. Gel batteries are sealed units, so unlike fluid-based batteries you cannot access the cells. The best way to fix and restore a gel battery is to discharge it as much as possible and then charge the battery slowly.
Check your battery is discharged before fixing and restoring it. Turn on your car's lights and other electrical equipment to use any power in the battery. The lights dim, when the battery is nearly discharged. It's not necessary to completely discharge the battery. As soon as the lights dim, turn them off and any other electrical equipment you previously turned on.
Squeeze the handles of the clamp on the end of the black cable from the battery charger using your hand so the jaws open. Place the open jaws over the gel battery terminal labelled "-" or "Neg" then release the pressure so the jaws close and tighten on the terminal. Repeat the process using the clamp on the end of the red cable from the charger, but position it on the battery terminal labelled "+" or "Pos."
Check the front of your charger to determine what charge settings you can set. It's important you charge your gel battery at the lowest charge setting. Do not use "Boost" or "Fast-charge," as you may damage the battery irreparably.
Set the charger to the lowest setting; it is usually marked "trickle-charge." Some chargers have a specific setting for gel batteries, so if you have one, use it. If you don't have gel or trickle charge settings ensure the charge rate is 20 per cent lower than the voltage output from the gel battery. The voltage is clearly labelled on the battery and is usually 12-volts. Using 12-volts as an example, you need to charge your battery at 10-volts or less.
Plug in your battery charger to the electricity supply. Turn on your charger and then let your battery charge. Feel the side of the battery after 6 hours. If it is warm, that's fine, so continue charging, but if it feels hot, turn off the charger and let the battery cool for about 30 minutes. Then turn on the charger again.
Continue to charge the battery, but check it every six hours to ensure it doesn't get too hot. After 24 hours, your gel battery is fixed, restored and fully charged, so turn off the charger. Disconnect the two clamps on the battery terminals.
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