Charging car batteries

5 Valuable Tips for Charging AGM and GEL batteries

CAELEX Tech Tips

Battery charging is something all too familiar to anyone who works on vehicles, whether it be professionally or as a hobby.

When it comes to charging your batteries, there are rules that sometimes apply depending on what kind of battery you are dealing with. For your convenience we have put together a short list of tips for charging AGM and GEL batteries, so that you don’t make the mistakes that many others have.

Read our list below, for some of you it may be common knowledge that’s worth recapping, and for others it might be fresh and new.

Either way, here are the 5 tips we’ve put together for you to read and save.


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1. NEVER USE A CONSTANT CURRENT CHARGER!

Only charge GEL batteries using a confirmed and reliable, temperature sensing, voltage regulated charger.

2. FOR THE BATTERY TO CHARGE AT ITS OPTIMAL RATE, THE RIGHT PRESSURE MUST BE USED AT THE RIGHT TEMPERATURE.

If too much pressure is used, current or charge will be forced through the battery faster than it can be stored. This will cause the battery to give off hydrogen and oxygen faster than it can be recombined leading to the destruction of the battery.

The amount of voltage dictates the rate at which the amps will be forced into the battery during the re-charge process. The temperature at which this process is taking place also effects charging.

3. WARMER BATTERIES ACCEPT RE-CHARGE EASIER.

At 25°C keep charging current in the range of 2.38 volts to 2.42 volts per cell for GEL cell batteries and in the range of 2.4 volts to 2.465 volts per cell for AGM batteries.

Compensation for battery temperature above or below 25°C can be made by
subtracting 0.005 volts per cell for each 1°C above 25°C or by adding 0.005 volts per cell for each 1°C below 25°C.

Read: 5 Basic Auto Electrical Problems Explained

4. YOU WILL NEED TO REPLACE 104% TO 112% OF THE CHARGE REMOVED TO REPLENISH THE AMPERE HOURS REMOVED IN THE DISCHARGE PROCESS.

Typically you should expect that it will take 60% of the charge time to return the battery to within 90% of its original capacity. It will take the remaining 40% of the charge time to completely recharge the battery.

The time it will take to re-charge will depend on certain variables such as the depth of the discharge, the ambient and battery temperature, the age and condition of the battery as well as the charger’s overall features

5. CONSIDER THE PROCESS OF RE-CHARGING A BATTERY COMPLETED WHEN THE CHARGE RATE DROPS BELOW OR EQUAL TO THE BATTERY’S SELF-DISCHARGE RATE.

For example a 100AH battery with a 3% self discharge rate should be considered to be re-charged when the charge rate reaches and remains stable at 3 amps

Read: Start-Stop Technology and Batteries

Download the tips as a PDF!

CHARGING TIPS FOR AGM AND GEL BATTERIES.