Reviving this thread.
one of my cars has an AGM battery and I am wondering if I need a special AGM charger for that.
I do have one that has an AGM button, but is a very big one and would prefer to use my good old CTek in hibernation mode as it seats neatly under the bonnet (hood) and I can keep it shut when the car is parked.
Also, the instrucrions on how to charge that make zero sense to me.
Why do all that and not just use the designated spots (positive on battery and negative on the strut tower)?
How to charge an AGM battery
Before anything, take off any jewelry, put on safety glasses and go to a well-ventilated area or outdoors.
- Plug in your AGM-compatible battery charger. Follow any other instructions for your specific charger.
- Connect a backup power supply to the onboard diagnostics OBD-II Port.
- Disconnect the car’s negative terminal and wrap it with a glove, rag or anything to prevent it from touching any metal. The negative cable is usually black, but you can also look for a minus (-) symbol on the cable as well.
- IMPORTANT: Select AGM or Absorbed for the battery type on your charger. A smart charger may detect the voltage and battery type when you connect it, but don’t leave it to chance. Select 12 volts to match the voltage of your AGM battery.
- Connect the charger to your car battery posts. Again, check the indicator lights and make sure they’re set to AGM or Absorbed.
- Start the charger and wait two to eight hours to fully charge your AGM battery.
- Disconnect the charger from the battery when it’s done. Your charger’s indicator light will signal when it’s done charging the battery. Again, avoid letting the charger’s clamps touch the battery’s loose negative clamp.
- Reconnect the car’s negative terminal to the battery. Disconnect the backup battery. Now you’re ready to hit the road with a fresh start.
All this seems quite confusing and pretty "black magic" stuff. Up to today, it was, pop the bonnet, connect, forget.
Why do this ritual and why can't I use a simple charger for AGM?