I have a couple questions about my Avalanche battery and battery use:

1. I saw a secondary battery holder under the hood on the driver side. If I install a second battery there, how to connect? Is there a special cable for this?

2. When I use a charger to charge the battery, after charging finishes, if I open the door, that will drop the voltage to the extent that will trigger the charger to recharge the battery. Is this normal?

Thanks!