If you are looking for the lightest overall package when running errands with the SeQual eQuinox, the 12 cell rechargeable lithium ion battery is the way to go. If you are looking to extend your time away from the charger, then it is highly recommended that you have a couple batteries on hand at all times so you can have a battery charging while simultaneously running one in the eQuinox. The 12 cell battery really packs a punch, delivering up to 2.7 hours on pulse flow and up to 1.2 hours on continuous flow. When the battery is installed, a battery gauge will appear on the control panel so you will always be aware of remaining battery life and know when it is the proper time to charge. There is also a battery gauge on the actual battery itself—with the push of a button, LED lights will replicate remaining battery life. Replacing the battery is simple: just align it up with the empty battery compartment and press down until you hear a “click,” signifying the battery is locked and ready to go. If you have the travel cart attached, you will not have to remove it to replace the battery. This battery weighs 1.5 pounds.