As I understand Lithium, you get full voltage (12+VDC) right until you get nothing. It appears that as long as capacity exists you are good and there is a cutoff when capacity gets too low. Recharging is also faster and as mentioned earlier, they recharge faster and can be recharged from any state of charge without issue. The price difference is huge but you don't need as many amp hour capacity as you can use nearly all (80 percent) of the capacity compared to any earlier from of battery (50 percent or less). So, you could replace 2 regular batteries with 1 Lithium battery for about the same capacity (in theory) making the price difference a bit easier to swallow.