Lithium Iron Phosphate Batteries

LiFePO4 (Lithium Iron Phosphate) batteries, on the other hand, are a newer and more expensive technology that offers several advantages over AGM batteries. They are much lighter, have a longer lifespan, and are more efficient at storing and releasing energy. LiFePO4 batteries also have a higher cycle life, meaning they can be discharged and recharged more times without losing capacity. They are more expensive than AGM batteries but can be a better long-term investment.

Other advantages of lithium include:

1. You can run them all the way down to 0% charge with no (or minimal) ill effect as long as they are recharged in a timely fashion. While this is not recommended , it does not affect them in the same way it does traditional lead-acid batteries.
2. You can let them sit unattended for long periods of time at partial SOC (State Of Charge) between 50-80%. They can sit like that for months with no ill effects, a lead-acid battery would probably be ruined or compromised under the same conditions (they generally need to be brought to full charge once a month).
3. You can add new ones to old ones as long as they are in the same approved categories, usually same manufacturer, sometimes same size but not always. this is huge of course, allowing users to expand over time in a way you could never do with traditional lead-acid.
4. You don't have to worry as much about cabling lengths between batteries for complicated reasons (a.k.a. the Peukert Effect).
5. They  generally have onboard computers these days (a.k.a. "internal BMS/Battery Management System") that take care of important things like not accepting charge below a certain temperature (there are also self-heating models now).