Lead batteries have pretty horrible characteristics compared to Lithium, especially around depth of discharge. They're good to start a car (lots of amps, fast),

Lead batteries have pretty horrible characteristics compared to Lithium, especially around depth of discharge. They're good to start a car (lots of amps, fast), but not very good to run a computer (low amps, for a long time). Discharge it below 50%, and you'll significantly shorten their lifespan. Below 25%, better try that only once or twice. Below 10%, might as throw them out.