A point rarely discussed when considering a batteries quoted capacity, usually in amp hours for any nominal voltage, is the Peukert effect. He discovered the rate of discharge impacts greatly the quoted capacity, maintained high discharge currents leaving a battery below the working voltage range of any load its supplying before the full capacity has been depleted. A simple explanation is that batteries provide chemical storage of electrical energy. When asked to release this energy there is a limitation on how quickly the chemical energy can be released as electrical. Consequently battery capacity is usually quoted at the 20 hour rate such that, for example, a 100 amp hour battery will provide a load of 5 amps for 20 hours (C/20) before being below the fully discharged voltage. Considerably less time if the load was increased to say 50 amps (C/2) and conversely exceed the quoted capacity for very light loads. This also explains why a lead acid battery can recover a little after a heavy discharge as chemical energy remains.
Peukert determined a mathematical law to calculate this effect of load v discharge time with an exponent of 1 for the perfect battery ranging to 1.35. Lead/acid flooded cell around 1.2 and AGM/gel a little higher. LiFePO4 batteries fair the best at 1.01 to 1.05 allowing intermittent very high discharge rates on EV's with little impact on capacity. The latter can also be safely charged at much higher rates as well although the Peukert effect relates to discharge only.
