It turns out that the usable capacity of a lead acid battery depends on the applied load. Therefore, the stated capacity is actually the capacity at a certain load that would deplete the battery in 20 hours. This is concept of the C-rate. 1C is the theoretical one hour discharge rate based on the capacity.
A 12V lead-acid battery typically has a capacity of 35 to 100 Ampere-hours (Ah) and a voltage range of 10.5V to 12.6V. The battery can be discharged up to 50% of its capacity before needing to be recharged.
The capacity of a lead–acid battery is not a fixed quantity but varies according to how quickly it is discharged. The empirical relationship between discharge rate and capacity is known as Peukert's law.
A battery at 10.5 - 10.8 volts at rest is probably damaged. A lead acid battery should never be below 11.80 volt at rest. ↩ 'bad' battery protection solutions will just start to oscillate as the battery voltage recovers (above the cut-off threshold) when the load is removed.
Personally, I always make sure that anything connected to a lead acid battery is properly fused. The common rule of thumb is that a lead acid battery should not be discharged below 50% of capacity, or ideally not beyond 70% of capacity. This is because lead acid batteries age / wear out faster if you deep discharge them.
Here’s how the different types compare: Flooded Lead-Acid Battery: High capacity, low voltage, and can handle high discharge rates. However, they require regular maintenance and can leak if not properly maintained. Sealed Lead-Acid Battery: Lower capacity and higher voltage than flooded batteries. They are also maintenance-free and leak-proof.