Solar batteries are intended to serve as a leisure battery for your campervan, motorhome or caravan. To ensure that your batteries last a long time, typical lead-acid /wet) batteries and gel batteries should not be discharged deeper than 40% of their rated power.
A deeper discharge of up to 50% is possible wih deep-cycle AGM batteries. High-quality lithium iron phosphate batteries (LiFePO4) can even take up to 90% discharge for a limited amount of time.
Recharging with solar power depends on the incoming radiation and cannot always fully recharge the battery. A solar battery should be fully recharged with a conventional charger as often as possible.
The typical cause for a battery failure is that it is not loaded properly after a partial discharge and so discharged too low too often.
You can prolong your battery's life-span significantly by fully recharging it regularly. Caution: Gel batteries have to be charged for at least another 6-8 hours after they are full!!
Deep-cycle AGM batteries
have a higher ciycle stability than most lead-acid batteries (500 cycles at 50%, 1200 cycles at 30% depth of discharge). Lithium iron phosphate batteries
can live through up to 2500 cycles at a discharge of 90%.