AGM / GEL battery
This kind of sealed battery use the "Absorbed Glass Mat" technology. The electrolyte is impregnated in the glass fiber and can not flow. The transport and handling are much easier.
AGM batteries are not really sensitive to damaging effects of frost as they contain no liquid. Those batteries are also more resistant to shock and vibration than conventional batteries.
They also have a very low self discharge rate (between 1% and 3% per month) which is ideal for long-term storage without frequent recharging.
The internal resistance of AGM batteries is very low, so there is little internal heat when they are used, it allows greater flexibility of charge or discharge rate.
For solar use, AGM batteries are ideal: no maintenance, no gas release, using conventional charge rate (lets you use any standard charging system), minimal maintenance during the winter season.