Additional, always look to decrease amperage in system if possible, that means 12V system not good for power over 150W. At 150W You have 150W/12V=12,5A and for 300W You have 300W/12V=25A, this is lots for standard card lead acid battery 55Ah 72Ah, this means You should use 100Ah and bigger 180Ah.
Some people wants 500W from 55Ah at 12V, this is lots for that battery, and will destroy battery (44A for longer discharge if there spirit of life in cells). For 500W go to 24V system or 48V.
Capacity of battery are based on 10h or 20h discharge time. 55Ah lead acid battery 55Ah/44A=1,5h this is theoreticaly one hour but in practice You will get much lower timer about 15min, because this is not in manufacturer advice for 10h or 20h discharge time for garanted capacity.
Always use Lead Acid batteries in very well ventilated room. Only Lead Acid with glass and gell may used in room and will not harm, but very expensive specially bigger capacity of battery, and they have up to 5 years life.
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I have old Bosch S3 car batery (starter) 55Ah made in 1999 year. Not full capacity but have about 50%-60%. Can start car, but not good if outdoor temp is under zero capacity will drastically decrease. (Of course I change bat in car with new, and this S3 goes to basement for resting).
I use desulfatisator on this battery very often, and I turn out battery from car at winter (very cold days -10C -18C )and put to charge in basement at 22C-23C.
Also I made battery AC tester of internal resistance. Its very usefull.