1. Try to adopt using multimeter for understanding the battery charging and discharging capacities. Buy one here

2. Never over charge the battery. 12v and 7ah means the battery can power maximum of 12v capacity instruments. When drawn 1 amp the battery should lasts ideally 7 hours on continuous usage. In real world the charge holding capacity of the battery depends on many factors. An an average a 7ah battery should last 6hrs when connected to 1amp instrument.

3. Should never over or deep discharge the battery. In many cases, it is seen that battery was under use even though the total volts in the battery when gone below 10. Ideally the 12v battery should exhaust when reaches 11v it means if you use the 12v battery at the rate of 1amps per hour by the end of 6hrs of usage the volts of the battery will go below 10v. This particular situation is called deep discharge. Continuous usage even below 10v will return the battery to no return it means battery can't be powered up again as the battery capacity has too low to charge the battery again. Never attempt to use battery below the rated capacity without properly charging again. The best way to do is in the place of one battery one should buy 2 batteries. And if we have a requirement of 2 batteries we should be buying 4 or more numbers so that compulsory running of the instruments can be conducted without looking or worrying deep discharge of the battery. Just to remember to replace the batteries every 5 hrs for a safe side, and place other spare to run the instrument, recharge the batteries for 10 hrs to reuse them.

When this cycle is properly followed a battery should lasts one to 1.5 years ideally.

4. Even unused batteries should be given a charge regularly once in 10 days one hour to keep batteries under healthy condition