suitable charger for 12vDC battery and 700w inverter ? does any relation between choose charger and inverter?

Answer 1

A 12V lead acid battery (I'm assuming that's the type of battery your're talking about) in a car will typically be kept charged by about a 13.6V constant-voltage source. And they should not be recharged at a rate greater than it's capacity in amp-hrs (example - do not charge a 25 amp-hr battery at greater than 25 amps).

The 2 most economical ways that come to mind are jumper cables from a running car's battery, or at home via a battery charger from an auto parts store or even Sears/Walmart/etc. More sophisticated high-power chargers, such as the ones we build at work for electric forklifts, will determine the battery's state-of-charge upon connection, charge at a programmed high rate of constant current until fully charged, then switch to constant voltage for top-off, and then even perform equalization charges at programmed intervals, typically one week. Example from where I work -

http://www.posicharge.com/

A 12V, 25amp-hr (you didn't mention the amp-hr capacity of your's) battery can theoretically supply
12*25 = 300 watt-hours of energy, but you'll get much better battery life if you don't discharge quite that deep. You don't mention what the load on your inverter is, so assuming it's the full 700W, that means you can only run for about 20 minutes on a 25 amp-hr battery. If you need to run longer, you can add lead-acid batteries in parallel - I'd recommend they all be identical batteries, otherwise you may need to occasionally (say once per 10 recharge cycles) separate the batteries and recharge them individually.

There's no direct relation between the charger and the inverter; you chose the inverter appropriate to the load, you choose the battery for the length of time you need to supply the load, and you choose the charger according to how quickly you want the charge cycles to complete.

Answer 2

The charger needs to supply a voltage of more than 12V and a current of a few amperes to take care of the batteries during the charge cycle. Trickle charging (charging with a relatively lower current like say 1 amp) is safe to the battery preventing overheating and too much gassing.

The inverter itself can be used to charge the batteries during the time when AC is On. And switch to inverter mode during the period when the AC is Off.