question about Dell Latitude CPX charge

I have a ASUS A3 laptop and want to know what kind of battery charger I will need and any suggestions on products. Also, besides the laptop not working, how do I know when battery is getting low?

A replacement ac adapter from asus designed for specific laptop. ac adapter differ in the amount of voltage and amperage they put out, depending on the make and model. Plug in the wrong one and you could have another battery go up in smoke and flames or just croak forever. sony VGP-BPS5A battery ,
sony VGP-BPS5 battery ,
sony VGP-BPL1 battery ,
sony PCGA-BP2NY battery ,
sony PCGA-BP2NX battery ,
sony PCGA-BP2SA battery ,
sony PCGA-BP2S battery ,
sony PCGA-BP2T battery ,
sony PCGA-BP51 battery ,
sony PCGA-BP2E battery ,