1.2V? I would imagine it should be either an 8.4v or a 9.6. Most likely an 8.4 if it came with the airsoft gun out of the box. Was it an additional purchase? if so what brand is it? Used or new?
On the simple wall charger that was most likely included if it came with the battery you will find some information in regards to the its out put charge rating. If it charges at a rate of say...350mAH per hour then for your 1500mAH batt you will need
1500 / 350 = 4.28 Hours to complete a charge. Give or take 15 minutes.
Its hard to say if your battery is quality or not, but if its just something out of the box I would hazard a guess and say its not the greatest but it will function for the time being.
You will most likely wish to purchase quality batteries and a quality charger soon.
I hope this clears everything up.
"Its only a little bit on fire"