Hi
here is config
4 x 2215 1000 kv chinese motors
30a esc
kk2.1
frame weight 400 gm
1250 mah 3s 25c lipo
auw = 900 gm
how much flight time i

How much flight  time i could expect as hover time ?

Bummp

what is the thrust produced ??
any spec sheet ?

By the time you get in air the battery would hardly have enough power. Try to increase the capacity to atleast 3000mah+

Tanmay in my opinion you ll get a flight time of around 2.5 to 3 Mins. Use atleast 2200mah so that u ll get flight time of around 5 mins.

The motors are cheap chinese those yellow 1000kv  the lipo is a 1250 mah 3s quadkopters.com lipo. 900 gm all up weight

The motors are cheap chinese those yellow 1000kv  the lipo is a 1250 mah 3s quadkopters.com lipo. 900 gm all up weight

1250 is way to less...wont last a min or two.....1300mAh are usually prefferd for 250 quads
Go for atleast 2200mAh

Could solar panels help ?

I live in rajasthan

Solar cells wont produce such amount of current unless u have resources from NASA
add another 1250 lipo in parallel
Also somehow even if u manage to get such amount of current from solarcells....the cells weight will anchor it to the ground

hope this helps

at the cost of solar cells from nasa you can get a full truck load of batteries.  so just get some bigger size battery like at least 2200mah

A 2200 mah can give you around 10mins of time and more if you reduce the weight to 700g. 900 is way too high. A 1200 can heat up unless its 40c or more.

2500 mah 
how much that'll give with a 700gm quad ??

first of all u need to know how much current the motor consumes for a given prop set... either do some thrust tests or search online for spec sheet of your motor

2500mah with 1045, ll give approx 6mins of flight time. Again actual output depends on what amount of power your motors consumes. But to be safer side 5-6 mins.

Read this blog post by Oscar , hope this will help you

If you have your specs decided I wonder weather you use ecalc.ch

It should answer all your questions and even help you decide the upgrade.

Happy Flying
-Pravin