OK!
Everything went great! It turns out that 741(yeah, i stick with it) indeed reacts only when input voltages are ~2v above -V(that's 0v in this case).
So i did as i said in preceding post, putting a LED in ground lead of LM35 to pull up output voltage to Vout+1.65v. Now i think that i should go for more because now it won't react on temperatures below ~30°C but in my case it doesn't matter
In attached sch D1 is mounted close to BC548 (mine touches it) so that they are at almost same temperature so that the voltage won't change much.
I also put back LED that eric told me to remove because i like it when i can see the state of 741's output
and it also drops the voltage enough so that the relay driver draws about 35mA which is enough to keep the relay on.
When the power is first applied relay is in off state and only the LM35 gets power.To start charging (which i didn't yet built) push-button must get pressed which applies enough current to base of driver transistor to turn it on and energize the relay coil which then closes contact and passes power to 741 and BC548. The trimmer resistor in base divider of BC547 serves to choose voltage at non-inverting input of 741 at which the circuit will cut-off power to itself and end charging process.
Only thing that is left to do is to build a constant current source to charge batteries.I'll use some NPN power transistor to do that since i have few of them laying around...it is only important to choose one that is capable of enduring 500mA of emitter current and that it doesn't get hot. As far as i know, Uce should be as low as possible so that the transistor itself dissipates as little power as possible.
Ok, now i'm going to that part... when it's finished i'll post it here
btw, thank you eric and Diver for your opinions and advices!!!