My 2 pennorth on cheap walkie talkies:
I bought a pair on amazon that claimed range of about 1km and used aaa batteries. Rubbish doesn't even start to define them.
TURNED OFF they depleted a set of Duracells in a day. Turned on 2 hours max. They would only work with rechargeables for about 20 minutes. Range did not extend 50 metres building to building.
So, invest in something at the next level of quality at least.